WSP07403

• File Number: 8270.100
• Description: Colorado River Basin Water Quality/Salinity -- Misc Water Quality
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 1/1/1985
• Author: USDOI
• Title: Quality of Water - Colorado River Basin - Progress Report No. 12 - January 1985 -- Part 1 of 2 -- Title Page through Part IX - page 128
• Water Supply Pro - Doc Type: Report/Study

PART III

CAUSES AND IMPACTS OF SALINITY

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Assuming a yield of 5.8 million acre-feet for the Upper Basin, this
leaves approximately 1.8 million acre-feet to be developed.

Consumptive use of water for irrigation within the basin and ex-
ports from the basin were responsible for the largest depletions of
the Colorado River, while reservoir evaporation and municipal and indus-
trial uses account for a lesser depletion.

Average water'use of the Colorado
for 1976-80[1]
(Unit--l,OOO)

River

Type of use
Reservoir evaporation
Irrigated agriculture
Municipal and industrial
Fish, wildlife~ and recreation
Transbasin exports
Deliveries to Mexico
Total

Ac re- fee t
2,114
3,473
271
50
3,525
2,847
12,280

.

The major part of the transbasin depletions in the Upper Basin is
made at higher elevat ions where the sali ni ty concentrat ions are very
low. This removal of high quality water results in the remaining flows
downstream becoming more concentrated even though some salts are removed
by the water delivered to another basin. Many transbasin diversions
have been made over the years and an additional number will occur in
the future.

Water exported from the Upper Basin during the period 1941-72 aver-
aged about 360,000 acre-feet per year. Completion of such large proj-
ects as the Colorado-Big Thompson, Duchesne Tunnel, and Roberts Tunnel
and more recent projects such as the San Juan-Chama, Fryingpan-Arkansas,
and Homestake resulted in increased exports to about 726,000 acre-feet
per year for 1976-80, with a peak in 1978 of 852,000 acre-feet.

C. Effects of Water Quality on Water Users

1. Recreation, Esthetics, and Fisheries

The major instream uses in the Colorado River include hydro-
electric power, propagation of fish and aquatic life, recreation (in-
cluding swimming, water skiing, boating, rafting, etc.), and esthetics.
A number of conflicts between water uses have become prominent issues in
recent years.

.

There can be many tradeoffs in water quality, eutrophication,
and esthetics both in the reservoir and downstream, depending on the
depth of reservoir withdrawal and the flushing rate. The depth of with-
drawal impacts the temperature and nutrient releases from a reservoir.
These releases can now be controlled by the use of selective withdrawal
structures; however, the optimum temperatures for cold water sport

14