HomeMy WebLinkAbout2001-11-20 Support Documentation Town Council Work Session
VAIL TOWN COUNCIL
WORK SESSION
TUESDAY, NOVEMBER 20, 2001
4:00 P.M. IN TOV COUNCIL CHAMBERS
AGENDA
1. ITEM/TOPIC: Preston Isom - 25 Year Anniversary. (5 min.)
Pam Brandmeyer
2. ITEM/TOPIC: Art In Public Places Project Announcement (20 min.)
Leslie Fickling
ACTION REQUESTED OF COUNCIL: Review, comment and instruct
AIPP to proceed.
BACKGROUND RATIONALE: AIPP has developed two projects for 2002 and
has approved the enclosed project prospectuses. AIPP now submits the projects
for Town Council approval.
Project One
The Public Works department is replacing the pedestrian bridge at Gore Creek
Promenade in May 2002. AIPP would like to integrate art into the project and
intends to put out a nationwide "call to artists" asking for an artist or craftsman to
design railings for the new bridge. One Hundred and Fifty lineal feet of rail will be
required. AIPP has set a budget of $34,000 for the project to include design,
fabrication, installation and site visits. AIPP intends to solicit public participation
and comment at all stages of the project. AIPP and the Public Works
department will share the cost of the new railings as follows:
Public Works $18750 cost for a standard railing
AIPP 15250 additional funds to upgrade the standard railing
TOTAL 34000
Project Two
AIPP plans to commission nine local artists to paint nine electrical transformer
boxes in Vail Village in July 2002. A juried competition will be open only to artists
residing in Eagle County. Artists will be awarded between $300 and $600 for
their work, depending on the size of the box. AIPP will announce the
competition in the local press and by any other appropriate means. A budget of
$4525 has been set for the project, which includes a fee payable to the utility
company.
STAFF RECOMMENDATION:
The staff recommends that the council endorse the projects.
3. DRB/PEC Report. (5 min.)
Allison Ochs
4. Information Update (5 min.)
5. Matters from Mayor and Council (5 min.)
6. Adjournment. (4:40 P.M.)
NOTE UPCOMING MEETING START TIMES BELOW:
(ALL TIMES ARE APPROXIMATE AND SUBJECT TO CHANGE)
THE NEXT VAIL TOWN COUNCIL REGULAR WORK SESSION
WILL BE ON TUESDAY, DECEMBER 4, 2001, BEGINNING AT 2:00 P.M. IN THE TOV COUNCIL
CHAMBERS.
THE NEXT VAIL TOWN COUNCIL REGULAR EVENING MEETING
WILL BE ON TUESDAY, DECEMBER 4, 2001, BEGINNING AT 7:00 P.M. IN TOV COUNCIL
CHAMBERS
Sign language interpretation available upon request with 24-hour notification. Please call 479-
2332 voice or 479-2356 TDD for information.
0
ENT-OF T y~2a
N o United States Department of the Interior
U.S. GEOLOGICAL, SURVEY
2,gRCH Box 25046 M.S. 415
IN REPLY REFER To: Denver Federal Center
Denver, Colorado 80225
October 31, 2001
MEMORANDUM
TO: Interested persons, U.S. Geological Survey report
i
FROM: William F. Horak, Colorado District Chief,
U:S. Geological Survey, Denver, Colorado
SUBJECT: Publication of Water Resources Investigations Report WRIR 99-4270
"Gore Creek Watershed, Colorado-Assessment of Historical and Current
Water Quantity, Water Quality, and Aquatic Ecology, 1968-98"
Knowing your interest in water resources of the Upper Colorado River Basin and your
interest in products from the U.S. Geological Survey, we are sending you a copy of the
subject report by Kirby H. Wynn, Nancy J. Bauch, and Nancy E. Driver. The report
provides an assessment of the historical and current water-quantity, water-quality, and
aquatic-ecology conditions in the Gore Creek watershed. The report was prepared in
cooperation with the Upper Eagle Regional Water Authority, Eagle River Water and
Sanitation District, and the Town of Vail.
If you want additional information or have questions about this publication, please
contact Kirby H. Wynn at (970) 245-5257 ext. 23 or khwynn @ usgs.gov.
rr~w
UOU0
science for a changing world
Prepared in cooperation with the
TOWN OF VAIL, EAGLE RIVER WATER AND
SANITATION DISTRICT, and the UPPER
EAGLE REGIONAL WATER AUTHORITY
Gore Creek Watershed, Colorado
Assessment of Historical and Current
Water Quantity, Water Quality, and
Aquatic Ecology, 1968-98
Water-Resources Investigations Report 99-4270
G ~i( J-
•
a
Ig 1
7M F!"
rr.
U.S. Department of the Interior
U.S. Geological Survey
Front cover:
Left photograph, Gore Creek
Right photograph, View of the Gore Range from Gore Creek
Back cover:
Upper photograph, Sunset on Gore Range
Lower photograph, Gore Creek in autumn
Photogaphs by Ken Neubecker
Gore Creek Watershed, Colorado
Assessment of Historical and Current
Water Quantity, Water Quality, and
Aquatic Ecology, 1968-98
s
By Kirby H. Wynn, Nancy J. Bauch, and Nancy E. Driver
U.S. GEOLOGICAL SURVEY
Water-Resources Investigations Report 99-4270
Denver, Colorado
2001
U.S. DEPARTMENT OF THE INTERIOR
GALE A. NORTON, Secretary
U.S. GEOLOGICAL SURVEY
Charles G. Groat, Director
The use of firm, trade, and brand names in this report is for identification purposes only and does
not constitute endorsement by the U.S. Geological Survey.
For additional information write to: Copies of this report can be purchased
from:
District Chief U.S. Geological Survey
U.S. Geological Survey Information Services
Box 25046, Mail Stop 415 Box 25286
Denver Federal Center Federal Center
Denver, CO 80225-0046 Denver, CO 80225
CONTENTS
Abstract 1
Introduction 2
Purpose and Scope 4
Acknowledgments 4
Description of Study Area 4
Data Sources and Compilation 7
Methods of Data Review and Analysis 18
Surface Water 20
Water Quantity 20
Water Quality 25
Field Properties 25
Inorganic Constituents 29
Organic Constituents 42
Sediment 43
Streambed Sediment and Tissue Chemistry 43
Organochlorine Compounds 43
Trace Elements 44
Ground Water 45
Water Quantity 45
Water Quality 45
Inorganic Constituents 47
Organic Constituents 50
Other Constituents 50
Other Ground-Water Data 50
Dating Analysis 51
Aquatic Ecology 52
Algae 53
Macroinvertebrates 56
Gore Creek 56
Black Gore Creek 60
Fish 61
Relations Among Water Quality, Aquatic Ecology, and Bed-Sediment and Tissue Chemistry 63
Summary 65
References Cited 69
FIGURES
1-6. Maps showing:
1. Location of the Gore Creek watershed 3
2. Average annual precipitation (1951-80) in the Gore Creek watershed 5
3. Geology of the Gore Creek watershed 6
4. Land use for the Gore Creek watershed 8
5. Surface-water-quality sampling sites in the Gore Creek watershed 13
6. Aquatic-ecology sampling sites, 1995-97 14
7. Graph showing distribution of sampling dates and period of record for nutrient
samples at surface-water sampling sites 15
8. Distribution of sampling dates and period of record for trace-element samples
at surface-water sampling sites 16
9. Map showing ground-water sampling sites, 1988-97 17
CONTENTS III
10-12. Graphs showing:
10. Mean annual streamflow at selected gaging stations in the Gore Creek watershed 23
11. Mean monthly streamflow at selected gaging stations in the Gore Creek watershed 24
12. Mean daily streamflow and specific conductance at the mouth of Gore Creek 26
13. Graph (A) and map (B) showing:
Distribution (A) and spatial distribution (B) of specific conductance 27
14. Graph showing trilinear diagram of major-ion data for site 29, at the mouth of Gore Creek 30
15. Graph showing distribution of nutrient concentrations for all surface-water sampling sites
in the Gore Creek watershed 31
16-22. Graphs (A) and maps (B) showing:
16. (A) Distribution of ammonia and (B) spatial distribution of median concentrations of
ammonia for surface-water sampling sites in the Gore Creek watershed 33
17. (A) Distribution of nitrate and (B) spatial distribution of median concentrations of nitrate
for surface-water sampling sites in the Gore Creek watershed 34
18. (A) Distribution of orthophosphate and (B) spatial distribution of median concentrations
of orthophosphate for surface-water sites in the Gore Creek watershed 35
19. (A) Distribution of total phosphorus and (B) spatial distribution of median concentrations
of total phosphorus for surface-water sites in the Gore Creek watershed 36
20. Streamflow and (A) nitrate and (B) total phosphorus concentrations, Gore Creek at mouth
(site 29), October 1995-December 1997 38
21. Temporal distribution of ammonia (A) and nitrate (B) at Gore Creek at mouth, site 29 40
22. Temporal distribution of orthophosphate (A) and total phosphorus (B) at Gore Creek
at mouth, site 29 41
23. Map showing ground-water sampling sites in the Gore Creek watershed, 1988-97 46
24. Map showing aquatic-ecology sites on Gore, Black Gore, and Polk Creeks 52
25-31. Graphs showing:
25. (A) Relative percent biovolume of the major algal divisions and (B) total biovolume
for nitrogen-autotroph diatoms at sampling sites on the main stem of Gore Creek 55
26. Chlorophyll-a biomass at sampling sites on the main stem of Gore Creek 57
27. Relative (A) and total (B) abundance of the major macroinvertebrate groups at sampling
sites on the main stem of Gore Creek 58
28. Abundance of Trichoptera individuals, by functional feeding mechanism 60
29. Relative (A) and total (B) abundance of the major macroinvertebrate groups in Black Gore
and Polk Creeks 62
30. Comparison of fish-community structure at the mouth of Gore Creek with a reference site
in Rocky Mountain National Park 63
31. Comparison of chlorophyll-a biomass with relative percent algivores at sampling sites on
the main stem of Gore Creek 64
TABLES
1. Surface-water, ground-water, and aquatic-ecology sampling sites, and data sources and types
in the Gore Creek watershed 9
2. Summary of procedure used to aggregate nutrient data in the Gore Creek watershed into selected
nutrient constituents 20
3. Generalized water budget for the Gore Creek watershed 21
4. Hydrologic characteristics for surface-water sampling sites in the Gore Creek watershed 22
5. Median nutrient concentrations for background and urban land-use categories for the Gore Creek
watershed, Upper Colorado River Basin, and the United States 37
6. Summary of the minimum, median, and maximum values for the water-quality properties and
constituents of monitoring wells sampled in the Gore Creek watershed, 1997 48
7. Summary of selected water-quality and habitat data for aquatic-ecology sampling sites in Gore,
Black Gore, and Polk Creeks 54
IV CONTENTS
CONVERSION FACTORS AND ABBREVIATIONS
Multiply By To obtain
acre-foot (acre-ft) 1,233 cubic meter
cubic foot per second (ft3/s) 0.028 cubic meter per second
foot (ft) 0.3048 meter
gallon (gal) 3.785 liter
gallon per minute (gal/min) 0.06308 liter per second
inch 25.4 millimeter
inch per year (in/yr) 25.4 millimeter per year
mile (mi) 1.609 kilometer
picocuries per liter (pCi/L) 0.3125 tritium units
pound (lb) 0.4536 kilogram
square mile (mil) 2.59 square kilometer
ton 0.9072 metric ton
Degree Fahrenheit ('F) may be converted to degree Celsius ('C) by using the following equation:
°C=5/9(°F-32)
Degree Celsius ('C) may be converted to degree Fahrenheit F) by using the following equation:
°F=9/5(°C)+32
Additional Abbreviations or Terms
cols/100 mL colonies per 100 milliliters
DOC dissolved organic carbon
DWA drinking water advisory
gpd/ft gallons per day per foot
HA health advisory
µg/g microgram per gram
µg/kg microgram per kilogram
µg/L microgram per liter
µm3/cmz cubic micrometers per square centimeter
µS/cm microsiemens per centimeter at 25 degrees Celsius
mg/L milligram per liter
mg/mz milligrams per square meter
mL milliliter
MBAS methylene blue active substances
MCL maximum contaminant level
MCLG maximum contaminant level goal
NTU nephelometric turbidity units
pfu plaque-forming unit
PMCL proposed maximum contaminant level
SMCL secondary maximum contaminant level
SOC suspended organic carbon
units/yr units per year
as N as quantified, as measured nitrogen
as P as quantified, as measured phosphorus
VOC volatile organic compound
CONTENTS V
Gore Creek Watershed, Colorado Assessment
of Historical and Current Water Quantity, Water
Quality, and Aquatic Ecology, 1968-98
By Kirby H. Wynn, Nancy J. Bauch, and Nancy E. Driver
Abstract Historically, suspended sediment
associated with construction of Interstate 70
The historical and current (1998) in the early 1970's has been of primary concern;
water-quantity, water-quality, and aquatic- however, recent data indicate that streambed
ecology conditions in the Gore Creek water- aggradation of sediment originating from
shed are described as part of a study by the Interstate 70 traction sanding currently is
U.S. Geological Survey, done in cooperation a greater concern. About 4,000 tons of coarse
with the Town of Vail, the Eagle River Water sand and fine gravel is washed into Black Gore
and Sanitation District, and the Upper Eagle Creek each year following application of traction
Regional Water Authority. Interpretation of materials to Interstate 70 during adverse winter
the available water-quantity, water-quality, driving conditions. Suspended-sediment concen-
and aquatic-ecology data collected by various trations were low in Black Gore Creek; however,
agencies since 1968 showed that background bedload-transport rates of as much as 4 tons per
geology and land use in the watershed influence day have been measured.
the water quality and stream biota. Water samples were collected during
Surface-water nutrient concentrations spring and fall of 1997 from five alluvial moni-
generally increased as water moved down- toring wells located throughout the Town of Vail.
stream through the Town of Vail, but concen- Nutrient concentrations generally were low in the
trations at the mouth of Gore Creek were alluvial monitoring wells. Specific-conductance
typical when compared with national data for values ranged from 265 to 557 microsiemens per
urban undeveloped sites. Nitrate concentrations centimeter at 25 degrees Celsius. Concentrations
of radon in monitoring-well samples exceeded
in Gore Creek were highest just downstream
the 300-picocuries-per-liter U.S. Environmental
from awastewater-treatment plant discharge, Agency proposed maximum contami-
but concentrations decreased at sites farther protection pant level (which has been suspended pending
downstream because of dilution and nitrogen further review). Low levels of bacteria and
uptake by algae. Recent total phosphorus concen- methylene blue active substances indicate
trations were somewhat elevated when compared there is little or no wastewater contamination
to the U.S. Environmental Protection Agency of shallow ground water in the vicinity of the
recommended level of 0.10 milligram per liter monitoring wells and one of the municipal water-
for control of eutrophication in flowing water. supply wells. Ground-water ages in the alluvial
However, total phosphorus concentrations at the aquifer ranged from about 2 to about 50 years
mouth of Gore Creek were relatively low when old. These ages indicate that changes in land-
compared to a national study of phosphorus in management practices may not have an effect
urban land-use areas. on ground-water quality for many years.
Abstract 1
Differences in macroinvertebrate- of Gore Creek and limited by macroinvertebrate
community structure were found among sites grazing and water-quality conditions in the down-
in Gore Creek by evaluating changes in relative stream reaches. The fish community has benefited
abundance, total abundance, and dominant func- from enhanced biological production in the
tional feeding groups of the major macroinverte- downstream reach of Gore Creek. Increases in
brate groups. Ephemeroptera (mayflies), algal biomass and macroinvertebrate abundance,
Plecoptera (stoneflies), Trichoptera (caddisflies), in response to higher nutrient concentrations,
and Coleoptera (beetles) exhibited relatively low provide ample food resources necessary to
tolerance to water-quality degradation when support the abundant fish community.
compared with Diptera (midges) and non-insects Trace-element data for surface water,
(sludge worms). More than 80 percent of the ground, water, streambed sediment, fish tissue,
macroinvertebrate community at sites located and macroinvertebrate tissue indicate that
farthest upstream was composed of mayflies, concentrations are generally low in the Gore
stoneflies, and caddisflies, indicating favorable Creek watershed. In streambed-sediment samples,
water-quality and habitat conditions. The relative cadmium, copper, and zinc concentrations were
percentages of midges and sludge worms greatly below background levels reported for the Upper
increased in the downstream reaches of Gore Colorado River Basin in Colorado. Concentra-
Creek, which drain relatively larger areas of tions of cadmium, copper, iron, and silver in
urban and recreation land uses, indicating the surface water have occasionally exceeded stream
occurrence of nutrient and organic enrichment standards in the past, but recent surface-water data
in Gore Creek. indicate these trace elements currently are not of
The macroinvertebrate community in Black concern. Manganese concentrations commonly
Gore Creek indicated adverse effects from sedi- exceeded the 50-microgram-per-liter stream stan-
ment deposition. Macroinvertebrate abundance dard in Black Gore Creek. Elevated manganese
was considerably reduced at the two sites where concentrations were primarily attributable to the
streambed sediment was more prevalent; however, sedimentary geology of the area.
differences in abundance also may have been Concentrations of organic constituents are
related to differences in habitat and availability low in the Gore Creek watershed. Pesticides were
of food resources. detected infrequently and at low concentrations
The lower 4 miles of Gore Creek, down- in surface-water, ground-water, bed-sediment, and
stream from Red Sandstone Creek, have been whole-body fish-tissue samples. Volatile organic
designated a Gold Medal fishery in recognition of compounds also were detected at low concentra-
the high recreational value of the abundant brown tions in surface- and ground-water samples.
trout community. Gore Creek contained twice as
many trout as a reference site with similar habitat
characteristics in Rocky Mountain National Park. INTRODUCTION
Moderate increases in nutrient concentra-
tions above background conditions have increased Gore Creek, which drains an area of about
the growth and abundance potential for aquatic 102 mil, flows about 19 miles, from an area along
life in Gore Creek, while at the same time, the Gore Range through the Town of Vail, joining
esthetic and water-quality conditions have the Eagle River near Vail in Eagle County, Colorado
remained favorable. The spatial distribution of (fig. 1). Development in the Gore Creek watershed
has the potential to detrimentally affect the water
nitrate concentrations was consistent with the quality in Gore Creek and its tributaries. To manage
observed spatial distribution of algal biomass water resources, local entities are interested in better
and macroinvertebrate-community characteristics. understanding water quality and its relation to land
Algal biomass was limited by available resources uses and natural factors in the Gore Creek watershed.
(sunlight and nutrients) in the upstream reaches In response to these concerns, the Town of Vail,
2 Gore Creek Watershed, Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
I COLORADO
i
Lost 10622'30"
Lake
3940' 10615'
.,1 _ o c r
Greek 1.
Eu,glrMiii Cree(- ~RFEk
Ri,
Minturn
r xr..ANATION 70
' linen n(b'uiI ~erpurute Iimi1 - ' 'r
106 15' .
l
39 32'30'. Lulus
0 1 2 3 4 5 MILES
0 1 2 3 4 5 KlLvivir i rrno Vail
Pass
Figure 1. Location of the Gore Creek watershed.
INTRODUCTION 3
the Eagle River Water and Sanitation District, Vail Ground-water-quality data were available
Associates, and the Upper Eagle Regional Water from six sites in the alluvial aquifer. These ground-
Authority created the Gore Creek Watershed water data were limited to periodic trace-element
Management Program in 1996. The goal of this samples collected from the Town of Vail water-supply
program is to provide information for the manage- well field during 1988-89, a sample collected from
ment and protection of water quality and aquatic a single well from the well field in 1997, and two
life in the watershed. samples collected from each of five alluvial moni-
The U.S. Geological Survey (USGS), in cooper- toring wells within the Town of Vail during 1997.
ation with the Town of Vail, the Eagle River Water The 1997 well-field and monitoring-well data, though
and Sanitation District, and the Upper Eagle Regional limited, provided valuable new information about the
Water Authority, compiled and analyzed the available age of ground water and a variety of inorganic and
information on the historical and current (1998) water organic constituents such as nutrients, trace elements,
quantity, water quality, and aquatic ecology in the pesticides, VOCs, bacteria, and radon.
Gore Creek watershed. These data were analyzed to
assess the effects of human and natural factors on the
surface- and ground-water resources in the watershed. Acknowledgments
The authors thank the many individuals and
Purpose and Scope agencies that provided data for the Gore Creek water-
shed. Special thanks to Russell Forrest, Town of Vail;
This report presents the available historical Caroline Byus, Eagle River Water and Sanitation
and current (1998) water-quantity, water-quality, and District; Joe Macy, Vail Associates; Bill Andree,
aquatic-ecology information for the Gore Creek water- Colorado Division of Wildlife; Robert Ray, Northwest
shed. Surface-water data are available for locations Colorado Council of Governments; and Dennis
throughout the watershed but are limited for long-term Anderson, Colorado Department of Public Health
analysis. Ground-water data are available only for the
alluvial aquifer that underlies the Town of Vail. Based and Environment. The authors thank Ken Neubecker
on available data in the Gore Creek watershed, specific for providing most of the photographs for this report.
objectives of this report are to: (1) characterize We also thank Cory Stephens, USGS, and David K.
existing water-resources data; (2) analyze historical Mueller, USGS, for their assistance in generating
data and assess the broad-scale spatial and seasonal some of the figures for this report, Janet S. Heiny,
variability in water quantity, water quality, and stream USGS, for reviewing the manuscript, and Stephen D.
biota; and (3) summarize the environmental setting Porter, USGS, for his assistance with the interpretation
and identify, describe, and explain, where possible, the of the ecological data and for reviewing the manu-
major natural and human factors that affect observed script. The authors also thank Mary Kidd for editorial
water-quantity, water-quality, and aquatic-ecology review of this report, Joy Monson for manuscript prep-
conditions in the Gore Creek watershed. aration, and Sharon P. Clendening for producing the
Available physical, chemical, and biological illustrations.
data useful for characterizing factors affecting water-
quantity, water-quality, and aquatic-ecology condi-
tions were compiled for 66 surface-water sites within DESCRIPTION OF STUDY AREA
the Gore Creek watershed. These data were collected
from 1968 to 1997. Some of the categories of data The Gore Creek watershed, located
include major ions, nutrients, trace elements, pesti- in the Southern Rocky Mountains physiographic
cides, volatile organic compounds (VOCs), and province (Apodaca and others, 1996), lies in a
algae, macroinvertebrate, and fish communities. In narrow valley surrounded by high mountains
addition, results from regional and national studies and drains an area of about 102 mil. Gore Creek
were compiled for comparison of surface-water originates in pristine alpine headwaters of the Gore
nutrient concentrations in the Gore Creek watershed Range and flows through the Town of Vail before
with other urban areas. joining the Eagle River. Land-surface elevation
4 Gore Creek Watershed, Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
i
in the watershed ranges from about 7.700 ft in per year (in/yr) in the lower valleys to between 40
the valley to about 13,200 ft in the Gore Range. and 50 in/yr in the higher peaks (Colorado Climate
Monthly average temperatures in Vail range from Center, 1984) (fig. 2). The average precipitation is
a low of -8°C in January to a high of 15°C in July 34 in/yr, of which two-thirds falls as snow. In the
(National Oceanic and Atmospheric Administration. Town of Vail, at an elevation of 8,225 ft, annual snow-
http://Ulysses.atmos.colostate.edLl/]nly_form.html, fall ranges from 79 inches to 313 inches (National
accessed September 24, 1998). Precipitation in the Oceanic and Atmospheric Administration, accessed
watershed ranges from between 20 and 30 inches September 24. 1998).
106 22 3C"
J
39 40' 106 15'
ti 2c
z 4 k NNOA
iY1i1/ Crcc'k ~
r.Ar>L.ANA110N
IfR tillANNU.AL PRECIPITATION, IN INCIIk,,
10 to 20
Greater than 20 to 10
Greater than 30 lip -In
T
Greater than 40 to 10
SST 1
0 1 2 3 4 5 MILES 106 :
0 1 2 3 4 5 KILOMETERS
39 32'30"
Figure 2. Average annual precipitation (1951-80) in the Gore Creek watershed.
DESCRIPTION OF STUDY AREA 5
1
The geology of the Gore Creek watershed yield small qu...of Watt, that are a.:.,yaate only for
varies older Pi,,..a,,,brian-age basement rocks domestic .,.jq lies. Where the Precaml„ia,t rocks are frac-
to Quaternary-age alluvial deposits (fig. 3). The tured, water may discharge from springs. Water from
Precambrian rocks, which are predominantly igneous these rocks is suitable for all uses (Voegeli, 1965).
with some meta,.,. vhics, form the mountains in the Sedimentary rocks of pre-Pennsyl,,a„iat, Pal,_.,._oic.
nor(,iz,i,t and ea,0_l11 p- I.,, of the watershed. The head- Pennsylvanian, and PGt,l>;at, age crop out in the southern
waitz,t~, area of Gore Creek consists of predomlt,a„tly and western parts of the watershed. Rocks in the Black
i11neous rocks. Fractured Preca,i UtL- I rocks generally Gore Creek watershed are Y-6orninantly sedi.„L„«,ry.
106 22'30"
I
W
39 4 106 15'
i
Prn fPm
Od Oil
Pm Ql PM Qd
- ~9
}
r,Ari.ANATION
I NC v.~S01_ID.AJED SL:rcnuAL DE PISILS:NN1) QI
ROCKS OF QUATERNARY AGE /J
GRAVEL AND ALLUVIUM (PINI'_D.ALEAND
BULL LAKE ACE)-[ nekude, Broadway and I ouviers Alluviums PM
w1 GLACIAL DRIFT OF PINEDALE AND 13ULL LAKE GL,ACIA"TION ,
~+1 InCludes.uinc uncla silted glacial deposits
Q(~ OLDER GLACIAL DRIFT )PRE-BULL LAKE AGE)
LANDSLIDE Dcrv,u S Lucall) inctuCles talus, rock. glacier, and 4W
thick COI uvial deposits
~I ANCIENT ALLUVIUM In isolated patches that may not all he of Q1
the same age
SEDIMENTARY ROCKS OF PERMIAN AND r uNiv.,YLVANIAN ACiI! 1~o io
7PM MAROON FORMATION Arkosic sandstone, siltsmnc. conglomerate.
and local z M '`C
111
SEDIMENTARY ROCKS OF PENNSYLVANIAN AGE
MINTURN FORMATION IN WEST-CENTRALAND SOUTH-CENTRAL 39°32'30 Od
COLORADO AND C„ - UNITS OF MIDDLE r-,.Ns ,.VANIAN
AGEArkosic sandstone, conglomerate, shake, and limc,tnnc
® SEDIMENTARY N,, OF PRE-PENNSYLVANIAN AGE
METAMORPHIC (,CKS OF PRECAMBRIAN AGE
0 1 2 3 4 5 MILES
l lv,,„- GNEISS. SL t, t..AAI1 MIG\1 Al [tE- t <<n~ miner
hnrnhlendc _nci,es. ctlt silicaiL. yu,~ anal is I. I)rr. J
principally trom seam r, 0 1 3 ) 5 KILONic i ~rsS
IGNEOUS ROCKS
GRANITIC ROCKS OF 1.701)-NI 1_ Vll t_ik()I I', I.n~u I., to A111 I J()\ V I AKS
Includes Bakei:, Bridec. Brotsn, l',,- 4'. 'ni.
Ruub_Icr ('reek. Drum (ICC . l< _ ` anCl I'll]' Nlyd,l-. (~ran,nliriir..
( I-' Crock ()u.lrv A4 .,...„_.:,mn'HIC11 crunitil W:k~
Figure 3. Geology of the Gore Creek watershed.
6 Gore Creek Wa ~I ed, Colorado-Asse-...:..t of His l and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
I
The Gore Creek watershed has undergone is about 85 percent developed: therefore, population
rapid land-use changes since the 1960's as the Vail growth is limited by availability of land for develop-
area shifted from traditional mountain ranchlands ment (Russell Forrest, Director of Community
to a four-season resort community. Land use/land Development, Town of Vail, oral cornmun., 1998).
cover in the Gore Creek watershed is 63 percent However, these population numbers only represent
forested land, 14 percent shrub-brushland or (nixed the permanent population, and unincorporated
rangeland, 14 percent tundra and exposed rock areas, towns are not included in the census. Also, many
8 percent urban, and I percent other land-use/land- tourists add significantly to the population of the
cover classifications (fig. 4). Forested lands, which watershed primarily daring the winter and summer
include deciduous, evergreen, and mixed forests, months. Therefore, the population census does not
dominate the area below timberline (about 12,000 ft) reflect the full demand on the water rCSUUrCCS in the
and above the valley floor. The north-facing slopes
area.
contain a greater percentage of aspen and evergreen
forests than the south-facing slopes, which contain
sparser vegetation dominated more by shrubs and
grasses. The U.S. Forest Service manages approxi-
mately 96 mi` of Federal land in the Gore Creek
watershed, including about 6 mi- of the Vail Mountain'
ski area. The urban classification includes residential, -014
transportation, commercial, and other urban catego-
vies. Residential, recreational, commercial, and trans-~
ortation development occurs near Gore Geek and
P
its tributaries to support the increasing permanent
and tourist population of the area. The Town of .
Vail (which is about 6 mi- along a narrow corridor
adjacent to Gore Creek), the Vail Mountain ski area,
and Interstate 70 comprise the major land develop-
ments in the watershed. Interstate 70 extends 18 miles
from Vail Pass along Black Gore and Gore Creeks Town of Vail. Photograph by Ken Neubecker,
through the Town of Vail. About one-half of the urban
classification is the Vail Mountain ski area. Nearly
all development is confined by terrain to the narrow DATA SOURCES AND COMPILATION
Gore Creek valley floor, which is about 3,000 ft
wide. All land-use/land-cover classifications were Data describing eater, sediment, and tissue
determined during the late 1970's (Fegeas and chemistry. water quantity: and macro ilive rtebrate, algal.
others. 1983) and redefined with 1990 population and fish communities were obtained from many local.
data (Hitt, 1995). State, and Federal agencies and individuals. Electroni-
The Population of Eagle County has increased cally available data were merged into a relational data-
about 192 percent between 1970 (7,498 people) base to facilitate analysis of the historical and current
and 1990 (21,928 people) (U.S. Bureau of the Census, (1998) water-quantity, water-quality, and ecological
1970, 1990). An increase of about 158 percent from conditions for the Gore Creek watershed. The type
the 1990 population is projected for Eagle County of data and its sources are summarized in table 1.
by the year 2020 (56.668 people). The population Data for many of the sampling sites listed in table 1
of the Town of Vail, about 17 percent of the Eagle were collected by more than one agency, and each
County population, has increased about 20 percent agency had its own site-numbering and naming con-
from 1990 (3,716 people) to 1997 (4,454 people) ventions. If a sampling site had several identification
(Russell Forrest, Director of Community Develop- numbers, the USGS site name and site identification
ment. Town of Vail, oral commun., 1998). Vail number, if available. were used and are listed in table 1.
DATA SOURCES AND COMPILATION 7
106 22'30"
W
39 40' 106 15'
~ vJJ 9e
JJ RE
Golf course
MJ! Crc•c•6 r~ ~ / .
Ski area 1
f N,
(J
N
Based on GIRAS (Geographic Information Retrieval and Analysis System)
land use data from the 1970's (Fegeas and others, 1983) and refined with
1990 population data (Hitt, 1995)
EXPLANATION
)
URBAN
RESIDENTIAL r
TRANSPORTATION. COMMUNICATION. AND SERVICES
COMMERCIAL AND SERVICES D6 '15
OTHER URBAN (SKI ARF,V GOI-F ('OLRSI>i
RANGELAND
SHRUB-BRUSHI.AND OR MIXED R:ANGLLAND 39'32'30' F"
Luker
FOREST
DECIDUOUS FOREST LAND
. EVERGREEN FOREST LAND
0 1 2 3 4 5 MILES
F7 MIXED FOREST LAND
OTHER 0 1 2 3 4 5 KILOMETERS
E MIXEDTUNDRA
BARE GROUND OR EXPOSED ROCK
® LAKES
TOWN OF VAIL CORPORrA111 LINII I
Figure 4. Land use for the Gore Creek watershed.
8 Gore Creek Watershed, Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
Table 1. Surface-water, ground-water, and aquatic-ecology sampling sites, and data sources and types in the Gore Creek watershed
[Data source: ASI, Advanced Sciences Incorporated, for Eagle River Water and Sanitation District; CDPHE, Colorado Department of Public Health and Environment, Water Quality Control Division;
ERWSD, Eagle River Water and Sanitation District; USFS, U.S. Forest Service; USGS, U.S. Geological Survey National Water Information System; Type of data: A, algal community and biomass;
B, bacteria; C, chlorofluorocarbons; F, fish community; FP, field properties; MB, methylene blue active substances; MC, macroinvertebrate community; MI, major ions; N, nutrients; OR, organics in water;
P, pesticides in water; P2, pesticides in sediment; P3, pesticides in fish tissue; Q, continuous streamflow; R, radon; S, suspended sediment; TE, trace element in water; TE2, trace element in sediment; TE3,
trace element in fish tissue; TE4, trace element in macroinvertebrate tissue; V, volatile organic compounds; Site type: GW, ground water; SW, surface water; Latitude and Longitude: degrees, minutes,
and seconds]
Site Period of Period of
number Site Identification Data Type discharge water-quality Site Latitude Longitude
(figs. 5-9) name number source of data record record type
1 Gore Creek at Upper Station, 09065500 ASI, USGS A, B, FP, MC, MI, 1947-56, 1976-96 SW 39° 37'33" 106° 16'39"
near Minturn N, Q, TE, TE2 1963-98
2 Gore Creek below Black Gore 393737106165900 USGS FP, MI, N, TE 1996 SW 39° 37'37" 106° 16'59"
Creek, near Vail
3 Gore Creek above Bighorn Creek, 393807106174600 USGS FP, MI, N, TE 1996 SW 39° 38'07" 106° 17'46"
near Vail
4 Gore Creek at Bighorn Subdivision, 393831 106181900 ASI, CDPHE, B, FP, MI, N, TE 1968-97 SW 39° 38'31 106° 18'19"
below Pitkin Creek USGS
5 Gore Creek above Katsos 393836106182500 USGS A, FP, MC 1997 SW 39° 38'36" 106° 18'25"
6 Gore Creek below Katsos 393848106185900 USGS A, FP, MC 1997 SW 39° 38'48" 106° 18'59"
7 Gore Creek above Wellfield 393844106192100 ASI, USGS FP, MI, N, TE 1988-96 SW 39° 38'44" 106° 19'21"
near Vail
8 Gore Creek at Booth Creek Road 393851106193100 USGS A, FP, MC 1997 SW 39° 38'51 106° 19'31"
9 Gore Creek at Golf Course at Vail 393844106195300 USGS FP, MI, N, TE 1995 SW 39° 38'44" 106° 19'53"
10 Gore Creek at Vail 09066250 ASI, USGS FP, MI, N, Q, S, 1974-79 1973-96 SW 39° 38'35" 106° 20'44"
o TE
D 11 Gore Creek at Vail WWTP Intake 393826106212900 USGS B, FP, MI, TE 1976-77 SW 39° 38'26" 106° 21'29"
O 12 Gore Creek downstream of Pulis 393825106213400 USGS A, FP, MC 1997 SW 39° 38'25" 106°21'34"
C Bridge
M
m 13 Gore Creek below Golf Course 393825106220000 USGS FP, MI, N, TE 1996 SW 39° 38'25" 106° 22'00"
fA at Vail
z 14 Gore Creek near Middle Creek 393826106223800 USGS A, FP, MC 1997 SW 39° 38'26" 106° 22'38"
n 15 Gore Creek above STP near Vail 393901 106231400 USGS B, FP, MI, N, TE 1976-77 SW 39° 39'01 106°23'14"
9 16 Gore Creek at Lower Station 09066310 ASI, ERWSD, A, B, FP, MC, MI, 1988-98 1997 SW 39° 38'28" 106°23'37"
:2 at Vail USGS N, Q, TE
r
D 17 Gore Creek 50 ft below WWTP GC50FBLWSTP ERWSD B, FP, MI, N, TE 1990-96 SW 38°38'29" 106° 23'38"
O
z
co
J
G) Table 1. Surface-water, ground-water, and aquatic-ecology sampling sites, and data sources and types in the Gore Creek watershed-Continued
a
M
.n 0 [Data source: ASI, Advanced Sciences Incorporated, for Eagle River Water and Sanitation District; CDPHE, Colorado Department of Public Health and Environment, Water Quality Control Division;
r- 1
fl; m ERWSD, Eagle River Water and Sanitation District; USFS, U.S. Forest Service; USGS, U.S. Geological Survey National Water Information System; Type of data: A, algal community and biomass;
17
B, bacteria; C, chlorofluorocarbons; F, fish communitY FP, field properties; MB, methylene blue active substances; MC, macroinvertebrate communitY MI, major ions; N, nutrients; OR, organics in water;
r*
P, pesticides in water; P2, pesticides in sediment; P3, pesticides in fish tissue; Q, continuous streamflow; R, radon; S, suspended sediment; TE, trace element in water; TE2, trace element in sediment; TE3,
p m N trace element in fish tissue; TE4, trace element in macroinvertebrate tissue; V, volatile organic compounds; Site type: GW, ground water; SW, surface water; Latitude and Longitude: degrees, minutes,
f0
.C :r and SeCOndS]
fD
1 Q
00 c Site Period of Period of
i Site Identification Data Type Site
ado number name number source of data discharge water quality type Latitude Longitude
n (figs. 5-9) record record
QI 18 Gore Creek below WWTP 393826106235300 USGS A, FP, MC 1997 SW 39° 38'26" 106°23'53"
n
w 19 Gore Creek below Red Sandstone 393823106240000 ASI, USGS FP, MI, N, TE 1988-96 SW 39° 38'23" 106° 24'00"
M
y Creek at Vail
N
3 20 Gore Creek 0.5 mile downstream GC1/2MDNSTP ERWSD FP 1994-95 SW 39° 38'17" 106°24'05"
of WWTP
21 Gore Creek 1 mile downstream GCI MDNSTP ERWSD FP 1994-96 SW 39° 38'01 106° 24'33"
of WWTP
N
° 22 Gore Creek below Buffehr Creek 393756106244300 USGS FP, MI, N, TE 1996 SW 39° 37'56" 106° 24'43"
w near West Vail
23 Gore Creek 1.5 miles downstream GCI5MDNSTP ERWSD FP 1994-96 SW 39°37'46" 106°24'53
CL of W WTP
24 Gore Creek at West Vail Exit 393738106251000 USGS FP, MI, N, TE 1996 SW 39° 37'38" 106° 25'10"
m
25 Gore Creek 2 miles downstream GC2MDNSTP ERWSD FP, 1994-96 SW 39° 37'32" 106'25'19"
of WWTP
m
26 Gore Creek at Stephens Park 393715106253600 USGS A, FP, MC 1997 SW 39° 37'15" 106° 25'36"
D 27 Gore Creek at West Vail 393713106253900 USGS FP, MI, N, TE 1995-96 SW 39'37'13" 106° 25'39"
c
m
28 Gore Creek near Dowds Junction 393649106263201 USGS FP, MI, TE 1983-84 SW 39° 36'49" 106° 26'32"
29 Gore Creek at Mouth, near Minturn 09066510 ASI, CDPHE, A, F, FP, MC, MI, 1944-56,1 1968-98 SW 39° 3634" 106° 26'50"
USGS N, OR, P, P2, 1995-98
P3, Q, TE, TE2,
D TE3, TE4,V
m
30 Black Gore Creek above Black Lake 393212106125800 ASI, USGS FP, MI, N, TE 1988-96 SW 39'32'12" 106° 12'58"
31 Black Lake 393253106132000 USEPA FP, MI, TE 1985 SW 39° 32'53" 106° 13'20"
32 Black Gore Creek below Black 393307106133200 ASI, USGS FP, MI, N, TE 1988-96 SW 39°33'07" 106° 13'32"
Lake #2
33 Black Gore Creek below Black 393303106133100 USGS FP, MC 1997 SW 39° 33'03" 106° 13'31
Lake #2
34 Black Gore Creek above Polk Creek 393535106144300 USGS FP, MC 1997 SW 39° 35'35" 106° 14'43"
Table 1. Surface-water, ground-water, and aquatic-ecology sampling sites, and data sources and types in the Gore Creek watershed-Continued
[Data source: ASI, Advanced Sciences Incorporated, for Eagle River Water and Sanitation District; CDPHE, Colorado Department of Public Health and Environment, Water Quality Control Division;
ERWSD, Eagle River Water and Sanitation District; USFS, U.S. Forest Service; USGS, U.S. Geological Survey National Water Information System; Type of data: A, algal community and biomass;
B, bacteria; C, chlorofluorocarbons; F, fish community; FP, field properties; MB, methylene blue active substances; MC, macroinvertebrate community; M1, major ions; N, nutrients; OR, organics in water;
P, pesticides in water; P2, pesticides in sediment; P3, pesticides in fish tissue; Q, continuous streamflow; R, radon; S, suspended sediment; TE, trace element in water; TE2, trace element in sediment; TE3,
trace element in fish tissue; TE4, trace element in macroinvertebrate tissue; V, volatile organic compounds; Site type: GW, ground water; SW, surface water; Latitude and Longitude: degrees, minutes,
and seconds]
Site Period of Period of
number Site Identification Data Type discharge water-quality Site Latitude Longitude
-9 name number source of data type
(figs. 5) record record
35 Polk Creek at Interstate 70 393527106143500 USGS FP, MI, N, TE, 1996 SW 39° 35'27" 106° 1435"
TE2
36 Polk Creek at 1-70 393530106143800 USGS FP, MC 1997 SW 39° 3530" 106° 14'38"
37 Black Gore Creek near Minturn 09066000 USGS FP, MC, MI, N, Q, 1947-56, 1996 SW 39° 35'47" 106° 15'52"
TE 1963-98
38 Black Gore Creek near Vail 09066050 ASI, USGS A, FP, MC, MI, N, 1974-79 1973-96 SW 39° 37'24" 106° 16'47"
Q, S, TE
39 Ditch near Juniper Lane 393737106170500 USGS FP, MC 1997 SW 39° 37'37" 106° 17'05"
40 Bighorn Creek near Minturn 09066100 USGS FP, MI, N, Q, TE 1963-98 1996 SW 39° 38'24" 106° 17'34"
41 Bighorn Creek near Vail 393813106174500 USGS A, FP, MC 1997 SW 39° 3813" 106° 17'45"
42 Bighorn Creek near Vail 393813106174501 USGS A, FP, MC 1997 SW 39°38'13" 106° 17'45"
43 Columbine Pond Outflow near 393816106180100 USGS FP, MC 1997 SW 39° 38'l 6" 106° 18'01"
East Vail
44 Pitkin Creek near Minturn 09066150 USGS FP, MC, MI, N, Q, 1966-98 1996 SW 39° 38'37" 106° 18'07"
TE
45 Booth Creek near Minturn 09066200 USGS A, FP, MC, MI, N, 1964-98 1992-96 SW 39° 38'54" 106° 19'21
Q, TE
D 46 Booth Creek Near Vail 393849106192000 USGS A, FP, MC 1997 SW 39° 38'49" 106° 19'20"
y 47 Booth Creek near Vail 393849106192001 USGS A, FP, MC 1997 SW 39° 38'49" 106° 19'18"
O 48 Mill Creek on Vail Mountain 393726106212000 USGS A, FP, MC 1997 SW 39°37'26" 106°21'20"
0
M 49 Mill Creek near Mouth at Vail 393814106221500 ASI, USGS FP, MI, N, TE 1988-96 SW 39° 38'14" 106° 22'15
m 50 Mill Creek near Vail 393824106221700 USGS A, FP, MC 1997 SW 39° 38'24" 106° 22'17"
Z 51 Mill Creek near Vail 393824106221701 USGS A, FP, MC 1997 SW 39° 38'24" 106°22'17"
0 52 Mill Creek near Mouth at Vail 393827106222100 USGS B, FP, N, TE 1976-77 SW 39° 38'27" 106° 22'21
0
O 53 Ditch at end of Rockledge Road 393829106225400 USGS FP, MC 1997 SW 39° 38'29" 106° 22'54"
M
:2 54 Ditch at 123 Beaver Dam Road 393828106224800 USGS FP, MC 1997 SW 39°38'28" 106° 22'48"
r
n 55 Middle Creek near Minturn 09066300 USGS FP, MI, N, Q, TE 1964-98 1996 SW 39° 38'45" 106° 22'54"
O
Z
J
N
C)
~ O
O. t
M n Table 1. Surface-water, ground-water, and aquatic-ecology sampling sites, and data sources and types in the Gore Creek watershed-Continued
c m'
m
x [Data source: ASI, Advanced Sciences Incorporated, for Eagle River Water and Sanitation District; CDPHE, Colorado Department of Public Health and Environment, Water Quality Control Division;
o m ERWSD, Eagle River Water and Sanitation District; USFS, U.S. Forest Service; USGS, U.S. Geological Survey National Water Information System; Type of data: A, algal community and biomass;
CD
0 B, bacteria; C, chlorofluorocarbons; F, fish community; FP, field properties; MB, methylene blue active substances; MC, macroinvertebrate community; MI, major ions; N, nutrients; OR, organics in water;
U P, pesticides in water; P2, pesticides in sediment; P3, pesticides in fish tissue; Q, continuous streamflow; R, radon; S, suspended sediment; TE, trace element in water; TE2, trace element in sediment; TE3,
i ? trace element in fish tissue; TE4, trace element in macroinvertebrate tissue; V, volatile organic compounds; Site type: GW, ground water; SW, surface water; Latitude and Longitude: degrees, minutes,
co o and seconds]
'p O
CL Site Period of Period of
O Site Identification Data Type Site
number name number source of data discharge water-quality type Latitude Longitude
w (figs. 5-9) record record
(DD 56 Middle Creek near Vail 393836106230101 USGS A, FP, MC 1997 SW 39° 3836" 106° 23'01"
N
B 57 Middle Creek near Vail 393836106230100 USGS A, FP, MC 1997 SW 39° 38'36" 106° 23'01"
3
rM. 58 Culvert near Lionshead 393836106230400 USGS FP, MC 1997 SW 39° 38'36" 106°23'04"
° 59 Red Sandstone Creek, near Minturn 09066400 USGS, USFS B, FP, MI, N, Q 1963-98 1978-90 SW 39°40'58" 106°24'03"
x
w 60 Lower Red Sandstone Creek above 393755106234500 USFS B, FP, N, 1978-82 SW 39° 37'55" 106° 23'45"
first switchback
m 61 Red Sandstone Creek near Vail 393852106234300 USGS A, FP, MC 1997 SW 39° 38'52" 106° 2343"
3
62 Red Sandstone Creek near Vail 393841106234200 USGS A, FP, MC 1997 SW 39°38'41" 106°23'42"
O.
n 63 Red Sandstone Creek near Vail 393841 106234201 USGS A, FP, MC 1997 SW 39° 38'41" 106° 23'42"
m 64 Red Sandstone Creek at Mouth 393829106234400 USGS FP, MI, N, TE 1996 SW 39° 38'29" 106° 23'44"
at Vail
d 65 Buffehr Creek near Vail 393801106244800 USGS A, FP, MC 1997 SW 39°38'01" 106°24'48"
D 66 Buffehr Creek near Vail 393801 106244801 USGS A, FP, MC 1997 SW 39° 38'01" 106°24'48"
67 Bighorn Park 393743106171000 USGS B, C, FP, MB, MI, 1997 GW 39° 37'43" 106° 17'10"
N, P, R, TE, V
68 S000508003DDB00-VAIL, Well 393844106193300 AS1, USGS B, C, FP, MB, MI, 1988-89, GW 39° 38'45" 106° 19'54"
m Field Composite, wells R-I, R-6, N, P, R, TE, V 1997
CD and R-7
D 69 Vail Golf Course 393830106210600 USGS B, C, FP, MB, MI, 1997 GW 39° 3830" 106°21'06"
m N, P, R, TE, V
70 Gerald R. Ford Park 393823106215900 USGS B, C, FP, MB, MI, 1997 GW 39° 38'23" 106°21'59"
N, P, R, TE, V
71 Pedestrian Bridge 393844106232300 USGS B, C, FP, MB, MI, 1997 GW 39°38'44" 106°23'23"
N, P, R, TE, V
72 Stephens Park Well 393718106253000 USGS B, C, FP, MB, MI, 1997 GW 39° 3718" 106° 2530"
N, P, R, TE, V
'Discharge record from discontinued station 09066500, 0.4 mile upstream from current station.
Most of the data used in assessing the water-quantity, and the Upper Eagle Regional Water Authority. Addi-
water-quality, and aquatic-ecology conditions in the tional information from numerous published reports
Gore Creek watershed were obtained from three pertaining to various aspects of water-quantity, water-
sources: (1) the USGS. (2) the Colorado Department of quality, and aquatic-ecology conditions in the Gore
Public Health and Environment, Water Quality Control Creek watershed are discussed in this report to aid in
Division, and (3) the Eagle River Water and Sanitation the interpretation and understanding of historical and
District. A large part of the available data from the present conditions in the watershed.
USGS was collected since 1995, as part of the USGS Water-quantity, water-quality, or aquatic-ecology
Upper Colorado River Basin (UCOL) National Water- data were collected at surface-water sites. The sites are
Quality Assessment (NAWQA) Program, and through listed as site numbers 1-66 in table l and are shown in
a cooperative agreement between the USGS, the Town figures 5 and 6. Sites, such as site 29, where surface-
of Vail, the Eagle River Water and Sanitation District, water quality and aquatic-ecology samples were
106 22'30"ice \
59
39`40' y 106 15' 0
1 60614
c 'p
6
55 45
191\ 1715 ,'S2 3 11 10 9 7 9~
22221 0 _ ~l 49 r f~ 4 44 ~c
Q0~ Crreek
25
I 27
28 2
38 1
~9~ Mill C'ree.<
\ >rJ ~ _I 1
37 /
Fk 35
F.XPI, ANATION
'T'own of Vail corporate limit )
J /
A 29 Surlace-water-quality rumpling site
32
106` 15'~ \ I
31
0 1 2 3 4 5 MILES
i I % 30 r~
I'
0 1 2 3 4 5 KILOMETERS 3932'30" ; -(J
Figure 5. Surface-water-quality sampling sites in the Gore Creek watershed.
DATA SOURCES AND COMPILATION 13
106`22'30"'
~ l
39 40'! 106 15'
61 `Q3 6258 N\~ % J 1
L l
7 65~ 45i 4
1 18 5 1 4 50/ 846
6566 r61 53 51. ` 12 a c 6 5 44
,ry_~ 441
J 246/j-
L 48~~
39 938
dl Creekk _
_yk
\i 37
EXPLANATION
- Trncn ul Veil cotpoi.i0.• limit ~ '
29
;aqu; li -hl- unpline >iic r
~ r
~ rT
33' I
106 15' l
0 1 2 3 4 5 MILES
0 1 2 3 4 5 KILOMETERS
39 32'30'
Figure 6. Aquatic-ecology sampling sites, 1995-97.
collected, are shown in both tigul-eS. Data available collected at 30 sites in the Gore Creek watershed, but
t()r surface-water-quality sites include continuous only 9 sites had more than 5 nutrient samples. Figure 8
stream flow; field properties (water temperature, specific shows the distribution and period of record for surface-
conductance, dissolved oxygen, pH, and alkalinity); water trace-element samples. Trace-element data were
major ions; nutrients; pesticides; dissolved and collected at 30 sites, and only 12 sites had more than
suspended organic carbon (DOC and SOC). suspended 5 trace-element samples.
sediment; VOCs; trace elements; and algae, macroin- Ground-water sampling sites are listed in table 1
vertebrate, and fish communities. Sampling media for (sites 67-72) and are shown in figure 9. Five ground-
the various chemical constituents are water, bed sedi- water-monitoring wells (sites 67 and 69-72) were
ment, fish tissues, and macroinvertebrate tissues. completed in the unconsolidated alluvium and were
Fi(,ure 7 shows the distribution and period of record sampled as part of an urban land-use study conducted
for surface-water nutrient samples. Nutrient data were by the USGS. Ground-water site 68 is a three-well
14 Gore Creek Watershed, Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
64 - SAMPLING PERIOD
• SAMPLING DATE
60
59
55
52
45
44
40
38
37
35
w ,
32
Z)
2 30
LL
29
w
J
Q 27
24
W
co 22
19
Z
w 17
H
N
16
15
13
11
10
9
7
4
3
2
Np~ro~ ~q1~ ^p~11 ~~~a A10 N0N~RP ~o,R`b ~~0b ~,:s~b6 ~~00 NC6p~0 -1q~I Ncbp~b ^~~0 Nce
YEAR
Figure 7. Distribution of sampling dates and period of record for nutrient samples at surface-water
sampling sites.
DATA SOURCES AND COMPILATION 15
64 - SAMPLING PERIOD
• SAMPLING DATE
55 ,
52
45
44
40
38
37
35
32
w 31
(_q 30 ,
29 - - - - - - - - -
LU
-J 28
co
H 27 _
cc
W 24 ,
00
22
Z
w 19
H
(n 17
16 _
15
13
11
10
9-
,
7
4 - - -
3
2
\Cb
YEAR
Figure B. Distribution of sampling dates and period of record for trace-element samples at surface-water
sampling sites.
16 Gore Creek Watershed, Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
C
f " G,
39 JC 106 '15' Op
\ y
71
GORE 69 Q ~a reek
G
A1ill reek 67 6-
CREEK
Ski area
EYPI,ANATION
URBAN
® RESIDENTIAL
TRANSPORTATION. COMMUNICATION, AND SI:RVI('ES
¦ COMMERCIAL AND SERVICES
OTHER URBAN (SKI ARIA. GOLF ('OURSF)
RANGELAND
SLIRUB-BRt'S111.,1NU OI: MI\IiD kANGIiLANp 106 15'
FOREST
DECIDUOUS FOREST LAND
EVERGREEN FOREST LAND 39 32'30"
~ r
MIXED FOREST LAND
OTHER
MIXEDTUNDR:A
BARE GROUND OR F.XPOSF.D RO('K 0 1 2 3 4 5 MILES
LAKES
TOWN OF VAIL. CORPORATE LIMIT 0 1 2 3 4 5 KILOMETERS
072
GROUND-W'ATF:R SAMPLING SITE AND IDENTIFIER
Figure 9. Ground-water sampling sites. 1988-97.
DATA SOURCES AND COMPILATION 17
municipal well field that is operated by the Eagle censored (reported below a laboratory reporting limit).
River Water and Sanitation District. Ground-water If more than one-half the data for a particular nutrient
data were available for field properties, major ions, constituent were censored at a site, estimates of the
nutrients, trace elements, pesticides, DOC, VOCs, 10th, 25th, 50th (median), 75th, and 90th percentiles
bacteria (total coliforms and Escherichia coli were calculated using the maximum likelihood
[E. coli]), methylene blue active substances (MBAS), estimation (MLE) method (Helsel, 1990; Helsel
and chlorofluorocarbons at the USGS sites. and Cohn, 1988). These estimated percentiles were
Aquatic-ecology data (stream and riparian used to construct the boxplots and provide median
habitat, and algae, macroinvertebrate, or fish commu- concentrations plotted on the maps. Statistical compar-
nity) were available for 36 sites in the Gore Creek ison of streamflow relations to nitrate and total phos-
watershed (fig. 6, table 1). Fish-community data at one phorus concentrations was performed using the
site were available for 1995-98. Algae, macroinverte- Mann-Whitney U test, which is a nonparametric
brate, and habitat data were available from a synoptic version of the two-group unpaired t-test (Helsel
study done in September 1997. Discussion of histor- and Hirsch, 1992). For this test, censored values were
ical and current aquatic ecology in this report focuses treated as equal to the reporting limit for that sample.
on sites in the main stem of Gore Creek as it flows Long-term temporal differences in the concentrations
from its headwaters through the Town of Vail and sites of ammonia, nitrate, orthophosphate, total phosphorus,
in Black Gore Creek as it flows from Vail Pass to its and specific-conductance values were compared statis-
confluence with Gore Creek along Interstate 70. Most tically for the 1968-97 period by using Tukey's
of the data from this synoptic study were collected by Significant Difference Test (Tukey test) on the rank-
the USGS for the Town of Vail, as part of a national transformed data (Helsel and Hirsch, 1992). Because
study by the U.S. Environmental Protection Agency of a high percentage of censored data values during
(USEPA) to assess the ecological benefits of storm- the spring and summer seasons, and because higher
water controls such as natural vegetation buffer strips nutrient concentrations occur typically during low
or swales (Watershed Management Institute, unpub. flow, only the winter season (November-April) was
data, 1996). Interpretation of the tributary-stream data tested statistically for trends for each constituent. For
is beyond the scope of this report. the Tukey test, censored values were treated as equal
to the reporting limit. Flow-adjusted concentrations
were not used to evaluate temporal changes in nutrient
METHODS OF DATA REVIEW AND concentrations because much of the available data
ANALYSIS lacked concurrent streamflow information and also
because a high percentage of the data was censored.
Water-quality properties and constituents are
presented graphically and statistically in this report. Boxplots were used to display the central
The surface- and ground-water-quality data were tendency and variability in specific-conductance
quality assured by examining the total cation and total values and nutrient concentrations. Boxplots (for
anion concentrations and the total nitrogen and total example, fig. 13) graphically show the central
phosphorus concentrations in all samples with avail- tendency of the data (the median, or 50th percentile
able data. For data used in this report, differences in line of the box, marked with a diamond for clarity), the
total cation and total anion concentrations were less variation of the data (interquartile range, or the box
than 10 percent. Fewer than 5 percent of the available height between the 25th and 75th percentiles), the 10th
nutrient samples were discarded for use in this report and 90th percentiles (shown by whiskers below and
because total nitrogen or total phosphorus concentra- above the box), and the skewness (quartile skew, or the
tions were less than the sum of the constituents that relative size of the box halves divided by the median
make up the total concentration. line) (Helsel and Hirsch, 1992). Data points plotted
Water-quality data were analyzed using below and above the boxplot whiskers represent data
nonparametric statistical methods. Nonparametric values that are less than the 10th and greater than the
statistical analyses of rank-transformed data are not 90th percentile, respectively.
unduly affected by outliers and are not dependent on a The water-quality data were compared with
normal distribution of the data. During assessment of drinking-water and stream-quality standards where
the spatial distribution of individual nutrient species, applicable. Drinking-water standards are set by the
greater than one-half of the data for some sites were USEPA and include the primary (MCL), secondary
18 Gore Creek Watershed, Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
(SMCL), and proposed (PMCL) maximum contaminant Triplicate samples were collected at selected
levels set for drinking water, and maximum contaminant sites for quality control of the algal-biomass and
level goals (MCLG), drinking-water advisory (DWA), algae- and macroinvertebrate-community sampling
and health advisory (HA) standards (U.S. Environmental in September 1997. Where triplicate samples were
Protection Agency, 1996). The USEPA standards are collected, the values discussed and shown on graphs
defined as the permissible level of a contaminant in represent the average value for that site. The standard
treated water delivered to users of a public water-supply error of the mean (standard deviation divided by the
system, and as such, do not relate specifically to the square root of the number of samples) was calculated
untreated water samples discussed in this report, except and included on graphs to show the variability of the
as a point of reference. The lowest applicable stream- sample results. For example, in figure 25B, the error
quality standards are discussed, where applicable, in this bars overlain on the graphs represent the standard error
report; values were calculated for Gore Creek by Wynn of the mean biovolume for nitrogen-autotroph diatom
and Spahr (1998) using the methods of the Colorado for the two sites where triplicate algae samples were
Department of Health (1996). These standards are gener- taken for quality-control purposes. Short error bars
ally the chronic or acute aquatic-life standards for the indicate less variability in sampling and processing
protection of aquatic life. methods. For example, the biovolume at site 26 is
Data collection in the Gore Creek watershed about 5.25x 107 µm3/cm2 plus or minus the standard
by the USGS since October 1995 has followed error of 0.75x 107 µm3/cm2. Because the standard
published protocols for the USGS NAWQA Program. error at site 26 overlaps the measured algal biovolume
The following information summarizes the sample- at site 18, one cannot say with confidence that algal
collection protocols followed by the USGS for water, biovolume at site 26 is significantly lower than algal
sediment, and stream-biota data collection. Surface- biovolume at site 18.
and ground-water samples were collected following Nutrient data for surface-water sites in the
the protocols described by Shelton (1994) and Koterba Gore Creek watershed were identified and compiled
and others (1995), respectively. As part of the UCOL from several sources (table 1). Because the data were
NAWQA assessment of surface- and ground-water collected by various groups for different purposes and
quality, quality-assurance samples constituted no less a variety of laboratory methods were used, nutrient
than 10 percent of the total number of environmental constituents were reported in numerous ways. The
samples. An interim report of surface-water quality- available nutrient data included 24 nitrogen and phos-
control sample results is presented by Spahr and phorus constituents that were collected at 30 sites
Boulger (1997). Fish-community data for the mouth between February 21, 1968, and December 16, 1997
of Gore Creek were collected by electroshocking (fig. 7).
in a 450-ft stream reach near the mouth of Gore Creek, For the evaluation of nutrient conditions in
using protocols described by Meador and others the Gore Creek watershed, nutrient constituents were
(1993). Fish- and macroinvertebrate-tissue samples aggregated to reduce the number of constituents from
were collected using the protocols described by 15 to 5. The procedures used to aggregate nutrient
Crawford and Luoma (1994). Algae samples were constituents follow the method of Mueller and others
collected from rock surfaces in riffle areas using (1995) and are summarized in table 2. The data aggre-
gation resulted in the creation of a nutrient-analysis
the protocols described by Porter and others (1993). data set that included the following constituents:
Streambed-sediment samples were collected using
the protocols described by Shelton and Cape] (1994). • ammonia nitrogen, as nitrogen (hereinafter referred
Macroinvertebrate-community samples were collected to as "ammonia");
from riffle areas by using a 1-m2 hand screen equi ped • nitrate nitrogen, as nitrogen (hereinafter referred to
with 425-µm2 mesh material. Generally, 1 to 2 in as "nitrate");
of substrate was sampled upstream from the hand . total nitrogen, as nitrogen (hereinafter referred to as
screen to collect a macroinvertebrate sample. "total nitrogen");
Macroinvertebrate-community abundance results
were normalized to the number of organisms per • orthophosphate, as phosphorus (hereinafter referred
square meter. Qualitative riparian and aquatic habitat to as "orthophosphate"); and
was scored using USEPA rapid bioassessment proto- • total phosphorus, as phosphorus (hereinafter
cols (RBP) described by Plafkin and others (1989). referred to as "total phosphorus").
METHODS OF DATA REVIEW AND ANALYSIS 19
Table 2. Summary of procedure used to aggregate nutrient data in the Gore Creek watershed into selected nutrient
constituents (from Mueller and others, 1995)
[mg/L, milligrams per liter; N, nitrogen; N03, nitrate; P, phosphorus; P04, orthophosphate; parameter determined by using the procedure listed for nitrite,
as N; parameter determined by using the procedure listed for nitrate, as N]
Constituent Nutrient data parameter name Nutrient data parameter code
Ammonia, as N Nitrogen, ammonia, dissolved (mg/L as N) 00608
Nitrogen, ammonia, total (mg/L as N) 00610
Nitrate, as N Nitrogen, nitrite plus nitrate, dissolved (mg/L as N) 00631
minus nitrite,2 as N
Nitrogen, nitrite plus nitrate, total (mg/L as N) 00630
minus nitrite,2 as N
Nitrogen, nitrate, dissolved (mg/L as N) 00618
Nitrogen, nitrate, total (mg/L as N) 00620
Nitrogen, nitrate, total (mg/L as N03) 71850 (multiplied by 0.2259)
Total nitrogen Nitrogen, total (mg/L as N) 00600
Nitrogen, total (mg/L as N03) 71887 (multiplied by 0.2259)
Nitrogen,3 ammonia plus organic, total (mg/L as N) 00625
plus nitrate,2 as N, plus nitrite,2 as N
Orthophosphate, as P Phosphorus, orthophosphate, dissolved (mg/L as P) 00671
Phosphate, ortho, dissolved (mg/L as P04) 00660 (multiplied by 0.3261)
Phosphorus, orthophosphate, total (mg/L as P) 70507
Phosphate, total (mg/L as P04) 00650 (multiplied by 0.3261)
Total phosphorus Phosphorus, total (mg/L as P) 00665
'From the USGS National Water Information System (NWIS) and the USEPA Data Storage and Retrieval system (STORET).
2Missing values or values less than detection are not included in this calculation.
3AIso called total Kjeldahl nitrogen. If value is missing or less than detection, total nitrogen is not computed.
SURFACE WATER over the drainage area (Colorado Climate Center,
1984). Because the Gore Creek watershed is a
Water-quantity, water-quality, streambed- headwater system, there are no surface-water
sediment chemistry, and tissue-chemistry data were inflows to the watershed except for an estimated
available for 37 sites in the Gore Creek watershed. maximum of 500 acre-ft/yr of water from the Eagle
These data and information were used to evaluate River for snowmaking (assuming snowmaking for
the historical and current water-quality conditions. all of November and December) (Jim Roberts, Vail
Predominant natural and human factors affecting Associates, oral commun., August 1998). This diver-
surface-water conditions were identified to the sion into Gore Creek is highly variable, depending
extent possible. upon the needs for snowmaking, air temperature,
and availability of other sources for snowmaking.
The remaining water inputs by interbasin-water trans-
Water Quantity fers and ground-water inflow are negligible. Water
outputs from the watershed are more diverse; the
The major tributaries of Gore Creek are Black predominant output is by surface-water outflow, which
Gore, Bighorn, Pitkin, Booth, Mill, Middle, and Red accounts for about 55 percent of the total water output.
Sandstone Creeks (fig. 1). The hydrologic characteris- Evapotranspiration, which is calculated as the residual
tics of the Gore Creek watershed can be represented in in the water balance, accounts for about 40 percent of
a generalized water budget (table 3). This generalized the total water output. Consumptive water use, esti-
budget provides an understanding of water storage mated to be 9,300 acre-ft/yr based on 1995 water-
and flux through the watershed. Average annual water use data, accounts for 5 percent of the total water
input for the watershed is 185,000 acre-ft, based on an output (R.G. Dash, U.S. Geological Survey, written
average annual precipitation of 34 inches distributed commun., 1998).
20 Gore Creek Watershed, Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
Streamflow has been measured at l 1 gaging for snowmaking during the winter months (Weaver
stations in the watershed, and in 1998, 9 of these and Jones, 1995). However, the annual Streamflow
stations were active (table 4). The first streamflow- pattern is similar to the other four stations and the vari-
gaging station in the area was established in 1944 ability in the streamflow is low (0.30). The Streamflow
on Gore Creek at the mouth; however, the longest pattern at Red Sandstone Creek near Minturn, a major
records of operation in the watershed are for two tributary to Gore Creek, is similar to the other gaging
upstream stations, Gore Creek at Upper Station near stations. The two downstream main-stem stations,
Minturn and Black Gore Creek near Minturn. About Gore Creek at Lower Station at Vail and Gore Creek at
80 percent of the annual streamflow is derived from Mouth near Minturn, have a streamflow pattern similar
snowmelt, which occurs in May, June, and July. to the other three gaging stations including low vari-
During most of the year, the daily flow is less than ability in streamflow; however, these two stations lack
one-third of the mean annual streamflow, which long-term streamflow data.
ranges from 5.95 to 140 ft3/s among selected stations Monthly streamflows for the five gaging
in the watershed (table 4). Mean annual runoff ranges
from 4,310 to 10 1,340 acre-ft/yr and reflects the stations (fig. ] 1) are similar and indicate streamflow
large amounts of precipitation in the watershed. Coef- in the Gore Creek watershed is dominated by snow-
large
of variation, which is a measure of the vari-
ability of streamflow from year to year, is low for tude of peak flows in this watershed can be quite
all 11 gaging stations, ranging from 0.26 to 0.37. large, exceptionally large snowmelt flows that cause
Water-quality conditions can be affected by variation severe flooding are uncommon. Because of the annual
in the timing and magnitude of streamflow from year nature of snowmelt flows, most stream channels are
to year. capable of carrying these flows without extensive
Annual streamflow patterns are similar at five overbank flooding (Apodaca and others, 1996).
selected stations (fig. 10). Streamflow at Gore Creek Reservoir storage and local diversions also diminish
at Upper Station near Minturn has no upstream diver- the magnitude of the annual snowmelt peak flows.
sions, and the variability in the streamflow is low The 10-year flood (table 4), which indicates that a
(coefficient of variation, 0.26). Streamflow in given peak flow has a 10-percent chance of occurring
Black Gore Creek near Minturn is affected by the in any given year, ranges from 106 to 1,715 ft3/S
operations of the Black Lakes, which are used to at the streamflow-gaging stations in the Gore Creek
mitigate the impacts of diversions of instream flows watershed.
Table 3. Generalized water budget for the Gore Creek watershed
[acre-ft/yr, acre-feet per year; less than]
Source Inputs Percentage Source Outputs percentage
(acre-ft/yr) (acre-ft/yr)
Precipitation 185,000 100 Evapotranspiration from nonirrigated 74,900 40
land (residual)
Surface-water inflow a500 <1 Surface-water outflow 6101,300 55
Interbasin transfers (negligible) 0 Consumptive water use c9,300 5
Ground-water inflow (negligible) 0 Interbasin water transfers 0
Reservoir evaporation Negligible
Ground-water outflow Negligible
Change in ground-water storage Negligible
Total (rounded) 185,500 100 185,500 100
aBased on estimated data 1996-98 (Jim Roberts, Vail Associates, oral commun., 1998).
bData from the U.S. Geological Survey National Water Information System.
Based on 1995 data (R.G. Dash, U.S. Geological Survey, written common., 1998).
SURFACE WATER 21
N
N
Ol ~
C O
CL
Dm
n
c ~
m ~
n F
m~
o
N Table 4. Hydrologic characteristics for surface-water sampling sites in the Gore Creek watershed
( S
N
i a
n [mil, square miles; ft3/s, cubic feet per second; acre-ft/yr, acre-feet per year]
00 0
0
CO W Period Mean Coefficient Mean 2-year, 10-year,
a Site no. Station Drainage 10-year
of record, annual of variation annual 7-day low- 7-day low-
(table 1, Site name identification area flood
in calendar 2 streamflow of annual runoff flow value flow value 3
y fig. 5) number years (mi) (ft3/s) streamflow (acre-ft/yr) (ft3/s) (ft3/s) (ft /s)
y 1 Gore Creek at Upper Station, 09065500 1947-56, 14.4 30.3 0.26 21,990 2.30 1.5 550
3 near Minturn, CO 1963-98
m
37 Black Gore Creek, near 09066000 1947-56, 12.6 17.4 .30 12,600 1.70 1.1 315
Minturn, CO 1963-98
y 38 Black Gore Creek, near Vail, CO 09066050 1974-79 19.6 27.3 .34 19,790 2.7 2.1 420
° 40 Bighorn Creek, near Minturn,CO 09066100 1963-98 4.54 10.1 .31 7,295 .63 .28 180
0
44 Pitkin Creek, near Minturn, CO 09066150 1966-98 5.32 11.8 .32 8,586 1.0 .4 194
d
' 45 Booth Creek, near Minturn,CO 09066200 1964-98 6.02 12.2 .28 8,864 .72 .35 249
CL
10 Gore Creek at Vail, CO 09066250 1974-79 57.3 90.4 .31 65,490 4.6 3.9 1,484
55 Middle Creek, near Minturn, CO 09066300 1964-98 5.94 5.95 .37 4,310 .19 No flow 106
3
16 Gore Creek at Lower Station, 09066310 1988-98 77.1 122 .32 88,690 8.70 6.0 1,664
at Vail, CO
m
p 59 Red Sandstone Creek, near 09066400 1963-98 7.32 9.23 .29 6,688 .75 .44 191
d Minturn, CO
29 Gore Creek at Mouth, near 09066510 11944-56, 102 140 .28 101,340 16.0 11.26 1,715
Minturn, CO 1995-98
1Streamflow data for the period 1944-56 are from discontinued station 09066500 located 0.4 mile upstream from station 09066510.
CD
D
c
n~
Gore Creek at Upper Station, near Minturn (site 1 in table 1)
60
50
40
30
20
10
0
(D O N a m m O N V m m O N V m N O N V (D W O N V to
V V LD m l17 O m m ID (D n n r r- r m m m m m m m m m
m m m m m m m m m m m m m m m m m m m m m m m m m m
Black Gore Creek, near Minturn, CO (site 37 in table 1)
35 .
30
25
Z 20
OU 15
U) 10
W
m 5 -ff . L
IL 0 SA 11
(D W O N a m m O N V (D W O N d ID m O N 'f co m C. N a m
d a m m ID M m m to (0 0 m r- r- n t` r m m m m m m m m m
W m m m m m m m m m m m m m m m m m m m m m m m m m m
W
LL
U
00 Gore Creek at Lower Station, at Vail, CO (site 16 in table 1)
Z) 200 .
U
z 150
Q 100
J
LL
50
Q
W
m 0
m m O N a (D W O N -~t 0 m O N a to m O N O (D W O N a m
d v D m (D m m to (D m m m n r- n n m m m m m m m m m
U) m m m m m m m m m m m m m m m m m m m m m m m m m m
Q
Z Red Sandstone Creek, near Minturn, CO (site 59 in table 1)
Q 14
z 12
w 10
g
6
4
2
0
(D m O N a m m O N a m m O N -~t O W O N a m m O N C (D
< m m ID In M m m m m m r n r r r m m m m m m m m m
m m m m m m m m m rn m m rn m m m rn m rn m m m m m m m
Gore Creek at Mouth, near Minturn, CO (site 29 in table 1)
250 .
200
150
100
50
0
W m ON a WOO O N a m W O N 1 *0 W O N a m 000".0W
V a lD to to m rn (D m to to (D r r n r n m m m m m m m m m
D' m D' D D' D' D' m m D' D' m m D' m m IT D' m D' D D' D' D' D' m
Figure 10. Mean annual streamflow at selected gaging stations in the Gore Creek watershed.
SURFACE WATER 23
Gore Creek at Upper Station, near Minturn (site 1 in table 1)
200
150
10
0 n n
50
0 JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC
Z Black Gore Creek, near Minturn, CO (site 37 in table 1)
z
0 100
U 80
U)
cc 60
w
CL 40
w 20
LL
F10 JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC
U
Z Gore Creek at Lower Station, at Vail, CO (site 16 in table 1)
800
0 600
u-
400
Q
~ 200
H
J 0 JAN FEB MAR Ar-7 F--I
PR MAY JUNE JULY AUG SEPT OCT NOV DEC
Q
Z
Z Red Sandstone Creek, near Minturn, CO (site 59 in table 1)
Q 60
Z
Q
w 40
20
0 JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC
Gore Creek at Mouth, near Minturn, CO (site 29 in table 1)
800
600
400
200
JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC
Figure 11. Mean monthly streamflow at selected gaging stations in the Gore Creek watershed.
24 Gore Creek Watershed, Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
u
a Ali
V ?
s
Water resources are in high demand year-round to AY"
support seasonal recreational activities. Photographs
by Ken Neubecker.`
Low flows in Gore Creek are sustained Field Properties
primarily by ground-water discharge and the
gradual melting of perennial snowfields. Knowledge Field properties such as specific conductance,
about the expected frequency of certain low flows is dissolved oxygen, pH, and water temperature are indi-
important because of potential detrimental effects to cators of water-quality conditions. Specific conduc-
stream biota resulting from depletion of dissolved trace provides .good measure of the amount of
oxygen and higher concentrations of dissolved dissolved constituents in water. Adequate concentra-
contaminants in low flows. The 2-year and 10-year tions of dissolved oxygen are critical to aquatic life.
7-day low flows (table 4) indicate the lowest mean Even infrequent periods of dissolved-oxygen depletion
streamflow for a period of 7 consecutive days that can have adverse effects on stream biota such as fish
have a 50-percent or 10-percent chance, respectively, and macroinvertebrates. pH is a controlling factor for
of not being exceeded in any given year the values partitioning of trace elements in sediment and water.
Low pH tends to increase solubility of trace elements
range from no flow to 16 ft-/s (table 4).
in water. Streams with very low pH, such as found in
streams affected by mining, can have much reduced or
Water Quality even nonexistent macroinvertebrate and fish communi-
ties. Temperature influences metabolic rates in stream
Water-quality property and constituent data organisms. Aquatic organisms are adapted to specific
available for surface-water sites consist of field temperature regimes-, for example, trout are considered
properties (specific conductance, dissolved oxygen, a cold-water fish.
pH, and water temperature), inorganic constituents Specific conductance. Specific conductance
(major ions, trace elements, and nutrients), sediment is proportional to the dissolved-solids concentration
(suspended sediment and bedload), and organic in a given water sample. The major ions that compose
constituents (DOC, SOC, pesticides, and VOCs). dissolved solids for water samples from the Gore
Data were collected at 37 sites throughout the Creek watershed are calcium. magnesium, sodium.
Gore Creek watershed (tic,. 5). potassium, silica, chloride, sulfate, and bicarbonate.
SURFACE WATER 25
Because of the direct relation between specific The spatial distribution of stream specific-
conductance and dissolved-solids concentrations conductance values can be related to natural and human
in water, and because specific-conductance data sources of dissolved constituents in the watershed. The
are more widely available for surface-water sites highest specific-conductance values in tributary streams
in the Gore Creek watershed, specific conductance to Gore Creek occurred at sites 38 and 49 on Black
will be discussed in this report. Gore Creek and Mill Creek, respectively (fig. 13A and
Because of dilution, specific conductance 13B). The higher values in these drainages can be partly
increases as streamflow decreases at site 29, attributed to natural sources, such as the Pennsylvanian-
at the mouth of Gore Creek (fig. 12). Specific- age sedimentary rocks, in these drainages. Human
conductance values were highest during December- activities in the Vail Mountain ski area also may
March 1996-97. These specific-conductance values contribute to the higher specific-conductance values
coincided with low-flow conditions, when ground in Mill Creek (fig. 13A). Application of traction sand
water accounts for a larger portion of streamflow, to the Interstate 70 roadway is also a contributing factor
and discharges from tributary streams to dilute point for elevated specific conductance in Black Gore Creek.
and nonpoint sources that enter Gore Creek are Lorch (1998) estimated that the Colorado Department
reduced. The peak-flow months of May-July 1997 of Transportation annually applies about 13,000 tons
coincided with the lowest values for specific conduc- of traction sanding material, including about 650 tons
tance (fig. 12), which can be attributed to large of rock salt by weight, to the Interstate 70 roadway
volumes of relatively dilute snowmelt waters entering between Vail Pass and the mouth of Black Gore Creek.
Gore Creek. From October 1996 to September 1997, Lorch estimated that about 30 percent of the applied
mean daily specific conductance at site 29 ranged traction sand is transported to Black Gore Creek annu-
from 94 µS/cm to 452 µ6/cm, with a median value ally; therefore, an estimated 195 tons of rock salt enters
of 306 0/cm. Black Gore Creek, providing soluble material that can
500 10,000 0
7,000 z
O
U) 450 SPECIFIC CONDUCTANCE 5,000 w
Z STREAMFLOW 4,000 (A
w
3,000 w
L'i 400 2,000
O w
w
U 350
o 1,000 U
LL,
Z 700
- ul 500 U
Ld 2 300 400 Z
U I- -
Z Z 300
J
U U 250 200 O
0 Lu
a LL
o
ZO 200 100 w
U 70
U_ ~
U_ 150 450
0
U
CL 30 QO
100
20 Z
Q
w 10
OCT NOV DEC JAN FEB MAR APR MAY JUNE JULY AUG SEPT
50 1996 1997
Figure 12. Mean daily streamflow and specific conductance at the mouth of Gore Creek.
26 Gore Creek Watershed, Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
A
600
(269) (28) (10) (35) (11) (93) (166) (19) (108) c.l.r ~ANATION
z (108) Number c; .,...,.,,les
w
2E 500 Data value
w 90th -
(n
p 75th
o=
U 400 50th (median) C- Percentiles
w
25th
w LU 10th
Z Z 300
Q w
H U
U ~
w
Z
Z 200
O
U
U '
LL
w 100
0 29 19 59 16 49 10 4 1 38
SITE NUMBER
B 10622'30"
59 Co-
39"40~- t v~ 106 15'
1 cc r ~ ~
CORE f rn Cr'e~v
16 49 - -10 4,
Mill
CreeF
9
~ 38
EXPLANATION
•10 Les, than I i0 mfc"", per ceniimcter A( k
• 29 c ea cr man 15 i0) _
- Town d Vail corpormc limit = J/
/ T
0 1 2 3 4 5 MILES 106 15"
l
0 1 2 3 4 5 KILUrvit i trs$ ~\V (r~y oc oU - 1~-/
Figure 13. Distribution (A) and spatial distribution (B) of specific conductance.
SURFACE WATER 27
increase stream specific conductance. Although infor- The Northwest Colorado Council of
mation regarding rock-salt application was quantified Governments (NWCCOG) (1993) reported that
only for the Black Gore Creek area, Interstate 70 is specific conductance was significantly higher at
adjacent to Gore Creek through the Town of Vail and is site 29 at the mouth of Gore Creek than at upstream
subject to traction sanding; therefore, some quantity of site 10 from 1978 to 1992. The NWCCOG study
salt probably enters Gore Creek from the Interstate 70 concluded that periods of low flow coincide with the
roadway downstream from the confluence with Black highest specific-conductance values when Gore Creek
Gore Creek. An additional source of salt that may affect is more strongly influenced by discharges from the
specific-conductance values in Black Gore Creek is wastewater-treatment plant. These results are consis-
liquid magnesium chloride (MgCl), which has been tent with the data discussed in this report (figs. 12
used since 1995 in conjunction with traction sand to and 13). The NWCCOG study also determined that
keep Interstate 70 open during snowstorms. The annual specific-conductance values showed significant
number of MgCl applications to Interstate 70 is upward temporal trends at sites 10 and 29 between
unknown; however, a single application from Vail Pass 1978 and 1992. These increases were at least partially
to Gore Creek requires approximately 1 ton of material. caused by stormwater runoff from the increasing
The use of MgCl is eventually expected to reduce the amounts of urban land-use areas within the watershed
amount of traction sand required on Interstate 70, but (Northwest Colorado Council of Governments, 1995).
there was no reduction during the winter of 1995-96 Values of specific conductance for site 29 were
(Lorch, 1998). compared statistically by using Tukey's Significant
Specific-conductance values in the Gore Difference Test on the rank-transformed data (Helsel
Creek watershed are relatively low (median value and Hirsch, 1992). The 1968-97 period of record
of 145 µS/cm for 32 sites) when compared to other was divided into three time periods-1968-79,
sites sampled in the Southern Rocky Mountains 1980-92, and 1995-97-and further divided into a
physiographic province (median value of 254 0/cm lower flow season (November-April) and a higher
for seven sites, Jeffrey R. Deacon, U.S. Geological flow season (May-October). The Tukey test indicated
Survey, written commun., 1998) as part of the UCOL no difference in specific-conductance values among
NAWQA Program. Specific conductance increased the three time periods when data for all months were
in a downstream direction in the main stem of Gore compared; however, the months of November-April
Creek (fig. 13). The lowest and least variable specific- did contain significantly higher specific-conductance
conductance values (median value of 40 gS/cm)
occurred at site 1, which represents background condi- values (alpha level = 0.05) during the 1995-97 period
tions with the crystalline bedrock. Specific conduc- When compared to the 1968-79 and 1980-82 time
tance increased slightly at sites 4 and 10, where lower Periods.
specific-conductance water from Gore, Bighorn, Dissolved oxygen. Surface water in the Gore
Pitkin, and Booth Creeks dilutes the higher specific- Creek watershed is well oxygenated and typical
conductance water from Black Gore Creek. Site 16, of high-gradient streams in the Southern Rocky
which is downstream from site 10, Mill Creek, Middle Mountains physiographic province. Concentrations
Creek, and urban and recreational land uses, had below the 6.0-mg/L aquatic-life stream standard
higher specific-conductance values than site 10. The were measured twice in Gore Creek. A concentration
highest specific-conductance values were at site 29, at of 5.9 mg/L was measured just downstream from
the mouth of Gore Creek. This site integrates all the the wastewater-treatment plant in July 1994, and a
natural and land-use-related sources of dissolved concentration of 5.6 mg/L was measured at site 29,
constituents that can increase specific conductance in the mouth of Gore Creek, in December 1978.
the watershed. During the stable low-flow conditions Seventy-five percent of the 783 dissolved-oxygen
in August 1996, Wynn and Spahr (1998) determined measurements taken at 37 sites in the watershed
that increasing values of specific conductance and exceeded 8.8 mg/L. The median dissolved-oxygen
dissolved solids in Gore Creek were partially caused concentration was 9.5 mg/L. Well-oxygenated stream
by inflows from tributaries such as Mill Creek and conditions like those in the Gore Creek watershed
Black Gore Creek that drain areas where sedimentary support aquatic organisms such as macroinvertebrates
rock is predominant. and fish.
28 Gore Creek Watershed, Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
pH. Values of pH ranged from 5.9 to 10.0 stan- The data were grouped in 3-month time periods in
dard units. Only 23 of more than 1,000 pH values were which the samples were collected (October-December,
outside the range of the recommended stream standard January-March, April-June, July-September) so that
for pH (6.5-9.0). Of those values, 18 were measured at seasonal (and associated streamflow) patterns could
site 29 between 1969 and 1997. There was no discern- be examined. Percentages of major cations indicated
ible long-term or seasonal pattern to the measurements little variation. Calcium was the dominant cation,
that were outside the recommended range for pH. accounting for more than 60 percent of cations in all
Eighty percent of the pH values were between 7.5 samples (fig. 14). The relative percentages of anions
and 8.6 within the Gore Creek watershed. The toxicity indicated seasonal variability. Bicarbonate accounted for
of dissolved ammonia increases with increasing pH, 50-60 percent of anions during January-March but as
but ammonia concentrations were low at site 29, much as 90 percent during high flow (April-June) when
precluding any possible concern for ammonia toxicity. most streamflow originates from snowmelt. Sulfate and
Water temperature. Water temperatures within chloride ions were prevalent, accounting for as much as
the Gore Creek watershed typically were low. More 50 percent of all major ions, during the annual recession
than 90 percent of the temperature measurements of the hydrograph (October-December) and during
were less than 1 l °C. During an August 1996 sampling winter low-flow (January-March) conditions when a
of 13 sites on the main stem of Gore Creek, Wynn large part of the streamflow consists of base flow rather
and Spahr (1998) found little variability in water than snowmelt (fig. 14).
Trace elements. Historically, concentrations
temperatures (8°-16°C). Temperature can influence
the composition of fish communities. Relatively low of several trace elements have occasionally (cadmium,
copper, iron, and silver) or frequently (manganese, in
water temperatures such as those in the Gore Creek Black Gore Creek) exceeded aquatic-life stream stan-
watershed provide favorable habitat for trout and dards in the Gore Creek watershed (Northwest Colorado
sculpin (Deacon and Mize, l 997). Council of Governments, 1995). Presence of all of these
trace elements except silver is at least partially attribut-
Inorganic Constituents able to bedrock geology (Northwest Colorado Council of
Inorganic constituent data for major ions, trace Governments, 1995; Steele and others, 1991; Wynn and
elements, and nutrients are useful for describing water- Spahr, 1998). However, studies in other locations have
linked increased copper and manganese concentrations
quality conditions. Major-ion data are needed to deter- to highway runoff and traction sand (Kobringer, 1984;
mine the relative significance of various sources of Novotny and Olem, 1994). Silver concentrations have
dissolved constituents in the water column such as been associated with treated wastewater effluent
ground-water discharge or precipitation runoff. (Northwest Colorado Council of Governments, 1993).
Trace-element data provide information about the Land disturbance near Black Gore Creek during
natural and human sources of contaminants such as construction of the Interstate 70 roadway in the 1970's
zinc or cadmium, which can be harmful to aquatic probably caused some of the documented increases
life. Nutrient concentrations can have a large effect in trace-element concentrations. Astudy of temporal
on stream biota. Seasonal differences and changes trends of trace-element concentrations in the watershed
in nutrient concentrations can be a primary factor for indicated that cadmium, copper, manganese, and zinc
changes observed in the algal and macroinvertebrate concentrations have decreased over time (Northwest
communities. Colorado Council of Governments, 1995). Part of the
Major ions. Concentrations of major ions decrease in trace-element concentrations may be related
(calcium, magnesium, sodium, potassium, silica, to the restabilization of the hill slopes that were disturbed
chloride, sulfate, and bicarbonate) in Gore Creek during highway construction. The stream standard for
vary with streamflow and season. Data collected peri- manganese, 50 pg/L, was exceeded only one time among
odically from 1995 to 1997 (46 samples) at site 29, 11 samples collected at 4 sites in Black Gore Creek in
at the mouth of Gore Creek, are plotted on a trilinear 1996 (Crowfoot and others, 1996; Lorch, 1998). That
diagram in figure 14. Trilinear diagrams are useful for sample, collected near Vail Pass where the creek flows
examining the relative percentages of major ions for into Black Lake (site 30), contained a manganese concen-
multiple samples so that trends or patterns in relative tration of 530 R/L. The range in manganese concentra-
major-ion chemistry may be determined (Freeze and tions for the 10 samples collected downstream from the
Cherry, 1979). Black Lakes in 1996 was 2-36 µg/L.
SURFACE WATER 29
EXPLANATION
90 90 y
%
Op 50 moo, / \ 50
~V11
41 10 0
to 10
Sulfate S
c type type,
J \
50 So \ 50/N~miPO
50 %
No No /
v dominan[ / ~ \ V dominant /
\ type , Sodium 90 90 \ type, /
Calcium \ \ Chloo~le
type or Bicarbonate /
typr' \ / potess'n,im tVPU \
IYp"
type DATA POINTS
50 50
nn) C.0 Chrondercu O OCTOBER-DECEMBER
CAI IONS ANIONS _
JANUARY-MARCH
v n
APRIL-JUNE
o 3 JULY-SEPTEMBER
k
,od, .
'
M{ Soy
Off/ s
~dS'J,. V moo' 0
q,
C
90 50 T 40 20 Na+K HC03 + C03 20 40 -r 60 ee CI
Calcium (Ca) Chloride (CI)
CA' I^NS ANIONS
PERCE"T MILLIEQUIVALENTS
PAR L.!TER
Figure 14. Trilinear diagram of major-ion data for site 29, at the mouth of Gore Creek.
30 Gore Creek Watershed, Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
1
Lorch (1998) found a significant correlation Nutrients. Distributions of concerrt,uLIons for
(p<0.000I ) between chloride and manganese concen- ammonia, nitrate, total nitrogen, orthophosphate, and
trations in 22 stream and runoff samples in and near total phosphorus for 30 surface-water sites are repre-
Black Gore Creek. Lorch attributed this correlation to sented by boxplots in figure 15. Ammonia concentra-
i„,t,arities in the salt material applied to Interstate 70 tions for all sites were low, with 75 percent of the
during snowstorms. Cadmium, chromium, nickel, and concentrations equal to or less than O.10 mg/L
zinc concentrations also were highly correlated with (fig. 15). The ammonia data contained a variety of
chloride concentrations (p<0.000I whereas cvt,Nc, mi„i,,,um reporting limits, and no discrete median
and lead concentrations were not as highly correlated concentration could be determined because more
with chloride (p-values were equal to 0.0003 and than one-half the data was below one of the «,pirtin-
0.0004, respectively). limits. The range of nitrate concentrations was
Silver concentrations exceeded the 0.08-µg/L the largest (three orders of magnitude) of the five
aquatic-life stream standard at two sites in Gore nutrient constituents, and the median concentration
Creek downstream from Red Sandstone Creek in was 0.40 mg/L. Four nitrate concentrations in samples
December 1988 (Advanced Sciences, Inc., 1990). collected during W I„,er 1976-77 exceeded the USEPA
The concentrations were 0.2 and 0.3 µg/L. Silver drinking-water maximum contaminant level (MCL)
was detected at a concentration of 0.1 pg/L in four
samples in 1989. Silver has not been detected in of 10 mg/L. Only 53 analyses were available for total
Gore Creek down,,, v-,,,, from Red Sandstone Creek nitrogen, which had the highest median concentration
in the 22 samples collected since 1989, however, the of 0.6 mg/L. The median orthophosphate concentra-
reportin~ limit (0.5 and LO µg/L) for most of those tion was 0.01 mg/L, and 90 percent of the data were
samples was higher than all of the previous silver 0.10 m,-,/L or less. Total phosphorus concentrations
detections. Trace-element sampling programs that were somewhat elevated. The median concentration
may be conducted for sites in Gore Creek in the future was 0.05 n1-/L, and 25 percent of the total phosphrn-us
should use analytical methods for silver analyses with concentrations were greater than 0.12 ma/L, which
a ct-itrting limit no higher than 0.05-0.1 µg/L to exceeds the USEPA recommended level of 0.10 n1L/I
ML iiiine whether silver concentrations are still for control of eutrophication in flowing water
EXPLANATIIC.
LLJ J (35) Number 1
CL Data
w 10
d
~ 90th
75th
Q 50th (medians rO1~~~''
0 1 25th
F 10th
Z 1
T
0.1
Z
O
H
Q
Z 0.01
w
U
Z
O
U
0.001
Ammonia Nitrate Total Orthophosphate Total
Nitrogen Phosphorus
Figure 15. Distribution of nutrient concentrations for all surface-water sampling sites in the Gore Creek watershed.
SURFACE WATER 31
Distribution of concentrations of ammonia, Median nitrate concentrations gradually
nitrate, orthophosphate, and total phosphorus increased in a downstream direction from sites l and
for sites with 10 or more analyses are shown in 38 to site 16, reflecting background conditions and
figures 16A-19A, and median concentrations for minor urban influences (fig. 17). At site 10, several
sites with five or more analyses are shown in map measurements of nitrate concentrations greater than
figures 16B-19B. When more than one-half the data 9 mg/L occurred in the 1970's; however, more recent
for a particular nutrient constituent at a site were data contained only low concentrations. The sharp rise
censored, estimates of the concentration percentiles in median nitrate concentration (to about 2 mg/L) at
were calculated using the maximum likelihood estima- site 17 was likely caused by nutrient inputs from the
tion (MLE) method (Helsel, 1990; Helsel and Cohn, Town of Vail wastewater-treatment plant. This effect
1988). These estimated percentiles were used to was localized, as the median concentration decreased
construct the boxplots and provide the median concen- to about 0.5 and 0.4 mg/L at downstream sites 19 and
trations plotted on the maps for sites and constituents 29. Two likely factors for decreased nutrient concen-
where data were censored at the 50th percentile. trations downstream from site 17 are dilution by addi-
Sites 1, 37, and 38 are located in forested areas tional streamflow inputs and nitrogen uptake by algae.
with minimal land-use effects on nutrient concentra- Median orthophosphate concentrations for
tions and are assumed to represent background condi- sites located upstream from site 29 were below or
tions. Sites 4, 10, 16, 17, 19, and 29 are located within near the detection limit of 0.01 mg/L but the median
or downstream from the Town of Vail and represent was 0.06 mg/L at site 29, the mouth of Gore Creek
urban and recreational land use. The Vail wastewater- (fig. 18). Median total phosphorus concentrations for
treatment-plant outfall is located between sites 16 and sites upstream from site 29 also were 0.01 mg/L or less
17, upstream from the confluence of Red Sandstone (fig. 19). The median total phosphorus concentration
and Gore Creeks. The concentration ranges in at site 29 was 0.12 mg/L, reflecting urban point and
figures 16B, 18B, and 19B (shown as different colored
dots) represent the 50th and greater than 50th percen- nonpoint sources. For site 29, more than one-half of
tiles of the median concentrations for all sites shown the analyses exceeded 0.10 mg/L, the recommended
on the map; whereas nitrate concentration ranges in USEPA level for control of eutrophication in flowing
figure 17B represent the less than 25th, 25th to 50th, water (U.S. Environmental Protection Agency, 1986).
51st to 75th, and greater than 75th percentiles for all Total phosphorus concentrations at sites that represent
the sites shown of the respective map figures. background conditions did not exceed 0.1 mg/L.
In general, nutrient concentrations were Historical nutrient concentrations for sites
higher in the downstream reaches than in the representing background conditions and urban
upstream reaches (figs. 16-19). Median concentra- land uses in the Gore Creek watershed can be
tions of ammonia, nitrate, orthophosphate, and total compared with concentrations at similarly classified
phosphorus were lowest at background sites 1, 37, and sites within the Upper Colorado River Basin (UCOL)
38 (forested areas with minimal developed land use). (Spahr and Wynn, 1997) in Colorado and throughout
Concentrations of nutrients were relatively higher at the United States (Mueller and others, 1995) (table 5).
urban and recreational land-use sites 4, 10, 16, 17, 19, The time periods of the available data used in this
and 29. This downstream increase in nutrients in the comparison are: Gore Creek watershed, 1968-97;
Gore Creek watershed also has been reported by the UCOL, 1980-94; and United States, 1970-92. Sites
Northwest Colorado Council of Governments (1993, in the Gore Creek watershed that are classified as
1995) and, for low-flow conditions in August 1996, representing background conditions and urban land
by Wynn and Spahr (1998). use equate with the background and urbanization
Ammonia concentrations were low throughout sites of Spahr and Wynn (1997) and background and
the watershed (fig. 16). Median concentrations for urban/undeveloped sites (combination of urban land
background sites were less than 0.02 mg/L and with forest land or rangeland) of Mueller and others
between 0.023 and 0.038 mg/L for urban sites. The (1995). For the Gore Creek watershed, nutrient data
median ammonia concentrations at urban sites did not for 10 headwaters sites were combined for the back-
change substantially in a downstream direction. Indi- ground classification, and data for site 29, at the
vidual ammonia concentrations greater than 0.50 mg/L mouth of Gore Creek, were chosen to represent
occurred only at site 29, the mouth of Gore Creek. urban land use.
32 Gore Creek Watershed, Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
I
A
10
11681 1271 gaol 1107> EXPLANATION
{1071 Number of --,.les
5 Data value
Q 90th
C7 1 75th
-j -v f 50th Percentiles
i
[t , - 25th
z LU_ ! 10th
J
Z r 0.1 Dashed lines show estimated values
Q w Data for sites with fewer than 10 samples
are not r -ted by boxplot
_g
Z -i t _i
O _r_
0.01 f I 1
Q
0.001
29 19 16 a
SITE NUMBER
100 « ou
B
106"1500
39 40'
J " ~9
I 16 ~ GoRZ~ L~
J, 19 - 4 L
IYIi!l Creek
29 1
LAr.ANATION
37%z
Les, than 0L02 milligram per liter 37 'd
X29 Greiner thin 0.02 milligram per liter
- Toy+'n oI Vail cuipuratc film(
1
0 1 2 3 4 5 MILES 10615
J
0 1 2 3 4 5 KILOMc i cr{5
39`32'30"'-
Figure 16. (A) Distribution of t. and (B) spatial distribution of median concentrations of a .(u is
for surface-vvaLIVI sampling sites in the Gore Creek watershed.
SURFACE WATER 33
A
100 -
w (176) (28) (19) (57) (86) (125) (77)
J
x (77) Number of samples
w
C Data value
(n 10
2 90th -
Q 75th
- <1 50th (median) Percentiles
J , - 25th
1
10th
z Dashed lines show
Z estimated values
Q 0.1
w L
Q
E--
Z
0.01
29 19 17 16 10 4 38
Si it NUMBr-H
B 106 22'30"
39 40'
41
r 9
JJ 16 t`o Creek
19 GORE 4
10 ~`M
Mill Creed I
I_ ~1
29 38
c
EXPLANAI fON
37 'f• ~ f\
Less than or equal to 0.1 milligram per liter 3 `'•k
038 Greater than 0.11 to 0.024 milligram per liter
016 G ea - than 0.025 to 0.50 milligram per liter ` j
T 1
017 G,ed,e+ than 0.51 milligram per liter I
\ ^r
Town of Vail corpoi- limit 106 15".
0 2 3 4 5 MILES
'
0 1 2 3 4 5 KILOrVrL rno 39 32'30"•-
Figure 17. (A) Distribution of nitrate and (B) spatial distribution of median w ~,tntrations of nitrate for surface-water
on, piing sites in the Gore Creek watershed.
34 Gore Creek Watershed, Colorado-Assessment of His.,,.:,,,-.1 and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
A
1C
(78) (85) (20) (76)
EXPLANH] IUIV
z (76) Number of samples
0 w 1 Data value
cn ~
a 90th
J
w LU 75th
Q 50th (i m n) I- Percentiles
_ Lo -I 25th
U, Q 0.1
0 < 10th
Dashed lines show
0 estimated values
2 J
O ~ 0.01
1 _
c -I- ~ I I
L _i
0.001
29 10 4 38
a1 I L Nbivior-rn
B 100 « 6u
~o
39'40'(--'
J GORE Creek
0_1 4
r•
4
29 38 _
1 0 EXPLANATION
Lcss than 0.011 milligram per liter \ <~Y
029 Greater than 0.011 milligram per liner lJ 37
Mown A fail limit
T
0 1 2 3 4 5 MILES 106 R~
0 1 2 3 4 5 KILOMt t Inb '
Figure 18. (A) Distribution of orthophosphate and (B) spatial dl.:huution of median ...LGrnrati-~ of
orthoph„~pi,.te for surface-water sampling sites in the Gore Creek wa« Ji led.
SURFACE WATER 35
A
10
136) 12) 93) EXPLANATION
(93) Number of r,
Z Data value
1 90th
cn w } 75th
Q J s 50th -u.n) FL-,:,,tiles
LL' -I 25th
d
O 0.1 10th
EL Dashed li-, I.ow
to Q estimated values
O~ i
= C7 1
IL J I
aJ 0.01
I
O 2E
A -I
~ I I I
` I I
I
0.001
29 16 4
SITE NUMBER
B
-0 11
c
39 40' 106 15' O~
610
~
1 s-
COK£ Urek
-
- 4 1 p
= rLli// C'rer6tir ~ ~
29
1
r.Ai'i.ANAiiVty - J
X16 Le- than 0.03 milliermn per liter ~ C,•p~~
29
Greater 37
~ Greater than 0.03 milligram per liter
1'u\ni limit
s
r_.
0 1 2 3 4 5 MILES
0 1 2 3 4 5 KILurvic i cRS
39`~c o~
Figure 19. (A) Distribution of total phosphorus and (B) opaual distribution of median t u ;ins of
total phosphorus for su iuui water sampling sites in the Gore Creek watershed.
36 Gore Creek Watershed, Col, aiN.-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
Table 5. Median nutrient concentrations for background data for Gore Creek at the mouth, site 29. For other
and urban land-use categories for the Gore Creek water- sites in the Gore Creek watershed, nutrient and(or)
shed, Upper Colorado River Basin, and the United States
streamflow data are limited temporally, and no
less than; mg/L, milligrams per liter] comparison between the two can be made. Concentra-
tions of most nutrients in Gore Creek at the mouth
Constituent and location Background Urban varied with streamflow from 1995 through 1997.
land use
Ammonia Because most analyses were below the 0.015-mg/L
Gore Creek watershed <0.02 mg/L <0.10 mg/L1 reporting limit, ammonia concentrations did not
Upper Colorado River Basing .02 .04 appear to vary with streamflow. Nitrate and total phos-
United States3 .02 .1 phorus data were plotted with streamflow and also
Nitrate were grouped into higher flow (May-September)
Gore Creek watershed 0.11 mg/L 0.38 mg/L1
Upper Colorado River Basin'- .09 3 and lower flow (October-April) (fig. 20). A Mann-
United States3 .14 .4 Whitney U test was used to test for significant differ-
Total Phosphorus ences in nitrate and total phosphorus concentrations
Gore Creek watershed <0.01 mg/L 0.12 mg/L1 between the groups (Helsel and Hirsch, 1992). Nitrate
Upper Colorado River Basinz .03 .04 concentrations and orthophosphate concentrations (not
United States3 .03 .16
shown) increased as streamflow decreased (fig. 20A).
Data for Gore Creek at mouth, site 29, urban integrator site for the Streamflow is highest during the higher runoff months
Gore Creek
Spahr Watershed. and Wynn (1997). of May through September. During these months,
Fro
3From Mueller and others (1995). Data listed for urban land use are nitrate concentrations were lower due to dilution. The
Mueller and others (1995) urban/undeveloped sites. peak flow months of May and June coincided with the
lowest concentrations for nitrate. Nitrate concentra-
tions were significantly higher (p<0.0001) in fall,
Median nutrient concentrations for the Gore winter, and early spring (October-April), when low
Creek watershed were generally less than for the streamflow conditions predominate, than during the
national study but greater than those reported in the May-September period (fig. 20A). Total phosphorus
UCOL study. The median ammonia concentration for concentrations also were significantly (p<0.0001)
background conditions in the Gore Creek watershed higher during the October-April months than in the
was less than the median ammonia concentration for higher flow months of May-September. Concentra-
the UCOL and national studies (table 5). The median tions of total phosphorus increased as streamflow
ammonia concentration for urban land use in the Gore decreased, except during the first large runoff event
Creek watershed was lower than the national study, of the year (fig. 20B). Total phosphorus concentrations
and, because the Gore Creek median is censored at decreased as streamflow gradually increased during
0.1 mg/L, no comparison can be made between March and April; however, when the initial large
median ammonia concentrations in the Gore Creek pulse of snowmelt runoff reached Gore Creek in
watershed and the UCOL study. The median nitrate May or early June, total phosphorus concentrations
concentrations for background and urban sites in the increased for a period of time because the total
Gore Creek watershed were greater than the median phosphorus concentration includes any phosphorus
for the UCOL study but less than the national study. adsorbed to suspended sediment. When streamflow
For total phosphorus, median concentrations for back- and suspended-sediment concentrations are highest,
ground sites in the Gore Creek watershed were lower as in May and June, bottom sediments are resus-
than the median concentrations for background sites pended, possibly accounting for the sharp rise in
in the UCOL study unit and the national study. The total phosphorus concentrations on the rising limb
median total phosphorus concentration for urban of the annual hydrograph.
sites was higher in the Gore Creek watershed than Temporal trends in nutrient concentrations.
the UCOL study unit but lower than the median total To partially address the question of whether water
phosphorus concentration for the national study. quality is changing over time in the Gore Creek water-
Nutrient concentrations and streamflow. The shed, temporal trends in nutrient concentrations were
relation between nutrient concentrations and stream- investigated. Some trends in data may be significant
flow can be examined by evaluating the most recent statistically but not environmentally; for example,
SURFACE WATER 37
m A
m 0 1,600 - -7- 10 10 -
3
o EXPLANATION
D p Streamflow (20) (26)
0 1,400 Nitrate (26) Number of samples
U Data value
co Q
M U zZ 1,200 2 0:: - 90th
76th
v O
o Z U 1 _j 1 50th (median) Percentiles
o - LU 1,000
> 25th
N 0 Cc Lij
10th
10 1 ¢ J w 800 z
t0 LL LL 0-- OD o ~ ~ Uj .
C Lj W LL 600 - IL
0.10 Q 0.10
~ 3
o u~i aoo -
~i I
rp 200 Z
P<0.0001
N 0 a a r fi . `i, -r < 0.01 0.01 - i_
c(o rn L0 (0 W rfl co (e (0 n r r r
a) a) May-Sept OctAPril
m m rn rn rn rn m m m rn m rn
U [U U U
N
O C) LL Q Q O C) LL Q Q O n
w DATE
0
0 B
m
d
:3 1,600 1 1 - - - -
Q
n Streamflow to 20) 26)
1,400 + Total phosphorus Q
rD ~
U
U
C) 1,200 J
tU J
cp z Z
O 0.1 2 0.1
0 -U 1,000 Ztr
_ - W
~J
0cc
_j w 800 ~ M
< LLLL
Q w = IL
w LL 600 CL
LL
0.01 to 0.01
O
(J (n 400
C
J
d Q
Y-
200 ' O p<0.0001
««i
0.001 0.001
0 Ln in Q0 (0 W rD W co r- r, r- r` r r May-Sept Oct-April
m rn m m rn rn m m rn m rn rn rn
U Q ~ ~ U Q N p7 U
U N ~ ~ C 7 U ~ ~ ~ C 7 U Q7
O 0 LL < Q O p LL < Q O p
DATE
Figure 20. Streamflow and (A) nitrate and (B) total phosphorus concentrations, Gore Creek at mouth (site 29), October 1995-December 1997.
when concentrations are very low or when the above 0.10 mg/L, and there was very little variability
rate of change is small. Also, trend results can in the 1995-97 data. Nitrate concentrations were
differ depending on the period of record. significantly higher during 1980-92 as compared to
The period of record for trends analysis, 1968-79, and there was no difference between concen-
1968-97, was separated into three time periods: trations during the 1980-92 and 1995-95 time periods
1968-79, 1980-92, and 1995-97, and further divided (fig._21B). Prior to 1984, it was uncommon for nitrate
into two seasons (May-October and November-April) concentrations to be higher than 1.0 mg/L. After 1983,
within each time period. This latter division accounts detections above this level were common. In the early
for the seasonal variation that occurs in nutrient 1980's, the Vail wastewater-treatment plant was
concentrations in Gore Creek. Nutrient data for most upgraded to convert ammonia into nitrate through the
or all,of the 1968-97 analysis period were available process of nitrification (Caroline Byus, Eagle River
only for site 29, the mouth of Gore Creek, and site 4, Water and Sanitation District, oral commun., 1998).
Gore Creek at Bighorn Subdivision below Pitkin The upgrade reduced discharges of ammonia while
Creek. Comparison of nutrients between time periods increasing discharges of nitrate. This wastewater-
at site 4 was not possible, however, because high processing change was made to reduce the exposure
reporting limits resulted in a large percentage of of stream biota to un-ionized ammonia, which can be
censored data. Hence, only data for site 29, which toxic at relatively low concentration levels (Thurston
represents an integration of all upstream land-use and others, 1974). The shift in nitrogen speciation
effects on water quality, were analyzed for temporal from ammonia to nitrate is evident in figure 21, with
changes. Because of a high percentage of censored ammonia concentrations lower and nitrate concentra-
data values during the spring and summer seasons, and tions generally higher after 1983. However, the total
because higher nutrient concentrations typically occur amount of nitrogen potentially available to algae
during low flow, only the winter season (November- has not necessarily decreased with the change in
April) was tested statistically for trends at site 29. wastewater-treatment methods. Few historical total
Although boxplots for the May-October months also nitrogen data are available for the Gore Creek water-
are included in figures 21 and 22 for comparative shed, and comparison of total nitrogen concentrations
purposes, the following discussion will be focused cannot be made between time periods.
on data collected during the winter seasons only. The difference in orthophosphate concentrations
Concentrations of ammonia, nitrate, orthophos- at the mouth of Gore Creek, site 29, between 1968-73
phate, and total phosphorus were compared statisti- and 1995-97 was not significant (fig. 22A). Total
cally using Tukey's Significant Difference Test on phosphorus concentrations were significantly lower
the rank-transformed data (Helsel and Hirsch, 1992). in 1995-97 as compared to 1974-79 and 1980-92
Results of the Tukey test are represented as letters (fig. 22B). Total phosphorus concentrations above
(a, b, or c) adjacent to the median on the November- 0.30 mg/L were common through 1992 but were
April boxplots in figures 21 and 22. Nutrient concen- not detected above this level during 1995-97.
trations for boxplots with different letters adjacent to The Northwest Colorado Council of
the median line are significantly different at an alpha Governments (1993) reported that total phosphorus
level of 0.05, which translates to a 95-percent confi- concentrations were increasing downstream from
dence level for the test results. For example, the the Town of Vail. Results of monthly and quarterly
November-April boxplots for ammonia each have a seasonal Kendall trend tests indicated increasing
different letter (a, b, or c) adjacent to the median; total phosphorus concentrations at site 29, the mouth
therefore, ammonia concentrations are significantly of Gore Creek, during the 1978-91 time period at a
different for each consecutive time period (fig. 21A). 95-percent confidence level. As stated previously, the
Median ammonia concentrations were signifi- analysis of the most recent phosphorus data indicated
cantly different for each of the three time periods a significant decrease in total phosphorus concentra-
(fig. 21A). Concentrations were highest during tions for site 29 between the 1980-92 and the 1995-97
1968-79 and lowest during 1995-97. Ammonia time periods. Therefore, it would appear that total
concentrations were highly variable during 1968-83, phosphorus concentrations have now decreased down-
with concentrations frequently exceeding 0.60 mg/L. stream from the Town of Vail. However, in the Upper
After 1984, only two detections of ammonia were Colorado River Basin, higher than average streamflow
SURFACE WATER 39
A
o q
(21) (29) (34) (38) (23) 1231
a o 10 10 EXPLANATION
D fD (n
.a n Q (23) Number of samples
DCj Data value
(D 1 J 1 90th
n J Q -T 75th
n m ~ w
p N cc: Z 50th (median) (Percentiles
rn Z~ a i _ 25th
0.10 • - - z cc o.1 - b loth
Q cc: cn w
a
LLJ m n as » . Q
00 1 o d z c
(D o
aD ZOO 0.01 - 0.01
O ? May-Oct -
Q Nov-Apr
I Q
N
0 0.001
CA N O N V' (D Co O N a CO W O N a (D 00 1968-79 1980-92 1995-97
3 (0 r r r N 00 00 00 00 m Q1 m T
~ C C C C ~ E C C C C C TIME PERIOD
m m w m M m c) m m M I M m m M
DATE
x
N
o B
n (25) M) 1341 1381 1231 1231
10 10 - - 1
d i
Q
n to
C
• a a
m
J 1 i a - a
J
z~ b
cc-
Z w
(n LU f (n CL
Q
0
Q 0.10 LL .1 - t
w _
m
H ~ ? May-oct
Z Ej Nov-Apr
Z
0
C
m 0.01 _ 0.01
- 1968-79 1980-92 1995-97
CO O N d (D N O N -4 (D O O N d (D 00
(D r r r t` r 00 T 00 op 00 Ql T T O m TIME PERIOD
_ C C C C C C C C G C C
~0 R1 (p ti A (0 (6 (p f0 (0 (0 f0 f4 N N
DATE
Figure 21. Temporal distribution of ammonia (A) and nitrate (B) at Gore Creek at mouth, site 29.
A
1 (15) (17) (23) (23)
1 EXPLANATION
z
w
(n l-- 0 w (23) Number of samples
Q J
w CC > Q J Data value
w 0.10 a - 7 90th
Q a- w 0.1 75th
to • •4 Q 50th (median) Percentiles
to to - 25th
0~ 0Oa- 2i
Q 1 10th
C7
0O -1 0.01 d 0 0.01
OJ
0~C~ 2J
O Z May-Oct
O Nov-Apr
0.001 0.001 -
00 0 (N v M co o N ~ (0 CO o N v cp co 1968-74 1995-97
(o r` r` r` 0u 09 T co 0? m m rn m T
C C c r= c c c c c c c c c c c c TIME PERIOD
CU M m co M m m co m m M m m co m
DATE
B
(7) (12) (33) (38) (23) (23)
a
Q_j a
w
~ F cnLU ;
~
Cr ~ 0.10 - - - U) 0.1
b
O'n ~w
V) O U)
O C7 a-
d_j 0.01 - OV) < El
w 0.01
_j J_ =O
a-
O z Q J May-Oct
f-- g~
Nov-Apr
O
0.001 0.001
(R 00 o N v to 00 o N a (0 00 0 (N -4 (0 00 1974-79 1980-92 1995-97
C 10 r` r~ r` r~ r~ 00 00 0o c0 w m m T T
C C: C: C: C: F_ C_C: C C C: C C C: C TIME PERIOD
M M M M ro 10 M(0 M M co M cc CU co
n
n DATE
M
D
-i
M
Figure 22. Temporal distribution of orthophosphate (A) and total phosphorus (B) at Gore Creek at mouth, site 29.
A
occurred during 1995-97. A difference in streamflow of Gore Creek. Each of these 10 DOC samples
between the time periods partially accounts for the was collected during peak runoff in May or June,
difference in total phosphorus concentrations, as indicating the source of DOC probably was from
concentrations tend to be higher during low flow nonpoint rather than point sources. The median
than during high flow. Streamflow data were not DOC concentration was 1.3 mg/L. Presence of
collected concurrently with the total phosphorus organic carbon could have a major influence on
data for much of the 1980-92 time period; therefore, macroinvertebrate-community structure.
direct comparison of flow-adjusted concentrations Pesticides. Historically, pesticides have not
is not possible. been identified as a water-quality concern in the
Censored data and the lack of concurrent watershed. Coincident with its application to the golf
streamflow data limited evaluation of nutrient condi- course, sampling for the fungicide "Banner" (propi-
tions for the Gore Creek watershed. For some sites, the conazole) was conducted in Gore Creek during 1992.
reporting limit was so high that no data were reported The fungicide was not detected during this sampling
above that level, thereby limiting the usefulness of the effort (Northwest Colorado Council of Governments,
data. Should additional nutrient data be collected in 1995). The USGS collected 10 samples for pesticide
the future, analytical methods with reporting limits analysis during various streamflow conditions during
low enough to provide uncensored data over the range 1996 and 1997 at the mouth of Gore Creek. These
of ambient water-quality conditions would be needed. samples were analyzed for a suite of 87 pesticides and
Along with the censored data, the lack of concurrent pesticide-degradation products (Timme, 1995). Of the
streamflow information prevented a thorough analysis 12 pesticide compounds detected at low concentra-
of temporal trends in nutrient concentrations. Because tions, 11 were herbicides and 1 was an insecticide
nutrient concentrations vary with streamflow, concur- degradate (DDE, a degradation product of DDT). The
rent discharge measurements are highly desirable concentrations for the 12 pesticides that were detected
to normalize nutrient concentrations that occur did not exceed USEPA drinking-water standards. Only
at different times of the year. samples collected between May and September 1997
contained detectable concentrations of pesticides.
Organic Constituents Atrazine was detected in the highest concentration,
0.014 pg/L, in a June 1997 sample. This sample also
Organic carbon. Organic constituent data contained low levels (less than 0.008 pg/L) of alachlor,
such as organic carbon, pesticides, and VOCs have benfluralin, bentazon, cyanazine, dacthal (DCPA),
been collected at site 29 since 1995. Dissolved and metolachlor, DDE, and trifluralin. The only pesticide
suspended organic carbon (DOC or SOC) can have detected more than once was DCPA, with three detec-
an important role in the transport of trace elements tions. Three other pesticides were detected one time
because many trace elements are readily bound at low concentrations: deethylatrazine, prometon, and
to the surface of organic carbon material and also simazine.
can provide food for bacteria and macroinvertebrates. Volatile organic compounds. Seven
Pesticides and VOCs can, at elevated concentrations, VOC samples were collected during February-
be harmful or toxic to stream biota and human health. September 1997 at site 29. The samples were
Major sources of organic carbon include analyzed for 87 different VOCs (Timme, 1995). Of
natural decay of plant or animal matter, runoff from the 10 compounds that were detected, 9 are classified
urban land-use areas, or discharge from point sources. as solvents and 1, methyl tert-butyl ether (MTBE), is a
DOC and SOC concentrations were low throughout fuel oxygenate. The USEPA MCLs for drinking water
the watershed; however, limited data (72 samples were not exceeded in any of the samples. Acetone was
collected at 25 sites since October 1995) were the most commonly detected VOC, with four detec-
available for interpretation. The DOC concentra- tions at 1-2 µg/L. Carbon disulfide was detected
tions generally were greater than SOC concentra- three times at concentrations ranging from 0.006
tions. Ten of the 12 highest concentrations of DOC to 0.01 pg/L. Methyl tert-butyl ether was detected
(2.8-4.6 mg/L) were detected at site 29, the mouth one time at a concentration of 0.02 µg/L.
42 Gore Creek Watershed, Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
Sediment Streambed Sediment and Tissue
Previous reports have identified sediment Chemistry
as one of the primary water-quality concerns in Many hydrophobic constituents such as orga-
the Gore Creek watershed. The earlier reports nochlorine pesticides and trace elements may be
identified suspended sediment flushing into Black present in water but commonly are at concentrations
Gore Creek, caused by land disturbance during that are below laboratory reporting limits. However,
construction of Interstate 70 during the early these constituents are more likely to be detectable or
1970's, as the major concern (Wuerthele, 1976; even elevated in other sample media such as streambed
Britton, 1979; Engineering Science Inc., 1980; sediment or the tissues of aquatic organisms such as
Resource Consultants Inc., 1.986). More recently, fish or macroinvertebrates. Organochlorine pesticides
traction sanding material, washed into Black Gore and many trace elements, because of their hydro-
Creek from the Interstate 70 road surface, has been phobic chemical properties, have a higher affinity
identified as the sediment of concern (Weaver and for sediment, organic matter, and(or) tissues than for
Jones, 1995; Lorch, 1998). water (Stephens and Deacon, 1998; Coles, 1998). For
Seventy-one samples collected at the mouth of this reason, streambed-sediment and tissue samples
Gore Creek since 1995 indicate that suspended sedi- provide better information than water samples about
ment is not a major water-quality concern. Suspended- the occurrence and distribution of organochlorine
sediment concentrations ranged from 0 to 172 mg/L, pesticides and trace elements.
with a median of 4 mg/L. Only 14 samples contained
sediment concentrations higher than 25 mg/L, and
each of those samples was collected during the high- Organochlorine Compounds
flow months of May and June, when increased stream
velocities are better able to transport sediment in Streambed-sediment and whole-body fish-
suspension. tissue samples were collected at the mouth of Gore
Using automatic samplers that were activated Creek in 1995 and the samples were analyzed for
following a predefined increase in streamflow, organochlorine-pesticide and polychlorinated biphenyl
Lorch (1998) measured order-of-magnitude higher (PCB) compounds. Sediment samples were tested
concentrations of suspended sediment, as much as for 32 compounds and fish-tissue samples were tested
112 mg/L in Black Gore Creek, when compared to for 28 compounds (Timme, 1995). PCBs were not
background sites in Polk and Gore Creeks. Although detected in sediment or fish tissue. Pesticides were not
detected in streambed sediment, and only one orga-
Lorch found relatively low concentrations of nochlorine pesticide degradate, DDE, was detected in
suspended sediment in Black Gore Creek, high fish tissue at a concentration of 8.2 µg/kg. This detec-
bedload transport rates of about 0.1 to 4 tons per lion was well below the l ,000-µg/kg National
day were measured during June and July 1996. Academy of Sciences and National Academy of
These measurements were made after the annual peak Engineering guideline for the protection of wildlife
flow and probably do not reflect maximum bedload that consume fish (National Academy of Sciences and
transport rates for Black Gore Creek. The source of National Academy of Engineering, 1973). DDE was
most of the bedload was identified as traction-sand detected in 12 of 14 whole-body fish-tissue samples
material from Interstate 70. Lorch determined that collected throughout the Upper Colorado River Basin
nearly 20 percent of the total traction sand washed during 1995 (Stephens and Deacon, 1998). The low
into Black Gore Creek originated from just two loca- concentration of DDE in fish tissue from Gore Creek
tions, and more than one-half of the total sediment (8.2 µg/kg) is similar to concentrations that ranged
input originated from 20 percent of the locations. from 6 to 15 µg/kg at five other sampling locations
Therefore, significant reductions in sediment transport in the Southern Rocky Mountains physiographic prov-
into Black Gore Creek may be possible by capturing ince, and is about one to two orders of magnitude less
sediment at relatively few locations before it reaches than concentrations at sites associated with agricul-
the stream. tural land use (Stephens and Deacon, 1998). The
SURFACE WATER 43
detection of DDE at the more remote sites in the U.S. Geological Survey, oral commun., 1998). The
Upper Colorado River Basin probably indicates that silver concentration in fish livers from site 29 was
widespread distribution is caused by atmospheric five times higher than the maximum silver concentra-
transport from areas of application. In 1993, DDE was tion observed nationally. Fish-liver samples were not
detected in a sample of sediment collected from the collected at the background sites on Gore and Polk
water hazard at hole number eight on the Vail golf Creeks, so comparisons cannot be made within the
course (Northwest Colorado Council of Governments, Gore Creek watershed.
1995). A repeat sampling in 1994 failed to detect DDE Because dissolved silver can be toxic at low
in sediment from the same location. levels to trout under certain conditions and because
Gore Creek is classified as a "Gold Medal fishery" by
Trace Elements the Colorado Division of Wildlife, additional samples
were collected at site 29 in April 1998 to verify the
Previous studies have concluded that both elevated silver concentration found in a brown-trout
streambed- sediment and fish-tissue samples are liver sample. Migration and mobility of fish compli-
needed for a complete assessment of the occurrence cate direct comparisons of land use and geology with
and distribution of trace elements (Deacon and trace-element concentrations in fish tissue. Therefore,
Stephens, 1998; Heiny and Tate, 1997; Carter, 1997). spring was chosen as the best time to collect additional
Streambed- sediment and fish-liver samples were fish samples to avoid the fall brown-trout spawning
analyzed for trace-element content from sites repre- season. Spring samples have a higher probability of
senting urban, mining, and background conditions being from resident brown trout instead of those that
in the UCOL in fall 1995 and 1996. Currently (1998) have recently migrated into Gore Creek from the Eagle
there are no State or Federal guidelines or standards River to spawn. Concentration of silver in brown-trout
for concentrations of trace elements in streambed liver was determined to be 16.7 pg/g, similar to the
sediment; however, the Ontario (Canada) Ministry of elevated silver concentration in brown trout from Gore
Environment and Energy (Persaud and others, 1993) Creek in 1995.
has developed guidelines for trace elements consid- To determine specifically whether silver
ered most toxic to aquatic life. Examples of trace in aquatic biota originated from natural or human
elements that can be toxic to aquatic life under certain sources in the Gore Creek watershed and(or) in the
duration and exposure levels are cadmium, copper, Eagle River, macroinvertebrate (caddisfly) samples
silver, and zinc. Samples of streambed sediment also were collected for silver analyses during the fish
collected at the mouth of Gore Creek did not exceed sampling in April 1998. Although some macroinverte-
these guidelines. Cadmium, copper, and zinc concen- brates drift downstream, the majority of the macroin-
trations in streambed sediments collected from site 29 vertebrate community is somewhat sessile. Therefore,
and background sites 1 and 36 (Gore and Polk Creeks) sampling the macroinvertebrate community may
were less than background concentrations calculated provide a better indication of upstream contaminant
for the UCOL (Deacon and Stephens, 1998). sources than sampling only fish. Samples were
Silver concentrations in streambed sediment collected at the mouth of Gore Creek, in the Eagle
also were low (less than 2.5 pg/g) at three sites in the River just upstream from the mouth of Gore Creek,
Gore Creek watershed. However, the concentration and in Brush Creek, a tributary to the Eagle River
of silver was elevated (19.7 pg/g) in a brown-trout near the town of Eagle. The three macroinvertebrate
liver sample at site 29 when compared to other sites sampling sites were chosen to estimate the bioavail-
in the UCOL (Deacon and Stephens, 1998). The silver ability of silver in Gore Creek, the Eagle River,
concentration in liver tissue from this site was more and a background site on Brush Creek. To minimize
than three times greater than the next highest concen- variability associated with rates of silver uptake
tration from a sample of liver tissue collected from the by different taxa, the same genus of caddisfly
Blue River in Summit County, Colorado, a stream that (Hydropsyche sp.) was collected at all three sites.
is known to be affected by mining land uses. In 159 Replicate samples were collected for quality-assurance
fish-liver samples collected during 1992-95 from purposes at each site and analyzed to determine
20 river basins throughout the United States, repre- variability within the sampling technique. Quality-
senting all land-use categories, the maximum silver assurance results indicated sample variability was less
concentration was only 3.6 pg/g (L. Rod DeWeese, than 5 percent between replicate samples for each site.
44 Gore Creek Watershed, Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
Caddisflies at the Brush Creek background from 5 to 100 gal/min but can exceed 500 gal/min
site contained silver concentrations of 0.04 µg/g, (U.S. Geological Survey, 1985). The combined yield
and caddisflies in the Eagle River and Gore Creek for the three wells in the ERWSD municipal ground-
contained concentrations of 0.13 and 0.67 pg/g, water supply system is 4,200 gal/min. Water-level
respectively. These results indicate that more bioavail- data were not available for these municipal wells,
able silver was present in Gore Creek than in the Eagle but water levels for five alluvial monitoring wells in
River or Brush Creek during winter/spring 1998. In the Town of Vail ranged from about 4 to 25 ft below
comparison, there were only 4 silver detections in land surface in 1997 (Lori Apodaca, U.S. Geological
49 caddisfly-tissue samples collected nationally by the Survey, written commun., 1998), indicating a shallow
NAWQA Program during 1992-95, and the maximum water table. Water levels were l to 5 ft higher in the
silver concentration was 0.60 pg/g (L. Rod Deweese, spring than in the fall.
U.S. Geological Survey, written commun., 1998). Data were not available for bedrock wells in
Although most of the 49 samples collected nationally the Gore Creek watershed. Precambrian-age basement
did not yield detectable silver, the laboratory reporting rocks are exposed in the eastern and northern moun-
limits were relatively high and ranged from 0.20 to tains of the Gore Creek watershed. Precambrian rocks
0.40 µg/g. Water-sample and streambed- sediment generally yield small quantities of water, suitable only
results discussed earlier indicate that background for domestic supplies, but water can discharge from
geology is an unlikely source of silver, but point or springs where the rocks are fractured (Voegeli, 1965).
nonpoint sources may be the source of silver in the The ERWSD well field consisting of three wells
Gore Creek watershed. Although silver concentrations provides most of the municipal water supplies for the
were elevated in two brown-trout liver samples Town of Vail (Tipton and Kalmbach Incorporated,
collected at site 29 during 1995 and 1998, a study 1990). The three wells, shown as site 68 in figure 23,
of silver toxicity determined that internal buildup are located near the confluence of Gore and Booth
of silver does not necessarily imply an impairment Creeks. The wells are hydraulically connected to
of biological function (Hogstrand and Wood, 1998). Gore Creek. Tipton and Kalmbach (1990) estimated
that operation of the well field for municipal water
supplies diverted 2,626 acre-ft from Gore Creek
GROUND WATER from October 1988 to September 1989. No estimate
of return flows was made for the 1988-89 period;
Ground-water-quality data were available for however, 1985-86 return-flow estimates indicated
only five shallow alluvial-aquifer monitoring wells that about 88 percent of well-field diversions from
and the Eagle River Water and Sanitation District's Gore Creek were returned to Gore Creek as treated
(ERWSD) alluvial municipal well field in the Town wastewater. Generally, there was a higher percentage
of Vail (fig. 23). The temporal scale of the data was of return flow to Gore Creek during the months of
limited; composite samples were collected from the October through May, when more consumptive water
municipal well field in 1988-89, one discrete sample uses such as lawn irrigation are negligible.
was collected from a single well from the well field in
1997, and two discrete samples were collected from
each of the five monitoring wells in 1997. The data Water Quality
from the 1997 samples included a variety of inorganic
and organic constituents, as well as bacteria and age- To assess the shallow ground-water-quality
dating information. conditions in the aquifer used for drinking-water
supply in the Gore Creek watershed, five monitoring
wells were installed in the alluvium along Gore Creek
Water Quantity as part of the UCOL NAWQA Program. These five
wells were each sampled twice for water quality in
Municipal wells completed in the alluvial April/May and October of 1997 (sites 67, 69-72,
aquifer in the Vail area provide most of the table 1, fig. 23). The wells were installed according
developed ground-water supplies for the Gore to NAWQA Program protocols (Lapham and others,
Creek watershed. Well yields from alluvial aquifers 1995) to minimize subsurface contamination and
in the Upper Colorado River Basin commonly range effects on ground-water chemistry due to well
GROUND WATER 45
i
39 40' . 106 15
~d
X71 i _
i
I G r69 U/
68
70 Golf course
J
- " 72 cwex~-
- _
• Ski area
6`_ _
7
EXPLANATION
URBAN ` -
RESIDENTIAL \J rte'
TRANSPORTATION. CUMMUNICA"PION, AND .tillR\'I(I ti •
¦ a
COMMERCIAL AND SERVICES
? OTHER URBAN (SKI AREA. GOLF COURS1
RANGELAND
SHRUB-BRUSHLAND OR MIXED RANGELAND
FOREST oe
DECIDUOUS FOREST LAND
EVERGREEN FOREST LAND A
El MIXED FORLS V L.-AND
39 32'30"
OTHER
MIXED TUNDRA '1j
BARE GROL .AI) OR IfNPOSI!D R0( K
¦ LAKES
0 1 2 3 4 5 MILES
- TOWN OF VAIL CORPORATE LIMIT
072 0 1 2 3 4 ti KILOMETERS
OROU ND-A~'An [R ti;A~41PI_ING SITI: AND IDEN'rIFIFI:
Figure 23. Ground-water sampling sites in the Gore Creek watershed, 1988-97.
construction and installation. Information from these and also a single sample collected from well R-1 of
shallow alluvial wells can be used to assess the effects the well field in August 1997 by the UCOL NAWQA
of land use on ground-water quality in the Town of Program (site 68, table 1 and fig. 23).
Vail. Additional water-quality data were available for Field properties measured by the USGS
27 periodic composite samples collected from the included temperature, pH, dissolved oxygen, turbidity.
ERWSD municipal well field during= 19,88 and 1089 ,pecific conductance. .Ind ~ilkalinity. Samples from
46 Gore Creek Watershed. Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
each well were analyzed for major ions, nutrients, 1997. For example, at site 70, Gerald R. Ford Park,
trace elements, radon-222, DOC, 87 pesticides, and spring and fall nitrate concentrations were 2.47 and
87 VOCs (Apodaca and Bails, 1999; Timme, 1995). 0.12 mg/L, respectively. All sites with higher concen-
Samples also were analyzed for total coliforms trations in the spring were associated with recreational
and Escherichia coli (E. coli) using the mENDO land use, either public parks or the golf course. The
and NA-MUG methods (American Public Health maximum nitrate concentration of 2.82 mg/L was at
Association and others, 1992; Britton and Greeson, site 72 in May 1997 and was well below the USEPA
1989; U.S. Environmental Protection Agency, 1991). MCL for nitrate of 10 mg/L (U.S. Environmental
Samples that tested positive for total coliform colonies Protection Agency, 1996).
on an mENDO plate were transferred to an NA-MUG Trace elements. Trace elements were detected
plate and tested for E. coli. The April and May 1997 at all five sites, generally at low concentrations, except
ground-water samples were analyzed for chlorofluoro-
carbons (CFCs) to determine the age of the ground for dissolved iron and manganese (table 6). Ground-
carbons water samples for sites 67 and 71 contained 10 trace
water (Plummer and others, 1993). W
samples were analyzed at the USGS National Water elements each, while site 69 contained the fewest
Quality Laboratory in Arvada, Colo. The CFC samples number of trace elements at 6. Dissolved aluminum,
were analyzed at the USGS CFC Laboratory in barium, boron, chromium, and uranium were detected
Reston, Va. at all sites. Concentrations of aluminum and chromium
for the spring samples were nearly twice the concen-
Inorganic Constituents trations for fall samples at four sites. The USEPA
SMCL (U.S. Environmental Protection Agency, 1996)
A summary of the water-quality properties for dissolved iron (300 µg/L) and dissolved manganese
and constituents for the five monitoring wells in (50 µg/L) were exceeded in both spring and fall
the Gore Creek watershed sampled by the UCOL samples at site 67, Bighorn Park. Iron concentrations
NAWQA Program in 1997 (10 samples total) is were 8,500 µg/L and 2,900 µg/L, and manganese
provided in table 6. Also included are USEPA concentrations were 1,020 µg/L and 394 µg/L in
drinking-water standards and health advisories. Data the spring and fall samples, respectively, at Bighorn
for the five monitoring wells are summarized in table 6 Park. High iron concentrations in drinking water
and discussed as a group because the well construc- form red precipitates that stain plumbing fixtures
tion, sampling, and laboratory analyses were all and laundry, and high manganese concentrations
performed in a consistent manner among wells. Water- can affect the taste and color of the water and deposit
quality data collected from wells in the ERWSD black-oxide stains (Hem, 1992). These elevated iron
municipal well field will be discussed separately. In and manganese concentrations are probably a result
the monitoring wells, pH values ranged from 6.5 to of local geology and reducing conditions that may
7.8, with a median value of 7.4. Dissolved-oxygen exist at the site. Dissolved-oxygen concentrations
concentration ranged from 0.8 to 4.7 mg/L; only were lowest (1.2 and 0.8 mg/L) at Bighorn Park
one concentration was less than 1.0 mg/L. Specific- when compared to the other sites during spring
conductance values ranged from 265 to 557 µ6/cm, and fall. Also, high manganese concentrations
and the median was 325 µS/cm. The dominant major attributable to minerals in bedrock of the upper
ions were calcium and bicarbonate. Black Gore Creek drainage have been detected in
Nutrients. Nutrient concentrations for all five Gore and Black Gore Creeks (Advanced Sciences,
monitoring-well sites were low and less than USEPA Inc., 1990). Similar minerals may be present in the
drinking-water standards. Nitrate was detected in alluvium at Bighorn Park, site of the well nearest to
90 percent of the samples. The other dissolved nutrient Black Gore Creek.
species (ammonia, ammonia plus organic nitrogen, Radon-222. Radon-222, a noble gas, is a
nitrite, orthophosphate, and total phosphorus) were natural decay product of uranium and radium-226.
detected at most in 3 of 10 samples (table 6). Nitrate Large quantities of radon occur naturally as gases
concentrations ranged from less than detection to below the land surface and are mostly derived
2.82 mg/L, with a median concentration of about from uranium and radium-226 in the solids in an
0.49 mg/L. For sites 67, 70, and 72 (fig. 23), nitrate aquifer (Hem, 1992). In the Gore Creek watershed,
concentrations were higher in the spring than fall of radon-222 was detected in all five wells sampled
GROUND WATER 47
Table 6. Summary of the minimum, median, and maximum values for the water-quality properties and constituents of
monitoring wells sampled in the Gore Creek watershed, 1997
no data; less than; µS/cm, microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; pg/L, micrograms per liter; NTU, nephelo-
metric turbidity units; cols/100 mL, colonies per 100 milliliters; pCi/L, picocuries per liter; USEPA, U.S. Environmental Agency; MCL, maximum contami-
nant level; SMCL, secondary maximum contaminant level; PMCL, proposed maximum contaminant level; MCLG, maximum contaminant level goal; HA,
health advisory level]
Properties and constituents Number of analyses/ USEPA drinking-water
and reporting unit number of detections Minimum Median Maximum standards or health
advisories
Field properties
Water temperature (degrees Celsius) 10/10 3.5 9.3 11.5
Specific conductance, field (µS/cm) 10/10 265 325 557
Dissolved solids (mg/L) 10/10 146 186 329 500 (SMCL)
Hardness total (mg/L as CaCO3) 10/10 t30 155 300
Oxygen, dissolved (mg/L) 10/10 0.8 2.9 4.7
pH, field (standard units) 10/10 6.5 7.4 7.8 6.5-8.5 (SMCL)
Alkalinity (mg/L, as CaCO3) 10/10 114 136 273
Turbidity (NTU) 8/8 0.72 29 120
Major ions
Bicarbonate, dissolved (mg/L) 4/4 159 244 329
Calcium, dissolved (mg/L) 10/10 42 51 95
Chloride, dissolved (mg/L) 10/10 1.4 4.7 19 250 (SMCL)
Fluoride, dissolved (mg/L) 10/2 <0.1 <0.1 0.11 2.0 (SMCL)
Magnesium, dissolved (mg/L) 10/10 3.3 6.2 15
Potassium, dissolved (mg/L) 10/10 0.87 1.3 2.0
Silica, dissolved (mg/L as SiO2) 10/10 5.2 6.6 10
Sodium, dissolved (mg/L) 10/10 3.3 4.4 12
Sulfate, dissolved (mg/L) 10/10 3.2 12 28 250 (SMCL)
Nutrients
Ammonia, dissolved (mg/L as N) 10/2 <0.015 <0.015 0.047 30 (HA)
Nitrite, dissolved (mg/L as N) 10/1 <0.01 <0.01 0.044 1 (MCL)
Nitrate, dissolved (mg/L as N) 10/9 <0.05 0.489 2.82 10 (MCL)
Nitrogen, ammonia plus organic, 10/1 <0.20 <0.20 0.21
dissolved (mg/L as N)
Orthophosphate, dissolved (mg/L as P) 10/3 <0.01 <0.01 0.035
Total phosphorus, dissolved (mg/L as P) 10/1 <0.01 <0.01 0.032
Trace elements
Aluminum, dissolved (µg/L) 10/10 4.0 9.1 14 50-200 (SMCL)
Antimony, dissolved (gg/L) 10/0 <1.0 <1.0 <1.0 6.0 (MCL)
Arsenic, dissolved (gg/L) 10/0 <1.0 <1.0 <1.0 50 (MCL)
Barium, dissolved (gg/L) 10/10 99 173 233 2,000 (MCL)
Beryllium, dissolved (gg/L) 10/0 <1.0 <1.0 <1.0 4.0 (MCL)
Boron, dissolved (([tg/L) 5/5 22 24 30 - -
Cadmium, dissolved (µg/L) 10/0 <1.0 <1.0 <1.0 5.0 (MCL)
Chromium, dissolved (gg/L) 10/10 1.5 3.1 7.7 100 (MCL)
Cobalt, dissolved (gg/L) 10/3 <1.0 <1.0 3.0
Copper, dissolved (ltg/L) 10/4 <1.0 <1.0 1.4 1,300 (action level)
Iron, dissolved (µg/L) 10/6 <3.0 13.8 8,500 300 (SMCL)
Lead, dissolved (µg/L) 10/0 <1.0 <1.0 <1.0 15 (action level)
Manganese, dissolved (µg/l_) 10/6 <1.0 2.1 1,020 50 (SMCL)
Molybdenum, dissolved (µg/L) 10/4 <1.0 <1.0 3.5
48 Gore Creek Watershed, Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
Table 6. Summary of the minimum, median, and maximum values for the water-quality properties and constituents of
monitoring wells sampled in the Gore Creek watershed, 1997-Continued
no data; less than; µS/cm, microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; pg/L, micrograms per liter; NTU, nephelo-
metric turbidity units; cols/100 mL, colonies per 100 milliliters; pCi/L, picocuries per liter; USEPA, U.S. Environmental Agency; MCL, maximum contami-
nant level; SMCL secondary maximum contaminant level; PMCL proposed maximum contaminant level; MCLG, maximum contaminant level goal; HA,
health advisory level]
Properties and constituents Number of analyses/ USEPA drinking-water
and reporting unit number of detections Minimum Median Maximum standards or health
advisories
Trace elements-Continued
Nickel, dissolved (µg/L) 10/7 <1.0 1.2 14 100 (MCL)
Selenium, dissolved (µg/L) 10/0 <1.0 <1.0 <1.0 50 (MCL)
Silver, dissolved (µg/L) 10/0 <1.0 <1.0 <1.0 100 (SMCL)
Uranium, dissolved (µg/L) 10/10 1.6 2.0 3.5 20 (PMCL)
Zinc, dissolved (µg/L) 10/0 <1.0 <1.0 <1.0 5,000 (SCML)
Pesticides
Atrazine, dissolved (ltg/L) 10/2 0.002 0.002 0.002 3 (MCL)
Prometon, dissolved (µg/L) 10/1 0.006
Volatile organic compounds
1,2,4-TrimethyIbenzene (µg/L) 1015 0.01 0.02 0.05
4-methyl-2-pentanone (µg/L) 10/1 0.09
10/1 52.4
Acetone (tot) (µg/L)
Bromodichloromethane (µg/L) 10/1 0.006 100 (MCL)
Carbon disulfide (tot) (µg/L) 10/2 0.01 0.05 0.1
Chloroform (µg/L) 10/8 0.007 0.035 0.05 100 (MCL)
Chloromethane (µg/L) 10/1 1
Diethyl ether (tot) (µg/L) 10/1 0.04
Ethyl chloride (µg/L) 10/1 1.23
lodomethane (tot) (µg/L) 10/1 0.02
Methylene chloride (µg/L) 10/1 0.182
Methyl ethyl ketone (tot) (µg/L) 10/1 1.22
Tetrachloroethylene (µg/L) 10/1 0.004 5 (MCL)
Other constituents
Carbon, organic, dissolved (mg/L as C) 9/9 0.6 1.0 1.9
Total coliform bacteria (cols/100 mL) 10/1 <1 <1 5 0 (MCLG)
E. coli bacteria (cols/100 mL) 1/0 <1 <1 <1 0 (MCLG)
Methylene blue active substances 5/2 <0.02 <0.02 0.05
(MBAS) (mg/L)
Radon-222, total (pCi/L) 10/10 978 1,174 1,517 300 (PMCL)
(table 6). The radon-222 concentrations ranged from of uranium-bearing minerals in association with
978 to 1,517 pCi/L, and the median was 1,174 pCi/L. bedrock (Lori Apodaca, U.S. Geological Survey,
The highest radon-222 concentrations were at sites 71 oral commun., 1998). Radon gas is important environ-
and 72. Every sample exceeded the USEPA-proposed mentally because it can cause lung cancer. It is soluble
maximum contaminant level (PMCL) for radon, in water and can enter the home through water use
300 pCi/L, which has been withdrawn pending addi- (U.S. Environmental Protection Agency and others,
tional review. Throughout the Southern Rocky 1992). After a new standard for radon is established,
Mountains physiographic province, radon concentra- ground water in the Gore Creek watershed may need
tions typically are above 300 pCi/L due to the presence to be treated prior to human use.
GROUND WATER 49
Organic Constituents Other Constituents
Dissolved organic carbon. Ground-water Bacteria. Water samples from the five
DOC concentrations in the Gore Creek watershed monitoring wells in the Gore Creek watershed were
were low relative to alluvial wells sampled during analyzed for bacteria (total coliforms and E. coli). The
1997 in the Fraser River watershed. The DOC concen- presence or absence of bacteria reflects the sanitary
trations ranged from 0.6 to 1.9 mg/L, with a median quality of water and the potential health risk from
concentration of 1.0 mg/L, in the Gore Creek water- waterborne diseases (Meyers and Sylvester, 1997).
shed (table 6). In comparison, DOC concentrations Total coliforms are correlated with the existence of
ranged from 0.6 to 7.3 mg/L, with a median concentra- several waterborne disease-causing organisms but
tion of 3.4 mg/L, in the Fraser River watershed usually do not cause disease themselves. E. coli is
(Apodaca and Bails, 1999). more closely related to fecal contamination. Total
Pesticides. Only two pesticides, both in very coliforms were detected only once in the watershed,
low concentrations, were detected in three of the five at the Pedestrian Bridge, site 71 (fig. 23), in the fall.
wells sampled in the watershed (table 6). Even at low This sample also was tested for E. coli, and none were
concentrations, the presence of pesticides indicates found. The concentration of total coliforms for site 71,
that there are some land-use effects on shallow 5 colonies/100 mL, exceeded the maximum contami-
ground-water resources. Atrazine was detected twice nant level goals (MCLGs) of zero total coliforms
at a concentration of 0.002 µg/L at sites 69 and 72, in drinking water (U.S. Environmental Protection
and prometon was detected once, at site 67, at a Agency, 1996). According to Meyers and Sylvester
(1997), the detection of as few as 4 colonies of
concentration of 0.006 µg/L. Atrazine was detected total coliform bacteria per 100 ml, is a public
in the spring and fall, but prometon was detected health concern.
only in the fall. Atrazine has been applied statewide Methylene blue active substances. The fall
to corn and sorghum and fallow land, and prometon 1997 sample from each well was analyzed for meth-
has been applied to National Forest lands (Bohmont, ylene blue active substances (MBAS), which can be
1993). indicators of nonpoint-source contamination by waste-
Volatile organic compounds. Thirteen VOCs water. The analytical procedure used can detect the
were detected in the five wells sampled in the Gore presence of anionic sulfate- and sulfonate-based
Creek watershed. Most detections (21 of 25) occurred surfactants (Burkhardt and others, 1-995) that are found
during spring. Chloroform, with eight detections, in soaps and detergents. The MBAS concentrations for
was the most frequently detected VOC, followed by the five wells were very low, with a range from less
1,2,4-trimethylbenzene with five detections, all in than 0.02 to 0.05 mg/L (table 6). Sites 67 and 72,
spring. Chloroform is used in various manufacturing where MBAS concentrations were 0.05 mg/L, were
processes and as a solvent. 1,2,4-Trimethylbenzene is the only locations with MBAS concentrations above
also used in manufacturing. Ten VOCs were detected the detection limit of 0.02 mg/L. Data from the five
only once, with 80 percent of these detections occur- wells indicate that there is little to no nonpoint-source
ring during the spring sampling at site 67, Bighorn contamination of ground water in the vicinity of the
Park (fig. 23). Eleven different VOCs were detected at wells by wastewater.
site 67, four at site 71, and three at site 69. Drinking-
water standards for VOCs were not exceeded at any Other Ground-Water Data
sites. Acetone, detected at site 67 at a concentration
of 52.4 ltg/L, was the only VOC with a concentration In addition to the ground-water-quality data
greater than 1.23 µg/L (table 6). Additional investiga- collected at five monitoring wells, data are available
tion is needed to determine the source of this VOC from 27 composite samples from the ERWSD alluvial
and the others detected in the Gore Creek watershed. water-supply well field (site 68, fig. 23), collected by
The presence of VOCs in the five wells indicates that In-Situ, Inc., and Advanced Sciences, Inc., between
shallow alluvial ground-water quality is susceptible September 1988 and September 1989 (Advanced
to land-use effects. Sciences, Inc., 1990) plus a single sample collected
50 Gore Creek Watershed, Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
by the USGS in August 1997 at well R-1, which In the Gore Creek watershed, ground-water data
is part of the well field. Composite water samples are lacking because of the small number of monitoring
from the well field were measured for field properties wells (five, excluding municipal supply wells) and
(dissolved oxygen and specific conductance) and infrequent sampling. A comprehensive water-quality
were analyzed for hardness, dissolved copper, lead, analysis and characterization of ground water in the
mercury, silver, and zinc, and dissolved and total iron watershed cannot be accomplished with the ground-
and manganese. No USEPA drinking-water standards water data that are currently available.
were exceeded in these samples. Dissolved-oxygen
concentrations were relatively high for ground water,
ranging from 6.4 to 9.6 mg/L, indicating a possible Dating Analysis
hydraulic connection to Gore Creek. However, unless
careful sampling methods are followed, it is relatively The concentrations of chlorofluorocarbons
easy to inadvertently introduce dissolved oxygen (CFCs), which are manmade and used as aerosol
while compositing ground-water samples. Specific- propellants, blowing and cleaning agents, refrigerants,
conductance values ranged from 133 to 158 µS/cm. and solvents, can be used to date young ground water
Copper was detected three times at 2-3 µg/L. Total (Plummer and others, 1993). As a result of their initial
iron was detected in 10 of 27 samples, with concentra- use in the 1940's, CFCs were introduced into the
tions ranging from 20 to 490 µg/L. Dissolved iron and atmosphere, and atmospheric concentrations of CFCs
dissolved manganese, which are subject to USEPA continued to rise until the early 1990's. Because
SMCLs, were not detected. Silver was detected in ground water acquires CFCs through recharge, the
time of ground-water
sample at 0.1 µg/L, and lead was detected twice at recharge can be determined
1 and 2 µg/L. Mercury was detected once at a concen- using knowledge of the temporal variations in
atmospheric CFC concentrations. The CFC data were
tration of 0.1 µg/L. Copper, total iron, lead, mercury, obtained from the five ground-water monitoring wells
and silver were all detected in a sample collected on installed in the Gore Creek watershed in 1997. Data
September 20, 1989. for site 67 (fig. 23) indicated that the ground water
In August 1997, the USGS collected a ground- recharged from about 1940 to 1950. However, low
water-quality sample from well R-1 of the municipal dissolved-oxygen concentrations (0.8 mg/L), such as
well field and analyzed that sample for the same prop- that measured at site 67, may have resulted in an incor-
erties and constituents as the five monitoring-well rectly old age determination. The CFC data for sites 69
samples. No USEPA drinking-water standards were and 71 indicated similar ages in the ground water, with
exceeded in this sample; however, the radon concen- recharge occurring during the early to mid-1990's.
tration (1,239 pCi/L) exceeded the former USEPA Ground water at site 70 was slightly older, from the
PMCL. Dissolved oxygen was 2.85 mg/L, which late 1980's. The youngest ground water, at site 72, was
is much lower than the 6.4 to 9.6 mg/L range in dated as "modern" (only about 2 years old). Based on
dissolved oxygen for the composite ground-water the CFC data for the five wells, recharge to the aquifer
samples from 1988 and 1989. Specific conductance would have occurred from about 2 to about 50 years
was 267 µS/cm, higher than the 133 to 158 µS/cm ago. These dates indicate that changes in land-use
range of values measured in the composite samples. activities may not affect ground-water quality for 2
The dominant major ions were calcium and bicar- to 50 years.
bonate. Ammonia, nitrite, and orthophosphate Supplementing water-quality data with the age
were not detected. Dissolved phosphorus and of ground water can provide a better understanding of
nitrate concentrations were 0.01 and 0.29 mg/L, the link between land use and the water quality in the
respectively. Dissolved copper, lead, manganese, underlying aquifer (Apodaca and Bails, 1999). The
and silver were not detected above the 1.0-µg/L implementation of land-management practices prior
reporting limit. Dissolved iron and zinc concentra- to land development may help to reduce the potential
tions were 11.77 and 1.88 µg/L, respectively. DOC contamination from land-use practices. Ground-water
concentration was 0.3 mg/L. Pesticides, VOCs, total dating can be used in conjunction with information
coliforms, and MBAS were not detected, indicating about ground-water flow paths so that managers can
that ground water was not severely affected by land select strategies for maintaining or improving ground-
use during this time period. water quality.
GROUND WATER 51
AQUATIC ECOLOGY Water Authority, algal- and macroimertebrate-
community data plus ancillary data and information.
Since 1995, the USGS has collected algal-, such as physical habitat and field properties, were
macroinvertebrate-, and fish-community data at sites collected at 15 sites in the Gore Creek watershed
in the Gore Creek watershed to assess the effects of
urban development on aquatic life. Fish-community during September 1997 (fig. 24). These ]5 sites were
data were collected annually at site 29, the mouth of chosen to evaluate differences in the aquatic c01111111-
111i-Gore Creek, during August 1995, 1996, and 1997. In ties as Black Gore Creek flows from Vail Pass along
cooperation with the Town of Vail, Eagle River Water Interstate 70, and as Gore Creek flows from its head-
and Sanitation District, and Upper Eagle Regional waters through urban land uses in the Town of Vail.
106 22'30"
~o
39°40'
g
6 16 8 Y~l Q``~o` Greek
_ ON
8 r14 6~ Qh
Golf course 5
Mille n -
Ski area -
29~ J
38C-"
EXPLANATION
URBAN
RESIDENTIAL 36
TRANSPORTATION. COMMUNICATION, AND SERVIChS
COMMERCIAL AND SlIRVICLS 34
OTHER URBAN (SKI AREA. GOLF COURSE)
RANGELAND `
SHRUB-BRl1SHLAND OR MIXED RANGELAND
r R
FOREST 106'15'
DECIDUOUS FOREST LAND
¦ F',ERGREEN FOREST):\,ND
MIXED FOREST LAND
OTHER 39 32'30
MIXEDTUNDRA ~=s
® BARE GROUND OR EXPOSED RO('K Vail
LAKES Pass
TOWN OF VAIL. CORPORATE LIMIT 0 1 2 3 4 5 MILES
29
O
GROUND-WA'I'F:R .SAMPLING Sllli;lND IDIiN"rIFIER 0 1 2 3 4 5 KILOMETERS
Figure 24. Aquatic-ecology sites on Gore, Black Gore, and Polk Creeks.
52 Gore Creek Watershed, Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology. 1968-98
In any biological assessment of a stream, values rangy*cd from 62 to 293 µS/cm at the sampling
water-quality, water-quantity, and habitat data are sites. Within Gore Creek, specific-conductance values
needed to understand the status and potential of were higher in the downstream reaches than in
the aquatic community. Water quality is commonly the upstream reaches. Values for pH ranged from
regarded as a major limiting factor for aquatic commu- neutral to somewhat alkaline (7.05 to 8.78 standard
nities; however, the quality and quantity of physical units).
habitat also has a major influence. Aquatic and Efforts were made to select sites with similar
riparian habitat influences the structure and function habitat characteristics to minimize the effect of
of the aquatic community in a stream (Barbour and habitat conditions on biological community structure.
others, 1997). However, the sites on Black Gore Creek generally
Macroinvertebrate-community, habitat, received lower habitat rankings because of higher sedi-
discharge, and field-property data were collected at mentation and embeddedness of rocks in the stream
10 sites on Gore Creek, 4 sites on Black Gore Creek, channel when compared with sites on Gore Creek
and I site on Polk Creek during September 1997 (table 7). The increased sedimentation and embedded-
(I'ig. 24). Algal-community data also were collected ness reduces available living space for stream biota.
at the same 10 sites on Gore Creek and site 38 at In Black Gore Creek, this effect is attributable to the
the mouth of Black Gore Creek. The Gore Creek lame inputs of sediment from traction sanding on Vail
sites (sites 1 throw*h 29, fig. 24) represent back- Pass (Lurch, 1998).
ground conditions as well as various land uses,
including the more densely developed sections in
the Town of Vail. Site 1, which is located upstream Algae
from Interstate 70 and any land development, repre-
sents "pristine" background conditions (fig. 24). Benthic al-ac are important primary produce!
Sites 5 and 6 are downstream from the confluence
ofGore and Black Gore Creeks and bracket an open- in streams, can be an indicator of water-quality condi-
tions, and are a source of food for higher trophic level, such as macroinvertebrates and fish (Stevenson and
space park. Sites 8 and 12 bracket a golf course. others, 1996). Sites with sufticient, but not excessi~e.
Site 14 is downstream from the ~olf course and the algal production generally support greater abundances
Vail Mountain ski area, which is drained by Mill of macroinvertebrates and fish. Algal communities
Creek, and also is adjacent to residential and commer- respond rapidly to changes in stream conditions such
cia] land uses. Sites 16 and 18 bracket the wastewater- as available nutrients or sunlight. Because of this quick
treatment plant and relatively dense urban develop- response to stream conditions, algal-community struc-
ment. Sites 26 and 29 were selected to evaluate the ture can reflect prevailing water-quality conditions
cumulative effects of upstream urban, transportation, for time periods ranging from several days to weeks
and recreational land uses. Sites 33, 34, 37, and 38 (Porter and others, 199')).
were selected to assess the macroinvertebrate-
community structure in Black Gore Creek. Site 36
on Polk Creek was selected to represent background
conditions for Black Gore Creek, which receives runoff from Interstate 70 for much of the lerioli FIZ1.1
-
of the creek.`
Specific conductance, dissolved oxygen,
pH, and temperature were measured at each site
addition to discharge and velocity (table 7). Rapid s
hioassessment protocols (RBP) (Plaflcin and othci-,
1989) were used to qualitatively document habitat
conditions at all the sites; selected habitat properties
are listed in table 7. Field-properties data did not
indicate any water-quality concerns at the sampling -
sites. Dissolved-oxygen concentration was high;
sites were well oxygenated and percent saturation Algae samples are processed by scraping algal mate-
rial from stream cobbles. Photograph by Kirby Wynn,
ran-ed from 85.2 to 119.5. Specific-conductance U.S. Geological Survey.
AQUATIC ECOLOGY 53
Table 7. Summary of selected water-quality and habitat data for aquatic-ecology sampling sites in Gore. Black Gore, and Polk
Creeks
[µS/em, micro,iemals per centimeter It _'i de~re~, Crlsiu~: 11IL/1" milligram, per liter: fCubic feet per ,"uml: LIC_rcC, ('CI>iu,: It/,. fzet I)CI ,«oncl I
Gore Creek Black Gore Creek
Property Reference Reference Sites 33, 34, 37,
(site 1) Sites 5-29 (site 36) and 38
Specific conductance, pS/cm 62.0 96-257 1214.0 192-29;
Dissolved oxygen, mg/L 8.3 8.39-10.1 11? 8.4-11
Percent sattn"ation 85.2 86.4-101.1 108.3 108.4-119.
5
pH, standard units 8.1 7.05-8.78 7.1 7.02-7.7
Discharge, ft;/s 2.4 31-72 2.1 0.65-7.6
Temperature. ° C 6.0 43-10.5 7.5 6.6-10.6
Velocity, ft/s 1.66 1.71 1.63 1.402
Embeddedness scoreI optimal optimal suboptimal marginal to suhoptimal
Sediment deposition scorel optimal suhoptimal to optimal suboptimal marginal to cuhoptim;ll
Habitat assessment total' optimal suhoptimal to optimal optimal suhoptimal
~Bascd on yualitativc hahital scorinL, mrthuJ in N,dkin ;mil othrn i 19ti9i.
The relative biomass (biovolume/cm2) for community hioVOILime at all but one site, the biovol-
the major algal divisions is shown in figure 25A for Limes of individual diatom taxa classified as nitro~tien-
the 10 sites on Gore Creek. Diatoms account for more autotrophs were summed to determine if nitrogen
than 70 percent of the algal community at all sites availability is affecting the algal-community structure.
except site 5, where green algae is the dominant group. Increases in biovolume for these taxa can be related to Z7 C
Dense assemblages of green algae also were observed increased availability of inorganic nitrogen (Van Dam
at site 38 (at the mouth of Black Gore Creek and and others, 1994).
not shown in figure 25A), which is upstream from Figure 25B shows the biovolume of all diatom
site 5, indicating that water-quality factors favoring taxi that are classified as nitrogen autotrophs by
reen algae over diatoms had a similar influence Van Dam and others (1994). The error bars overlain
at both sites. The occurrence and biovolume of on the graphs represent the standard error of the mean
diatom taxa have been used as indicators of environ- of the nitrogen-autotroph diatom biovolume for the
mental factors such as nitrogen availability, pH, and two sites where triplicate samples were taken for
dissolved-oxygen concentration (Van Dam and others, quality-assurance purposes. The biovolume of
1994). Because diatoms accounted for most of the nitrogen autotrophs observed at sites 1-12 was consid-
erably lower than at sites 14-29, indicating increased
availability of nitrogen downstream. Increases in
' Vol hiovolume at sites 14 and 16 indicate an increase
in available inorganic nitrogen upstream from the
F
wastewater-treatment plant that is consistent with
41"
the moderate increases in nitrate concentrations that
, 't T.:. ~ were discussed previously in this report (fig. 17A).
-r J
BiOVO1LImeS were greatest at sites 18 and 26 and appar-
ently were affected by increased inorganic nitrogen
discharged by the wastewater-treatment plant. A large
llw decrease in nitrogen-autotroph biovolume occurred
! y
at site 29, the mouth of Gore Creek, when compared
to upstream sites 18 and 26. This decrease may be
caused by two related factors: decreasing amounts of
available inorganic nitrogen and grazing on algae by
An example of undisturbed (optimal) habitat conditions
including stream meanders and dense native vegeta- algivores (macro invertebrates that feed on algae). The
tion. Photograph by Ken Neubecker. decreasing nitrate in the downstream reaches of'Gore
54 Gore Creek Watershed, Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
EXPLANATION
Blue-green algae
A Green algae
100
cc 90 v afim~ r
O
Q
O 80
w 70
~U)
~ Z
J O 60
O
> >
p 50
00
J
Q
w C7 40
CC Q
w
IL 30
w
20
Q
J
W
10
0 -
29 26 18 16 14 12 8 6 5 1
SITE NUMBER
B
7x107
I Standard error
of the mean
w Z 6x107
2 w
U) (3
~ O C/) 5x107
wz~
2i O
o LL-
O q
U 4x107
L _
U w0
7
m l- F- 300
l- F- O Z O
w F-
U D
2x10
= Q 7
OQ
>O
d
FO 1x107
0 -
29 26 18 16 14 12 8 6 5 1
SITE NUMBER
Figure 25. (A) Relative percent biovolume of the major algal divisions and (B) total biovolume for nIL UyU autvt mph
diatoms at ~a l./ .g sites on the main stem of Gore Creek.
AQUATIC ECOLOGY 55
Creek was discussed previously in this report, and a Maeroinvertebrates
direct comparison of algivores and algal biomass in
Gore Creek is presented in the "Relations Among Because stream macroinvertebrates spend most
Water Quality, Aquatic Ecology, and Bed-Sediment of their life in the water column, they are strongly
and Tissue Chemistry" section of this report. affected by prevailing water-quality, streamflow, and
Similar to benthic algal-community structure, habitat conditions. Organisms living in a body of water
benthic algal biomass (the mass of organic matter are, in effect, sampling the water continuously; there-
attributable to algae that has accumulated on an area of fore, the community reflects the average water quality
substratum over time) can be an indication of water- over time (Davis and George, 1987). The Gore Creek
quality conditions, especially nutrients. Chlorophyll-a watershed contains abundant and diverse macroinver-
(photosynthetic pigment concentration of algae in tebrate fauna that are indicative of the favorable water-
milligrams per square meter) was used to estimate quality and habitat conditions.
and compare algal biomass among sites. According
to BiQcys (1996), median chlorophyll-a values in unen- Gore Creek
riched and moderately enriched streams are reported Abundance. Differences in the macroinvertebrate-
to be 1.7 and 21 mg/m2, respectively. Chlorophyll-a. community structure were observed among the Gore
biomass at sites 1-12 was less than 2 mg/m', and it Creek sites. Relative abundance of the five most common
~,,enerally exceeded 2 mg/m' at sites 14-29 (fig. 26), macroinvertebrate groups-Ephemeroptera. Plecoptera,
which corresponds with nutrient availability (fig. 26). Trichoptera, Coleoptera, Diptera-and non-insects can
Sites 8 and 12 bracket the golf course (fig. 24); be useful for determining water-quality conditions
however, the algal biomass did not increase at (fi(,. 27A). The Ephemeroptera (mayflies), Plecoptera
site 12. During similar, stable low-flow conditions (stoneflies), Trichoptera (caddistlies), and Coleoptera
in August 1996, Wynn and Spahr (1998) reported (beetles) exhibit relatively low tolerance to water-quality
gradual increases in nitrate concentrations of 0.07 degradation when compared to Diptera (midges) and
to 0.17 mg/L from site 1 to site 16. Figures 17A and non-insects (sludge worms) that generally are more
17B in this report also show some increase in nitrate tolerant (Barbour and others, 1997; Cairns and Dickson,
concentrations at site 16, relative to sites upstream. 1971; Johnson and others, 1993). Mayflies, stoneflies,
Sites 14 and 16 both show a response (increased and caddisflies dominated more than 80 percent of the
biomass) to nutrient enrichment that is consistent with community at sites 1, 5, 6, 8, 12, and 14, which is an
the moderate increases in the available nitrogen deter- indication of favorable water-quality and habitat condi-
mined by Wynn and Spahr (1998) and in this report. tions. There was a much-reduced relative abundance of
~ r
`~4yY ~ ~"Y' '1, fCldl^fi
Macroinvertebrate sample collection. Photograph by Kirby Wynn,
U.S. Geological Survey.
56 Gore Creek Watershed, Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
20
cc 18 I Standard error
w of the mean
a-
c)
16
Q
C7 14
J
J
Z UJ 12
W
Q w 10
0
a 8
m ~
J
} 6
d
cC 4-
0
J
2
U 2
x
29 26 18 16 14 12 8 6 5 1
SITE NUMBER
Figure 26. Chlorophyll-a biomass at sampling sites on the main stem of Gore Creek.
mayflies, stoneflies, and caddistlies at sites 16, 18, 26, Interstate 70 and where similarly low abundance levels
and 29, which are downstream from larger areas of urban were measured at site 38. Embeddedness at site 5 was
and recreational land uses. The increased dominance of rated as optimal; however, more sand was observed in
tolerant midges and sludge worms at these sites is an the interstitial spaces of the cobble stream bottom than
indication of point- and nonpoint-source contaminants at sites I and 6. Large increases in abundance were
in Gore Creek. recorded at sites 18, 26, and 29, which are downstream
In addition to relative abundance, analysis of total from the wastewater-treatment plant outfall and most of
abundance within the macroinvertebrate groups can be the urban areas in the watershed. Most of this increase is
useful for evaluating stream conditions and estimating attributable to large numbers of pollution-tolerant
secondary production (macroinvertebrates are the midges. Wuerthele (1976) also reported increased abun-
primary food source for fish). Figure 27B shows the dances of midges downstream from the wastewater-
total abundance (organisms per square meter) of macro- treatment plant and cate.-orized the quality of the
invertebrate groups at the Gore Creek sites. The error macro invertebrate community as reduced because of
bars overlain on the graphs represent the standard error organic enrichment. Wuerthele made this determination
of the mean of the total abundance for the six sites by comparing equitability, a calculated metric related to
where triplicate samples were collected for quality- Shannon-Weaver diversity that is more sensitive to
assurance purposes. The abundance of macroinverte- slight to moderate levels of water-quality degradation
brates at sites 1, 5, 6, 8, 12, 14, and 16 is variable, (Weber, 1973; Wuerthele, 1976). Equitability values
ranging from 117 to 1,415 organisms per square meter. above 0.6 indicate unpolluted streams, and values
Abundance at site 5 was less than 10 percent of the below 0.5 indicate some water-quality degradation
abundance at adjacent sites 1 and 6. Habitat scores, field effects on the macroinvertebrate community. In 1975,
properties, and streamtlow were similar for the three equitability values at three sites upstream from the
sites. The lower abundance at site 5 may be related more wastewater-treatment plant were 0.79-0.87, while
to physical factors (sediment deposition) than to chem- values at three sites downstream from the wastewater-
ical factors. Site 5 is downstream from Black Gore treatment plant were 0.33-0.45. The data collected in
Creek, which receives Iar-c volumes of sediment from 1997 show similar results with equitability values
AQUATIC ECOLOGY 57
A
100 ¦ EXPLANATION
Non-insect (sludge worm)
Diptera (midge)
Coleoptera (beetle)
w 80 Trichoptera (caddisfly)
U
z Plecoptera (stonefly)
0i Ephemeroptera (mayfly)
Z
D I Standard error of the mean
Q 60
f-
Z
w
U
CC 3
w
0- 40
W
Q
J
W
Ir 20
0 29 26 18 16 14 12 8 6 5 1
B SITE NUMBER
10,000
z i T .i
LU 1,000
(D
ow
ww i
UC[:.
zQ
Q~
od
zU)
D W 100 -
< CL
Q f
O
H
10 29 26 18 16 14 12 8 6 5 1
SITE NUMBER
Figure 27. Relative (A) and total (B) abundance of the major macroinvertebrate groups at sampling sites on the main stem of
Gore Creek.
58 Gore Creek Watershed, Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
.T
(14
21-
F T
N 4k
. Z
w Gore Creek near the golf course (site 12). Photograph by Ken Neubecker.
ranging from 0.68 to 0.93 at sites 1-16 and 0.29 to The observed upstream to downstream changes in
0.60 at sites 18-29, indicating that, based on equita- the caddistly community from predators to collector-
bility, water-quality conditions may not have changed filterers probably are caused by increases in organic
much since 1975. food sources suspended in the water column.
Functional feeding groups. The dominant Non-insects such as sludge worms are abundant in
feeding mechanisms for macroinvertebrates at a site can streams affected by industrial contamination or organic
be an indication of the water quality as it relates to avail- enrichment (Goodnight, 1973, Brinkhurst and Gelder,
able food resources such as coarse (CPOM) or fine 1991; Johnson and others, 1993). The relative abundance
(FPOM) particulate organic matter or algae (Cummins of sludgy=e worms increases from less than 10 percent at
and Klug, 1979). Analysis of the relative abundance of sites 1-14 to about 30 percent of the macro invertebrate
the different functional feedinc- Rroups at sites can be an community at site 16 and remains elevated at sites 18-29
indirect measure of underlying water-quality factors (tig. 27A). In reference to the level of organic enrichment,
such as organic or nutrient enrichment. For example,
the water-quality conditions, with sludge worms ranging
a site dominated by predator organisms that survive from 20 to 25 percent, are still considered favorable at
by consuming other macroinvertebrates can indicate sites 18-29 according to Goodnight (1973). However,
water quality that supports an abundance of prey
organisms. At these sites, the predators may outcompete the increase in abundance of sludge worms at site 16 is
the filter-feeding groups, which must acquire food by unexpected because the suspected source of organic
filtering FPOM from the water column. The dominant enrichment (the wastewater-treatment plant outfall) is
functional-feeding mechanism for caddistlies clearly located about 600 ft downstream from the site. There is
changes from predators at upstream sites 1-12 to clearly a response in the aquatic community to organic
collector-filterers at downstream sites 16-29 (tig. 28). enrichment upstream from the wastewater-treatment
This change from predators to col lector-filterers could plant, suggesting a point or nonpoint source of organic
reflect an increase in suspended organic material from material upstream from site 16. Potential sources Could
point and nonpoint sources as Gore Creek flows include leaking sewer lines, abandoned septic systems,
through urban areas. Stream velocity alone can cause or runoff from urban land-use areas. A study in 1966
changes in caddisfly community structure (Gallep, (Federal Water Pollution Control Administration,
1977). However, stream velocities at the sampling sites 1968) deternined that sludge worms composed less
ranged from about l to 2.5 ft/s, well within the upper than 1 percent of the macroinvertebrate community
and lower velocity limits cited by Gallep (1977). near site 26: however. a 1977 study indicated that
AQUATIC ECOLOGY 59
700
EXPLANATION
Shredder
w
Z 600 Scraper
Q w
O . Predator
Z w
m :2 500 Collector-filterer
Q
Q
d 400
0=
Dw
Q0-
U_ U) 300
QU)
LUZ
IL 200
00
2 ~
U 0
F 100
29 26 18 16 14 12 8 6 5 1
SITE NUMBER
Figure 28. Abundance of Trichoptera individuals, by functional feeding mechanism.
the abundance of the sludge worms had increased to Black Gore Creek
ch
about 1 I percent (Four Corners Environmental Research
Institute, 1976). The transport of sediment from the
Interstate 70 roadway to Black Gore Creek has
Collector-filterers and collector-gatherers such long been considered a primary water-quality and
as pollution-tolerant midges commonly are abundant at ecological concern for Black Gore Creek and. to a
sites affected by moderate levels of organic enrichment lessee extent. Gore Creek (Wuerthele, 1976: Resource
(Cairns and Dickson. 1971: Johnson and others, 1993). Consultants Inc., 1986: Britton, 1979; Weaver and
The percentage of collector-gatherers such as midges
(and other Diptera) ranged from 37 to 62 percent at Jones, 1995). Larch (1998) estimated that approxi-
sites 18-29 and was largest at site 18 downstream mately 4,000 tons of coarse sand to fine-gravel-sized
from the wastewater-treatment plant outfall (fig. 27A). sediment is transported annually into Black Gore
C
Midges accounted for about 8.5 percent of the dipterans reek. Lorch indicated that the aquatic habitat is
at sites 18 and 29 and about 60 percent at site 26, indi-
cating a response by the macroinvertebrate community compared to reference sites in Gore and Polk Creeks.
to organic material discharged to Gore Creek from the Finer grained substrate, one-third fewer pools, and
wastewater-treatment plant. The shift to midge domi- much shallower pools were caused by infilling of
nance also may be related to changes in physical habitat the stream channel by sand in Black Gore Creek
associated with increases in algal biomass (Hynes, 1964, (Lorch. 1998). Peak runoff during spring snowmelt
Cairns and Dickson, 1971). This relation between midge delivers much of the sediment to Black Gore Creek.
dominance and algal biomass also is supported by However, greater adverse effects to habitat may
figure 26. As compared with site 18, the macroinverte- occur during early fall (September-October)
brate community at sites 26 and 29 contained decreased when snowstorms that require traction sanding of
relative percentages of midges with similar increases Interstate 70 are followed by periods of warmer
in mayflies, stoneflies, and caddisflies (individuals weather. During these periods, snowmelt generates
less tolerant to organic enrichment), indicating some sufficient runoff to deliver sediment to the stream
improvement in stream conditions from site 18 to but not enough velocity to flush the sediment from
site 29. the pools. This results in accumulation of sediment
60 Gore Creek Watershed, Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
in pools that could serve as brown trout spawning water-quality and land-use factors were observed in
habitat and adversely affects the available over- the community structures for these data. However, the
wintering habitat for fish and macroinvertebrates available data represent only a relatively short period
(Lorch, 1998). of time and do not reveal temporal variations that may
Abundance. The 1997 macroinvertebrate study exist between seasons or from one year to the next.
partially supports Lorch's findings. The relative abun- A more comprehensive assessment of macroinverte-
b
dance of the major macroinvertebrate groups at site 36 rate and algal communities may have been possible
on Polk Creek and sites 33, 34, 37, and 38 on Black if additional data were available for more than a single
Gore Creek are shown in figure 29A, and the total year and season. Future macroinvertebrate and algae
abundance (organisms per square meter) is shown in sampling programs in the Gore Creek watershed
figure 29B. Site 36, the reference site on Polk Creek, should incorporate spring and fall data collection into
is diverse and abundant with more than 90 percent of the the sampling strategy. In particular, collection of addi-
community composed of relatively less tolerant mayfly, tional data immediately before spring snowmelt, in
stonefly, caddisfly, and beetle taxa. Site 33 also contains April, may provide valuable information on the condi-
abundant organisms but includes about 20 percent of the tion of the aquatic community at a time when stream-
more tolerant midges. Site 33 is downstream from Black flows are at annual lows and the winter recreational
Lake and several beaver ponds (a potential nutrient season is just past its peak.
source) and contained abundant growths of filamentous
algae (a preferred mid=e habitat) (Hynes, 1964). There- Fish
fore, a relative increase in midge abundance was not
unexpected. The abundance of macroinvertebrates at A fish community is an assemblage of fish that
sites 34 and 38 was much less than the abundance at share the same area of a stream and interact with each
site 37 (fib-. 29B). The difference in abundance may be other. The structure of a fish community is detennined
related to habitat and available food sources. Greater by the species present, their relative abundances, their
amounts of sediment were observed at sites 34 and 38 life stages and size distributions, and their distributions
than at site 37. Also, site 37 had accumulated leaf packs in space and time (Meador and others, 1993). Natural
(a food source), which can have a large positive effect variability in fish communities can be attributed to
on the abundance of macroinvertebrate shredders and differences in elevation, water temperature, water
collector-gatherers (Ward, 1992). chemistry, and physical habitat. The abundance and
Recent algae and macroinvertebrate data were species composition of fish communities can he influ-
limited to a single set of samples collected at sites enced by water quality and habitat modified by
in Septemher 1997. Patterns attributable to specific surroundin« land use (Deacon and Mire. 1997).
. $ K y
a" N
4
s .
Each fish is measured and weighed during an assessment of the fish
community at the mouth of Gore Creek. Photograph by David Manzella.
AQUATIC ECOLOGY 61
A
100 EXPLANATION
Non-insect (sludge worm)
90 Diptera (midge)
Coleoptera (beetle)
W 80 Trichoptera (caddisfly)
Z Plecoptera (stonefly)
U
Q 70 _ Ephemeroptera (mayfly)
O
Z r
co 60 x,
F-
Z
W 50
U
w
d 40
W
F-
J 30
W
tr
20
10
0
38 37 34 33 36
SITE NUMBER REFERENCE
B SITE
10,000
W
W
W
W
Q
d
U)
w 1,OOo
EL
U
Z
Q
C7
tr
0
w
U 100
Z
Q
Z
m
Q
J
Q
0
0
38 37 34 33 36
SITE NUMBER REFERENCE
SITE
Figure 29. Relative (A) and total (B) abundance of the major macroi nverte b rate groups in Black Gore and Polk Creeks.
62 Gore Creek Watershed, Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
The lower 4 miles of Gore Creek, downstream abundant in 1996 and 1997 as the RMNP reference
Red Sandstone Creek, have been designated a site. Large numbers of 1„ uw„ trout and mottled sculpin
Gold Medal trout fishery by the Colorado Division that are indicative of high-quality fisheries in the
of Wildlife, in recognition of the high recreational Southern Rocky Mountains ecoregion were at
value of the brown-trout community in that stream both sites. In Gore Creek, mottled sculpin abundance
reach (Weaver and Jones, 1995). As part of an ongoing for 1998 was ly double the abundance for 1996
water-quality and aquatic-ecology study by the USGS, and 1997. This in,,ase may be more a factor of
the fish community was assessed at site 29, at the nag„t ling efficiency than an indication of a change
mouth of Gore Creek, during August for three consec- in community structure. Water clarity was noticeably
utj v~::: years (1996-98). Results of these assessments better in 1998 as ..,,,,Pared to 1996 and 1997, and
are compared to fish-,,~,,,,,,anity data collected in mottled sculpin capture rates i,i,p,v%/ed O.R. Deacon,
August 1996 and 1997 at a reference site in the U.S. Geological Survey, oral commun., 1998).
Colorado River at Rocky Mountain National Park
(RMNP) (fig. 30). Both sites have optimal habitat
when assessed using the RBP qualitative habitat RELATIONS AMONG WATER QUALITY,
V,OLUL,oi (Platkin and others, 1989): however, the AQUATIC ECOLOGY, AND BED-
habitat in Gore Creek received a slightly lower rating SEDIMENT AND TISSUE CHEMia ti f
than the RMNP reference site because of on&,:...
sedimentation and lower quality riparian-zone vegeta- Analysis of water quality and aquatic ecology in
tion. Neither site has been part of a fish-stocking the Gore Creek watershed is enhanced by -L„LC.&,ating
program in recent years. The area uP~t,eam from interpretive results for va,;uus indicators of stream
the RMNP site does not have urban, „a„V)pU„auon, quality such as water, sediment, and tissue chemistry.
or rational land uses that affect water quality, algal-, mak., oM,/ertebrate-, and fish-cc ty struc-
and the water is somewhat more dilute, with 1„wc, ture, and stream-habitat conditions to develop a more
dissolved-solids and suspended-sediment cone entra- holistic understanding of environmental conditions
tions (Deacon and Mize, 1997). The trout P,,, ,ion and responses. Because these indicators are inter-
of the fish ck,,,,,,unity at Gore Creek was twice as depenL_..t, an int. L4,aLed approach can use multiple
450
Rocky Mountain Gore Creek EXPLANATION
400 National Park Mottled sculpin
350 Cutthroat trout
_ Brook trout
~ 300
LL ¦ Rainbow trout
LL
Q 250 Brown trout
OC
W
200
Z
Z 150
100
50
0
1996 1997 1996 1997 1998
YEAR
Figure 30. Comparison of fish-community structure at the mouth of Gore Creek with a refe site in Rocky
Mountain National Park.
RELATIONS AMONG WATER QUALITY, AQUATIC ECOLOGY, AND BED-SEDIMENT AND TISSUE CHEMb n1 63
lines of evidence to develop hypotheses and support can indicate stream conditions over several years
conclusions about effects of land use on the quality (Cuffney and others. 1993). Because of these varying
of aquatic resources. For example, algae are the time scales, it is important to consider interpretive
primary producers in Gore Creek, providing the results for these water-quality indicators within the
primary food sources to support higher trophic levels context of spatial and temporal scales of condition
such as macroinvertebrates and fish. Algae are depen- and response.
dent on adequate available resources (nutrients and The spatial distribution of nitrate concentrations
sunlight) to reproduce and grow. Many types of is consistent with the observed spatial patterns in algal
macroinvertebrates depend on benthic algae as a biomass and macroinvertebrate-comm unity structure.
microhabitat, food source, or both. The abundance Nitrate concentrations gradually increased from
of algae-dependent macroinvertebrates (algivores) the headwaters through the Town of Vail to the
may increase or decrease, depending on the abundance wastewater-treatment plant, with a large increase
of their microhabitat and food resources. In other immediately downstream from the wastewater-
cases, macro irive rtebrates feeding on algae can control treatment plant, followed by a large decrease at
the amount of aLae at a site (Deacon and Spahr, 1998; sites farther downstream to the mouth of Gore Creek
Gallep, 1977). Because the fish in Gore Creek are (fi(,. 17A). Algal biomass followed a similar pattern
insectivores, their abundance and growth rates are tied of moderate increases from the headwaters to the
to the abundance and composition of the macroinverte- middle reaches of Gore Creek, then larger increases
brate community. below the wastewater-treatment plant, followed by
Water, sediment, and tissue-chemistry and subsequent decreases in the downstream reaches
biological-community data each represent stream (fig. 26). The increased abundance in the macroinver-
conditions at differing time scales. Water samples tebrate community in the downstream reaches of Gore
represent water quality at the time of sample collec- Creek (fig. 27B) is most likely attributable to similar
tion, whereas algae integrate water-quality conditions increases in nutrients, algal biomass, and organic
over several days to weeks depending on hydrologic enrichment. Figure 31 shows the somewhat parallel
conditions (Porter and others, 1993). Nlacroinverte- changes in relative abundance of algivores and algal
brate data integrate chemical and habitat conditions biomass (chlorophyll-a). Under certain conditions,
over a span of many weeks to a year, while fish data algivores may be reducing the amount of algae at a
100 18
90 ? Algivores (sum of 16
I- percent scrapers Z_
Z 80 and collector-gatherers)
I 14
U Chlorophyll-a c~l1
w
LLJ 70 biomass Q
0 12 ~wW
> w U 60 m d V)w
~z 10 2i 2
Q~ 50
8 -j (D Q
~m
40 = J
J d
LU 6 C) 2E V)
Oc 30
O O
C7 20 4 =
2 U
10
0 • a 0
29 26 18 16 14 12 8 6 5 1
SITE NUMBER
Figure 31. Comparison of chlorophyll-a biomass with relative percent algivores at sampling sites
on the main stem of Gore Creek.
64 Gore Creek Watershed, Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
site. For example, both chlorophyll-a and percentage concentrations in the Gore Creek watershed is attribut-
of algivores increased from site 8 to site 14 as Gore able mostly to sedimentary bedrock mineralogy in the
Creek flows through the golf course and urban land- southern and western parts of the watershed (Steele
use areas. In this segment of Gore Creek, algal and others, 1991).
biomass was probably resource controlled (controlled Surface-water, ground-water, bed-sediment, and
more by growth factors such as available sunlight fish-tissue analytical results indicate few detections
and nutrients than by algivores). Algal biomass at and low concentrations of pesticides in the Gore Creek
sites 16-29 was more likely controlled by algivore watershed. DDE, an environmentally persistent orga-
grazing than by the availability of resources. There nochlorine insecticide, was detected at low levels in a
was a large increase in the percentage of algivores bed-sediment sample from the Vail golf course, in fish
at sites 16 and 18 but little increase in algal biomass, tissue, and in a water sample from Gore Creek. Since
despite relative increases in nutrient concentrations. 1996, several other pesticides and VOCs have been
At site 26, the percentage of algivores decreased and detected at low concentrations in water samples from
the algal biomass increased, suggesting reduced Gore Creek and alluvial monitoring wells.
grazing pressure on benthic-algal biomass. At site 29,
the percentage of algivores was about the same as at
site 26, but algal biomass was reduced by one-half. SUMMARY
The decrease in algal biomass may be related to two
competing factors: (1) decreased availability of nutri- Data were compiled from local, State, and
ents as indicated by water chemistry (fig. 17A) and Federal sources to assess the historical and current
increased nitrogen-autotroph biovolume (fig. 25B) and (1998) water-quantity, water-quality, and aquatic-
(2) increases in the total numbers of macroinverte- ecology conditions in the Gore Creek watershed.
brates (fig. 27B), including algivores (fig. 31). Most of the data and information were available
The fish community, in terms of abundance, from: (1) the U.S. Geological Survey, (2) the
probably benefits from the current (1998) level of Colorado Department of Public Health and Environ-
available nutrients. The fish community at the mouth ment, Water Quality Control Division, and (3) the
of Gore Creek is very productive, particularly when Eagle River Water and Sanitation District. Streamflow
compared to a reference site with similar habitat data have been collected at surface-water sites since
characteristics but much lower levels of available 1946. Surface-water-quality and aquatic-ecology data
resources. The amount of algae increased downstream have been collected at 66 sites from 1968 to present.
in Gore Creek in response to increased nutrient avail- Ground-water-quality data were more limited, with
ability. This increase in algae provides considerable data available for six sites. Ground-water samples
food resources to support large increases in the macro- were collected at one site in 1988-89 and six sites
invertebrate community, thereby providing ample food in 1997.
resources (aquatic insects) that are necessary to Located in the Southern Rocky Mountains
support a productive trout fishery. physiographic province, the Gore Creek watershed
Recent data indicate concentrations of many is a narrow valley surrounded by high mountains and
trace elements are low in the Gore Creek watershed. drains an area of about 102 square miles. Land-surface
Cadmium, copper, zinc, and silver concentrations elevation in the watershed ranges from about 7,700 ft
were detected at low concentrations in streambed- in the valley to about 13,200 ft near the Gore Range.
sediment and surface- and ground-water samples. Precipitation within watershed ranges between 20
However, elevated levels of silver in brown-trout fish- and 30 in/yr in the lower valleys to between 40 and
liver and caddisfly samples require further investiga- 50 in/yr in the higher peaks of the watershed. Geology
tion to understand sources and fate of silver in the in the headwaters of Gore Creek predominantly
Gore Creek watershed. Further comprehensive assess- consists of Precambrian-age igneous rocks, whereas
ment of silver or other trace elements in the watershed the southern and western parts of the watershed are
should consider including analyses of biological primarily sedimentary rocks of pre-Pennsylvanian
tissue. Iron and manganese concentrations were one Paleozoic, Pennsylvanian, and Permian age. Most of
to two orders of magnitude higher in ground-water the low-lying areas along Gore Creek are overlain with
samples than in stream samples, which supports the Quaternary-age alluvial deposits. Land cover in the
hypothesis that the history of elevated manganese watershed is primarily forested, with about 8 percent
SUMMARY 65
of the land area classified as urban or recreation. natural and regulated more by physical conditions
Most urban development is confined to a narrow in the aquifer. Manganese concentrations in surface
corridor along Gore Creek. Population increased about water appear to have declined from historical levels.
20 percent, to 4,454 people between 1990 and 1997. Concentrations of trace elements generally
This population density does not account for the were low in streambed-sediment and tissue samples.
substantial numbers tourists that add significantly In streambed-sediment samples, cadmium, copper,
to the population, primarily during summer and and zinc concentrations were below background
winter. levels reported for Upper Colorado River Basin in
Surface-water-quality property and constituent Colorado. Silver concentrations also were low in
data were available for field properties, major ions, streambed-sediment samples. However, the concentra-
trace elements, nutrients, suspended sediment, tion of silver was elevated in brown-trout fish-liver
bedload, organic carbon, pesticides, and volatile and caddisfly samples collected at the mouth of Gore
organic compounds (VOCs). Sample media for Creek when compared to samples collected from sites
surface-water chemical constituents were water, representing mining and other land uses in Colorado
sediment, fish tissue, and macroinvertebrate tissue. and the Nation.
Ground-water-quality property and constituent data Nutrient concentrations generally increased as
were available for field properties, major ions, trace water moved downstream through the Town of Vail;
elements, nutrients, organic carbon, pesticides, VOCs, however, the concentrations at the mouth of Gore
radon-222, bacteria, and chlorofluorocarbons (for age
dating). Aquatic-ecology data were available for Creek were typical when compared to national data
aquatic and riparian habitat, and algae, macroinverte- for urban/undeveloped sites. Nitrate concentrations
brate, and fish community. in Gore Creek were highest just downstream from
the wastewater-treatment plant, but concentrations
Average annual precipitation of 34 inches decreased at sites farther downstream, probably
in the Gore Creek watershed provides a water input because of dilution from tributary streams and nutrient
of about 185,000 acre-ft/yr. Surface-water outflow
averages about 55 percent of water inputs, and evapo- uptake by benthic algae. Since the 1970's, ammonia
transpiration accounts for the loss of about 40 percent concentrations have decreased and nitrate concentra-
of inputs. Consumptive water uses average about tions have increased in Gore Creek because of changes
9,300 acre-ft/yr, or 5 percent of water inputs. About in wastewater-treatment methods. Recent ammonia
80 percent of annual streamflow is derived from snow- concentrations at the mouth of Gore Creek were
melt and occurs during May, June, and July. Annual mostly below the 0.015-mg/L reporting limit. Ortho-
variability of streamflow is low, with coefficient of phosphate concentrations were low at the mouth of
variance ranging from 0.26 to 0.37 at Gore Creek Gore Creek and have remained relatively stable over
and tributary gaging stations. time. Total phosphorus concentrations were signifi-
Trace-element concentrations in surface cantly lower at the mouth of Gore Creek during
water generally were low in samples collected during 1995-97 when compared to concentrations from the
1995-97. Past exceedances of aquatic-life stream 1974-79 and 1980-92 time periods. Part of the differ-
standards for trace elements such as cadmium, copper, ence was probably caused by dilution from above-
iron, and manganese were attributed to soil distur- average streamflow observed during 1995-97. Recent
bance and natural, geochemical properties of the Gore total phosphorus concentrations are still somewhat
Creek watershed. Historically, manganese concentra- elevated when compared with the U.S. Environmental
tions commonly were elevated, or in exceedance of Protection Agency (USEPA) recommended level of
stream standards in Black Gore Creek. Manganese 0.10 mg/L for control of eutrophication in flowing
concentrations in Black Gore Creek primarily were water. However, total phosphorus concentrations at
attributable to the sedimentary geology of the area the mouth of Gore Creek were relatively low when
and likely were exacerbated by land disturbance compared to a national study of phosphorus in urban
during construction of Interstate 70 during the early land-use areas. Analysis of nutrient conditions in the
1970's. Manganese concentrations were one to two watershed was limited by high percentages of data that
orders of magnitude higher in samples from a ground- were censored at multiple reporting levels and by the
water monitoring well near Black Gore Creek than in lack of concurrent streamflow data. For some sites and
stream samples, suggesting the source of manganese is nutrients, the reporting limit was so high that no data
66 Gore Creek Watershed, Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98
were reported above that level, thereby limiting the An alluvial well field provides most of the
usefulness of the data for interpreting water-quality municipal water supply for the Town of Vail. These
conditions and trends. wells were sampled for field properties and trace
Surface-water quality in the Gore Creek elements. Water from the wells was well oxygenated,
watershed was good in relation to field properties. suggesting hydraulic connection with Gore Creek.
Dissolved-oxygen concentrations were high and Copper, lead, mercury, and silver were detected at
water temperatures were low throughout the water- low concentrations in several samples.
shed. Specific-conductance values generally were Two samples, collected during spring and fall
higher in the downstream reaches of Gore Creek and of 1997, from each of five alluvial monitoring wells
in tributaries to Gore Creek that drain sedimentary located throughout the Town of Vail, provided the
rock formations. Rock salt and magnesium chloride most comprehensive information about ground-
applied to Interstate 70 are primary sources for water conditions. Specific-conductance values in
some of the dissolved constituents affecting specific the samples ranged from 265 to 557 0/cm. Nitrite
conductance in Black Gore and Gore Creeks. Specific- and total phosphorus were detected at low concentra-
conductance values were relatively low in the water- tions in only t of the 10 samples. Orthophosphate was
shed when compared to other sites in the Upper detected in three samples, also at low concentrations.
Colorado River Basin in Colorado, although values Nitrate concentrations ranged from less than detection
have increased over the 1978 to 1992 time period in to 2.82 mg/L, with concentrations typically higher in
areas affected by urban runoff. spring than fall. Dominant major ions were calcium
Aggradation of sediment in stream channels, and bicarbonate.
rather than suspended sediment currently is the Concentrations of radon exceeded the
primary sediment concern in the upstream reaches 300-pCi/L USEPA proposed maximum contaminant
of the watershed. The median suspended-sediment level (which has been suspended pending further
concentration at the mouth of Gore Creek was only review) in all five monitoring wells and one of the
4 mg/L for 71 samples collected since 1995. About municipal water-supply wells. Radon concentrations
4,000 tons of coarse sand and fine gravel is washed above 300 pCi/L are typical for the Southern Rocky
into Black Gore Creek each year as a result of traction Mountains physiographic province because of the
sanding on Interstate 70. More than 50 percent of this presence of uranium-bearing minerals in Precambrian-
material is delivered to Black Gore Creek from only age rocks.
20 percent of the drainage locations. During the Total coliforms were detected in one
months of September and October, snowstorms that monitoring-well sample. The presence or absence
require traction sanding on Interstate 70 were followed of bacteria reflects the sanitary quality of water
by periods of warmer weather. During these periods, and the potential health risk from waterborne disease.
snowmelt generates sufficient runoff to deliver sedi- The sample that contained total coliforms was tested
ment to the stream but not enough velocity to flush for E. coli and none were found. Methylene blue active
sediment from pools. This process has resulted in substances (MBAS) were detected at low levels at
accumulation of sediment in streams reducing the two sites. Low levels of bacteria and MBAS indicate
available habitat for brown trout spawning as well as that there is little or no wastewater contamination
overwintering habitat for fish and macroinvertebrates. of alluvial ground water in the vicinity of the moni-
Sample results indicated organic constituents toring wells.
were not a primary concern in the Gore Creek water- Chlorofluorocarbon sample results indicated
shed. Median dissolved-organic-carbon concentrations that the age of the alluvial ground water in the
in surface and ground water were 1.3 mg/L and Gore Creek watershed ranged from about 2 to about
1.0 mg/L, respectively. Pesticides were occasionally 50 years old. These dates indicate that changes in
detected in low concentrations in surface-water, land-use activities may not affect ground-water
ground-water, bed-sediment, and whole-body fish- quality for 2 to 50 years.
tissue samples. VOCs also were detected at low Since 1995, habitat, algal-, macroinvertebrate-,
concentrations in surface- and ground-water samples. and fish-community data have been collected at
The presence of pesticides and VOCs in ground-water sites in the Gore Creek watershed to assess the
samples indicates that alluvial ground-water resources effects of urban development on aquatic life. Algal-
may be susceptible to human sources of pollution. and macroinvertebrate-community data, in addition
SUMMARY 67
to stream and riparian habitat data, were collected increases in macroinvertebrate abundance were
during September 1997 at 15 sites. These 15 sites observed at the three sites downstream from the
were selected to evaluate differences in the aquatic wastewater-treatment plant outfall and a majority of
community as Black Gore Creek flows from Vail Pass the urban areas in the watershed. Most of this increase
along Interstate 70, and as Gore Creek flows from its was attributable to large numbers of pollution-tolerant
headwaters through urban and recreation land uses midges. The macroinvertebrate community at the two
in the Town of Vail. Although efforts were made to sites farthest downstream had reduced percentages of
select sites with similar habitat conditions, the Black midges with similar increases in mayflies, stoneflies,
Gore Creek sites generally received lower habitat and caddisflies, indicating some improvement in
scores because of higher levels of sedimentation and stream conditions near the mouth of Gore Creek.
substrate embeddedness. Fish-community data were Sludge worms are abundant in streams affected by
collected annually at the mouth of Gore Creek during organic enrichment. Sludge worms accounted for less
August of 1995-97. than 10 percent of the macroinvertebrate community
The benthic-algal community was dominated at the six upstream sites and 20-25 percent of macro-
by diatoms at 9 of 10 sites in Gore Creek. The algal invertebrates at four downstream sites. One of the
community was responsive to small changes in avail- downstream sites with a large abundance of sludge
able inorganic nitrogen. Upstream sites containing worms was located upstream from the wastewater-
relatively low nitrate concentrations contained treatment plant outfall. Sources of organic enrichment
comparatively less algae (nitrogen-autotroph diatom at this site are unknown.
biovolume and chlorophyll-a biomass) than down- The macroinvertebrate community in Black
stream sites where nitrate concentrations were rela- Gore Creek showed signs of impairment by sediment.
tively higher. Large increases in algal biovolume and Macroinvertebrate abundance was reduced consider-
biomass were measured at sites downstream from Red ably at the two sites where streambed sediment was
Sandstone Creek, where nitrate concentrations were more evident; however, differences in abundance may
much higher due to point and nonpoint sources. No have been related partially to differences in habitat and
significant differences were observed in algal biomass food resources.
or community structure between sites located Patterns attributable to specific water-quality
upstream and downstream from the Vail golf course. and land-use factors were observed in algal- and
Differences in macroinvertebrate-comm unity macroinvertebrate-community structures. However,
structure were observed among sites in Gore Creek the available data collected in September 1997 only
by evaluating changes in abundance and dominant represent a relatively short period of time and do not
functional feeding groups of the major macroinverte- indicate temporal variations that may exist between
brate groups among sites. Ephemeroptera (mayflies), seasons or from one year to the next. A more compre-
Plecoptera (stoneflies), Trichoptera (caddisflies), and hensive assessment of macroinvertebrate and algal
Coleoptera (beetles) exhibited relatively low tolerance communities would be possible if data were available
to water-quality degradation when compared with for more than a single year and season.
Diptera (midges) and non-insects (sludge worms). The lower 4 miles of Gore Creek, downstream
More than 80 percent of the macroinvertebrate from Red Sandstone Creek, have been designated a
community at six upstream sites was composed of Gold Medal fishery in recognition of the high recre-
mayflies, stoneflies, and caddisflies, indicating favor- ational value of the productive brown trout commu-
able water-quality and habitat conditions. There was a nity. In comparison to a reference site in Rocky
large increase in relative percentages of midges and Mountain National Park, Gore Creek contained twice
sludge worms at four downstream sites on Gore Creek as many fish, primarily brown trout, rainbow trout, and
that represent relatively larger areas of urban and mottled sculpin. The enhanced productivity of the
recreation land uses. The increased dominance of fishery in Gore Creek is attributable to the responses
tolerant midges and sludge worms at those sites indi- of the algal and macroinvertebrate communities to
cates the occurrence of nutrient and organic enrich- increased nutrient availability. Large increases in
ment in Gore Creek. Part of the increase in midges was algal biomass in turn caused order-of-magnitude
probably related to changes in physical habitat associ- increases in the macroinvertebrate community, thereby
ated with increased algal biomass because benthic providing ample food resources (macroinvertebrates)
algae provide excellent habitat for midges. Large needed to support a productive trout fishery.
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and Aquatic Ecology, 1968-98
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