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() Benefits of vegetated agricultural drainage ditches (VADD) as a best management practice in California.

Moore, M1, Denton, D2, Cooper, C1, Miller, J3, deVlaming, V4, Barbour, M5, Williams, W6, Rodgers Jr., J7, Robins, P8, 1 USDA Agricultural Research Service, Oxford, MS, USA2 US EPA Region IX, Sacramento, CA, USA3 AQUA-Science, Inc., Davis, CA, USA4 University of California - Davis, Davis, CA, USA5 Tetra Tech, Inc., Owings Mills, MD, USA6 Waterborne Environmental, Inc., Leesburg, VA, USA7 Clemson University, Clemson, SC, USA8 Yolo County Resource Conservation District, Woodland, CA, USA

ABSTRACT- Widespread contamination of California water bodies by the organophosphate insecticides diazinon and chlorpyrifos is well documented. While their use has decreased over the last few years, a concomitant increase in pyrethroid usage (replacement insecticides) has occurred. Researchers have also documented diazinon toxicity pulses in California′s Central Valley due to dormant orchard drainage. Vegetated agricultural drainage ditches (VADD) have been proposed as a potential economical and environmentally efficient management practice to mitigate the effects of pesticides in dormant season runoff. VADD have been effective in mitigating simulated pyrethroid runoff storm events in the Mississippi Delta; however, California poses a different scenario in timing of runoff (winter), rainfall intensity, and ditch vegetation and soil types. Multiple lines of evidence will be required to determine the effectiveness of VADD as an applicable management practice in California. This research will incorporate temporal and spatial sampling and chemical testing of water, sediment, and plants, in addition to ditch biological assessments and toxicity evaluations. Initial data will provide baseline information for model generation to predict necessary ditch conditions for appropriate pesticide mitigation. Utilizing a multidisciplinary team approach, the effectiveness of VADD in California will be determined. Such economical and environmentally successful management practices will offer farmers, ranchers, and landowners a viable alternative to more conventional (and sometimes expensive) practices currently suggested by conservation organizations.

Key words: California, pesticide, BMP, TMDL

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