Can the NAWQA assessment help to predict pesticide occurrence in unmonitored areas?
USGS data and analyses are now sufficiently extensive to support national statistical models that can be used to estimate concentrations or the occurrence of some pesticides in streams and ground water where they have not yet been measured. Expanding this predictive capability is a critical step for national water-quality assessments, as well as for cost-effective management of water resources, because both require more information than can be directly measured. NAWQA’s WARP (Watershed Regressions for Pesticides) model was developed from measured pesticide concentrations in streams, together with information on pesticide use and land use, climate and soil characteristics, and other natural features. This model can be used to predict the likelihood that the annual average concentrations of atrazine in untreated stream water exceeds specified levels of concern. Atrazine concentrations were predicted to be highest in the Corn Belt and parts of the southern Mississippi River Valley, where
