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I THE SOLUTION 4 costs. Agricultural losses (either through lower yields or higher production/management costs) begin when salinity levels of applied irrigation water reach 700 to 850 mg/L, depending upon soil conditions and type of crop grown. Annual flow- weighted average Location TDS (mg/L) Below Hoover Dam 723 Below Parker Dam 747 Below Imperial Dam 879 In the late 1960's and early 1970's, leaders at the regional and national levels began to recognize the total problem and to seek comprehensive solutions. THE SOLUTION In 1972, an amendment to the Federal Water Pollution Control Act, Public Law 92-500 (now known commonly as the Clean Water Act), sets forth a public policy embracing the restoration and maintenance of water quality, pollution effluent discharge limitation, and eventual zero pollution discharge. EPA interpreted the Act to require water quality standards, including bene- ficial use designations, numeric salinity criteria, and a plan of imple- mentation for the Colorado River. Numeric criteria were subsequently established at three stations by the Colorado River Basin Salinity Control Forum (Forum). The criteria and a plan of implementa- tion were adopted by each of the Basin States and approved by EPA. The criteria, set in terms of milligrams per liter of TDS, are shown in the following tabulation. To meet these criteria, under future conditions, approximately 1.0 million tons of salt annually will need to be removed from the river's waters. The overall strategy in meeting the standards is to prevent salt from entering and mixing with the river's flow. A number of agricultural, point, and diffuse sources of salinity have been identified throughout the Basin. The salinity control program will implement controls at those sites which contain salt sources that can be intercepted, reduced, and/or prevented from entering the river at least cost. In June 1974, Congress enacted the Colorado River Basin Salinity Control Act, Public Law 93-320, which directed the Secretary of the Interior to proceed with a program 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 Public Law 93-320 enables the United States to comply with its obligations under the agreement with Mexico dated August 30,1973 (Minute No. 242 of the International Boundary and