Sediment-Phosphorus Response to Reduced Point Source Loading in the James River Watershed, Southwest Missouri

Eutrophication of lakes due to increased loading of nutrients negatively affects water quality, warranting worldwide efforts to reduce the limiting nutrient in most lakes, phosphorus (P). Government regulations on excess nutrient loads entering the James River Arm (JRA) of Table Rock Lake, Missouri began in 2001 with upgrades at a major sewage treatment plant (STP). The present study aims to quantify the spatial and temporal distribution of sediment P in the James River Basin by (1) quantifying present sediment-P concentrations in the basin, (2) describing the spatial patterns of sediment-P reduction, and (3) investigating the link between upstream sediment and P sources and JRA sediment-P response. Lake sedimentation zones are identified based on physical and chemical sediment characteristics and lake morphometry. Sediment-P concentrations are highest immediately downstream of the STP (620-1,190 ppm) and in the JRA (370-1,580 ppm) and are lower in the James River (170-640 ppm). Sediment-P concentrations in the JRA are strongly correlated to depth and Mn (r2 = 0.92). Sediment-P concentrations have decreased downstream of the STP since 2001, ranging from 14-58% in stream sediments, and 31-36% in the JRA. Lake sediment-P reductions are greatest in deeper areas of the JRA. Concentrations of Al have decreased by 9-70% in the James River and Wilson\u27s Creek, and have increased in the JRA by 9-34%, potentially reflecting the influence of STP treatment procedures or variable sediment sources on sediment geochemistry. Nonpoint P may have increased since 2001, warranting future attention