Predicting the Impact of Detention Pond / Constructed Wetland Systems on Phosphorus Loads to a Multi-Reservoir Water Supply System

Previous studies have demonstrated that detention ponds in series with constructed wetlands can reduce phosphorous loads to receiving waters and improve water quality. Significant land acquisition and engineering costs, however, dictate that a predictive model be applied to analyze the effectiveness of pond/wetland systems on water quality in large watersheds. Such a model was developed for the series of 12 reservoirs that comprise New York City's Croton water supply system. Potential detention pond/wetland sites in the watershed of each reservoir were preliminarily identified based on a review of available maps. The viability (less than 5% slope, a source of water, and no significant wetlands) of the potential sites were verified in the field and approximate boundaries of the 46 viable sites were located using a Global Positioning System (GPS). The land use within the catchment of each site was delineated on geographic information system (GIS) maps.