The Impacts of Climate Variability and Climate Change on the Discharge of 40-springs, Arba Minch, Ethiopia.

Abstract

The present study area (40-springs near Arba Minch) is located in the southern part of the Ethiopian Rift Valley. In this thesis, the trends in the observed climate (Temperature, Rainfall, Potential evapotranspiration, Relative humidity, Sunshine hour duration, and Wind speed) at Arba Minch during 1987-2006, as well as in the future climate (obtained by downscaling the GCM projections to the study area and using GrADS) these are Temperature, Rainfall and Potential evapotranspiration for the period 2007-2100 have been examined, by using parametric and non-parametric trend detection techniques. In a similar way, the future annual Discharge of the 40-springs also has been projected using SMAR hydrological Model. Finally, the impact of the trends in the observed, as well as the projected climate on the 40-springs Discharge over the periods (1987-2006 and 2007-2100) has been assessed. In general, the temperature, rainfall, potential evapotranspiration, wind speed, and Relative humidity over the study area show an increasing trend. However, the slight increasing trend in the observed rainfall is found to be statistically insignificant. The 40-springs discharge shows a slight decreasing trend, which is significant for the observed period (1987-2006), but slight decreasing over the projected period (2007-2100). The slight decreasing trend in the annual discharge of the 40-springs has been attributed to the significant increase in the maximum temperature at Arba Minch. In addition to the changes in the climatic factors (temperature and heavy precipitation events leading to soil erosion), some non-climatic man-made (like urbanization and agricultural expansion) processes also may be responsible for the observed decreasing trend in the annual discharges of the 40-springs.