COLORADO RIVER BASIN REGION 7
73-271 Highway 111, Suite 21
Palm Desert, California 92260
Phone: (619) 348-7491
SALTON SEA WATER QUALITY
PREPARED BY REGIONAL BOARD STAFF
NOVEMBER 20, 1991 PUBLIC WORKSHOP
The Salton Sea is situated in the Salton Trough which is at the north end of the actively spreading rift valley that runs along the bottom of the Gulf of California. The Salton Trough is separated from the Gulf of California by the delta of the Colorado River. For many thousands of years, the Colorado River has periodically flowed north across the delta into the Salton Trough forming large, temporary lakes. These lakes dried up when the Colorado River again flowed south to the Gulf. The last large lake of this type is known as historic Lake Cahuilla. Lake Cahuilla's surface elevation was about 270 feet above the current level of Salton Sea (40 feet above sea level) about 1,500 years ago.
In 1905 the low area of the Salton Trough was called Salton Sink and its low point was about 278 feet below sea level. For two years, the Colorado River flowed into the Salton Sink until the River was diverted back to the Gulf of California in 1907. This new lake had a surface level of 196 feet below sea level and area of 520 square miles. It's water level rapidly declined due to evaporation until about 1925 when it was about 250 feet below sea level. Since 1925 the diversion of Colorado River water into the Imperial Valley for agriculture has raised the level of the Salton sea to a current elevation of 226 feet below sea level with a surface area of about 240 square miles.
Currently the elevation of the Salton Sea is relatively stable because there is an equilibrium between inflow of water to the Sea and evaporation from the Sea. Annual inflow is about 1,300,000 acre-feet and evaporation is about 6 feet per year. About 46% of the inflow is from the Alamo River and 38% is from the New River. The remaining 16% of inflow to the Sea comes from the Whitewater River/Coachella Valley Storm Water Channel, San Felipe Creek, Salt Creek, small agricultural drains, and ground water seepage. About 12% of the total inflow comes form Mexico and is carried primarily by the New River.
Although the water level of the Salton Sea is currently stable, the salinity of the Sea is constantly increasing. About 5 million tons per year of salt is carried into the Sea from its tributaries, but no salt is removed because the Sea has no outlet. The current Total Dissolved Solids (TDS) content of the Sea is about 45,000 mg/l (milligrams per liter) or 4.5%. Currently the TDS (salinity) of the Sea increases by about 800 mg/1 per year. Ocean water has a salinity of 35,000 mg/l.
The current resource value of the Sea is based on its recreational and wildlife uses. Recreational uses include fishing, boating, swimming, camping, sightseeing, etc. Wildlife uses include aquatic habitat for organisms (e.g. microorganisms, plants, invertebrates, fish) and terrestrial habitat, primarily for waterfowl. The Salton sea is host to state park and recreation areas and state and federal wildlife refuges.
The Regional Board has listed the Salton Sea as "impaired" in its Water Quality Assessment based on a violation of the Salinity Objective. the Regional Board's water quality objective for Salton Sea is to reduce the salinity level to 35,000 mg/1 "unless it can be demonstrated that a different level of salinity is optimal for the sustenance of the Sea's wild and aquatic life." A determination of this type would be made by the California Department of Fish and Game. However, this objective is to be achieved "without affecting the primary purpose of the Sea which is to receive and store agricultural drainage, seepage, and storm water." An additional regional Board caveat to this objective is that "because of economic considerations, 35,000 mg/l may not be realistically achievable. In such case, any reduction in salinity which allows for survival of the Sea's aquatic life shall be deemed an acceptable alternative or interim objective."
Although the potential loss of the fish and other organisms dependent on the Sea is related mainly to the salinity increases, there are also significant water quality concerns related to selenium and other contaminants. the Regional Board has provided funding since 1988 to the U.S. Geological Survey (USGS) to determine the sources and effects of selenium and, to a lesser extent, other contaminants.
The studies conducted by the USGS (in conjunction with the U.S. Fish and Wildlife Service) have indicated that the selenium getting into the Salton Sea is originally from the Colorado River. Colorado River water contains 1-2 ppb (parts per billion) of selenium. The Colorado River water is brought by canals into Imperial Valley and the selenium becomes concentrated due to the evaporation and evapotranspiration that occurs during farming. The agricultural drains carry the selenium enriched water into the Salton Sea via the New and Alamo Rivers. The New and Alamo Rivers contain about 7-8 ppb of selenium when they enter the Sea. This selenium is apparently taken up and concentrated by small organisms in the Sea. These organisms are eaten by larger organisms which further concentrates the selenium. A health advisory has been issued that advises limiting the amount of Salton Sea fish that should be consumed to 4 ounces every 2 weeks. This advisory is based on fish tissue concentrations of 8 ppm (parts per million) dry weight. Fish in the Sea have an average selenium concentration of about 10 ppm. Birds that feed on fish from the Sea may have tissue levels up to 40 ppm. Levels this high may cause health problems in birds and this possibility is currently being studies.
The source of most of the organochlorine pesticides that affect the local fish and wildlife is form agriculture in Imperial Valley. Levels of these chemicals in Salton Sea fish are not high enough to cause impairments or health concerns. However, the concentrations of these chemicals in the fish in the agricultural drains and the New and Alamo Rivers are higher than the levels found in Salton Sea fish by a factor of ten or more. Birds also accumulate high levels of these chemicals and the U.S. Fish and Wildlife Service is studying the problem. They are also investigating whether boron could cause problems to affected organisms in the area.
The Regional Board has established a toxicity objective that "all waters shall be maintained free of toxic substances in concentrations which are toxic to, or which produce detrimental physiological responses in human, plant, animal, or indigenous aquatic life." the Regional Board has focused its efforts to control the toxic compounds, described above, on the agricultural drains in the Imperial Valley which convey them to the Salton Sea.
ISSUE 1. Mitigation of Environmental Effects Due to Water Conservation
The State Water Resources Control Board has ordered the Imperial Irrigation district (IID) to develop a water conservation plan to "conserve at least 100,000 acre-feet per annum by January 1, 1994" (Board Order WR 88-20). This Order also states that 367,099 acre-feet per annum of conservation "is a reasonable long-term goal which will assist in meeting future water demands." In the process of developing a water conservation program, IID prepared an Environmental Impact Report (EIR) has required by the California Environmental Quality Act (CEQA). The final EIR came out in October 1986 prior to State Board approval of WR 80-20. This EIR lists some of the potential environmental impacts that would be caused by a water conservation program. Four of these are listed below:
14. Decrease in terrestrial biota use of the Salton sea aquatic and riparian habitats.
15. Accelerated loss of biota and fishery in the Salton Sea, including the desert pupfish (endangered species.
18. Accelerated loss in recreational value of the Salton Sea.
19. Accelerated loss in resort and property values near the Salton Sea.
The mitigation measures cited in the EIR for the above impacts are as follows (except for No. 14 which also had additional measures):
"Because the IID does not have the economic ability, authority, or jurisdiction to carry out mitigation for this impact, all concerned federal, state, and local agencies must be involved. This impact will not be mitigated to an acceptable level unless there is action by others as described. It should be noted, however, that the IID is committed to participate in and support a task force currently being organized by the California Secretary of Resources to examine solutions to the impacts."
State Board Order WR 88-20 states that "Implementation of a water conservation plan must be in compliance with the California Environmental Quality Act. In addition to the mitigation measures identified in the 1986 EIR, CEQA requires that if new information of substantial importance becomes available regarding environmental impacts and mitigation measures, such information must be evaluated in a supplemental environmental document or documents and appropriate mitigation measures taken."
The State Board staff report dated August 12, 1988 that was produced to support adoption of WR 88-20 stated the question of CEQA compliance in slightly different language. It stated that "In view of the very general nature of the water conservation program approved by IID in 1986, the EIR certified in that year should be considered a Program EIR which provides a general assessment of the overall environmental effects of increasing water conservation efforts in IID. Prior to approval of a specific water conservation program by IID, either a subsequent EIR or a supplement to the existing EIR may be required in accordance with the criteria specified in the State CEQA guidelines. (CCRD, Title 14, Sections 15162 and 15163)."
The Chairman of the Regional board, Stu Gummer, sent a letter dated May 8, 1991 to Don Maughan the Chairman of the state Water Resources Control Board (State Board), that discussed this issue. In describing the effects of the mandated water conservation on the Sea, Mr. Gummer stated that "implementation of such measures will increasingly make the goal of Salton Sea salinity control more costly and less technically feasible." Mr. Gummer went on to pose the question: "In consideration of the above, should the Regional Board continue to expend resources to attempt to preserve the present beneficial uses of the Salton Sea?" Mr. Maughan responded to Mr. Gummer's comments in a letter dated July 15, 1991. Mr. Maughan noted that previous state Board decisions were based on their conclusion that "a prolonged delay in water conservation measures would not save the fishery for an appreciable length of time" and that previous State Board decisions made 'the assumption that the decline of the Salton Sea appeared to be inevitable." However, Mr. Maughan noted that previous State Board decisions were made in "the context of waste and unreasonable use" of water and the decisions were not "the result of a state Board proceeding to review the beneficial uses of the Salton Sea and proposals for maintaining such uses." Mr. Maughan concluded by discussing a possible reexamination of Order WR 88-20. He stated that "a major factor in the State Board's approach will be the degree of local interest in having the State Board reexamine the findings of Order WR 88-20 regarding long-term water conservation goals. In this respect, we are interested in local views of responsible agencies or public organizations regarding reexamination of our earlier findings in conjunction with current proposals to maintain salt levels in the Salton Sea. We are particularly interested in financial feasibility."
ISSUE 2 Implementation of Selenium Control Measures
As described above, the elevated concentrations of selenium in Salton Sea fish has resulted in the issuance of a health advisory recommending against excessive human consumption of these fish. Elevated levels of selenium in Salton Sea waterfowl may also pose a threat to the health of these birds. The primary source of selenium in these organisms is from selenium carried by the New and Alamo Rivers and Imperial Valley Drains. Fish and birds living in these rivers and drains also have significant levels of selenium in their tissues. Studies by the Regional Board, the U.S. Geological Survey, the U.S. Fish and Wildlife Service, and the California Department of Fish and Game have fairly conclusively established the source of the problem and the mechanisms of selenium transport within the Salton Sea watershed. Work is still needed to determine the severity of the threat to biota, and research is needed to investigate methods to reduce the selenium levels.
The average concentration of selenium in the New and Alamo River and Imperial Valley Drains in about 7-8 ppb (parts per billion). This exceeds the recently adopted statewide objective of 5 ppb in surface waters to protect freshwater aquatic life (per the Inland Surface Waters Plan, April 1991). The federal criteria is also 5 ppb for aquatic life protection. the concentration of selenium dissolve din the Salton Sea is 1-2 ppb. It is lower in the Sea as compared to its tributaries, apparently because it is rapidly removed from the waters in the New and Alamo River estuaries by microorganisms. However, this allows the selenium to enter the food chain of the Salton Sea aquatic ecosystem.
Methods to control selenium in the Salton sea watershed are most effective if they deal with the selenium at its point of highest concentration. this point has been identified as the subsurface agriculture drains (tile drains) which provide about one third of the flow in the Imperial Valley Drains. the average selenium concentration in these tile waters is about 25 ppb. It is diluted by tail water and leakage form the canals so that the overall average of drain water is 7-8 ppb of selenium. Some methods that are effective in preventing pesticides from entering the drains have the effect of reducing the amount of tailwater. Since the tailwater is a source of relatively low selenium waters, removing it from the drains will cause overall selenium levels to increase.
Many techniques used to conserve water (see Issue 1, above) have the effect of reducing the flow of low selenium water into the drains. This also will cause an overall increase in selenium levels in the drains and rivers, if implemented. One of the techniques that has already been tested in Imperial Valley, and is currently used on a small scale, is a tailwater pump-back system. Methods like this that reduce pollutants and/or conserve water are known as Best Management Practices (BMP's) and are often encouraged by the state and federal Nonpoint Source (NPS) Management Programs. Tailwater pump-back systems will both conserve water and reduce pesticide levels in water coming from fields using the method. However, the flow in the tile lines under these fields will be increased. These tile line flows will have higher salinity and selenium levels in them than the overall drain system.
In Chairman Gummer's letter to the State Board (see discussion, above) he notes that widespread implementation of BMP's that reduce the low salinity and low selenium drain water, (e.g. tailwater pump-back systems could result in an increase of overall selenium levels in the drains by as much as three times (i.e. 25 ppb). Mr. Gummer addresses the key issue in his letter when he asks the question "Should either the State or Regional Board recommend measures for conservation and/or pesticide/sediment/nutrient/bacteria reduction when we know in advance that implementation of these measures will substantially exacerbate the present selenium problem? Who should be made responsible if problems develop from selenium under these circumstances? Even if problems do not develop, the levels will undoubtedly be well in excess of federal objectives. Shouldn't planning be done now in anticipation of this problem?"
ISSUE 3 Long Range Goals for Salton Sea
The successful resolution of water quality problems and related ecological and economic problems at Salton sea would be more likely if local, state, and federal agencies and the public share common long-term goals for the Sea. However, some of the suggested long-term goals may be in conflict with each other. For example, the goal of promoting large scale water conservation may make the goal of preserving the existing Salton Sea fishery very difficult. Also, the goal of maintaining the Sea's current elevation and shoreline may be in conflict with a goal of reducing freshwater inflow to the Sea. Part of the process of resolving conflicts between goals will be to prioritize the different goals. Analyzing the consequences of adopting particular goals is also important. For example, if salinity is allowed to increase to the level where the fishery resource is lost, then a goal of developing and planning for an alternative aquatic ecosystem based on invertebrates would become much more important. A good first step is to have interested parties clarify and rank their goals.