Characterizing ponds in a watershed simulation and evaluating their influence on streamflow in a Mississippi watershed

Small water bodies, such as ponds and wetlands, are common landscape features, but often are not simulated within a watershed modeling framework. The wetland modeling tool, AgWET, uses a GIS framework to characterize the features of ponds and wetlands so that they can be incorporated into watershed simulations using the Annualized Agricultural Non-Point Source (AnnAGNPS) pollution model. AgWET was used to characterize farm ponds on the Goodwin Creek Experimental Watershed in northwest Mississippi and AnnAGNPS simulated watershed hydrology. Monthly streamflow was validated at four watershed gauges with Nash-Sutcliffe efficiency values between 0.91 and 0.94. Ponds influenced watershed hydrology at various scales, with a decrease in average streamflow by 4% at the watershed outlet, 8% at the sub-watershed scale, and an average of 56% immediately downstream of the ponds. AgWET can be used to simulate ponds in watershed assessments for improved results and evaluation of future scenarios.