Arabian Aquifer System
The Arabian Aquifer system, which supplies water to 60 million people in Saudi Arabia and Yemen, is in a critical state. Before the invention of modern farming, the Arabian Aquifer held around 120 cubic miles of water underneath the Saudi desert, which is enough water to fill Lake Erie. But due to extensive pumping and inability to be replaced by rainfall in such a dry area, there is an estimated one-fifth of the original quantity left in reserve (National Geographic, 2017).
https://worldwaterreserve.com/water-crisis/causes-of-water-conflict/
Water Issues 