Areas upland from surface water sources used for public drinking water supplies.  The areas are limited to 30 miles upstream from the intakes.  If you need the entire catchment areas, contact DOH.  This layer is used in the Source Water Assessment Protection application https://fortress.wa.gov/doh/swap/index.html.  Data is updated Monday mornings.  Check the "Data updated:" date in the Details section.  Metadata dates are not automatically updated.