West and Rhode River pollution mitigation

The West and Rhode Rivers cover 80 square kilometers of watershed and subestuary along the Chesapeake Bay. Key metrics for water quality were found to deviate substantially from desired threshold levels, indicating poor water quality in the subestuary [1]. The project´s sponsor, the West and Rhode Riverkeeper, needed to identify and implement mitigation measures to improve water quality in the subestuary. The Center for Watershed Protection (CWP) outlined a set of mitigation measures; however, the report did not include quantitative predictions from the implementation of mitigation measures or a qualitative assessment of the Riverkeeper´s objectives. CWP recommended mitigation measures to reduce the influx of nutrients without a concise evaluation of the problem space to determine if nutrient reduction resulted in measurable improvements in water quality. This project designs a decision support system (DSS) which enables the Riverkeeper to quantitatively predict the effect of implementing mitigation measures on water quality. The DSS facilitates key tradeoff analysis in accordance with the Riverkeeper´s objectives and identifies an additional mitigation measure. The DSS is comprised of a utility function that is reflective of the Riverkeeper´s values, and a predictive tidal nutrient/sediment transport model system. Since nitrogen and sediment are considered surrogate measures of water quality, the model yields a transfer function from watershed use to water quality by predicting nitrogen and sediment concentrations in the subestuary. A cost benefit analysis and a final rank order of potential mitigation measures are derived from the DSS.