WSP07728 - Laserfiche WebLink

Home Browse Search

CHAPTER I I NEED F'OR ACTION . 2. Salt concentration occurs from consumptive use, which re- duces water volume in the river without reducing the tota.l amount of salt it carries. Examples include municipal and industrial use, transpiration from crops and natural vege- tation, and evaporation. w .:.. 00 C) As the water is used and reused several times along the len~th of the river, these effects contribute to the increasing salinity. The process is likely to continue since the potential demands on the river exceed its dependable supply. The high salt concentration in the Lower Colorado River Basin ad- versely affects more than 17 million people and about I million acres of irrigated farmland in the United States. Affected most severely are municipal and industrial water users in the Las Vegas, Los Angeles, and San Diego areas and irrigators in the Imperial Valley of southern Cali- fornia who all experience economic losses. . According to a 1980 study by the Water and Power Resources Service (now Bureau of Reclamation), estimated economic losses in the Lower Colo- rado River Basin averap;e 5540,000 annually for each increase of I mg/L when salinity concentrations at Imperial Dam range from 875 to 1,225 mg/L (based on January 1983 prices). The losses consist of 5378,000 in munic- ipal and industrial losses and 5162,000 in agricultural impacts per mg/L, Losses associated with municipal and industrial use occur pril'lari ly from increased water treatment costs, accelerated pipe corrosion and appli- ance wear, increased soap and detergent needs, and decreased drinking water palatabi Ihy. For irrigators, the higher concentrat ions calise de- creased crop yields, altered crop patterns, increased leachin~ and drain- age requirements, and increased management costs. Other unestimated and indirect losses occur in the Upper Colorado River Basin, The historical salt load fluctuates annually with the overall ~asin water supply, Between 1949 and 1970. the general trend of the concen- tration at Imperial Dam was upward. Since 1970, however, the concentra- tion has decreased both as a result of Colorado River Storage Project (CRSP) reservoirs mixing high and low TDS water and as a result of a generally more moist weather pattern increasing the amount of water available to dilute the salts, The future salinity concentration at Imperial Dam through the ye.u 2010 without water quality improvement projects is expected to follow an overall rising trend as depletions continue to increase. In response to the Federal Water Pollution Control Act and its amendments (Public Law 92-500, 1972), the seven Colorado River Basin States adopted and the Environmental Protection ~ency approved 1972 salinity concentrations at three points on the Lower Colorado River as salinity control standards. The standards are shown in Table 1, . 8