Status of soil salinity in California by sck19707


									    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-   criteria. Bills now before Congress would
    Proposed solutions                            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 U S . 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 U S .        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 U S . 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           M y r o n B Holburt, formerly Chief Engineer. Colorodo
                                                                                                River Board of California, i s now Assistont Generol M a n
    and a Basinwide salinity control plan.        to reduce salinity in Grand Valley and in     oger of the Metropolitan Woter District of Southern Coli
        A t 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-
    ment was reached in 1972 providing that
                                                  Status of soil salinity in
    the average annual salinity of water de-
    livered to Mexico at the northerly inter-
    national boundary would not be more
    than 115 ppm (plus or minus 30 ppm)
    over the average salinity a t Imperial        Virgil L. Backlund      Ronald R. Hoppes
        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 U S . 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

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 a t the low         federal and nonfederal land) will in-
ble 2). These acreages are based on           level; barley is very sensitive a t 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-
                                                                                                  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 I S State Soil Screntrst, both wrth U S
                                                                                               Drpartment of Agriculture Sod Conseruation Service, Da
                                                                                               L I\ California

                                                                                                        CALIFORNIA AGRICULTURE, OCTOBER 1984             9

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