Groundwater tends to be a common property resource. In places like Yemen, where ownership rights are not clearly defined it tends to be overexploited. So much so, that they’re looking at running out within the next 10 years. Peter Salisbury has an article in Foreign Policy.
Most potable water in Yemen is produced from a series of deep underground aquifers using electric and diesel-powered pumps. Some of these pumps are run by the government, but many more are run by private companies, most of them unlicensed and unregulated. Because of this, it is nigh on impossible to control the volume of water produced. By some (conservative) estimates, about 250 million cubic meters of water are produced from the Sanaa basin every year, 80 percent of which is non-renewable. In recent years, the businessmen who produce the water have had to drill ever-deeper wells and use increasingly powerful pumps to get the region’s dwindling water reserves out of the ground.
–Salisbury (2012): Yemen’s water woes in Foreign Policy.