7806

• UCREFRP Catalog Number: 7806
• Author: U.S. Department of the Interior.
• Title: Quality of Water, Colorado River Basin.
• USFW Year: 1997.
• USFW - Doc Type: Progress Report No. 18,
• Copyright Material: NO

SUMMARY

The Quality of Water, Colorado River Basin, Progress Report is prepared every 2 years to
summarize the status of water quality in the Colorado River Basin. The Colorado River and its
tributaries provide municipal and industrial water for more than 18 million people in the seven
Basin States and irrigation water to nearly 3 million acres of land. The threat of salinity is a
major concern in both the United States and the Republic of Mexico. Increases in salinity are
important in the Colorado River Basin because of its effect on crops and on municipal and
industrial users: Damages -in the 'Upper Basin and Mexico are unquantified, but damages in the
Lower Basin have increased to about $750 million per year.

The Colorado River Basin Salinity Control Act (Salinity Control Act) (Public Laws [PL.] 93-320,
98-569, and 104-20) authorizes the Secretaries of the U.S. Department of the Interior (Interior) and
U.S. Department of Agriculture (USDA) to enhance and protect the quality of water available in
the Colorado River for use in the United States and the Republic of Mexico.

Title I of the Salinity Control Act authorizes the construction and operation of a desalting plant,
brine discharge canal, and other features to enable the United States to deliver water to Mexico
having an average salinity no greater than 115 parts per million (ppm) +/- 30 ppm over the annual
average salinity of the Colorado River at Imperial Dam.

In addition to earlier, unit-specific authrorities provided under Title II of the Salinity Control Act,
P.L. 104-20 authorizes the Secretary of the Interior to implement a new, basinwide approach to
salinity control. Although originally authorized as a separate program, P.L. 104-127 authorizes
the Secretary of Agriculture to implement salinity control measures as part of the USDA's
Environmental Quality Incentives Program.

The 1996 Review, Water Quality Standards for Salinity, Colorado River System found that the
"flow-adjusted" salinity levels at the Hoover, Parker, and Imperial Stations were above the numeric
criteria levels of the salinity standards discussed in chapter 6. "Flow-adjusted" salinity represents
the salinity that would be expected under normal (average) flow conditions in the river.
Fortunately, the observed salinity levels continue to be below the numeric criteria because of
existing controls (621,400 tons per year) and favorable hydrologic conditions. However, once the
impacts of recent water developments work their way down through the reservoir system, salinity
levels are expected to exceed the numeric criteria by 418,200 tons per year.

Reclamation estimates that nearly 1.5 million tons of salt per year will need to be removed from
the river system by 2015 to maintain average salinity below the numeric criterion level of
879 milligrams per liter (mgIL) at Imperial Dam. Even with these controls in place, there will
still be temporary excursions above the numeric criterion of 879 mg/L due to the natural variations
in climatic conditions, hydrology, and water usage.

The Salinity Control Act directs the Secretary of the Interior to implement units based on cost
effectiveness (cost per ton of salt removal). The units under construction within the Bureau of
Reclamation (Reclamation) program are nearing completion and will have an average cost
effectiveness of $73 per ton. The U.S. Department of Agriculture program has averaged $44 per
ton through 1994. Both programs have been very effective and complement each other with