Impacts of Precipitation, Land use Land cover and Soil type on the Water Balance of Lake Chad Basin

Abstract

Lake Chad Basin (LCB) has experienced drastic changes in land cover and poor water management practices during the last 50 years. The successive droughts in the 1970s and 1980s resulted in a decrease in surface water and groundwater resources. This problem of drought has a devastating implication on the natural resources of the Basin with great consequence on food security, poverty reduction and quality of life of the inhabitants in the LCB. Therefore, understanding the precipitation variation, land use / land cover changes and soil type must be a first step to find how they impact on the hydrological cycle in the LCB. Integrated hydrologic modeling is one of most effective approaches used for analyzing hydrologic feedbacks. A rapid process of hydrological modeling is necessary in terms of cost effectiveness and computational efficiency, but limited data availability, especially in Africa, affects the practical use of the model. A spatially distributed water balance model WetSpass is employed in this study to simulate a long-term average change of seasonal and spatial distribution of surface runoff, interception, evapotranspiration and recharge in the LCB of Africa. The model is especially suitable for studying the effect of land use/land cover change and soil type on the water regime in the LCB. Soil evaporation, transpiration and surface runoff show higher correlations with precipitation. Surface runoff account for about 50 - 70% for the built-up areas, which is 2 to 3 times higher than the runoff from the agricultural land. The annual mean interception in LCB for the period 2003 - 2010 ranges from 0 - 63 mm with the mixed forest intercepting more water than open vegetation such as grass and shrub. Also the annual mean actual evapotranspiration ranges from 60 - 400 mm, which constitute 90% of the annual precipitation (69 – 430 mm) from 2003 - 2010. The analysis also shows that the shrub and agricultural land are more sensitive to the change of precipitation for balancing of transpiration and soil evaporation. The study shows that agriculture and built-up on sand, loamy sand and sandy loam produce the highest recharge. All water balance components except recharge have high variation throughout the study period in the LCB