9317 ‎(2)‎

• UCREFRP Catalog Number: 9317
• Author: Spahr, N. E., L. E. Apodaca, J. R. Deacon, J. B. Bails, N. C. Bauch, C. M. Smith and N. E. Driver.
• Title: Water Quality in the Upper Colorado River Basin, Colorado, 1996-98.
• USFW Year: 2000.
• USFW - Doc Type: Denver.
• Copyright Material: NO

I Salinity in the Colorado River Basin

A serious water-quality issue in the Colorado'River Basin is salinity defined'
as the concentration of dissolved mineral salts or total dissolved solids in
water. Salinity increases in the Colorado River in a downstream direction; the
dissolved-solids concentration is about 50 mglL in the upstream mountain I
areas and averages about 850 mglL at Imperial Dam, Arizona (Kircher, 1984).
In the UCOL, annual dissolved-solids loads in the Colorado River ranged.. I
from about 17,700 tons at Hot Sulphur Springs in the Southern Rocky Moun-
tains to more than 3,300,000 tons near the Colorado-Utah State line.
Major sources of salinity in the Colorado River Basin are mineral springs I
and nonpoint-source runoff. The major human influence is irrigated agricul-
ture. About II percent of the salt load in the Colorado/River near theUS.-
Mexico border is contributed from the Grand Valley and Uncompahgre Valley I
(lower Gunnison River Basin) agricultural areas (US. Department of the
Interior, 1999). Much of the soil in these areas is derived from and overlies the i
Mancos Shale, a saline marine deposit. Deep percolation of irrigation water I
and seepage losses from irrigation systems leach salt from the soil and shale, I
increasing the salinity of return flows. Salinity-control projects have been con-
structed throughout the Colorado River Basin, including two projects in the I
UCOL-the Grand Valley Unit and the Lower Gunnison Basin Unit.
As part of the study of salinity in the Colorado RiverBasin;trend~,in dis~
solved-solids concentrations in the basin have been investigated in numerous
studies (Vaill and Butler, 1999; Bauch and Spahr, 1998; Butler, 1996; Lieber- I
mann and others, 1989; Kircher, 1984). The most recent study (Vaill and
o Butler, 1999) determined that
3,500.000 7,000 z
cp~~~~~~o 8 since the 1960s there have
6.000 ~ been, in general, downward
~ trends inflow-adjusted annual I
5,000 ~ and monthly dissolved-solids
~ concentrations and loads in the
4,000 ::J '
o Colorado River Basin upstream
~
3,000 ~ from Lake Powell in Utah,
o
~ except in the Yampa River
2,000 ~ Basin. In the UCOL, there
ti w'ere downward trends both
1,000 -'
~ upstream and downstream
~ from the salinity-control
~ projects in the Grand Valley
and the lower Gunnison River
Basin. With the downward
trends as evidence, it appears
that both natural processes and
human efforts such as salinity-
control projects may be
decreasing salinity loading in
the Colorado River Basin.

C/)
z 3,000,000
l2
~
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w
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2,500,000

o LOAD
. STREAMFLOW

2,000,000

.

1,500,000

Southern
Rocky
Mountains

o

1,000,000

.

500,000

o

.

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~."
Q) .C
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a:~
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000
U(5
:t:
- DOWNSTREAM DIRECTION ------

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00
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Mean annual dissolved-solids loads increase greatly
between sites in the Southern Rocky Mountains and
sites in the Colorado Plateau. Data based on water
years 1970 to 1993. (Butler,1996; Bauch and Spahr,
1998)

20 Water Quality in the Upper Colorado River Basin