ABSTRACT

The Chicot Aquifer system is the largest source of drinking water in the state of Louisiana and it is the main source of water for the Lafayette area. It represents a valuable resource that needs to be protected and understood so that there will be an adequate supply of water for the future. In the Lafayette area, it consists of thick sands with thin interbedded clays that are capped by loess and other surficial deposits. The layers generally dip gently to the south and outcrop to the north in south-central Louisiana. It forms what is typically called a semi-confined or leaky artesian aquifer in which most of the recharge is thought to come from areas where the geological/hydrological units form outcrops. This paper summarizes evidence that points to potential but significant recharge from within Lafayette Parish.

In our earlier study, we mapped the Chicot Aquifer in the subsurface and modeled various properties of the aquifer in Lafayette Parish. Based on information from that investigation, we found additional evidence which indicated that the area around the Francois Coulee drainage network could be acting as a local freshwater recharge site. This is based on several lines of evidence: 1) relatively higher resistivity readings in this part of the Chicot Aquifer indicate fresher water than in adjacent regions; 2) local, more permeable point bar deposits in the shallow subsurface beneath the Francois Coulee drainage act as potential conduits to the underlying aquifer; 3) higher elevations in this area create a positive hydrologic gradient which will cause ground-water movement toward the south; and 4) models that we have generated show a potential connection from the surface near Francois Coulee to the region beneath the northside water production plant for the city of Lafayette.

As a result, we would recommend the following precautionary steps be taken to safeguard our water supply. First, monitor surface activities in the affected areas and perhaps modify or expand the "Wellhead Protection Program" as provided by the Louisiana Department of Environmental Quality. Second, check for any potentially harmful discharge in that area. Third, discourage any new activity or industry that may choose to locate in this hydrologically sensitive region.