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Home , Coachella Canal, Salton Sea

Delta Mendota and Aqueduct water. The supply water averaged 234 mg/L in , and the soil water, assuming a doubling or tripling in con- Case history: Salton Basin centration due to evapotranspiration, would be expected to reach nearly 700 Jewel1 L. Meyer Jan van Schilfgaarde mg/L. However, measurements and model calculations demonstrated the soil water to be 7,000 to 8,000 mg/L. This is he Salton Basin extends 200 In March 1905, silt that had built up in water that would penetrate deeper into miles from San Gorgonio Pass in the River near the headgates the profile and that would be captured by T the north through the Coachella, south of Yuma, , diverted the drains to be discharged elsewhere or re- Imperial, and valleys to the first of several floods into the canal cycled for crop production. The 10-fold . The basin covers a system. Flood water flowed through the increase in concentration is attributed to drainage area of about 8,000 square canals and the into the dissolution of soil minerals, principally miles and at its deepest point is 273 Salton , cutting a new, 60-foot gypsum. Although a few crops could tol- feet below sea level - about the same gorge, the New River. The , erate such concentrations for selected as . nearly dry in 1904, filled to a level of periods, the long-term maintenance of The climate is characterized -195 feet; the sea covered 500 square irrigated agriculture using such waters is by long hot summers, short mild win- miles and was 80 feet deep by early 1907, doubtful. ters, and sporadic rainfall averaging when the Southern Pacific Railway In summary, the major effects of sa- only about 3 inches per year. If water Company finally closed the breach. linity on soil properties are swelling of can be supplied, the climate and alluvial The Imperial Irrigation District, soil clays, dispersion of fine soil particles, soil are ideal for many vegetable, fruit, formed in 1911, had consolidated most of crust formation, and decreases in water- and field crops. the mutual water districts under a single transmission properties. The amount of Irrigation water delivery to the Impe- entity by 1916 and enlarged its potential sodium adsorbed on the soil and the rial Valley began in June 1901. Within boundaries to over 1/z million acres. With amount of sodium and salt in the irriga- three years, over 150,000 acres were federal assistance, was tion water greatly influence the degree to being planted to barley, grain sorghum, built on the and the All- which salinity affects soil properties. alfalfa, and cantaloupes, despite prob- American Canal was constructed. Water lems with transportation and water de- delivery to the through Dennis E. Rolston, J W.Biggar, and Donald R. Nielsen are Professors, Department of Land, Air, and Water Re livery, and severe living conditions for these facilities started in 1943. sources, University of California, Davis. the new settlers. In contrast to the Imperial Valley,

The 8,000-square-mile Salton Basin, one of the most productive agricultural areas in the world, as seen by a Landsat camera. The Salton Sea serves as the for saline irrigation waters from the Imperial, Coachella, and Mexicali valleys.

CALIFORNIA AGRICULTURE, OCTOBER 1984 13 ry estimated that 150,000 acre-feet per year were lost during 1900-48 by seepage from the before comple- tion of the Coachella Branch of the All- American Canal through the eastern edge of the Imperial Valley. As waterlogging and salinity problems increased, open ditch drain construction began in about 1921, supplemented with attempts at subsurface drainage. In the 1940s, federal agencies, the University of California, and local interests cooperated in an extensive drainage program. By 1981, over 27,800 miles of drain tile (tube) had been installed under 427,500 acres of Imperial Valley land - equiv- alent to drains spaced 125 feet apart. Drainage removes that amount of wa- ter that must be passed through the crop root zone to satisfy the leaching require- Nearly dry in 1904, the Salton Sea was filled to a level of 195 feet below sea level by flooding of the Colorado River. It later dropped but has risen gradually in recent years ment. If, for example, a field receives 2 to its current level of approximately -227 feet. feet of water and the leaching require- ment is 10 percent, 0.2 foot of water must pass through the root zone and be re- development in the nitic alluviums formed from recent moved. Leaching may take place started slowly in about 1900 with use of outwashes of intermittent streams of the throughout the cropping season as part fresh water from artesian wells. When it southern Sierra. The Imperial Valley has of normal irrigation, but if not enough is was recognized that irrigation by wells fine-textured lacustrine or basin soils applied or if the soil takes in water too would deplete groundwater and limit de- formed from the intermittent flooding of slowly to keep up with crop demand, velopment, the Coachella Valley County the Colorado River through the Alamo additional leaching is needed off-season. Water District in 1934 contracted with and New Rivers into the . Between 1946 and 1950, an area of 9,000 the US. Government to construct the Although their soil conditions differ sig- to 20,000 acres in the Imperial Valley Coachella Branch of the All-American nificantly, both valleys drain into the was leached by continuous ponding. Canal to deliver Colorado River water to landlocked Salton Sea, and both have Now, because of better drainage and man- the Valley. By the time the project was salinity problems where drainage is inad- agement, the area ponded is negligible. completed in 1948, 23,000 acres were equate. Average salt balance calculations de- being irrigated. The area irrigated has In Coachella, adverse effects of high termined from input-output studies, as since expanded to 60,000 acres and water tables and resulting high soil salin- in the Coachella Valley, may be mislead- pumping of ground water has been great- ity led to a drainage program beginning ing: some fields may be “salting out” ly reduced. in 1950. By 1970, well over half of the while others are adequately leached; also, Coachella Valley soils are coarse gra- land was subsurface-drained. Field stud- salts of geologic origin or those stored ies by the US. Salinity Laboratory and underground long before irrigation start- the water district indicated that, before ed may affect the salt-output figures 1963, irrigation water added more salt to while there is still excessive accumula- the land than was removed to the Salton tion in the root zone. Extensive calcula- Sea in drainage water. As the drainage tions made in the Imperial Valley during system expanded, the salt balance shift- the 1970s by Rhoades and Kaddah, of ed in the other direction in 1963. The the US. Department of Agriculture Agri- relatively coarse-textured soils simplified cultural Research Service, showed that the design and construction of the drain- only one-third of the salt discharged to age system, and the closed-conduit water the Salton Sea came from the root zone. conveyance system helped minimize wa- The rest came from the groundwater. ter spills. The much finer soils in the Imperial Present situation Valley made drainage systems more diffi- The Imperial Valley has 460,000 irrigat- cult abd more expensive to construct. ed acres, 130,000 of which are double- The open-ditch conveyance system, with cropped. The Imperial Irrigation District essentially no storage except in the ca- receives 2.8 million acre-feet of water per nals themselves, made it difficult to year in the All-American Canal and de- avoid some spillage. Leakage from canals livers 2.6 million acre-feet of this to farm added to a water table problem. For headgates, for an average application example, a study by the Imperial Irriga- depth of 5.6 feet. This water contains, on tion District and US. Salinity Laborato- average, between 850 and 900 mg/L of A sophisticated irrigation and drainage salt. system maintains the salt balance in the About a million acre-feet are dis- Imperial Valley. Growers have spent charged to the Salton Sea, with an aver- millions of dollars to line irrigation canals age salt content of about 3,000 mg/L. and reduce water losses. Evaporation has concentrated the salin- C.A. Beasley 14 CALIFORNIA AGRICULTURE, OCTOBER 1984 The rising water level in the Salton Sea has flooded adjacent farmland and recreational Below: Salt added to Imperial Valley soil Max Clover property and has jeopardized the Sea’s role as a collecting basin for saline drain water. by irrigation is leached out by continuous Evaporation of the land-locked Sea, shown here at the entrance of the Alamo River, has or intermittent ponding. “Berms” hold made it more salty than the . water in fields. ity in the sea to nearly 40,000 mg/L, slightly more than that of sea water. However, since the drought years of the 1930s, evaporation has not been suffi- cient to prevent a slow, somewhat irregu- lar rise in the Salton Sea’s water level (see graph). Storms have also caused dramatic increases: in September 1976, the water level rose 0.8 foot after a single storm; in August 1977, 0.5 foot. In the spring of 1981 and 1982, the level was above -227 feet. This rise has caused flooding of farmland as well as recrea- tional property near the water. A question being considered is wheth- er it is technically and economically fea- sible to reduce the amount of water drained into the Salton Sea without ad- versely affecting agricultural production. With the present crop mix and produc- tion, water use by crops presumably would remain essentially the same, and a reduction in drainage flow would be ac- companied by reduced diversions at Im- perial Dam. Recent studies (1984) by researchers C.A. Beasley CALIFORNIA AGRICULTURE, OCTOBER 1984 15 Oster, Meyer, Hermamier, and Kaddah, water and are assessing the potential for at the University of California and the “dead level” surface irrigation to elimi- U.S. Department of Agriculture Agricul- nate tail water. tural Research Service, have provided The University of California operates some data on the partitioning of water. a “Mobile Lab” with instruments and In the Imperial Valley, 12 percent of the equipment, working from the Imperial water diverted becomes deep percolation County Cooperative Extension office in (leaching water), and runoff (tail water) El Centro, to monitor water use and accounts for 16 percent. In the Coachella suggest ways to improve irrigation effec- Valley, the leaching fraction is somewhat tiveness. Trained personnel take the lab higher, and there is hardly any tail water. into the fields of cooperating farmers, Quantitative information from these where they measure tail water. They also studies supports the belief that, techni- check soil moisture status with neutron cally, a reduction in drainage flow is probes and recommend irrigation sched- 1983 feasible. The UC Mobile Lab monitors water use to uling programs. Measurements in Steps have been taken in recent years help Imperial Valley growers improve showed that tail water was noticeably to initiate water savings and assess the irrigation efficiency. reduced from that observed in earlier economic consequences of such prac- years. This reduction was attributed to tices. The federal government finished greater awareness of the problems associ- lining the Coachella Canal in 1981. The 24-hour delivery, an irrigator now can ated with excessive water use, together Imperial Irrigation District has acceler- request a reduction in delivery as late as with increased off-canal storage and ated its canal lining activities, and it has noon of each day and limited changes up more flexible delivery policies by the constructed four off-site reservoirs to to 3:OO p.m. during the final delivery day. irrigation district. provide temporary storage, with plans to Research workers from the Agricultural construct two more. The District also Research Service are investigating the Jewel1 L. Meyer w Irrigation and Soib Specialidt, Cooper- has established more flexible rules for substitution of drainage water (with ative Exterwion. Uniuersity of California, Riverside. and Jan van Schilfsaarde.I is Director, US.Salinitv Laboratom water orders: instead of receiving a fixed 3,000 mg/L salt) for part of the irrigation Riverside.

Development of the problem The drainage problem became serious in Case history: the Valley when a full water supply was assured. In the northern area (essentially San Joaquin Valley within the San Joaquin Basin), problems began about a decade after the Delta- Mendota Canal was built and started to Louis A. Beck deliver water in about 1950. During the 1960s, tile drain systems were installed to allow farmers to continue normal pro- duction. Most of the water from these ost of the San Joaquin Valley in production. Perched saline ground- systems is discharged to the San Joaquin has been farmed in one fash- water within 5 feet of the soil surface River. Because of the relatively small Mion or another for more than a causes a loss of 10 percent or more in volume and the dilution in the river, hundred years The Valley trough was annual crop production. discharge of drainage water causes only generally dry-farmed until deep-well This perched water can be con- slight degradation of the quality of the turbine pumps were developed in the trolled by the installation of tile drains river and minor changes in agricultural 1930s and 1940s and irrigation became - a system of perforated pipes 6 to 8 practices. common. Even though much of the land feet belowground that keep the water A water supply to the Tulare Basin was in production, it was not irrigated level below the root zone. The drains was guaranteed when the California every year: there was some pattern of conduct the water to a corner of the Aqueduct started delivering water to the rotation, such as dry-farming for one field, where it is discharged to a dispos- San Luis service area of the federal Cen- year, irrigation for two, and fallow for al system. tral Valley Project and to the State Wa- one. Now, almost 5 million acres of The perched water in the Valley ter Project service area in 1968. Drainage agricultural land on the Valley floor are trough is saline, ranging from 3,000 to problems began by the end of the 1970s. irrigated. 25,000 mg/L of total dissolved solids. In Now several agencies are starting to im- The Valley, about 250 mile? long and other areas where the perched water is plement local interim solutions to solve 50 miles wide, consists of two drainage not saline, it can be used for irrigation their drainage disposal problems; drain basins: the northerly San Joaquin Ba- or discharged to watercourses. Saline tile will not help, since there is no river to sin, which drains to the San Joaquin water must be disposed of so that it discharge to or any other system to carry River and then to the Sacramento-San does not affect surface or ground- the drainage waters away. Joaquin and San Francisco water. It is the lack of safe disposal Bay; and the southerly Tulare Basin, systems, areas, or methods that Solution which normally has no outlet. causes the drainage problem in the It was proposed during the 1960s that Salinity problems in the San Joaquin trough of the San Joaquin Valley. The the state and federal governments to- Valley have adversely affected almost problem area is expected to exceed 1 gether construct drainage disposal facili- 600,000 acres of agricultural land now million acres within the next 50 years. ties that would serve the entire Valley

16 CALIFORNIA AGRICULTURE, OCTOBER 1984