GIS Techniques for Assessing Water Supply Watersheds and Protecting Source Waters, Alexandra Orrego

Since 1996, all states are required to enact Source Water Protection Programs to protect their drinking water sources from contamination. The initial step in the development of the program was to prepare an inventory and assessment of each water supply watershed in the state, called the Source Water Assessment Plan (SWAP). In 2000, the Atlanta Regional Commission completed SWAPs for 28 Metro Atlanta public water systems. In 2017, the Metropolitan North Georgia Water Planning District (the District) contracted with Georgia Environmental Protection Division (EPD) and the Georgia Environmental Finance Authority to complete the update/creation of SWAPs for 42 public drinking water intakes within the 15-county metropolitan Atlanta region, which were approved by EPD in September 2020. This assessment was done following EPD’s Source Water Implementation Plan (2000), with adaptations in susceptibility ranking calculations using advanced geographic information systems (GIS) techniques. These adaptations were made possible through advancements in data availability, data quality, and GIS technologies. Specifically, the District delineated the watershed area for each public drinking water source, conducted an inventory of potential sources for contamination (both Individual source and non-point source pollution), and determined the susceptibility of the water supply to contamination within the watershed assessment area resulting in an overall watershed susceptibility to contamination ranking of low, low-medium, medium, medium-high, and high. In this presentation we explore those adaptations and advanced GIS techniques used to determine a water supply’s potential susceptibility to contamination from nearby facilities and non-point sources.