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<br />000291 <br /> <br />Reportl to the Congress <br />By the Secretary of the Interior <br /> <br />Modifications to Projects of <br />Title 1 ofthe Colorado River Basin Salinity Control Act <br />(Public Law 93-320, As Amended, 43 U.S.C. 9 1571) <br /> <br />Introduction <br /> <br />In 1974, the Congress authorized and directed the Secretary of the Interior (Secretary) to <br />proceed with a program to enable the United States to comply with the agreement of <br />August 30, 1973 (Minute No. 242 of the International Boundary and Water Commission, <br />United States and Mexico) regarding the management of salinity of the Colorado River <br />water delivered to Mexico under the Mexican Water Treaty of 1944. Title I of the <br />Colorado River Basin Salinity Control Act (P.L. 93-320,43 U.S.C. 9 1571, June 24, 1974) <br />authorized construction ofthe Yuma Desalting Plant (YDP) near Yuma, Arizona, (See <br />Frontispiece Map) to meet the salinity control provisions of Minute No. 242 and to recover <br />saline agricultural drainage water from the Wellton-Mohawk Division of the Gila Project <br />for delivery to Mexico. The Act also authorized construction of a Bypass Drain to <br />transport untreated saline agricultural drainage water and the more saline wastewater (i.e., <br />the reject stream) from the desalting process to the Cienega de Santa Clara in Mexico <br />(Cienega) near the Gulf of California. <br /> <br />Because the Colorado River has had many years of surplus flow available, the YDP <br />operated for only a few months in 1992. With the exception of 1992 the U.S. salinity <br />control obligations to Mexico have been met through the Qxpass of about 108,000 acre-feet <br />ear2 of saline agricultural drainage water to the Cienega, wlthou ar e agamst the <br />, United States' Treat del. bli ation to Mexico an ou selective pum mot e <br />Iemaining Yu~Area a.gricultural dramage. _,.~cause" e amage wa er m the bypass <br />drain is not desalted and returned to the rive~?~~,Q,,~f~@penitiofl;resu1ts in the release,y ;d <br />trom Lake Mead of comparable Quantities ofwater?....wmchotheiwise would not be needed ' ,I <br />if the bypassed water was delivered to Mexico as a part of the U.S. Treaty delivery l~.~ <br />obligation. Were this substitution release from Lake Mead to continue indefinitely, the 1 \ 1', }f~ <br />declining storage in Colorado River Basin reservoirs could cause additional and/or larger ~ ). I (' ~ ~ <br />water supply shortages in the future to Colorado River water users in the United States. ~ l t \~~ <br />~{; <br /> <br />Although the Colorado and Gila Rivers experienced above-normal runoff during the 1980's <br />and 1990's, storage in the mainstem Colorado River Basin reservoirs has now dropped to a <br />30-year low. This reduced runoffhas caused mainstem reservoir storage to decline from <br />about 60 million acre-feet (full) in 1999 to the January 2003 level of about 37 million acre- <br />feet. Operational forecasts suggest that mainstem reservoir storage will further decline to <br /> <br />1 This Report was prepared for the Lower Colorado Region, Bureau of Reclamation, by Michael Clinton <br />Engineering of Las Vegas, Nevada. <br />2 The actual amount of water reaching the YDP in any year fluctuates above and below this quantity, which is <br />used in this report for analytical purposes only. <br /> <br />9 <br />