ESTIMATING THE EFFECT OF CLIMATE CHANGE ON GROUNDWATER RECHARGE AND BASE FLOW IN TEKEZE SUB CATCHMENT, TEKEZE RIVER BASIN, ETHIOPIA

Abstract

Water is indispensable for life, but its availability is threatened by many factors, of which climate plays a leading role. The effects of climate change are visible on surface water resources. But most concern should be focused on the effect of climate change on groundwater resources. Since, it is the main available source of water for living things and for irrigation agriculture. In understanding the effect of climate change on groundwater resources and water balance system, we need to understand the influence of these factors on groundwater recharge and base flow. Therefore, the present study was focused on the estimation of effect of climate change on groundwater recharge and base flow in Tekeze sub catchment, Tekeze basin, Ethiopia. Projected future climate variables were obtained from CORDEX Africa program for Representative Concentration Pathway (RCP) of two scenarios (RCP 2.6 and RCP 4.5) were used for future climatic conditions of the two future periods (2020 – 2079). The Mann-Kendall statistical test and Sen‘s slope estimator were used for trend detection using XLSTAT software. Further, the downscale and bias corrected precipitation, temperature and potential evapotranspiration outputs was used as input to the WetSpa model to simulate future water balance changes based on RCP 2.6 and RCP 4.5 climate change scenarios. The study results indicate that the decreasing trend in current annual rainfall. However, current average temperature and evapotranspiration reveals increasing trend. Projections of future rainfall show that annual rainfall decreases in both scenarios. The overall analysis of future average temperature and evapotranspiration showed that increasing trend in both scenarios. A fully distributed hydrological model, WetSpa was used to simulate the reference period and future (2020-2079) water balances. At the catchment level, precipitation decreases by 20% for both scenarios, and actual evapotranspiration show 0.4% and 8.1% increment, respectively for RCP 2.6 and RCP 4.5 scenarios. Moreover, the recharge decreases by 3.4% for RCP 2.6 and 1.31% for RCP 4.5. Baseflow will also decrease by 1.5% and 0.55% for RCP 2.6 and RCP 4.5 scenarios, respectively. This study would help governmental and nongovernmental organizations working in climate change and water resource studies.