Over the past three decades, Saudi Arabia has been drilling for a resource more precious than oil.
Since the late 1980s, engineers and farmers in Saudi Arabia have tapped hidden reserves of water to grow crops in the desert. The underground water source was reached by drilling wells through sedimentary rock, as much as a kilometer beneath the desert sands. The plants that rise out of the desert are quenched by water that dates back to the last Ice Age. In a more temperate past about 20,000 years ago, the water filled aquifers that are now buried deep under the sand seas and limestone formations. Rainfall averages just 100 to 200 millimeters per year and usually does not recharge the underground aquifers, making the groundwater a non-renewable source. Although no one knows how much water lies beneath the desert—estimates range from 252 to 870 cubic kilometers—hydrologists believe it will only be economical to pump it for about 50 years. Watch the video to see the evolution of agricultural operations in Saudi Arabia's Wadi As-Sirhan Basin from 1987 to 2012, as seen by USGS-NASA Landsat satellites.