A Brief Description of Its Current
Conditions, and Potential Remediation Projects
The Salton Sea Authority, October 3, 1997
The Salton Sea
The Salton Basin is an 8,360 square mile, closed, sub-sea level basin in the low desert of southern California and northern Mexico. The basin is actually part of the Colorado River delta: in the last thousand years, the Colorado River has meandered west and filled the basin at least three times forming a freshwater lake called Lake Cahuilla. Each time, the River eventually returned to its more easterly channel leaving the lake to evaporate.
The Salton Sea was formed in 1905 when massive flooding caused the Colorado River to break through an irrigation canal headwork and flow freely into the Salton Basin for 18 months. Since then, the Sea's existence has been maintained primarily by agricultural return flows from the Imperial, Coachella, and Mexicali Valleys.
The Salton Sea is California's largest lake. At a surface elevation of 227 feet below sea level, it has a surface area of 243,718 acreas (381 square miles). The maximum depth of the Sea is about 51 feet and the average depth 31 feet. The annual inflow to the Sea averages about 1,300,000 acre-feet, carrying approximately 4,000,000 tons of dissolved salt.
Values of the Salton Sea
Below an elevation of -220 feet, the Salton Sea is designated by the federal government as a repository for agricultural drainage. Without this use of the Sea, land in the Imperial and Coachella Valleys would be too water logged and/or saline for agriculture.
In the 1950s the California Department of fish and Game (CDFG) stocked a variety of fish species into the Salton Sea in a successful attempt to create a sportfishery. For decades the Sea was a noted destination for anglers. A 1985 CDFG study found that the Salton Sea was more productive (fish caught per angler hour) than any California marine fishery and equal to the most productive freshwater fisheries.
The Salton Sea is a key stop on the Pacific flyway for many species of migratory birds; its importance has been magnified by the tremendous loss of wetlands in California. The Salton Sea National Wildlife Refuge has over 380 species of birds, among the highest totals of all national refuges.
The Salton Sea provides important habitat for several endangered species including the desert pupfish, Yuma clapper rail, and brown pelican.
Salton Sea Problems
The Salton Sea is beset by several serious problems. Because the Sea has no outlet, water is lost only through evaporation , leaving dissolved salts behind and graually raising salinity. The Sea's salinity has now reached 44 parts per thousand (ppt), about 25% higher than ocean water. This elevated salinity may partially explainan apparent decline in orangemouth corvina, the most popular sportfish.
The Sea's elevation has also gradually risen. Homes and businesses have been flooded and abandoned. Paradoxically, the rise in the Sea's level has also been beneficial by keeping salinity from rising even higher.
The inflows to the Salton Sea contain high levels of nutrients making the Sea a highly eutrophic (very productive) body of water. This high primary productivity explains the productivity of the fishery but also contributes to periodic fish kills via deoxygenation due to decomposition of 1(the heavily organic sediment after it has been resuspended by high winds, or 2)dead algae following planktonic 'blooms.'
Approximately 10-15% of the inflow to the Salton Sea originates in Mexico and is carried to the Sea via the New River. Because of the discharge of industrial pollutants and poorly treated sewage in the Mexican city of Mexicali, the New River has been called the most polluted river in the country. However, the discharge of at least some industrial pollutants has declined in recent years and the remainder is diluted by Imperial Valley agricultural drainwater. The sewage essentially undergoes natural treatment during its 60 mile passage to the Sea: data collected by the Regional Water Quality Control Board indicate that the bacterial load is greatly diminished at the mouth of the river. The Sea's high salinity may also serve as a barrier to bacterial pollution.
The Salton Sea has unfortunately become known for its massive fish and bird dieoffs. fish kills due to deoxygenation have occurred in the Sea since the fishery was established. Winter dieoffs of tilapia, an African fish introduced in 1964, are also common due to that species intolerance of low temperatures. More recently, the U.S. Fish and Wildlife Sesrvice has identified a dinoflagellate parasite Amyloodinium ocellatum as a potential explanation for other tilapia dieoffs. Sever dieoffs have also occurred among a variety of bird species: eared greebes (cause unknown, possibly toxin from a red tid), cormorants (Newcastle disease), and pelican (botulism transmitted through tilapia infected with the vacteriumVibrio alginolyticus). Whatever the proximal causes of these mortality events, the Sea's elvevated salinity likely plays some role in their occurrence by increasing the overall physiological stress on the organisms.
The trace element selenium has caused mortality and/or developmental deformities among wildlife at several irrigated areas in the western U.S. and has been studied in the Salton Basin by the U.S. Department of the Interior. Unlike the situation at Kesterson reservoir in central California - the most infamous case of selenium poisoning - selenium in the Salton Sea is derived from irrigation water, not irrigated soils. The selenium concentration in Salton Sea water is very low, about 1 part per billion, but levels in the Sea's sediment and biota are at levels of concern. Selenium is unlikely to be a direct cause of wildlife mortality in the Salton Sea but, like salinity, may be contributing to physiological stress, in particular weakening immune systems.
A tremendous range of mechanisms have been suggested over the years for remediating the Salton Sea. One of the most common proposals is the construction of pipelines/canals between the Salton Sea and the ocean, usually the Culf of California but sometimes the pacific Ocean. The idea of simply enxhanging Salton Sea water for ocean water has obvious intuitive appeal. Unfortunately, the volume of water necessary to make this idea work also makes it improactical. For example, to exchange sufficient water to bring the Sea's salinity back down to 40,000 ppm in 10 years would require moving 1,100,000 acre-feet of water in each direction each year. With continuous, simultaneous pumping, this would require two 16-foot diameter pipelines. Pipelines to the pacific Ocean would have to overcome a rise of several thousand feet over the Coastal Mountain Range;pipelines to the Gulf of California would require rights of way through Mexico. In either case, the kpumping would have to go on indefinitely; as soon as it stopped the Sea's salinity would begin to rise again.
The mechanism of salinity control recommedned by all major Salton Sea studies conducted over the past 30 years is the construction of a within-Sea diked impoundment. The impoundment would act as an artificial outlet for the Sea: Salton Sea water would passively flow from the main body of the Sea through control gates in the dike into the impoundment where it would evaporate. The main body of the Sea would continue to receive the relatively fresh inflow water, whose dilution power would be enhanced by the reduced size of the main body. to minimize construction cost, most studies have recommended locating the impoundment in a shallow area of the Se. Operation and maintenance costs of this option are minimal.
The Salton Sea Authority
The Salton Sea Authority is a joint powers agency chartered by the State of California in 1993 for the purpose of ensuring continued beneficial uses of the Salton Sea. The Authority is composed of four local agencies:
A number of federal, state, and tribal agencies are ex-officio members of the Authority.
The Salton Sea Authority has made a concerted effort to collect all known suggestions for remediation of the Salton Sea and subjected these proposals to formal review against specific criteria. As a result of this effor the Authority has determined that a within-Sea diked impoundment is the most technically and financially feasible methos of improving conditions in the Sea.
The Salton Sea Authority is also taking concrete steps in proparation for the detailed planning of a remediation project. The Authority commissiioned an updated bathymetry map of the Sea and is also funding a comprehensive study of the Sea's water movements.
Where Would the Impoundment be Located?
Although the Authority has endorsed a diked impoundment as the preferred approach, it has not selected a specific project location. This would be determined only after a detailed study of technical, environmental, and social factors. It should be noted however, that an impoundment located in the central part of the Sea provides the greatest salinity control for the longest period.
Impact of Water Conservation
Water from the Colorado River is apportioned among the states in the Colorado River basin. For years the state of California has been able to take more than its share because other states were not utilizing their full allocations. This situation is changing, increasing the pressure to find other sources of water for southern California and possibly leading to water transfers from agricultural to municipal water uksers.
If Colorado River water currently utilized within the Salton Basin is diverted to other parts of southern California, inflows to the Salton Sea will decline. Inflows to the Sea could fall from the historic average of 1,300,000 acre-fee/year to 1,000,000 acre-feet/year or less.
Reduced Salton Sea inflow would alter the effectiveness of any remediation projects. For example, at an annual inflow of 1,000,000 acre-feet, the water exchange project described above would now take over 20 years, instead of 10, to reduce the Sea's salinity to 40,000 ppm. To maintain the same goal of reaching 40,000 ppm in 10 years would require pumping over 2,000,000 acre-feet in each direction each year (two 22-foot diameter pipelines). In other words, twice as much water would be pumped in each direction as otherwise flowing into the Sea.
Shoreline impoundments would also lose their effectiveness because they would be left largely high and dry, losing much of their surface area and therefore their ability to dispose of high salinity water. The effectiveness of an impoundment located in the central portion of the Sea would be only slightly diminished.