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<br />. <br /> <br />C) HISTORY OF WATER RESOURCE DEVELOPMENT (Continued) <br />CO <br />tot:>. <br />1\) As of this writing each of the Colorado River Basin States are <br />following their individual authority and procedures to adopt the 1978 <br />Revision as a part of their water quality standards. The Forum found <br />that the numeric criteria adopted in 1975 for the lower main stem sta- <br />tions are still adequate and the plan of implementation requires only <br />minor modifications from that adopted in 1975. <br /> <br />4. Relations With Mexico <br /> <br />. <br /> <br />The average annual salinity of the water delivered to Mexico at the <br />Northerly International Boundary increased in 1961 from about 800 mgll <br />to nearly 1400 mg/l and to over 1500 mg/l in 1962. The completion of <br />thg :j!rainage wells and subsequent pumping of 151,500 acre-feet (187 x <br />10 m ) of drainage water in 1961 from the Wellton-Mohawk District added <br />over 1 million tons (907,000 t) of salt to the Colorado River. The <br />digt3ict further increased their pumping to 213,000 acre-feet (263 x <br />10 m ) in 1962 and added over 1.7 million tons (1.5 million t) of salt, <br />If the flow in 1961 leaving Imperial Dam and arriving at the Northerly <br />International Boundary (NIB) had remained at the same volume as in 1960, <br />the salinity at the NIB would have been less in 1961. Since the flow in <br />1961 was limited to aP8r~ximately the treaty obligation, about <br />800,000 acre-feet (987 x 10 m ) less than in 1960, a larger salinity was <br />observed resulting in a water quality of nearly 1400 mgll at the NIB. <br />The reduced flow was the result of low runoff and the installation of <br />structures in the Colorado River Basin in the United States that allowed <br />retention of large volumes of water for future use. Approximately 75 <br />percent of the rise in the salinity at the NIB was caused by the <br />Well ton-Mohawk Drainage returns. The remaining 25 percent was caused by <br />the reduction in the excess deliveries to Mexico. <br /> <br />The increase in salinity resulted in negotiations between the <br />United States and Mexico, In March 1965, Minute No. 218 was signed and <br />approved by the two Governments. Beginning on November 16, 1965, <br />Well ton-Mohawk drainage flows were bypassed around Morelos Dam and <br />replaced by water from other United States sources during pe'i;i~s of <br />minimum flow which amounted to ab~ut 55,00g acre-feet (68 x 10 m ) per <br />year. The minimum flow of 900 ft Is (25 m Is) at the NIB occurs during <br />the winter months for a period not to exceed 180 days. This agreement <br />was in effect until June 30, 1972, and reduced the average annual <br />salinity of waters delivered to Mexico at NIB under the treaty to about <br />1,245 mgll. <br /> <br />. <br /> <br />On July 14, 1972, another agreement, Minute No. 241, was entered <br />into, This Minute provided that the United States would increase the <br />bypass of Well ton-Mohawk drainage, without charge against scheduled <br />Treaty de~illfries to Mexico, to the annual rate of lIB ,000 acre-feet <br />(146 x 10 m ) and substitute equal volumes of other waters of better <br />quality to be discharged to the Colorado River above Morelos Dam. This <br /> <br />24 <br />