An artesian well feeds water into a canal at Abu Minqar in Egypt.

The isolated farming community draws water from 15 wells—some more than a kilometer deep—that tap into a thick layer of saturated sandstone beneath the Sahara.

This underlying aquifer stretches into Chad, Libya, and Sudan, and goes all the way to the Sinai and southern Israel. (See map.)

The sandstone is highly porous rock that acts like a sponge, holding water in some place and oil in others, but experts are unsure of how and when these got there.

The aquifer is not being replenished. "The issue is not if it will run out,'' said Richard Tutwiler, director of the Desert Development Center of the American University in Cairo. ''It is when.''

In most of Egypt's desert farms, irrigation by flood is considered outdated and has been replaced by the more efficient drip and sprinkler irrigation. But these technologies are not available in Abu Minqar, and the farmers are only allowed to flood one acre of land for an hour every 15 days.

Abu Minqar didn't exist on the map until the government drilled the first well in 1987 and encouraged people to move here.

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