Modeling the depletion of groundwater storage over time in the Levant: lessons learned from a water-stressed region

Globally, the demand for water is continuously increasing, placing many regions under the burden of water stress thus leading to transboundary water conflicts and overexploitation of existing water resources. Managing water resources in many of these water-stressed regions are hampered by the lack of long-term spatio-temporal observations of surface and groundwater resources and an inadequate understanding of changes associated with increased groundwater pumping. In this study, observational data from the Gravity Recovery and Climate Experiment are combined with data from the Global Land Data Assimilation System land surface models to assess regional changes in water storage over time in the water-stressed Levant region of the Middle East. Results show that the Levant has been witnessing an overall drop in its total water storage at a rate of 10.64 ± 0.48 mm/year, equivalent to the loss of 80% of the volume of Lake Tiberias—the largest natural freshwater body in the region. More than 90% of the water losses were attributed to overexploitation of groundwater resources, with annual groundwater losses estimated to exceed 40% of the consumed groundwater. Time series analysis of changes in total water storage supports a temporally constant loss rate rather than an abrupt change to the system instigated by the onset of the 2007 regional drought, which severely affected the wider Middle East region. An assessment of current and projected non-conventional water supply projects in the region show that their capacities will be limited to less than 40% of the model estimated annual drop in groundwater storage. These findings highlight the importance of increasing water use efficiency, particularly in the agricultural sector in an effort to reverse the groundwater storage losses.