Development of a Coupled WEPP-WQ model

Non-point source (NPS) pollutants, especially from agriculture, continue to be a primary source of water quality degradation problems. Farmers need to take effective land managements at field scales for minimizing nutrient losses that could pollute streams. But existing NPS models cannot directly estimate the impacts of different land managements or testify the effectiveness of combined BMPs in a distributed way at farm scale with the application of USLE or its improved version in a lumped way. Here we developed the coupled WEPP-WQ model and evaluated simulations of hydrology, soil erosion and water quality from this coupled model. WEPP is a well-established process-based model that simulations runoff and erosion processes from a hill slope. The water quality components are based on the SPELL OUT (EPIC) model and the water quality algorithms within SPELL OUT (SWAT). Our test case uses a single Overland Flow Element (OFE) to represent land use on a hill slope, but in the next phase of development we will evaluate WEPP-WQ's ability to modify the transport of nutrients and sediment as runoff from the hill slope encounters multiple OFEs representing different land uses. WEPP-WQ was tested by comparing simulated values from the coupled model and observed nutrients and sediment concentrations in surface runoff following storm events at an experimental site near Waterloo, IN, U.S..