Abstract
According to Intergovernmental Panel on Climate Change (IPCC) rising of global surface temperature, sea level rises, arctic and land ice decrease, erratic precipitation and increase of CO2 concentration are the main indicators of climate change. The main objectives of the study was to investigate the possible hydrological impacts of climate change on stream flow and sedimentation in Tikur Wuha watershed, by downscaling canESM2 (Canadian Earth System Model of second generation) global climate model using Statistical Downscaling Model (SDSM). Based on IPCC recommendation baseline periods (1987–2016) were used for baseline scenario analysis. Future scenario analysis was performed for the 2020s, 2050s, and 2080s. canESM2 model consists of Representative Concentration Pathway (RCP) RCP2.6, RCP4.5 and RCP8.5 scenarios. Impact assessment on stream flow and sediment yield was done by Soil and Water Assessment Tool (SWAT) hydrological model. SWAT model performance in simulating monthly stream flow for the study area was satisfactory with R 2 (0.77 and 0.87), N SE (0.70 and 0.77) and D (-16 and -9) for calibration and validation periods respectively. The result of downscaled precipitation and temperature reveals a systematic increase in all future time periods for all three scenarios; RCP2.6, RCP4.5 and RCP8.5 scenarios. These increases in climate variables are expected to result in increase in mean annual stream flow of 8%, 13%, and 15 % for RCP2.6 scenario, 17%, 24%, and 31% for RCP4.5 scenario and 14%,24% and 35% for RCP8.5 scenario for the 2020s, 2050s, and 2080s, respectively. This leads to increment of sediment yield from different sub watershed. The estimated soil loss rate from different sub-watersheds had ranged from 0.42 tons/ha/yr to 28.31 tons/ha/year (1987-1999), whereas the annual weighted average soil loss rate from the watershed was estimated 16.80 tons/ha/year (2000-2100). Future work need to consider studying the effects of different climate change adaptation strategies. Keywords: Climate change Scenarios, Ethiopia, Hydrological impact, SWAT model DOI: 10.7176/JEES/10-2-04 Publication date: February 29 th 2020
Highlights
The increment is most dramatic in January for both RCP2.6, RCp4.5 and RCP8.5 scenarios in which the precipitation increases by 67% (2050s), 40% (2050s) and 70.5% respectively
Rizwan et al (2010) carried out research in northern part of Ethiopia on the upper Blue Nile using different General circulation model (GCM) out puts including HadCM3 and canESM2 and the results showed that the runoff increases in the future in the major rainy seasons (June-September) which causes the possibility of flood occurrences in the future due to extreme runoff
The precipitation showed that increasing trends for the future time horizons mainly in the major parts of the rainy season (June to September), Seasonally in Belg and Kiremt season while it decreases in Bega season
Summary
The shift in temperature and precipitation patterns affects the hydrology process and availability of water resource (IPCC, 2013). Developing countries, those in Africa are likely to be vulnerable to climate change as recurrent droughts, flood and siltation of water bodies continue to bring misery to millions in Africa (Nawaz et al, 2010). Studies at Bilate watershed in the Ethiopian Rift valley basin suggested that climate change could affect by decreasing of water resources (Tekle, 2014). Research conducted on Upper Blue Nile River Basin shows the positive change of precipitation in future (Mekonnen and Disse, 2016) Both researchers indicated that climate change strongly affects Ethiopian agriculture and socio-economic aspect. Www.iiste.org current study were: (1) to generate ensembles of future rainfall and temperature series using SDSM for a range of representative scenarios, (2) to simulate projected impacts of climate change on hydrological characteristics of the Tikur Wuha watershed using the hydrological model (SWAT)
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