Water Quality Sampling and Assessment in a Coastal Agricultural Watershed in Louisiana, USA.

Many water bodies in coastal Louisiana are not meeting the EPA standard for their designated usages, and, therefore, they are included in 303(d) list of impaired water bodies. In order to determine the effectiveness of agricultural BMPs in reducing nutrients, sediments, and biological oxygen demanding substances entering the water body, we monitored surface water quality of Bayou Chene in southwestern Louisiana from June 2012 to June 2016. Water quality sampling involved the weekly collection of surface water samples from each locations (initially at four locations and later at 10 locations) by grab using a Van Dorn sampler. Laboratory determination of these samples included TSS, TDS, TS, BOD5, NO3/NO2-N, TKN, SRP, TP, Cl, Fl, and SO4. Surface water temperature, DO, Turbidity, conductivity and pH were determined in the field using YSI Sonde. While average annual TSS, TDS, TS, and nutrients and turbidity values declined remarkably in the fourth year as compared to the first year of the study, the DO and BOD5 values showed further impairment of the water body. Average concentrations for sediments and nutrients were higher for the upstream sites compared to the sites located downstream where more BMPs were implemented during the study. It is suggested that BMPs should be implemented focusing on the hotspots emphasizing agricultural activities that occur specially during the months of March-September for nonpoint source pollution control in the watershed.