ASSESSMENT OF CLIMATE CHANGE IMPACT ON SURFACE WATER AVAILABILITY AND ALLOCATION IN SHABELLE RIVER BASIN, SOMALIA

Abstract

On a global scale, climate change is projected to have detrimental impacts on harm water avail- ability. This situation will become more severe due to climate change's accumulated impacts and anthropogenic activities. This study aims to investigate climate change impact on water availability and allocation in the Shabelle River Basin, Somalia using the Soil and Water As- sessment Tool (SWAT) and Water Evaluation and Planning (WEAP) models. Bias corrected Regional Climate Model (RCM) from CORXDEX Africa derived by the ICHEC-EC-EARTH global climate model under two scenarios RCP 4.5 and 8.5 was used in this study. The future periods are divided into three-time horizons with equal length of time as the base line period 2025–2048, 2049–2072 and 2073–2096. The projected annual average precipitation increase reached 8.6% under RCP4.5 and 32% under RCP8.5. Under the RCP4.5 emissions scenario the average monthly maximum temperature increased up to 2.56°C and 1.68°C for minimum temperature, similarly under RCP8.5, temperature increased up to 4°C and 3.7°C respective for maximum and Minimum temperature. The calibration and validation of SWAT were per- formed using monthly discharge, and the result showed agreement between the observed and simulated data sets. The model assessment statistics, Nash Sutcliffe Efficiency (NSE) and coef- ficient of determination (𝑅2) values were 0.68 and 0.69, for the calibration period and 0.68 and 0.71, for the validation period. The average annual discharge volume will increase to 12% un- der RCP4.5 and 17% under RCP8.5, excluding the 9.3% that will be decreased in the near term (2025-2048). On the other hand, climate change has resulted in a reduction in future water shortages. The unmet demand is anticipated to decline by 48% underRCP4.5 and also 49% under RCP8.5 in all scenarios. Based on a single GCM output may not give a clear represen- tation of future changes, A comprehensive study is highly needed, and the issue has to be ad- dressed at a scale relevant to decision-making based on multiple GCMs under new climate change emission scenarios for better understanding of the potential impacts