Unfortunately, the answer to this question, much like the Mississippi River, is a bit murky in Louisiana. The Louisiana Department of Health and Hospitals (DHH) supervises public water systems. The Louisiana Department of Natural Resources (DNR) manages state groundwater resources. The Louisiana Department of Environmental Quality (LDEQ) regulates surface water quality and can address pollution issues.
If you are have a concern with your drinking water and are on a public water system then contact DHH. If you have a concern about your drinking water and you have a private water well you are responsible for the maintenance and water quality testing of the well. If you believe that your well has been contaminated by external pollution sources then contact LDEQ.
DNR Office of Conservation Ground Water Resources Program: (225) 342-8244
The Louisiana Citizens’ Guide To Environmental Engagement