ABSTRACT
The hydrology and water quality of a stream or reservoir can be affected due to rapid urbanization and land use change in its watershed. Climate change, if it occurs, is likely to have additional impacts on hydrology and water quality of the watershed system. In this study, a watershed model WARMF (Watershed Analysis Risk Management Framework) was applied to the Saugahatchee Creek Watershed which includes two stream branches that were listed on State of Alabama’s 303(d) list of impaired water for nutrients and organic enrichment/dissolved oxygen. WARMF model for the Saugahatchee Creek Watershed was developed and model calibration and validation were performed. The model was then used to investigate hydrologic and water quality response to two different land use scenarios (LU 2009 and LU 2030) and four statistically downscaled future climate scenarios derived from Canadian Global Coupled Model (CGCM3) and Hadley Centre Coupled Climate Model (HadCM3). Temperature, dissolved oxygen, total nitrogen, total phosphorus, and algal concentration were the water quality parameters simulated along with flow. Based on monthly average of daily predicted values, the effect due to land use change was not significant except for nutrient concentration. The monthly average of daily total phosphorus concentration for LU 2030 is predicted to increase up to 72% more than baseline (LU 2009) under past climate conditions (1981–2010). Based on model results, the monthly average of daily surface water temperature is predicted to rise for all future climate scenarios. The monthly average of daily flow is predicted to increase corresponding to CGCM3 (annual average increase of 88%) and decrease corresponding to HadCM3 scenarios (annual average decrease of -49%). Accordingly, nutrient concentration is expected to decrease corresponding to CGCM3 and increase corresponding to HadCM3 scenarios. DO concentration are predicted to fall up to 2.3 mg/l (monthly average), especially in summer for the four climate scenarios. Combined land use and climate change scenarios cause the increase in nutrient concentrations for future land use and climate scenarios (e.g., annual TP from 0.082 mg/l for the baseline to 0.203 mg/l for HadCM3 A2 20s scenario). Chlorophyll-a concentration during the growing season is expected to increase to 25.8 and 26.3 μg/l under HadCM3 A2 and B2 scenarios due to combined effect, respectively, in comparison to 18 μg/l for the baseline (1981–2010 and LU2009). The results of this study can be incorporated into watershed management and planning strategies.