Nonpoint Source Pollutant Reduction in a Dense Agricultural Watershed in Northeast Louisiana Using a Filter Strip-Retention Pond BMP System.

Tensas River (Subsegment 081201), located in northeast Louisiana in the larger Ouachita River basin and covering approximately 1,006 mi², was included in the 305(b) by the Louisiana Department of Environmental Quality (LDEQ) for not supporting its designated use of fish and wildlife propagation. It was cited in the 1996, 1998, 2002, and 2004 reports. Causes of impairment include pesticides (DDT, toxaphene, and carbofuran), nutrients, suspended solids, and turbidity while runoff from agricultural field was cited as the main source of impairment. Over 440, 000 acres of agricultural land lie within the Tensas River watershed, representing a significant source of nonpoint source (NPS) pollutants. The total maximum daily load (TMDL) models for the river, developed in 2002 by the U.S. Environmental Protection Agency (USEPA) Region 6), suggested a 68% load reduction during the wet season in order for the Tensas River to comply with existing standards (TSS of 40 mg/L and turbidity of 50 NTU). Another TMDL, suggested a 93 % load reduction in order to meet the DO standard of 5.0 mg/L during the critical condition of lowest flow and hottest temperature. As a part of a restoration effort, a watershed implementation plan was developed by the LDEQ in 2005 to identify and address potential sources and causes of nonpoint source pollutant loads in Tensas River watershed. This plan details and encourages the implantation of best management practices (BMPs) to reduce pollutant export to the river. In support of this effort, this particular project is designed to evaluate the effectiveness of a combination of BMPs (vegetated filter strip-retention pond systems) in reducing NPS pollutant load reaching the river. Thus, findings from this project will be presented.