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Hydrosphere
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  'Huge' water resource exists under Africa

Scientists say the notoriously dry continent of Africa is sitting on a vast reservoir of groundwater.
They argue that the total volume of water in aquifers underground is 100 times the amount found on the surface.
The team have produced the most detailed map yet of the scale and potential of this hidden resource.

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RE: Ancient mega-lake
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An expedition to seek out a huge underground pocket of ancient water in Darfur, Sudan, is being prepared by geologists.
About 100 metres beneath the arid sands in the north-west of the region there just might be the makings of an oasis in the form of a hidden mega-lake, discovered in April 2007 using satellite imagery.
The lake could provide much-needed relief to the war-torn African region, believe several UN agencies, the government of Sudan, and non- governmental organisations, which are backing the project.

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Darfur lake is a 'mirage'

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Ancient Darfur lake
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A vast underground lake that scientists hoped could help to end violence in Sudan's Darfur region probably dried up thousands of years ago, an expert says.
Alain Gachet, who used satellite images and radar in his research, said the area received too little rain and had the wrong rock types for water storage.

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RE: Ancient mega-lake
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A team of researchers has discovered an ancient underground lake in Sudan's war-ravaged Darfur region, raising hope of easing the area's water scarcity.
The researchers, from Boston University in the United States, hope to drill 1,000 wells across the drought-ridden territory, in an effort to ease tensions about water and to help the region's peace process.
Geologist Farouk El-Baz led the discovery using satellite and radar data from space. He said the lake measures about the size of Lake Erie, one of the American Great Lakes.


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Northern Darfur Mega-Lake
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Researchers at the Boston University Centre for Remote Sensing used recently acquired topographic data from satellites to reveal a now dry, ancient mega-lake in the Darfur province of northwestern Sudan. Drs. Eman Ghoneim and Farouk El-Baz made the finding while investigating Landsat images and Radarsat data. Radar waves are able to penetrate the fine-grained sand cover in the hot and dry eastern Sahara to reveal buried features.

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Credit: Boston University Centre for Remote Sensing

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Ancient mega-lake
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Researchers at the Boston University Centre for Remote  Sensing used recently acquired topographic data from satellites to reveal a now  dry, ancient mega-lake in the Darfur province of northwestern Sudan. Drs.  Eman Ghoneim and Farouk El-Baz made the finding while investigating Landsat images and Radarsat data. Radar waves are able to penetrate the  fine-grained sand cover in the hot and dry eastern Sahara to reveal buried features.
Segments of the lake's shoreline were identified at the constant  altitude of 573 ± 3 meters above sea level. Ghoneim incorporated these segments  with the Shuttle Radar Topography Mission (SRTM) data into a Geographical Information System to reconstruct the lake and the ancient river  courses that led to it. At its maximum extent, the lake occupied an area of  about 30,750 km² (larger than the area of Massachusetts) and would have  contained approximately 2,530 km³ when full of water in the past.
The researchers made no inferences regarding the age of the lake; however, its vast extent suggests that it existed for a long period of time when rainfall was plentiful in the eastern Sahara.

"Field investigations and samples will determine the exact age of the  lake.  One thing is certain -- much of the lake's water would have seeped  through the sandstone substrate to accumulate as groundwater" -  Farouk El-Baz, director of the Boston University Centre for Remote  Sensing.

"This ancient lake, which represents indisputable evidence of the past  rainy conditions in the eastern Sahara, will have significant consequences  for improving our knowledge of continental climate change and regional palaeohydrology" - Drs.  Eman Ghoneim.

According to the researchers, mapping the site of the former lake,  named the Northern Darfur Mega-lake, will help with groundwater exploration  efforts in the Darfur region, where access to fresh water is essential for refugee survival.
As proven by El-Baz in Egypt, just north of Darfur, former lakes in  this part of the Sahara are underlain by vast amounts of groundwater. His  earlier detection of the "East Uweinat" basin in southwestern Egypt -- where  the groundwater rises to 25 meters below the surface -- resulted in the  drilling  of 500 wells to irrigate 100,000 acres of agricultural land.

"Such large sedimentary basins have potential not only in groundwater resources, but also oil and gas resources at depth" - Farouk El-Baz.

A paper detailing the discovery will be published in an upcoming issue  of  the International Journal of Remote Sensing.
The Boston University Centre for Remote Sensing is a research facility  that was established in 1986. Researchers at the Centre apply techniques of remote sensing and geographic information systems (GIS) to research in  the fields of archaeology, geography and geology. In 1997, the Centre was recognised by NASA as a "Centre of Excellence in Remote Sensing."
Founded in 1839, Boston University is an internationally recognized institution of higher education and research. With more than 30,000 students, it is the fourth largest independent university in the United States. BU contains 17 colleges and schools along with a number of multi-disciplinary centres and institutes, which are central to the  school's research and teaching mission.

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