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