Managing Louisiana’s Public Water Supply With GIS

The U.S. Safe Drinking Water Act amendments of 1996 require all states to develop a Source Water Assessment Program (SWAP) to ensure safe water for all citizens through the protection of water resources. In Louisiana, more than 3,200 public water wells and 50 surface water intakes supply the four and one-half million people of the state along with its estimated 20 million annual visitors.

For the Louisiana SWAP, the only way to fully harness all the components of a vast and diverse public water network in the state was to develop a full-scale GIS. This map is a compilation of some components that represent the many different avenues public water is distributed along with identifying potential risks that could affect quality and/or availability. From 1,000-foot deep wells to intakes along lakes and the Mississippi River, spatial and attribute information was collected so that various calculations could be applied. Geospatial technologies were used to assemble data from more than 20,000 field-collected GPS points, 25 statewide data sets, and information obtained from local water system operators, resulting in an extensive geodatabase.

This information was compiled to assess Louisiana’s potable water source sensitivity (using information about the water source including depth, age, groundwater recharge potential, aquifer, and source of water), vulnerability (using distance, ranking, and density calculations of various potential sources of contamination), and susceptibility (a combination of vulnerability and susceptibility). Reports and maps were generated (both in hard copy and via the Web) to notify appropriate state and local individuals of their water source status so that action could be taken if necessary.