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Technical Report

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SWAT models, water monitoring, Arkansas, watershed


Arkansas Natural Resources Commission has identified three priority hydrological unit code (HUC) 8 watersheds, the Upper Saline (HUC 08040203), Poteau (HUC 11110105), and Strawberry Watersheds (HUC 11010012). SWAT models have been developed to estimate nutrient and sediment loads in these watersheds where limited water‐quality data was available. The purpose of this project was to collect additional water samples across these HUC 8 watersheds to better understand how water quality changes across subwatershed with differing land use mixes, as well as estimate nitrate‐nitrogen (NO3‐N), total phosphorus (TP), and total suspended sediment (TSS) loads. Water samples were collected at twenty sites near HUC 12 outlets or other desired locations within each of the three selected watersheds. These sites included seven existing USGS stage and discharge monitoring stations. The sites were sampled monthly from October 2011 through September 2012, and storm samples were collected through March 2013. Constituent loads were estimated for calendar year 2011 and 2012 at the seven sites where the USGS records discharge data and compared with SWAT model output. We also ranked the subwatersheds based on mean concentrations of NO₃‐N, TP, and TSS and calculated a Spearman rank coefficient (ρ). The knowledge attained from this project helped validate the SWAT modeling output, and improved the level of confidence that we had in the subwatershed prioritizations based on the SWAT output.

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