Sediment Magnetic Susceptibility and Instream Water Quality across the Coulee Baton Microwatershed in Southwestern Louisiana

Timothy Duex, Sean Comisky, Durga Poudel, and Carl Richter
University of Louisiana at Lafayette, Lafayette, Louisiana 70504

Surface water quality impairment of rivers, lakes, and streams and its negative impact on their designated uses have become one of the major environmental concerns in recent decades. Although channel contribution to sediments and water quality impairment in a water body is widely acknowledged, information on this issue is scattered and limited. This study was designed to study the variation in sediment character and instream surface water quality in a watershed that is primarily agricultural. We identified seven sites for sediment collection, water quality sampling, and channel characterization in Coulee Baton microwatershed in southwestern Louisiana. Samples were collected on a monthly basis for one year. The water quality parameters pH, temperature, turbidity, conductivity, and dissolved oxygen were measured in the field. Total Suspended Solids (TSS), Total Combustible Solids (TCS), 5-day Biological Oxygen Demand (BOD5), and Fecal Coliform (FC) Counts were determined in the lab. Sediment was collected from three spots at each site (left bank, center of stream, and right bank) and analyzed using Magnetic Susceptibility as a proxy for pollution. Doppler readings were taken to measure discharge at the primary drainage outlets of the watershed. Heavy metals and pollutants apparently are trapped deep in the clay and show a seasonal variation. The TSS concentration at the main outlet of the watershed is indicates that suspended sediment is one of the major pollutants in the watershed. Results of FC analyses shows that water bodies near residential areas have excessively high FC counts. It is recommended that appropriate Best Management Practices be implemented for controlling sediment load and Fecal Coliform pollution in the Coulee Baton microwatershed.

AAPG Search and Discovery Article #90158©2012 GCAGS and GC-SEPM 6nd Annual Convention, Austin, Texas, 21-24 October 2012