7378

• UCREFRP Catalog Number: 7378
• Author: Wydoski, R. S.
• Title: Potential Impacts of Alterations in Streamflow and Water Quality on Fish and Macroinvertebrates in the Upper Colorado River Basin.
• USFW Year: 1980.
• USFW - Doc Type: 77-147
• Copyright Material: YES

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the salinity problem (1972 Federal Water Pollution Control Act Amendments.

PL 92-500; 1974 Colorado River Basin Salinity Control Act. PL 93-320).

Recently. the U.S. Environmental Protection Agency (1971) reviewed the

water quality problem caused by minerals and outlined some management as-

pects for the Colorado River. It has been estimated that the salinity

results from two-thirds natural causes and one-third man-made causes.

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The salinity from diffuse sources. both natural and man-made. accounts

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for 84 percent. and that from point sources accounts for 16 percent--6 per-

cent from natural mineral springs and 10 percent from artificial drainage

(Utah Water Research Laboratory. 1975; Williams. 1975). Since only a

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LAKE MEAD
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small portion can be identified from point sources. it appears that only

a small quantity of salt can be reduced. Salinity has been increasing in

the Colorado River system for various reasons with about 10 million tons

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13 21 2t 37 41 13 fll fl9 77 II S3 101 109 117
MILES AIOVE DAM

going downstream annually. If the Environmental Protection Agency guide-

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lines for this river are to be met. then about 2.5 million tons per year

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will need to be removed. However. Unplementation of all salinity control

measures on the Colorado River will provide for a maximum reduction of

1975). Current damages to agricultural crops are estimated to be between

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Figure 5. Sediment Deposits in Lake Mead from the Colorado River
Between 1935 and 1948

about 1.6 million tons annually or about 150 mg/l at Imperial Dam (Bessler.

$110.000 and $230.000jor each mg/l increase in salinity at Imperial Dam.

California.

The relationship between streamflow and salinity must be understood

to visualize the problems confronting the upstream and downstream users

Source: H, R. Gould. Sedimentology, Lake Mead Comprehensive Survey,
1948-49 (Reston, Va., U,S, Geological Survey, 1954) fromJ. K. Neel, "Impact
of Reservoirs." in D. G, Frey, ed., Limnology in North America (Madison.
Wisc" University of Wisconsin Press. 1963) p, 583.

of water (U.S. Environmental Protection Agency (1971); Utah Water Research

Laboratory. 1975). For example. salinity of the water may decrease as the

flow increases. but the total amount of salt passing a particular point

may increase. The potential effects of increased salinity on fisheries

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