How to Interpret SWSA Maps
The PWS well capture zone maps that come with the SWSA report are specific to your water system. The capture zones were created using computer algorithms based upon the hydrogeology of the area and each respective well's construction. When some of this information was missing, a half-mile diameter circle, a fixed radius, was automatically delineated as the capture zone.
The PWS intake capture zone maps consist of the area of primary influence (API) and the watershed. Nearby PWSs may share the same API and/or watershed. The API is based upon a 1000-foot buffer from a waterbody shoreline. It may extend upstream for PWS intakes drawing from rivers or streams. How far upstream the API extends depends upon a two-hour time of travel. The API boundaries were determined by characteristics that are specific to the TCEQ’s source water assessments. The API applied the same characteristics for boundary determination for each PWS. The watershed boundaries were determined by the natural topography specific to the particular PWS being assessed.