The implications of climate change on freshwater resources in the arid and semiarid Mediterranean environments using hydrological modeling, GIS tools, and remote sensing

Precipitation partitioning in arid and semiarid environments is not well understood due to scanty precipitation, its temporal distribution, and the lack/absence of adequate measurements of the hydrometeorological components. Simulation methods have the potential to bridge the data gap, thereby providing a window to estimate the water balance components. The present investigation evaluates the water balance components of a typical watershed situated in the southeastern Mediterranean for the period 1979 through 2019 using daily meteorological data and a grid spacing of 250 m. Generated runoff results were commensurate with corresponding values obtained using the SWAT model. Computed groundwater recharge is also compatible with recharge values calculated using the chloride mass balance method. Results show that average runoff and groundwater recharge for the entire period was similar to 24 mm a(-1) and 19 mm a(-1), giving a precipitation ratio of 9.5% and 7.5%, respectively. Substantial interannual variability in the water balance components was observed during the study period which reflected the significant precipitation fluctuations typifying the Eastern Mediterranean. Results show that the period extending from 1998/1999 through 2018/2019 witnessed an 18% drop in annual precipitation, while surface runoff and groundwater recharge experienced a reduction of similar to 34% and similar to 67%, respectively. Although groundwater recharge is a complex function of numerous meteorological and geological factors, the NDVI can provide an excellent indicator of groundwater recharge in marginal Mediterranean environments. This is highly beneficial in areas where climate records are scanty or absent. The presented results emphasize the significant impacts of global warming and aridification on the future availability of water resources in the semiarid marginal climates in the Eastern Mediterranean and point out clearly that water resources in this area will become scarcer, leading to multiple security threats at national and regional levels.