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.
