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<br />- -:-lfC:Z 18 2 <br /> <br />INTRODUCTION <br /> <br />BACKGROUND <br /> <br />The Colorado River basin salinity control program consists of two <br />subprograms, Title I and Title II, designed to control increasing <br />salinityl of the Colorado River. The program is a ~ajor undertaking, as <br />the Colorado River basin covers 243,000 square miles in the states of <br />Arizona. California. Colorado, Nevada. New Mexico. Utah, and Wyoming. <br />The River itself extends within the basin for about 1,400 miles, <br />providing water for 18 million people and 1.7 million acres of farmland. <br />Because the amount of water available from the River is limited, it has <br />been allocated among the basin states by judicial decisions and <br />interstate compacts. In addition, since the River naturally flows across <br />the international border, the Republic of Mexico also has an asserted <br />right to a share of the River's water. Mexico's entitlement to at least <br />1.5 million acre-feet2 annually was formally established by treaty in <br />1944 with the United States. Annual allocations of river water total <br />16.5 million acre-feet. even though the River's average annual flow is <br />estimated to be only 15 million acre-feet. <br /> <br />The addition of salt to the River is attributable to both nature and ~an. <br />Salinity occurs naturally because the River flows through areas of <br />salt-laden soil and because it is fed by highly saline tributaries and <br />springs. Prior to development, the natural salinity level of the River <br />near Yuma, Arizona, was estimated to be about 400 parts per million.3 By <br />1974, development of the River had then doubled the salinity level to <br />approximately 830 parts per million by adding new sources of salt and bv <br />depleting the River's flow. For example, irrigation water taken from th~ <br />River but not consumed by crops dissolves salts from the soils it passes <br />through and carries them back to the River, thus increasing its salt <br />concentration. At the same time, any water that evaporates or is <br />consumed by the crops cannot return to the River, and this leaves less <br />water available to dilute the remaining salt in the River. The water <br />users in Mexico have fared worse than those in the United States because <br />their water allocation has been significantly affected by farmlands in <br />Arizona. The irrigation drainage from those farms is so saline that it <br />increased the River's salinity level to a point where the crops in Mexico <br />were being damaged. Mexico formally protested this s:.tuation in 1961, <br />but attempts to mitigate the problem over the next 11 years were <br />unsuccessful. This caused Mexico's President to make a direct protest to <br />Congress in 1972, Congress reacted to the protest and to the <br /> <br />ISalinity is a measurement of the amount of dissolved solids or salts <br />present in water. <br /> <br />2An acre-foot of water is the amount required to cover an acre of land to <br />a depth of one foot (approximately 326,000 gallons). <br /> <br />3The level of salinity is g6'l'\erally expressed in parts per million or <br />~illigrams per liter (these measurements are essentially the same). <br /> <br />1 <br />