Statistical evaluation of bmp effectiveness in reducing nutrient impairment in mermentau and vermilion-teche river basins
Document Type
Conference Proceeding
Publication Date
10-26-2009
Abstract
The Mermentau and Vermilion-Teche River Basins consisting of 11 watersheds are located in the southwestern part of Louisiana and encompass a drainage area of approximately 17,431km2, 52 of which is cropland, primarily rice (34) and soybeans (17). Stormwater runoff and rice field discharges from January through May result in high pollutant and nutrient loadings containing nitrogen, phosphorous, and TOC (total organic carbon). As a result, the Louisiana 1998 305(b) Report indicates that 95 of the waterbodies within the basins are not fully supporting their designated uses. Since 1990, a variety of Best Management Practices (BMPs) has been implemented in the Mermentau and Vermilion-Teche River Basins. However, effectiveness of the BMPs in improving water quality and particularly in reducing nutrient impairment is largely unknown due to the lack of source information and to the spatio-temporal variability in hydrological and hydrometeorological parameters controlling nonpoint source pollution. This paper presents a statistical method for evaluating the effectiveness of Best Management Practices (BMPs) in reducing nutrient impairment using water quality data monitored from 1980 - 2006 in the Mermentau and Vermilion-Teche River Basins. The statistical method mainly involves (1) determination of seasonal variations in nutrient (NO2+NO3, TKN, total phosphorous, TOC) loading rates in order to identify critical months of nutrient impairment, (2) mapping of mean annual nutrient loads for pre-BMPs and post-BMPs, and (3) evaluation of the effectiveness of BMPs in reducing nutrient impairment based on the trend analysis. Results of the statistical evaluation show that (1) nutrient loading rates vary both seasonally and spatially. Nutrient loading rates become high in winter and spring (January - May) and low in summer and fall. The main impairment in January - March is caused by wet weather runoff. The severe impairment in April and May is related to the releases of muddy rice-field water. High nutrient loading rates are concentrated in the three watersheds: Bayou Queue de Tortue, Bayou Nezpique, and Vermilion River; (2) Since the implementation of BMPs in 1990, water quality in the two river basins has shown an improving trend in terms of nutrient impairment while it was worsening from 1980 - 1990; and (3) BMPs need to be enhanced in the two river basins. © 2009 ASCE.
Publication Source (Journal or Book title)
Proceedings of World Environmental and Water Resources Congress 2009 - World Environmental and Water Resources Congress 2009: Great Rivers
First Page
6436
Last Page
6445
Recommended Citation
Deng, Z., & Chowdhary, H. (2009). Statistical evaluation of bmp effectiveness in reducing nutrient impairment in mermentau and vermilion-teche river basins. Proceedings of World Environmental and Water Resources Congress 2009 - World Environmental and Water Resources Congress 2009: Great Rivers, 342, 6436-6445. https://doi.org/10.1061/41036(342)652