Evaluating Potential Impacts of Climate Change on Hydro- meteorological Variables in Upper Blue Nile Basin, Ethiopia

Abstract

Climate change impacts are the main concern for sustainability of water management, water use activities and agricultural production throughout the world. Climate changes alter regional hydrologic conditions and results in a variety of impacts on water resource systems. The objective of this study is to assess the impact of climate change on the hydro climatology of Finchaa Sub-basin located in upper Blue Nile Basin of Ethiopia. The GCM (General Circulation Model) derived scenarios (HadCM3 A2a & B2a SRES emission scenarios) were used for the climate projection. The statistical Downscaling Model (SDSM) was used to generate future possible local meteorological variables in the study area. The down-scaled data were then used as input to the Soil and Water Assessment Tool (SWAT) model to simulate the corresponding future stream flow in of Finchaa Sub-basin. The time series generated by GCM of HadCM3 A2a and B2a and Statistical Downscaling Model (SDSM) indicate a significant increasing trend in maximum and minimum temperature values and a slight decreasing trend in precipitation for both A2a1 and B2a2 emission scenarios in sub-basin for all three bench mark periods. The hydrologic impact analysis made with the downscaled temperature and precipitation time series as input to the SWAT model suggested an overall decreasing trend in annual and monthly stream flow in the study area, in three benchmark periods in the future. Potential evapotranspiration in the watershed also will increase annually on average 3 to 16 % for the 2020s and 4 to 19 % for the 2050s and 2080s for both A2a and B2a emissions scenarios. As a result, at the ut let of the watershed the projected on average annual flow decrease by 5.59 %,9.03 %,11% and 2.16 %,4.15 and 3.46 % for the 2020s,2050s and 2080s for both A2a and B2a emissions scenarios. The paper also includes potential strategy recommendations to communities, policy and decision makers for measuring and enhancing effective adaptation option for future climate change impacts on hydrology.

Keywords: A2a, B2a, climate change; Finchaa sub-basin, GCM, SDSM, stream flow; SWAT