Applications of the California pesticide use reporting database in more than 25 years of U.S. Geological Survey hydrological studies

The U.S. Geological Survey (USGS) has been collecting data on the occurrence of pesticides in California surface and ground water since the 1970’s. The design of these studies benefited from the availability of the Pesticide Use Reporting (PUR) database of the California Department of Pesticide Regulation. Actual locations and dates of applications of active ingredient allow for effective design of studies that seek to understand which compounds can be mobilized from the point of application as well as the hydrological or climate-related factors that enhance the off-site transport. Key studies from the 1970’s to the present are discussed here and demonstrate how the USGS both designed studies and improved their analytical methodology to keep up with changes in how pesticides are used in California.