Quantifying Forest Management Impacts On Hydrology and Water Quality Using a Modeling Approach.

Abstract.

This study was conducted in Upper Pearl River Watershed (UPRW) in Mississippi. The watershed have been identified as “impaired waters” under Section 303(d) of the Federal Clean Water Act due to high levels of sediment, nutrient, and pathogens. Clear-cut forest harvesting can have significant environmental effects due to the removal of forest cover. The objective of this study was to quantify hydrologic and water quality impacts of clear-cut forest harvesting from the Upper Pearl River Watershed (UPRW) in Mississippi by using the Soil and Water Assessment Tool (SWAT) model. The SWAT model was calibrated and validated using long-term monthly observed stream flow data at five USGS stations. Daily sediment yields were also verified at Lena USGS gage station using eleven months of observed data. The model results for stream flow were evaluated statistically using coefficient of determination (R²), Nash-Sutcliff efficiency (NSE), root mean square error (RMSE), and percentage bias (PBIAS). The model showed relatively good fits between observed and simulated values for both stream flow and sediment. The results of this study indicated substantial increase with increase in the percentage of forest area harvested, which would be important to develop future forest management practices in the UPRW and other forested watersheds.

Keywords.  Clear-cut, forest management, hydrology, water quality, SWAT