An evaporation pond in the Tulare Lake Basin.
|Photo by Lloyd Carter.
Throughout history, salinity has threatened mankind’s existence. Ancient civilizations disappeared as salt poisoned their land and water. Today, salinity increases are silently choking off our water supply while draining away hundreds of millions of dollars in salinity damages each year.
The most under-recognized water-quality problem in California is salinity. Referred to as total dissolved solids (TDS), salinity is the concentration of dissolved salts in water. Salts are added to water supplies by consumers, irrigated agriculture, confined animal waste practices, and other human, industrial, and natural processes.
Salt accumulation can degrade the quality of fresh water, limiting the use of water for agricultural, industrial, municipal, and other purposes.
The resulting financial impact on the nation is enormous. In the Lower Colorado River Basin alone, the Bureau of Reclamation estimates that the economic damage of salinity to the Colorado River has reached over $350 million a year.
The Central Valley Regional Water Quality Control Board wrote in its "Salinity in the Central Valley" overview report in May 2006:
When water is used, salts are left behind. Every time a farmer irrigates a field, every time a managed wetland is flooded, every time an industrial facility conducts some water-requiring process, and every time you or I take a shower, we contribute to the salinity problem because the water we use and release has a higher salinity concentration than what we started with. Sometimes this is because we add salt intentionally (home water softeners, plant fertilizers), but even when no salts are added to the system, evaporation and consumptive use act to concentrate unused salts. Additionally, salts move with water so salts originating in one basin will turn up in another. This is a significant problem when the receiving basin has no reliable way of disposing salt, as is the case in the Tulare Lake Basin; or has only limited capacity to discharge salt, which is the case in the San Joaquin River Basin.
Click on images to enlarge.
|Courtesy of Central Valley Regional Water Quality Control Board, May 2006.
Many lands of the western San Joaquin Valley and southern Kern County are plagued with mounting salinity in soils and irrigation drainage, from both naturally occurring salts in the source rocks and soils of the Valley as well as from the importation of salt to the service areas of the State Water Project and federal Central Valley Project. This salt originates in the tidally-influenced waters of the Delta, where export pumps lift water from the Delta into the great aqueducts that run the length of the Valley's west side. By comparison, very little salt drains in the rivers from the Sierra Nevada.
The Central Valley Regional Board report also noted these facts:
- The recently completed Draft Soil Survey of Fresno County, California, Western Part states that approximately 400 thousand acres of saline-sodic soils currently exist in the survey area. This acreage constitutes approximately 48 percent of the irrigated land within the boundaries of the survey area, up from approximately 33 percent of the irrigated saline-sodic land identified in 1985, an increase of approximately 120 thousand acres in 18 years.
- There are currently 4470 acres of active evaporation basins in the Tulare Lake Basin, and this number may be increasing due to recent legislation allowing Integrated Farm Drainage Management Systems for individual farms in salt impaired areas. The Board has stated that evaporation basins are, at best, interim salt management tools, not a final disposal option.
- Approximately 113 thousand acres on the west side of the San Joaquin Valley have been retired (permanently removed from irrigation) due to regional drainage problems (high salinity, shallow groundwater). More land retirement is anticipated.
- Salinity problems are often complicated by the presence of other materials. Soils on the west side of the San Joaquin Valley are high in selenium, so any salt management program in the area must also address selenium management. Approximately $40 million in both public and private funds has been spent (as of 2005) to manage salt and selenium problems in the Grassland Drainage Area alone.
Poisoned Lands, Polluted Waters