Is Chloride Concentration Increasing
in the Sparta Aquifer of North-Central Louisiana?
Douglas Carlson and Thomas Van Biersel
Louisiana Geological Survey – Louisiana State University,
3079 Energy, Coast and Environment Bldg., Baton Rouge, Louisiana 70803
The Sparta Aquifer serves as the source of over 90% of groundwater pumped for seven parishes (Bienville, Claiborne, Jackson, Lincoln, Ouachita, Union, and Winn) in north-central Louisiana, of which a portion was identified by the Louisiana Department of Natural Resources as an area of groundwater concern. As a result of pumping over the past century, the potentiometric level within the Sparta is declining. This decline has been observed and plotted on maps for the past 35 years in a number of previous studies. In addition, it has been observed that on the eastern edge of the aquifer there is a saltwater front that runs from Morehouse Parish to Sabine Parish. This front is documented in past studies. This study is the first to evaluate whether this front is advancing and whether chloride concentrations within the aquifer are increasing.
This study includes a collection of samples for chloride analysis from approximately 100 wells owned by approximately 30 public water utilities throughout the Sparta Aquifer. After collection, water samples are stored on ice and then analyzed using the Louisiana Geological Survey’s Dionex® ICS-1000 Ion Chromatography System. Results are mapped and compared with past results to document trends in chloride concentration and movement into the Sparta Aquifer by the front of higher chloride concentration toward the west.
This study’s results, similar to past studies, show the high concentration of the chloride front. Regionally,
chloride concentrations have changed little; however, near the front chloride concentrations show a general increasing trend.