WSP06755

• File Number: 8270.100
• Description: Colorado River Basin Water Quality/Salinity -- Misc Water Quality
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 1/1/1995
• Author: USDOI
• Title: Quality of Water - Colorado River Basin - Progress Report No. 17 - January 1995
• Water Supply Pro - Doc Type: Report/Study

Total

Upper Basin use Lower Basin use
(1.000 allyr) 1 (1.000 allyr)
812 1.255
2,312 5,101
203 841
0 30
669 4,063
3,996 11,290

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645,000 people. At the present rate of population increase, M&I sources will be
increasing salinity by approximately 133,000 tons per year by the year 2010.
However, most municipal wastes are relatively low in salt concentration in comparison
with natural, industrial, and agricultural sources. Complete elimination of such waste
discharges would be expensive when compared to other salinity control methods.

Consumptive Use of Water Increases Salinity

Addition of salts to the river system is not the only cause of increased salinity in the
Colorado River Basin. The consumption (depletion) of water reduces the dilution of
saline inflows to the river system, increasing the concentration of salinity. Water use
is evaluated as part of the Bureau of Reclamation's responsibilities in managing the
river system, The Colorado River Basin, Consumptive Uses and Losses Report[4]
summarizes water use in the Basin. Table 2 summarizes the Colorado River Basin
uses for 1981-85, including tributaries to the Colorado River in the Lower Basin.
Work is underway to update these estimates.

Table 2.-Water use in the Colorado River Basin (1981-85)

Type of use

Reservoir evaporation and channel losses

Agriculture (within basin)

Municipal and induslrial

Fish, wildlife, and recreational

Transbasin exports

1 Acre-feet per year.

With the exception of the Central Arizona Project (CAP), the Lower Basin has already
developed most of its water supply. CAP is the last major development to deplete
water from the Lower Colorado River (approximately 1.5 million acre-feet per year).
Agriculture use is the single largest cause of depletions of the Colorado River.
Exports, reservoir evaporation, and M&I uses also account for lesser but significant
depletions.

Most of the exports from the Upper Basin are made at higher elevations where the
salinity concentrations are very low. This loss of high quality water results in the
remaining flows downstream becoming more concentrated. Water exported from the
Upper Basin during the period 1941-72 averaged about 360,000 acre-feet per year.
Completion of such large projects as the Colorado-Big Thompson, Duchesne Tunnel,
Roberts Tunnel, and more recent projects increased exports to about 727,000 acre-feet
per year for 1976-80, with a peak in 1978 of 852,000 acre-feet.

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