As cities and communities grow, and land use patterns change, the water quality within a watershed is impacted by increased point, non-point source discharges, and altered hydrology. Therefore, decision-makers are always attempting to determine the best choices for sustaining economic growth, while protecting the environment. A new framework for conserving and restoring watershed health that is gaining traction lately focuses on holistically identifying and addressing water quality impairments in collaboration with state and local stakeholders. This framework is deemed the "watershed approach." To implement a watershed approach, robust data-driven hydrologic models capable of predicting the effects of land use changes on water flow and quality are needed, which can be challenging, especially for watersheds that are largely karst. Several previous studies have attempted to model the complex karst hydrology only with limited success. In this study several existing hydrologic models were evaluated for their use in the largely karst Falling Water River watershed, located in the Highland Rim region of Tennessee. Comparing simulated flow to observed flow, results indicated that the model, TopoSWAT, was better able to represent watershed flow. The flow calibrated TopoSWAT model produced an NSE and PBIAS values of 0.77 and 1.4%, respectively. Further, sediment and total nitrogen calibration was attempted with limited success due to sparse water quality data. Using the outputs from the model, a preliminary Water Quality Index (WQI) was calculated using a hybrid CCME WQI method. In addition, an easy-to-use Geographic Information System (GIS) based WQI tool was developed to integrate water quality data and allow evaluation of various watershed management alternatives. Although the WQI tool needs further improvement with additional hydrologic and water quality data, it can be used to illustrate the impacts, whether positive or negative, of land use changes. This tool can provide a way to enhance decision-making capabilities, leading to efficient management of watersheds while meeting the needs of urban development.
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