The Kesterson Reservoir is part of the current San Luis National Wildlife Refuge in California. Formerly a unit of the Kesterson National Wildlife Refuge, the reservoir was an important stopping point for migratory waterfowl. Kesterson once consisted of 12 evaporation ponds totaling approximately 1,280 acres, and was historically used for agricultural drainage. Kesterson gained national attention during the latter half of the 20th century due to selenium toxicity and rapid die off of migratory waterfowl, fish, insects, plants and algae. The reservoir was closed in 1986, and concentrations of selenium at the site have continued to be monitored throughout remediation efforts.
Background The Kesterson National Wildlife Refuge is located approximately 18 miles west of Merced County in the San Luis National Wildlife Refuge, in the San Joaquin Valley of central California. The refuge is 26,609 acres (107.68 km2) and includes a variety of wetland and riparian habitat which supports a large variety of waterfowl, mammals and other wildlife across four units, the Kesterson Reservoir, Freitas, Bear Creek and original San Luis Units. The San Joaquin Valley, considered by historian Kevin Starr as "the most productive unnatural environment on Earth", supports approximately 25% of the United States’ agricultural products including grapes, cotton, nuts, citrus, and vegetables. Cattle and sheep ranching also contribute to the agricultural output of the area. The valley grew rich in phosphoric acid during prehistoric times, when as an inland lake it provided a habitat for clams. The accumulation of these shells made the land rich in phosphoric acid. The San Joaquin Valley is bordered on the west by the Coast Range and on the east by the Sierra Nevada mountains. The Coast Range include Cretaceous and Tertiary marine sedimentary rocks. Weathering and oxidation of the Moreno Formation, a black marine shale, produces Pyrite, FeS2, and Iron Selenide, FeSe2. As the weathered products concentrate in evaporative minerals and salts, selenates (for instance, Na2SeO4 · 10 H2O or Na2Mg(SeO4)2 · 4 H2O) and Sulfates (Na2SO4 · 10 H2O or Na2Mg(SO4)4 · 4 H2O) can form. This results in selenium salts and selenium rich soils that are sloughed off the mountains via debris flows or landslides into the San Joaquin valley. Additionally, the San Joaquin Valley has a shallow aquifer bounded by impermeable clays. Large-scale agricultural production relies on similarly large-scale irrigation projects in order to keep fertile farms in operation. A side effect of irrigation in the San Joaquin Valley was that ground water levels began to rise over time. This led to a condition where excess water was accumulating and harming crops. In 1968, the Bureau of Reclamation proposed a 290-mile long drainage canal, called the San Luis Drain. As part of the large drainage canal the Kesterson Reservoir, which consisted of 12 evaporation ponds, was completed in 1971 within the Kesterson National Wildlife Refuge.
Timeline 1960s: The San Luis Drain (290-mile drainage canal) was proposed by California officials. 1971: As part of the larger drainage canal, Kesterson Reservoir was completed by the Bureau of Reclamation. 1975: After only 82 miles of the 290-mile drainage canal was completed, the project was suspended due to environmental concerns and Kesterson became the temporary terminus of the drainage system. 1978: The Westland's Water District, part of the San Joaquin Valley, began draining 7,300 ace-ft on average of subsurface drainage annually into Kesterson. 1983–1985: Research as Kesterson was conducted to evaluate the effects of agricultural drainage water on aquatic birds. Due to the initial findings, the California State Water Resources Control Board ordered the closure of the reservoir. 1986: Scientists discovered bird deformities at Kesterson. 1989–2014: Remediation efforts and monitoring were conducted by the United States Bureau of Reclamation and the US Department of Interior. 2000–2013: Westland landowners issue several lawsuits against the Federal Government to provide an alternative drainage system. 2014: Se concentrations reached relatively stable levels below concentrations of 4 μg/g.
… excerpt ends here. Continue reading the full article.
