Alternative irrigation-management systems in California rice fields have significantly reduced the flow of pesticides into the Sacramento River, according to a five-year study by a team of University of California researchers. In past years, conventional "flow-through" irrigation of flooded fields was blamed for increased levels of rice pesticides, such as molinate, bensulfuron and carbofuran, in the Sacramento River and its tributaries. To alleviate the problem, rice growers began experimenting with alternative drainage systems. The UC study of "recirculating" and "static" water-management systems found that the seasonal discharge of molinate, bensulfuron and carbofuran decreased by 97 percent, 95 percent and 58 percent, respectively. This was primarily due to reduced water outflow from the rice fields. Sylvie Brouder, a UC Davis postgraduate researcher in the agronomy and range science department, will present the findings at 9:25 a.m. Tuesday, March 15, in the Marriott Hotel during a symposium on pesticides in surface waters.