Landsat (15m) Satellite Image of Wadi As-Sirhan, Saudi Arabia Crop Circles in the Desert
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Image credit: NASA/USGS
Saudi Arabia has been steadily developing agricultural fields using center pivot irrigation. A remarkable example is in the Wadi As-Sirhan Basin in northwest Saudi Arabia.
The thirsty plants that rise out of the Arabian desert are quenched by water that dates back to the last Ice Age. In a more temperate past about 20,000 years ago, this “fossil” water filled aquifers that are now buried deep under the sand seas and limestone formations.
Saudi Arabians have reached this underground water source by drilling wells through sedimentary rock, as much as a kilometer beneath the desert sands. 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.
Rainfall averages just 100 to 200 millimeters per year and usually does not recharge the underground aquifers, making the groundwater a non-renewable source. As of 2006, the country had 2.4 cubic kilometers of renewable fresh water resources at the surface, according to the Food and Agricultural Organization; consumption for human, industrial, and farming uses was 23.7 cubic kilometers per year. The volume of water used for desert agriculture tripled from about 6.8 cubic kilometers in 1980 to about 21 cubic kilometers in 2006.