SIMULATING HYDROLOGIC AND WATER QUALITY IMPACTS IN AN URBANIZING WATERSHED

摘要

The Hydrologic Simulation Program-Fortran (HSPF) waS calibrated and used to assess the future effects of various land development scenarios on water quality in the Polecat Creek watershed in Caroline County, Virginia. Model parameters related to hydrology and water quality were calibrated and validated using observed streamflow and water quality data collected at the watershed outlet and the outlets of two subwatersheds. Using the county's Comprehensive Plan, land use scenarios were developed by taking into account the trends and spatial distributions of future development. The simulation results for the various land use scenarios indicate that runoff volume and peak rate increased as urban areas increased. Urbanization also increased sediment loads mainly due to increases in channel erosion. Constituent loads of total Kjeldal nitrogen, orthophosphorus, and total phosphorous for Polecat Creek watershed slightly decreased under future develop-ment scenarios. These reductions are due to increases in urban areas that typically contribute smaller quantities of nitrogen and phosphorous, as compared to agricultural areas. However, nitrate loads increased for the future land use scenarios, as compared to the existing land use. The increases in nitrate loads may result from increases in residential land and associated fertilizer use and concurrent decreases in forested land. The procedures used in this paper could assist local, state, and regional policy makers in developing land management strategies that minimize environmental impacts while allowing for future development.