Implications of Land Use and Climate Change on Water Balance Components in the Sigi Catchment, Tanzania

Abstract

Whereas normal water flow in a catchment is necessary for all forms of life, the hydrologic systems in the Sigi catchment is susceptible to land use and climate changes. Over the past three decades, water balance of the Sigi Catchment has indicated changes with unknown forms and magnitudes. To uncover the dynamics, this study used SWAT model to simulate water balance to a separate and combined impact of land-use and climate change. SWAT simulation showed good performance with NSE=0.58 and R2=0.67 for calibration, and NSE=0.56 and R2=0.64 for validation periods. Land use change scenarios indicated increase in surface runoff by 16.1mm, while base flow and water yield decreased by 23.1mm and 7.2mm, respectively. Climate change scenarios indicated an increase in surface runoff by 29.9mm, while base flow and water yield decreased by 36.1mm and 14.2mm, respectively. The combined land use and climate change scenarios indicated increase of surface runoff by 19.0mm, and decrease in base flow and water yield by 29.7mm and 10.7mm, respectively. From the study, it is clearly that the impacts of climate change on water balance components of the Sigi catchment are larger than land use change. Owing to the dilemma facing water resources in this era of climate change, long-term planning that balance households’ livelihood options and water resources management option is needed.