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The effects of land use and precipitation on nutrient and sediment export from three Ohio watersheds.
Bowling, Anna*,1, Vanni, Michael1, Renwick, William1, Christian, Alan1, 1 Miami University, Oxford, OH, United States
ABSTRACT- Land use, precipitation, soil and landscape characteristics can drive variation in the quantity and quality of nutrients and sediments that are exported from a given watershed. Although numerous studies have shown that nutrient export rates are higher in agricultural watersheds than in forested watersheds, export rates are highly variable due to variation in precipitation, physical factors, and sampling regimes. This variation can obscure trends in land use effects, and highlights a need for comparative studies with consistent and intensive sampling. Our research focused on how land use and precipitation affect the amounts of nutrients and sediments exported in streams from three Ohio watersheds. Our study sites included Acton Lake watershed (88% agriculture, 9% forest), Pleasant Hill Lake watershed (51% agriculture, 45% forest), and Burr Oak Lake watershed (14% agriculture, 81% forest). We used a storm-intensive sampling program to quantify particulate, as well as inorganic and organic dissolved forms of nitrogen (N) and phosphorus (P), and suspended solids. We found a strong and consistent effect of land use on nutrient and sediment export. Thus, the concentration of NO3-N was highest in Acton Lake watershed (0.99-11.98 mgN/L), followed by Pleasant Hill (0.81-2.29 mgN/L), and then Burr Oak (0.01-0.53 mgN/L). Most of the dissolved N exported was in the from of NO3-N for the agricultural watershed (Acton Lake), whereas most of the N exported in the forested watershed (Burr Oak) was in the form of dissolved organic N. Concentrations of soluble reactive P were also highest in Acton Lake watershed (4.06-132.37 ugP/L), followed by Pleasant Hill (3.82-40.08 ugP/L) and then Burr Oak (2.55-9.57 ugP/L). Most nutrient loading (dissolved and particulates) occurred during storm events. Particulates ( particulate P and suspended solids) exhibited the greatest variation in response to precipitation.
Key words: nutrient export, watershed, land use