Quantification of Groundwater Recharge in Arid Regions: A Practical View for Resource Development and Management

Abstract

The rate of aquifer replenishment is one of the most difficult of all factors in the evaluation of groundwater resources to measure. Estimates, by whatever method, are normally, and almost inevitably, subject to large error. Through discussion of a logical series of questions, the manner in which this factor affects practical resource development and management are defined and the limitations of various evaluation methods are discussed, with reference to examples from arid regions, especially the Botswana Kalahari and the Peruvian Atacama. When confronted by such uncertainty technical and economic analyses of sensitivity of development and management decisions to error in recharge estimates is essential. A pragmatic approach involving careful monitoring of aquifer response to heavy medium-term abstraction in a representative area and subsequent data evaluation using a distributed-parameter numerical aquifer model is advocated. This will often be the only realistic way forward given normal project constraints and data limitations under complex hydrogeological conditions and in developing nations, and will also allow time for appropriate field research into groundwater recharge mechanisms and storage controls.