Assessment of Climate Change Impact on the Future Inflow Potential of the Upper Awasli River Basin, Ethiopia

Abstract

/Changes in climate factors like temperature, precipitation amount, patterns and intensities and evapotranspiration caused by global warming have direct impact on hydrological cycle component of stream flow in rivers. This will affect ecological, social and economical systems . The climate impact studies in hydrology often require climate change information at fine spatial scale than coarse scale that obtained from General Circulation Mode ls (GCMs).Thercl'orc the output from a GCM has to be downscaled to obtain information relevant to hydrological studies. To estimate the level of impact of climate change on the watershed's waler availability, clirna!c change scenarios of precipitation and temperature were developed for th�·ee future periods. The outputs of HadCM3 coupled atmosphere-ocean GCM model for the SRES A2 and 82 e mission scenarios downscaled to the watershed scale through the appli cation of the SDSIVl model to produce the future s cenarios. Minimum temperature, maximu m temperature and precipitation downscaled usin g SDSM. were used as input to the HEC-HMS hydrological model which was calibrat ed a nd . validated with · historical dat a to simulate the corresponding stream flow change. 1__...-.. The result of this study addresses. t hat the average ann u a l minimum temperature w il l be increased by 4.05 �C & 3.22 °C for Akaki cat chment, 3.74 °C & 2 . 95 °C for Berga catchment , 4.16 °C & 3.2:'.° C for Mclkakunture Catchment, and 4.26 °C & 3.3 3 °C for Hombolc for A2 ,\'.. 82 scenarios respectively. The maximum temperature would also incr ease by 4 . 76 °C & 3 .84 °C for Akaki c a tchment , 2 . 8 7 °C & 2.2 4°C for Berga catchment, l .4 8 ° C & l .2 8 ° C for Mclkakunturc Cat c hme n t , and l. 04 °C & . 7 5 ° C for Hombole for A2 & 82 s c enario s respectively. The metrological variables mini mum tem perat ure .maximum tempe rat ure a n d prcci pitat ion downscaled from SDSlVl were used as inp u t in HEC-HM S hydrological model wh ic h was calibrat e d and validicatcd wi th historical data to inv est ig at e the pos sible im pact of climate change in the catchcme,:'..: The r e s ult or t he study indic ate that there is signific�t varia tion in mon t hly in fl o w. The mont hl y flow will be reduced in t he rain y s ea s on a'nct. i ncre as ed dur i ng wint e r r eas on. The c h a n g e range bet ween +5m 3/:-. and - l 0•. 1 }/s for Berga Catchcmern, <tl0m 3 /s and - 50m 3 /s for Akaki Catchcrncnt · +20m'/s a nd - 1 05 m 3 / s in t he next hundred years will be expected i11 tile Upper Awash Basin.