DECLINING WATER STORAGE IN THE MIDDLE EAST AS OBSERVED BY GRACE, ALTIMETRY, HYDROLOGICAL MODELS, AND IN-SITU DATA

The arid Middle East is experiencing water scarcity due to shortages in rainfall, ongoing drought, overexploitation of surface water and groundwater, and economic development. Evaluating long-term trends of water resources and the interaction with climate forcing and human intervention is crucial for future water resource management. In this context, we integrated data from the Gravity Recovery and Climate Experiment (GRACE) satellites, altimetry, global land surface and hydrological models, and in-situ observations to assess trends in total water storage (TWS), surface water (SWS) and groundwater (GWS) from 2003 to 2017, over the transboundary aquifer and at the country scale.

Results show that the Middle East experienced negative or positive trends for the TWS and GWS before 2007. However, after 2007, declining trends became more significant in all regions, except eastern Turkey. The most affected regions include Iran, Iraq, and northern Saudi Arabia. The drought resulted in significant decline in groundwater resources. The total loss in groundwater storage (2007 – 2017) is about 827 km³. We developed a drought index based on the total water storage deficit in the region. GRACE-derived groundwater storage declines compare favorably with results from in-situ monitoring (~570 wells) and regional groundwater models in Iran and northern Saudi Arabia (R² > 0.78). The results highlight current groundwater depletion in the Middle East attributed to drought and over-exploitation and underscores the need to expand the portfolio of water sources to meet increasing water demands.