The U.S. Geological Survey (USGS), in partnership with the Sonoma County Water Agency, the cities of Santa Rosa, Rohnert Park, Cotati, and Sebastopol, the Town of Windsor, California American Water, and others, conducted a 5-year study of the Santa Rosa Plain Sub-basin to characterize the surface water and groundwater resources of the Santa Rosa Plain Watershed. The study provided a wealth of information and valuable tools for local stakeholders to use to develop the Ground Water Management Plan.