Abstract
The availability and the future of freshwater resources are major challenges in the Middle East, and a vital issue for the Kingdom of Saudi Arabia. Temporal Gravity Recovery and Climate Experiment (GRACE) data along with other datasets are employed to monitor the spatiotemporal trends in freshwater availability over the Red Sea Hills, and to examine natural and anthropogenic factors controlling these trends. Results indicate that the Red Sea Hills are witnessing GRACE-derived terrestrial water storage (TWS) depletion of -3.92 +/- 0.09km(3). TWS depletions are attributed mainly to decline in annual rainfall amounts during the investigated period (April 2002 to December 2016; 70mm) compared to that of the previous two decades (1979-2001; 115mm). Higher TWS depletion rates (-6.31 +/- 0.10km(3)/year) are observed over the central and northern parts of the Red Sea Hills compared to those observed over the southern parts (-1.89 +/- 0.30km(3)/year). The Red Sea Hills witness lower TWS depletion rates (-1.22 +/- 0.51km(3)/year) during the first 4years of the investigation (April 2002 to August 2006; Period I); higher TWS depletion rates (-4.31 +/- 0.15km(3)/year) are observed during the remaining part of the investigation (September 2006 to January 2017; Period II) due to the temporal variability in annual rainfall amounts (Period I 85mm; Period II 65mm). Findings demonstrate the successful use of GRACE data for monitoring freshwater availability in the Red Sea Hills and potential for use in studying freshwater resource availability in other hydrologic systems around the globe.