7641

• UCREFRP Catalog Number: 7641
• Author: U.S. Department of the Interior.
• Title: Quality of Water, Colorado River Basin.
• USFW Year: 1987.
• USFW - Doc Type: Progress Report No. 13,
• Copyright Material: NO

SUMMARY

The Quality of Water, Colorado River Basin, progress Report is prepared
and updated every 2 years to summarize the status of water quality in the
Colorado River Basin (Basin). Although several water quality parameters are
reviewed, salinity is by far the most serious and is allotted a major portion
of this report.

The Colorado River provides municipal and industrial water for over 18
million people in 7 states and irrigation water to over 1.7 million acres of
land. The Colorado River Basin reservoirs now have a combined storage
capaci ty of about 60 million acre-feet. While water quality is generally
adequate for industries, wildlife and livestock watering, and public water
supplies, nutrient loading to the main stem reservoirs is becoming a problem
as development and its ~ssociated pollution increase.

Increases in phosphorus and nitrogen compounds that are essential to the
growth of algae, the base of the food chain in reservoirs, are causing some
portions of the reservoirs to become eutrophic (overly productive).
Eutrophication of reservoirs can impair municipal, industrial, and
recreational uses by causing taste and odor problems, creating toxins, and
reducing the dissolved oxygen available for fish.

While nutrients in some reservoirs are causing them to become eutrophic,
reservoirs further downstream are becoming nutrient poor due to the trapping
of nutrients in the upstream reservoirs. This has the effect of reducing the
productivity of the fisheries by limiting their food supply. studies are
described in Parts III and IX which help to define and resolve some of these
problems in the Colorado River Basin.

Another major concern in the Colorado River Basin is the threat of
salinity in both the united states and the Republic of Mexico. Increases in
salinity are important in the Basin because of the impact of salinity on crops
and on municipal and industrial users. The higher salinity increases water
treatment costs, damages plumbing and fixtures, increases maintainance on
pumps and distributions systems, lowers crop yields, and increases the need
for special drainage facilities on farms.

Historically, the Colorado River carries about 9 million tons of salt
past Hoover Dam in 10 million ac~e-feet of water per year. The salinity comes
from natural diffuse sources, saline springs, and agricultural sources;
natural sources add almost half the total salt load, irrigation return flows
add over one-third, and a minor part of the salt load added is from municipal
and industrial sources.

Development in the Basin, which reduces the flow of the river and its
ability to dilute the salt in the river, is projected to reduce the flow in
the river by 2.7 million acre-feet per year by 2010, causing salinity to
increase dramatically. To maintain the salinity at acceptable levels in the
United States and to meet our obligations with Mexico, several laws have been
passed by Congress.

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