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0';2967 Present average salinity of the river varies from 50 mil- ligrams per liter (mg/L) at the headwaters to about 861 mg/L at Imperial Dam near Yuma, Ariz. The Bureau of Reclamation, currently investigating the river's sa- linity problems, projects future salinity levels ofl150 mg/L at Imperial Dam by the year 2000 unless cor- rective action is taken. Corrective Legislation Recent Federal legislation is aimed at alleviating some of the problems of the Colo- rado River. The Federal Water Pollution Control Act of 1972 and the Colorado River Basin Salinity Con- trol Act of 1974 established public policy and objectives for water quality manage- ment in the basin. For example. under the Fed- eral Water Pollution Control Act, salinity standards along the lower stem of the river have been set at 1972 levels. Title I of the Colorado River Basin Salinity Control Act authorized measures to en- able the United States to comply with international agreements with Mexico. A large-scale desalting plant With increasing salinity lev- els in the Lower Basin, eco- nomic losses also occur. These losses presently aver- age about $53 million per year and could increase to $122-$165 million by 2000 if no salinity control meas- ures are undertaken. Eco- nomic damages to agricul- tural, municipal, and indus- trial water users could amount to an average annual loss of more than $300,000 per mg/L increase in con- centration at Imperial Dam. Salt deposits on irrigation drain- age banks in Grand Valley, Colorado will be constructed near Yuma. Ariz. This plant. along with agricultural improve- ments. will assure that water delivered to Mexico will not exceed specified limits in excess of the salinity as measured at Imperial Dam. r ~! I~ Title II of the Colorado River Basin Salinity Control Act authorized initial construc- tion and exped ited study of basinwide salinity control programs. Appraisal and feasibility studies were start- ed under the Bureau of Rec- lamation's Colorado River Water Quality Improvement Program. The overall goal is to maintain Lower Basin river salinity at or below 1972 levels while the Basin States continue to develop compact-apportioned wa- ters. To attain this goal un- der future conditions to the year 2000, the removal of about 2.8 million tons of salt each year from the river system will be required. Control Units ,. I! I' ~ To help regulate the salinity level of the river, 17 control units are under investiga- tion. These include point source control which re- moves salt from localized areas such as mineral springs, wells. and geysers; diffuse source control wh ich involves land treatment. col- lection and disposal facili- ties. and watershed man- agement; and irrigation source control which re- duces salt loading and con- centration by improving irrigation efficiencies. Cooling water for power generation New types of distribution sys- tems will conserve water and decrease salt loads in irrigatior return flows