Alcovy Watershed Assessment: Simulating Best Management Practices and FutureDevelopment Using the BASINS Framework

摘要

The Alcovy River watershed (312 square miles) spans Gwinnett, Walton, Newton andrnJasper counties which are served by the Northeast Georgia Regional DevelopmentrnCenter. The Northeast Georgia RDC has taken a proactive stance in protecting thernAlcovy River watershed. In anticipation of significant growth and protection of valuablernwater resources, the group has requested the preparation of the Alcovy River WatershedrnAssessment Report and the Alcovy Watershed Protection Plan. This project discusses thernmodeling portion of these larger studies. The purpose of this study was to develop arncalibrated watershed water quality model in order to simulate the impact of differentrnfuture scenarios. The BASINS interface to HSPF was selected as the watershed waterrnquality model for the Alcovy River watershed. Water, sediment, phosphorus and fecalrncoliform were the constituents modeled. The hydrologic portion of the model wasrncalibrated to continuous daily USGS flow data available at a station on the Alcovy River.rnIn-stream water quality data used for the model were obtained from four USGS stationsrnlocated on the Alcovy River and fifteen additional stations located throughout the studyrnarea. Upon completion of calibration, the model simulated the impact of futurerndevelopment using a projected land cover for the year 2020 and increased loads fromrnpoint sources. Eight future scenarios incorporating various management practices werernmodeled. These scenarios include the simulation of conservation subdivisions, riparianrnbuffer ordinances, impervious surface restrictions, storm water quality controls andrnimproved enforcement of erosion and sedimentation controls. Model simulationsrnindicate that the phosphorus load nearly doubles for almost all future scenarios asrncompared with current conditions. Furthermore, no single management practice indicatesrna significant pollutant load reduction. Sediment and fecal coliform results showedrnsimilar trends. Modeled results indicate that a combination of best management practicesrnmust be implemented in order to achieve any noticeable reduction in pollutant loading tornthe Alcovy River. This hydrologic and water quality model demonstrates that thernanticipated growth and development will be detrimental to the water quality of thernAlcovy River watershed. If only the BMPs simulated for this project are considered, it isrnexpected that the degradation of water quality will be slowed, but not eliminated.