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Status of Soil Salinity in California

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Status of Soil Salinity in California it a major item in his joint presentation percent of construction, operation, and Although progress has been made, the to Congress and meeting with former maintenance costs. Basin states see the need for expanded President Nixon in 1972. In 1975, the Forum recommended wa- salinity control to maintain the numeric ter quality standards for salinity, includ- Proposed solutions criteria. Bills now before Congress would ing numeric criteria of 723 mg/L below authorize five additional salinity control The salinity problem has the potential to Hoover Dam, 747 mg/L below Parker units to be constructed by the Depart- cause lengthy legal and political battles Dam, and 879 mg/L at Imperial Dam. ment of the Interior, give the US. De- between the Upper and Lower Basin Their proposal also called for prompt partment of Agriculture specific author- states. The Lower Basin wants to pre- construction of the salinity control units ity for a program of on-farm Colorado vent salinity increases that would result authorized by P.L. 93-320, construction River salinity control measures in coop- from further upstream development; Up- of additional units upon completion of eration with local landowners, and pro- per Basin states are concerned that the planning reports, implementation of on- vide for 25 percent of the construction salinity issue could prevent future in- farm water management practices to costs to be paid by the Basin states. creases in their water use. control salinity, limitations on industrial In other efforts to control the river’s The states began to work together and municipal discharges, use of saline salinity, the Basin states have adopted a and with the federal government in the water for industrial purposes, and the policy calling for a no-salt return from late 1960s, and in the early 1970s several inclusion of the salinity components of industrial discharges and limiting the steps were taken to deal with the prob- water quality management plans devel- incremental increase permitted from lems. In 1972, the US. Bureau of Recla- oped by local governments. The salinity municipal discharges. The states have mation identified 16 salinity control standards were adopted by each of the also called for the use of saline and/or projects. These would be grouped into Rasin states and approved by the US. brackish waters in lieu of high-quality three categories: point source projects Environmental Protection Agency. water for industrial purposes. such as salt springs, diffuse sources that Two of the four authorized salinity covered extensive areas, and agricultural control units are under construction. Conclusion projects that involved lining of canals The Paradox Valley Unit, a point salt These combined efforts of the seven Ba- and on-farm measures. That year, the source in Colorado, will be controlled by sin states and the federal government seven Basin states adopted a policy to collection of highly saline brines and represent a significant step toward con- maintain salinity at or below 1972 levels their disposal through deep well injec- trol of salinity in the Colorado River and in the lower Colorado River while the tion. The Grand Valley Unit, also in reduction of the economic damage it states continued to develop their appor- Colorado, will reduce salt contribution causes. Through timely implementation tioned waters. The federal Clean Water by reducing the amount of deep percola- of all phases of the Basinwide program, Act of 1972 required the establishment of tion of conveyance system seepage and the salinity standards can be maintained salinity standards for the Colorado Riv- irrigation water into the underlying sa- in the lower river while the states contin- er. In 1973, the seven states formed the line soils. The US. Department of Agri- ue to develop their apportioned waters. Colorado River Basin Salinity Control culture has implemented a cost-share Forum to establish salinity standards program of on-farm water management Myron B Holburt, formerly Chief Engineer. Colorodo River Board of California, is now Assistont Generol Man and a Basinwide salinity control plan. to reduce salinity in Grand Valley and in oger of the Metropolitan Woter District of Southern Coli At the same time, negotiations were the Uinta Basin, Utah. fornia, Los Angeles under way to solve the salinity problem with Mexico. In 1962, salty drainage water and reduced river flows had in- creased salinity of the water delivered to Mexico from 800 to 1,500 mg/L. After several temporary measures, an agree- Status of soil salinity in ment was reached in 1972 providing that the average annual salinity of water de- livered to Mexico at the northerly inter- California national boundary would not be more than 115 ppm (plus or minus 30 ppm) over the average salinity at Imperial Virgil L. Backlund Ronald R. Hoppes Dam. In 1974, Congress passed the Colora- aline and sodic soils occur natu- vation agricultural lands drains into the do River Basin Salinity Control Act, rally in arid and semiarid re- problem areas, bringing salts and con- Public Law 93-320, to implement both gions, and as water develop- tributing to the high water table prob- the Mexican and domestic control pro- me; brings more land into irrigation, lem (see drawing). Difficulties increase posals. The Act authorized a desalting the salinity problem expands. The con- when surface irrigation water is of poor plant at Yuma, Arizona, to reduce the dition is aggravated by poor soil drain- quality, containing more than 300 to 800 salinity of the Wellton-Mohawk Valley age, improper irrigation methods, poor mg/L in total dissolved salts. Ground- drainage water and other facilities neces- water quality, insufficient water supply water supplies also are deteriorating in sary to meet the obligations to Mexico. for adequate leaching, and insufficient quality, because the groundwater over- The domestic salinity problem was ad- disposal sites for water that leaches draft occurring in these areas de- dressed by provisions for implementing salts from the soil. Problems caused by creases the amount of water and there- the salinity policy adopted by the Basin soil salinity are compounded when a fore increases the salt concentration. states in 1972, planning studies on 12 high water table impedes root develop- Recent surveys by the US. Depart- salinity control units, and constructing ment and concentrates salts in the al- ment of Agriculture Soil Conservation and financing four units by the United ready limited root zone. Service indicate that salinity affects States, with the Basin states repaying 25 Irrigation water applied to higher ele- 4.18 million acres of the 55.6 million 8 CALIFORNIA AGRICULTURE, OCTOBER 1984 Source: USDA. Soil Conservation Service Irrigation water applied to soils at higher elevations can have an impact on soils at lower elevations. The excess water drains to the more slowly permeable soils in the basin, contributing to salinity and high water tables. acres of nonfederal land in California field beans yield only 40 percent of Staff in 1977 (unpublished data) indi- (table 1). More startling, however, is their potential even at a low soil salinity cate that acreage with salinity prob- that 2.9 million of the 10.1 million acres level of 4 dS/m. Cotton, dates, and lems in the San Joaquin Valley (both irrigated in California are affected (ta- sugarbeets are not affected at the low federal and nonfederal land) will in- ble 2). These acreages are based on level; barley is very sensitive at this low crease to 3.6 million acres by the year soils that now have an electrical con- level only during germination. Many 2000 if corrective actions are not taken. ductivity of 4 decisiemens per meter growers have a production loss of 20 Installing drainage systems can reduce (dS/m) (about 2,500 mg/L salt) or more. percent without being aware of drain- production losses caused by high wa- Five of the nation’s top ten agricul- age and salinity problems, recognizing ter table and salinity problems, but in- tural counties are in the San Joaquin the situation only as problems become sufficient disposal sites for the saline Valley and have salinity and drainage more severe. drainage water (especially in the San problems. Crop yields decrease as soil Projections made by the Soil Con- Joaquin Valley), high installation costs, salinity levels increase. For example, servation Service River Basin Planning and agricultural economic conditions have kept landowners from carrying out needed measures. Disposal of saline drainage water thus represents the biggest challenge in solving California’s salinity problems. Both on-farm evaporation basins and district or regional facilities would re- quire areas equal to about 20 percent of the irrigated lands to be drained. (This estimate assumes that each acre with a high-water-table problem will discharge 1 acre-foot of effluent each year and that evaporation from evaporation ba- sins will average 5 feet per acre per year. Each acre with a high water table will therefore require 0.2 acre for evap- oration.) Additional methods of disposing of saline water are being explored by re- searchers at the University of California and other institutions. They include a master drain to provide the necessary outlets for the water and the use of saline wastewater for cooling electrical energy plants. Virgil L Backlund 1s Water Management Engineer. and Ronald R Hoppes IS State Soil Screntrst, both wrth US Drpartment of Agriculture Sod Conseruation Service, Da L I\ California CALIFORNIA AGRICULTURE, OCTOBER 1984 9 .
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