WSP09197

• File Number: 8270.100
• Description: Colorado River Basin Water Quality/Salinity -- Misc Water Quality
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 1/1/1981
• Author: USDOI
• Title: Quality of Water - Colorado River Basin - Progress Report No. 10 - January 1981 -- Part 2 of 2 -- Part X - page 99 through end
• Water Supply Pro - Doc Type: Report/Study

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SPECIAL STUDIES (continued)

4. Two Dimensional Reservoir Modeling

The Water and
fiscsl year 1981,
possibly Lake Mead
for reservoirs.

Power Resources Service is planning to contract in
a two-dimensional reservoir model of Lake Powell and
to improve temperature and salinity modeling capability

Two dimensional reservoir modeling is necessary to more accurately
predict salinity levels throughout the system. The major reservoirs tend
to selectively route the high quality spring runoff and trap the cold
saline winter base flows which have greater density. These large seasonal
variations in salinity and temperature produce density currents which
result in significant horizontal and vertical total dissolved solids
variance in the reservoirs. Two-dimensional reservoir modeling together
with a comprehensive reservoir sampling program should provide valuable
data .for more accurately predicting salinity levels throughout the river/
reservoir system. This study is scheduled to last 2 years.

I. Geologic Factors that Affect Salinity in the Upper Colorado River
Basin

In 1977 the U.S. Geological Survey compiled a report for the Bureau
of Land Management that describes the effects of geology in the Colorado,
Utah, and Wyoming parts of the Upper Colorado River Basin on salinity
in the river system (U.S. Bureau of Land Management, 1978, p. 15-23).(2)

J. Salt Pickup and Transport 1n Surface Runoff from Rangelands and
Ground Water

The Bureau of Land Management (BLM) is continuing to study the process
of salt pickup and transport in surface runoff from rangelands and ground
water. The 1978-79 Salinity Status Report (Bently et. al., 1980) discusses
results and conclusions of BLM's efforts through 1979 fiscal year. (24)

I. Ground Water investigations

Recent investigations on the contribution of interflow to salinity
of ground water in arid and semiarid regions of western Colorado reveal
that recharge does not come from precipitation falling on large areas of
rangeland. Salinity profiles in the weathered materials suggested these
soils are not an avenue for recharge. Evidence from both regions indicates
the direction of net water movement in soils is upward rather than down-
ward. It is theorized recharge occurs when runoff of snowmelt on the upper
borders of the watershed intersects exposed bedrock. Data from a series of
observed wells shows that ground water moves along a contact between
bedrock and the soild profile.

The U. S. Geological Survey conducted an extensive ground water
study for BLM in that part of the Upper Basin above the confluence of the

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