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<br />chapter 2
<br />SALINITY IN THE
<br />COLORADO RIVER BASIN
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<br />The Colorado River Basin
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<br />The Colorado River stretches 1,400 miles
<br />through the southwestern United States and
<br />northcrn Mexico before emptying into the Gulf
<br />of California. Its drainage basin covers a
<br />244,000 square mile area and includes portions
<br />of thc fivc dricst states in the nation (Nevada,
<br />Arizona. Utah, Wyoming, and New Mexico), the
<br />scventh driest (Colorado), and the desert por-
<br />tions of California. The climate of the Basin ex-
<br />tends from the snowpacked Rockies and high
<br />plains of Wyoming and Colorado to the arid
<br />desert of Arizona.
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<br />The water resources of the Colorado River
<br />Basin are inadequate in quantity to meet all
<br />legitimate demands for their use, even though
<br />water is customarily utilized by a succession of
<br />users as it flows downstream. The Colorado
<br />River waters currently irrigate 2.5 million acres
<br />in the Basin and thousands of acres outside the
<br />Basin through c~port. The river providcs water
<br />for about 2.5 million people in the Basin, and
<br />through export provides full or supplemental sup-
<br />plies to another population of 14.5 million and
<br />irrigates hundreds of thousands of acres of
<br />farmland outside of the Basin, primarily in
<br />southern Califotnia but also in eastern Colorado
<br />and central Utah. In addition, the river supplies
<br />1.8 million people and irrigates about a half a
<br />million acres in Mexico. Estimates from the
<br />seven Basin slates indicate that California,
<br />Arizona, Ncw Mexico, and Nevada have already
<br />or within the next several years will be fully using
<br />thcir Compact apportioomcnts. The growing
<br />demands for water by metropolitan populations
<br />and potential large demand by manufacturing in-
<br />dustrics and by mineral and energy developers,
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<br />in addition to the heavy dependence on water by
<br />agriculture, will cause an ever.growing gap be-
<br />tween water supply and need. This may force
<br />borh a curtailment of some demands and a
<br />reallocation of water supplies among potential
<br />users, resulting in some negative economic, so-
<br />cial, and environmental consequences.
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<br />Colorado River Salinity and Its
<br />Causes
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<br />A companion problem to limited supply is
<br />that of water quality. The Colorado River grows
<br />naturally salty from its headwaters through the
<br />seven basin states to the Gulf of California. In
<br />the Lower Basin states (Arizona, Nevada, and
<br />California) and in the Republic of Mexico,
<br />salinity can reach levels that reduce the river's
<br />usefulness and cause economic penalties to
<br />many water users. As expected economic
<br />development continues, salinity will increase
<br />unless offset by salinity control measures to
<br />renlOve over onc million tons of salt pcr year
<br />from the river.
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<br />Nearly half (47 perccnt5) of the river's
<br />salinity occurs naturally as thc river and its
<br />tributaries dissolve minerals and salts from river
<br />beds, receive runoff that has transversed saline
<br />land, and are fed by saline springs and
<br />groundwater returns. The hot dry climate in-
<br />creases river and reservoir evaporation, further
<br />concentrating these salts. Even without the
<br />development created by man, the Colorado
<br />would remain saltier than most other rivers in
<br />this country.
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<br />Irrigated agriculture is the major man-
<br />created contributor to Colorado River salinity
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<br />5U.S. I?epartment of the Interior, Bureau of Reclarnalion, Colorado River Water Quality Oflicc, Status Report:
<br />C.olorado River Water Oualiry Imnrovcmenl Proi'ram, Denver, Colorado: author, January 1983, p. 4.
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