Estimation of groundwater recharge by chloride mass balance (CMB) method in some selected wadis, Western Saudi Arabia in (1966–2018)

Abstract

Optimal management of groundwater requires conducting numerous studies and measurements to assess its sustainability, especially in arid regions like Kingdom of Saudi Arabia (KSA). The Quaternary aquifer, which serves as a vital source for drinking water, domestic needs, and irrigation in various wadis in Western Saudi Arabia (WSA), represents the most important renewable groundwater resource within the study area. Therefore, estimating the amount of recharging source to groundwater of this coastal aquifer is one of the most important parameters for predicting groundwater availability to support practical approaches for extraction. This research presents an application of the conventional chloride mass balance (CMB) approach for recharging estimation in three representative wadis in WSA, based on hydrological and hydrochemical characteristics. Results revealed that The Quaternary aquifer system exists under an unconfined condition at depth ranging from 1 m to 110 m in wadi Marawani, from 1.2 m to 100 m in wadi Fatimah and from 0.8 m to 21.7 m in wadi Qanunah, respectively. The estimated recharge to quaternary aquifer lies between 0.75% and 4.25% of effective annual rainfall over each basin. Qanunah basin in the south represents the highest recharging rate compared to wadi Marawani and Fatimah basins in the northwestern direction. These findings are in agreement with recharge rates of similar studies observed in different dry and semi-arid regions of the world such as Western United States Great basin.