Evaluation Of The Influences Of Land Use Land Cover And Climate Change On Agricultural Water Availability In Baro− Akobo Basin, Ethiopia

Abstract

1. BACKGROUND INFORMATION 1.1 Introduction Water resources are indispensable for all social-economic activities and ecosystem functions. Water is one of the most important natural resource required for the survival of all living Species. In addition, changes in water resources have great significance for agricultural production. The Nile River is a main water resource for different transboundary countries which is already under immense pressure due to various competitive uses as well as social, geopolitical, and legislative conditions. Due to these, several previous studies show that many parts of the Nile Basin are sensitive to climatic variations (Kim et al., 2008; Beyene et al., 2009). Water scarcity and fragility, unequal distribution in space and time and its mismanagement are regarded as serious issues in most developing countries. These issues are mainly due to population pressure and fast urbanization as well as industrial and agricultural development (Raje & Mujumdar, 2009). Rapid population growth, unplanned urbanization and landuse and land cover changes have been recognized as major challenges for water resources management (Hunter, 2003). Land use and land cover change can alter the basin hydrology by affecting evaporation, soil infiltration capacity, and surface and subsurface regimes and ultimately affecting water quantity and water quality (Cuo et al., 2013). Climate change, which has been recognized as one of the 21st century’s most important environmental issues, has a significant impact on hydrology, ecology, agriculture and social− economical systems (Tanzeeba &Gan 2012). Impacts of climate change on temperature and precipitation are expected to have considerable consequences on water resources (IPCC 2014). The recurrent drought and rainfall variability in Ethiopia are wake up calls to imagine the impact of climate change on the social− ecological system, which are very vulnerable to the impacts of climate change. This calls for a robust study that explores the long− term climate trend and variability in different parts of Ethiopia to devise climate change adaptation and mitigation strategies (Tabari et al., 2015). In fact there are some studies that estimated climate change in Ethiopia; however, such studies cover large area and fail to inform detailed information at the local scale. For example, (NMA, 2007) & McSweeney et al., 2009) reported that over the last decades, temperature in Ethiopia has increased at about 0. 28 and 0. 0.37 °C per decades. The increase in minimum temperatures is more pronounced with roughly 0.4 °C per decade. Precipitation, on the other hand, remained fairly stable over the last 50 years when averaged over the country. However, the spatial and temporal variability of precipitation are high (NMA, 2007). Hydrological models, SWAT will also be used to predict impacts of climate change and land management change. These models used mathematical equations to estimate biophysical processes. The modeling approaches range from simple conceptual to sophisticated modeling approaches. The Soil and Water Assessment Tool (SWAT) is a physically based model developed to predict the impact of land management practices on water, sediment, and agricultural chemical yields in large complex watershed with varying soils, land use and management conditions (Neitsch et al., 2012). The performance of SWAT and RCM model will be evaluated using the Nash− Sutcliffe efficiency value (ENS) and the coefficient of determination (R2). In this study, mainly climate change impact evaluation for the period 1981−2100 on the hydrology will be carried out for the Baro Akobo basin, which contributes a significant flow to the main Nile particularly for the Sobat river basin Sudan. For this research climate change scenarios data from the newly available CMIP5 (Taye et al., 2011) RCM output of CORDEX− Africa for African domain projections under Representative Concentration Pathways (RCP4.5 and RCP8.5) after applying appropriate bias correction methods will be used as input data to evaluate climate change and hydrological model.