Assessing the Impact of Climate Change on Groundwater Recharge: Case Study of Akaki Catchment, Central Ethiopia

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Date

2021-01-17

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Addis Ababa University

Abstract

This study was conducted in the Akaki catchment to assess climate change and its impacts on groundwater recharge with a total area of (1470 km2). To analyze the possible impacts of future climate change on the groundwater recharge, climate projections for rainfall and temperature data have been carried out using downscaled GCM (MIROC5) model output which in turn was used as input to the WetSpass model to simulate future groundwater recharge and other hydrological components based on RCP 4.5 and RCP 8.5 scenarios. The linear scaling bias correction method was applied to adjust the bias for both temperature and rainfall projections. The bias corrected MIROC5 has shown that near perfect match with observation in each meteorological station. The change in mean annual precipitation during 2050s is expected to decrease by 2% in RCP4.5 but, increased by 3% in RCP8.5. During 2080s it expected to increase by 1% and 3% in RCP4.5 and RCP8.5 respectively. The rainfall shows an increasing trend under RCP8.5, but it is decreasing under RCP4.5 respect the baseline. In the period 2050s, the change in mean annual temperature expected to increase by 1.5oC and 1.8oC in RCP4.5 and RCP8.5 respectively. During 2080s is also expected to increase by 2.1oC and 3.5oC in RCP4.5 and RCP8.5 respectively. The change in temperature is expected to increase in the two projected periods. The simulated results from the WetSpass model showed that the annual average precipitation (1131) mm is distributed as 42% of mean annual evapotranspiration (469mm), 35% of runoff (396 mm), 23% of groundwater recharge (266mm) in the baseline. In 2050s, mean annual groundwater recharge is expected to be 257 mm and 269 mm under RCP4.5 and RCP 8.5 respectively. This shows decrease by 3 % in RCP4.5, but an increase by 2% in RCP 8.5. In 2080s this is expected to be 268 mm for RCP4.5 and 270 mm for RCP 8.5. It expected increase by 1% and 2 % under RCP 4.5 and RCP 8.5 respectively. Based on the results of the model, the groundwater recharge shows an increasing trend in all scenarios, except in the period 2050s under RCP4.5. But, this result considered only future precipitation, maximum and minimum temperatures scenarios by assuming other parameters are constant. The rapid population growth in the catchment area, higher demand for water resources is inevitable. As a result, sound and effective groundwater management is compulsory.

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Keywords

Groundwater Recharge, Wetspass Model, Bias Correction, Akaki Catchment

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