WSP00390 - Laserfiche WebLink

Home Browse Search

PROBLEMS AND NEEDS Colorado River Water Quality The Colorado River at its headwaters in the mountains of north- central Colorado has a salinity (dissolved mineral concentration) of only about SO mg/L. The salinity progressively increases downstream as a result of water diversions and salt contributions from a variety of sources. In 1979, the salinity averaged about 810 mg/L at Imperial Dam, the last major diversion point on the Colorado River in the United States. The high salt load of 10 million tons annually in the Lower Colorado River Basin adversely affects more than 17 million people and about 1 million acres of irrigated farmland in the United States. Municipal and industrial water users and irrigators experience estimated direct and indirect annual economic losses of $472,000 (January 1981 prices) for each increase of 1 mg/L in salinity at Imperial Dam. The salinity also adversely affects water users in Mexico. The losses associated with municipal and industrial use occur primarily from increased water treatment costs, accelerated pipe corro- sion and appliance wear, increased soap and detergent needs, and decreased drinking water palatability. The Public Health Service recom- mends that drinking water contain no more than 500 mg/L of total dis- solved solids (TDS). For irrigators, high concentrations cause decreased crop yields, altered crop patterns, increased leaching and drainage requirements, and increased management costs. Agricultural losses, either through lower yields or increased production/management costs, begin when salinity levels of applied irrigation water reach 700-850 mg/L, depending upon soil conditions and the type of crop grown. Salt loading occurs as a result of weathering and the dissolution of soluable salts in soil and substrata. In addition, salt concentration occurs due to consumptive use, such as agricultural or industrial appli- cations of water in the basin. In the Uinta Basin, the application of irrigation water results in increased salt concentrations because of both salt loading and salt concentration. The historical salt load fluctuates annually with the overall basin water supply. As the following graph illustrates, since 1949 the general trend of salinity at Imperial Dam has been upward. Since 1970 the salinity has been on a downward trend however, possibly as a result of the construc- tion and initial filling of Colorado River Storage Project reservoirs, such as Glen Canyon. This is believed to be a temporary phenomenon and the projected salinity concentration levels through the year 2010 without the water quality improvement program are expected to follow the overall rising trend as shown on the following page. "\ . r .< ~~.. u'J,.I:ivl 10