Estimating groundwater recharge in the humid and semi-arid African regions: review

Reliable estimation of groundwater recharge rate is crucial for the assessment of groundwater resource potential in Africa. In this study, we reviewed existing studies on groundwater recharge, especially in the semi-arid and humid regions of Africa. After the assessment of the main advantages and disadvantages of each method, we strongly agree that among the distinct existing methods, Water-Table Fluctuations (WTF), Recession-Curve Displacement, and Chloride Methods can be used with a better certainty of improved estimation of groundwater recharge in these regions. In addition, the features of existing studies on groundwater recharge are outlined. The major challenge of these regions on recharge study is the lack of basic data. Therefore, this paper suggests methods for dealing with this limitation and also the future outlook using recently developed technologies such as Remote Sensing (RS) and Geographical Information System (GIS). Watershed hydrologic modeling, which is a robust method for recharge estimation that is widely applied around the world, should also be applied for future perspective by solving the problems of its use and data requirements to find a better result. Strictly speaking, the key to the successful estimation of groundwater recharge lies in the utilization of a variety of independent methods. Therefore, by bringing together the advantages, limitations, and cost of each method, the study of the recharge estimation in different climatic environments of African regions can enter a new era.