The Sacramento-San Joaquin River Delta (the Delta) is an important agricultural center and a large water source for various end uses across California. Dry-land crop production on wetland peat soils in the Delta have led to soil oxidation and levee instability, as well as create large hydraulic gradients that promote seepage concentrating dissolved organic carbon (DOC) and nitrogen (N) in drainage return ditches. DOC poses potentially serious health concerns when Delta waters are used as drinking water, since disinfection through ozone or chlorination is required for virtually all domestic waters derived from surface waters, during which DOC and bromide form disinfectant bi-products (DBP's). CALFED recognizes this serious health issue and aims to provide safe, reliable, and affordable drinking water from the Delta, to be achieved through a cost-effective combination of alternative source waters, source control, and treatment technologies. Our research suggests converting existing row-crop land in the Delta to another use such as wetland rice production, coupled with the use of best management practices (BMPs), is a means to improve water quality as well as gain other benefits such as increased waterfowl habitat and subsidence mitigation. We have converted approximately 150 acres of Delta cornfields to rice fields managed under a variety of BMPs, on which DOC and N exports will be characterized over approximately two years. Monitoring is designed to capture water quality changes during periods of BMP implementation, and a relationship between BMP and resulting outflow water quality will be developed. We anticipate that rice production will reduce DOC exports, and additionally DOC and N exports will vary with different BMPs. This project is funded by the State Water Resources Control Board as part of the Bay Delta Authority Drinking Water Program.
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