"I hope that they find water," said Alain Gachet of Radar Technologies France. "But I am scientifically convinced that they can't in this context."
El-Baz said that the ancient lake once covered much of the state of North Darfur and was about the size of Massachusetts.
While that lake is now dry, much of its water likely seeped into deposits of sandstone located hundreds of feet under the Earth's surface, he said, and could be pumped to the surface for wells and irrigation.
But Gachet countered that, while there may be isolated patches of water-rich sandstone in North Darfur, they are not enough to produce the quantities of water that El-Baz is predicting.
"I am very skeptical of the potential of this lake," Gachet said.
Gachet has mapped most of Darfur's freshwater resources as part of a relief project sponsored by the U.S. State Department.
In 2006 he provided aid groups with a detailed atlas of rain-fed underground streams that could be tapped for fresh water. Seventy-five wells have been dug so far.
Using ground-penetrating radar, "we peeled Darfur like an onion," Gachet said. "There is enough fresh water to sustain three or four million people."
In just a few months El-Baz and Gachet will both have a chance to see who's right.
The Egyptian ministry of water and irrigation has agreed to fund 20 initial test wells. The United Nations Mission in the Sudan has agreed to drill four.
In time, as many as a thousand wells could be pulling water from Darfur deserts, said El-Baz, who traveled to Sudan last month to discuss the find with Sudanese President Omar Al-Bashir.
Water Alone Won't Heal
Today's Sahara, an arid abode of sand dunes and fossils, was a much wetter environment 5,000 years ago. Desert cliff drawings from that time depict giraffes, elephants, and hippos.
Much of the water that fed that ecosystem seeped through layers of sandstone to form "fossil water"—nonrenewable aquifers dating from 5,000 to 10,000 years ago.
Agricultural projects harnessing fossil water have been successful in several places. The world's biggest effort to reclaim such deposits, for example, is the Great Man-Made River in Libya.
There, 1,500 wells pump as much as 1.7 billion gallons (6.5 million cubic meters) of fresh water each day from the Sahara to cities on the Mediterranean coast.
And 500 wells now provide fossil water to irrigate 100,000 acres (40,470 hectares) of farmland in the former desert of Sharq el-Oweinat in southwestern Egypt. North Darfur could become another Sharq el-Oweinat, El-Baz said.
There are likely several more underground lakes to be found under the deserts of North Africa, he added.
"We are scanning the whole of the eastern Sahara," he said. "There are several similar depressions we haven't yet analyzed."
But even if northern Darfur were to become rich in water, many other factors are likely to prolong the violence there, analysts said.
The Darfur conflict began in February 2003, when ethnic-African groups rebelled against the Arab-led central government.
According to UN investigators, the government responded by arming nomadic Arab militias, which carried out a campaign of murder and rape on civilians. The Sudanese government denies these charges.
Since then, the three original main rebel alliances have cracked into more than a dozen groups, further frustrating efforts to negotiate an end to the conflict.
Much of the underground lake that El-Baz has described now lies in rebel-held territory.
"What you see is not simply a competition for the scarce resources of Darfur," Eric Reeves, a leading Darfur researcher and activist, told the Boston Globe.
"If we want to look at the violence in Darfur, we don't look underground, we look at the political realities that exist today.''
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