Variable Source Watershed Model for Reducing Dissolved Phosphorus Concentrations in Surface Waters

Abstract:

Although established procedures for treatment of point sources have been available for the last fifty years, effective and efficient management procedures for reducing non-point source pollution are still being developed. One of the reasons for the slow development is that the various management practices need to be tailored to the landscape in order to be optimal. Water quality simulation models for watersheds would be ideal for designing these effective practices but in many cases are only validated at the watershed outlet where the monitored data are available which does not guarantee that the spatial distribution of runoff and pollution sources inside the watershed are simulated correctly. Especially, in rural, humid regions where runoff is associated with saturation-excess processes from variable source areas our modeling of the hydrology and water quality is limiting. Recently, we adapted successfully a watershed model El-SWAT that realistically can simulate saturation excess surface runoff and interflow by introducing a perched water table reservoir that can transfer water via the subsurface to the wet areas in the watershed and thereby overcomes one of the major limitation of the SWAT model. For this presentation, we have combined El-SWAT with a set of spatially dependent phosphorus sub routines developed by us for simulating spatially dependent phosphorus losses in upstate New York State. In this presentation we will show its application in designing effective best management practices in the New York City Source Watersheds in the Catskill Mountains.