Scientific African (Sep 2022)
Hydrological impacts of climate change in selected ungauged sub-watersheds of Lake Tana Sub-Basin, Upper Blue Nile Basin, Ethiopia: A regionalization approach
Abstract
Climate change is a global issue affecting the world's hydrology and water resources. Quantifying climate change impacts on hydrology is important for integrated water resources management. The ungauged watersheds of Lake Tana sub-basin are vital for different habitats and communities where various socio-economic activities such as irrigation, and fishing are carried out. Therefore, assessment of the impact of climate change on this sub basin is critical to settingup an integrated water resource management plan for susitnablity of livelihoods. Climate effect evaluation on ungauged catchments' hydrology using continuous hydrological modeling is difficult with the absence of adequate measured hydro-meteorological data for modeling. This study, thus, used a regionalization approach for ungauged watershed impact assessment and an HBV hydrological model for simulation of flow for different RCP scenarios and time domains. Impacts of climate change on the hydrology of the ungauged sub watersheds namely (Gilgel Abay, Gumara, Megech, and Ribb) were studied using two ensemble GCM driven by one RCM(RCA4) under RCP4.5 and RCP8.5 for the 2040s (2020-2049), and 2070s (2050-2079) time domains. The following results were obtained: Summer rainfall drops for RCP4.5, and increments for RCP8.5 with a decline from March to June. Rainfall decreased under RCP4.5 and RCP8.5 in the spring. It was conclude that increased flow in the dry seasons, provided water for agriculture and other uses while, a decrease flow during the rainy seasons would reduce Lake Tana's storage during the summer. Summer storage is useful for the Tana Belles Hydropower project as it, potentially influences water demand and lake's Navigation depth. In the future these changes will potentially have a severe influence on agricultural production by reducing water supply, thereby calling for the successful implementation of adaptation measures to reduce vulnerability. As the study results revealed that there would be future dry flow decreases and wet flow increases, it is therefore,important that the government, and decision-makers should plan for integrated water resources management activities where for example, wet season flow could be stored for dry season use by providing storage structures.
