Assessments of Climate Change Impact on Water balance (Case study on Lake Hawassa, Ethiopia)

Abstract

Nowadays the climate change and its impact are being witnessed on different natural and manmade systems, in one or other ways. One of this impact concerns to understand hydrological components and subsequent changes in water balances. The aim of this study was to understand the climate change impacts on water balances of Lake Hawassa located in central main Ethiopian Rift Valley, using the Regional Climate Model (RCM). A hydrological model, HBV-96 was utilized to simulate surface inflow. The A1B scenario of Regional Climate Model organized by IWMI is used for future climate scenario condition. Linear scaling approach is applied in order to bias correction of precipitation, maximum and minimum temperature. The performance of the hydrological model was assessed through calibration and validation process and resulted R 2 =0.72 during calibration and R 2 =0.66 during validation, which is good representation of the catchment. The projected future climate variable has two future time horizons2030s (2031-2040) and 2090s (2091-2100), for both future time horizon shows an increasing pattern for both maximum and minimum temperature. However, precipitation doesn‟t mainfest a systematic increase or decreasing pattern in the next century. Over lake mean monthly precipitation will increase in the months of November and August by15.09 % in 2030s and 28.0% in 2090s and will decrease in the months of January and February by 34% in 2030sand 41% in 2090s respectively. Over lake- evaporation shows increasing pattern for all future time horizons. Seasonal mean inflow may shows increase up to 10.8% and 13.7% in kirement (JJAS) for 2030s and 2090s time period respectively.