8227

• UCREFRP Catalog Number: 8227
• Author: U.S. Geological Survey.
• Title: The Upper Colorado River National Water-Quality Assessment Program Surface-Water-Monitoring Network.
• USFW Year: 1996.
• USFW - Doc Type: \
• Copyright Material: NO

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National Water-Quality Assessment Program
Surface-Water-Monitoring Network

Upper Colorado River
Basin Study Unit
(shown in red)

National NA WQA Study Units
(shown in gray)

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Photograph by John Elliott

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U.S. Department of the Interior-U.S. Geological Survey

INTRODUCTION
The U.S. Geological Survey began full imple-
mentation of the National Water-Quality Assessment
(NA WQA) program in 1991. The long-term goals of
the NAWQA program are to (1) describe current
water-quality conditions for a large part of the
Nation's freshwater streams, rivers, and aquifers;
(2) describe how water quality is changing over
time; and (3) improve understanding of the primary
natural and human factors that affect water-quality
conditions (Leahy and others, 1990). To meet these
goals, 60 study units representing the Nation's most
important river basins and aquifers are being investi-
gated. The program design balances the unique
assessment requirements of individual study units
with a nationally consistent design structure that
incorporates a multiscale, interdisciplinary approach
for assessment of surface and ground water.

The Upper Colorado River Basin (UCOL) is
one of the 60 NA WQA study units; hydrologic and
water-quality assessments of the UCOL began in
1994. The study unit has a drainage area of about
17,800 mi2, and the primary river within the basin,
the Colorado River, originates in the mountains of
central Colorado and flows about 230 mi southwest
into Utah. Major tributaries to the Colorado River in
the study unit are the Blue, Eagle, Roaring Fork,
and Gunnison Rivers. The Colorado River is the
major supply of water to the southwestern United
States. Streamflow from the study unit accounts for
about 40 percent of the streamflow of the Colorado
River at Lees Ferry.

The UCOL study unit is divided almost equally
into twoyhysiographic provinces-the southern
Rocky Mountains in the eastern part and the
Colorado Plateau in the western part. The Southern
Rocky Mountain province is characterized by north-
northwest-trending mountains of crystalline rocks
that range in elevation from 11,000 to more than
14,000 ft. The Colorado Plateau province consists
of high plateaus of sedimentary rocks with eleva-
tions ranging from about 5,500 to 8,500 ft.

Land use, classified as rangeland or forest,
accounts for about 85 percent of the basin. The other
major land uses in the basin are agriculture, mining,
and urban. Surface water used for irrigation
accounts for about 97 percent of the total offstream
water use. A surface-water-monitoring network for
the UCOL study unit was designed considering the
critical natural and human factors that affect surface-
water quality in the basin.

WATER-QUALITY ISSUES
The following water-quality issues in the
UCOL study unit have been identified as high-
priority local-scale issues of concern to State and
local water-resource managers.

"Effects of increasing urban development
"Effects of hydrologic modifications
"Effects of metal mining
"Effects of nonpoint- and point-agricultural sources
"Effects of salinity from natural, agricultural, and
municipal sources
A national scale synthesis of the results
generated by each NA WQA study unit is an inte-
gral component of the NA WQA program. The
national synthesis allows a comprehensive assess-
ment of specific water-quality issues at a national
scale by comparative analysis of individual study-
unit findings. National synthesis has identified
pesticides, nutrients, and volatile organic contami-
nants to be the most important national water-
quality issues. These local and national issues will
partially be addressed by the use of a network of
surface-water monitoring stations in the UCOL
study unit.

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EXPLANATION

- - County Boundary
. - Basin Boundary

20 40 MILES
I I I I
20 40 KILOMETERS