A review on sources of uncertainties for groundwater recharge estimates; insight to data Scares Tropical, Arid, and Semiarid regions

Successful sustainable groundwater management requires accurate information on recharge for a given aquifer system. However, recharge estimates are usually used in a relative term rather than an absolute sense. A review of available studies on groundwater recharge estimate uncertainty as well as tools for uncertainty analysis was conducted. Nonetheless, except for the handful research that have conducted proper uncertainty analysis, most studies inclined to implement multiple methods as an indication of the range of uncertainty. The global trend indicates that considering the significant number of methods for recharge estimation, very little has been done to assess the uncertainty of each method. Therefore, more focus should be given to the individual uncertainty analysis of selected methods as much as using multiple methods recommended for investigating uncertainty. Insight of the review indicates, when used carefully, that tracer-based analysis can be effective and coupling is required for uncertainty analysis. Furthermore, spatial uncertainty due to input data could be potentially minimized by using input data from multiple sources. Better conceptualization of the hydrogeological process can reduce the uncertainty of numerical modelling. This review is limited to widely used methods and excludes uncertainty due to inappropriate method implementation as well as controlled experimental uncertainties.