Pesticide residues in agricultural drains, southeastern desert area, California

A study is being made to determine the occurrence and distribution of pesticides in the agricultural drains for approximately 3/4 million irrigated acres in the southeastern desert area of California. This report describes the results of the first year of sampling and analyzing (1) water in the drains , (2) bed material in the drains, (3) water from field tile-drainage lines, and (4) irrigation tailwater and water in the drains directly exposed to drift from aerial application of pesticides. Residues of almost all the pesticides selected for monitoring were found in water in the drains. Examination of the data to determine the probable source of pesticides indicated generally slight concentrations from bed material in the drains, usually no detectable concentrations from field tile-drainage lines, and apparently large concentrations from irrigation tailwater and drift from aerial application. (Woodard-USGS)