It took more than five years for Martin Quinger and his German-Namibian team of hydro geologists to piece together this 75 kilometer-long and 40 kilometer-wide “giant puzzle.”
At the end of 2006, they stumbled upon the first clues of an aquifer located 300 meters underground. "We never though it would turn out to be so vast!” says Quinger, the leader of the German Federal Institute for Geosciences and Natural Resources project.
After some 20 drillings and an electromagnetic image analysis, the scientist was finally able to reveal his discovery at the end of July: Ohangwena and Oshana, Namibia’s dry northern regions, have a substratum that is full of water.
“At the very least, five billion cubic meters of water, but it could be up to three times as much,” says Quinger. “It isn’t a giant subterranean lake but a layer of rock that is saturated with water.”
From an Angolan mountain located 350 kilometers away on the other side of the border, rainwater has slowly flowed throughout the centuries and infiltrated the sand and micro-crevices in the rock. Stopped by an impermeable layer, the water then started to fill every single little corner of the underground space, thus forming a reservoir.
A boon for development
This discovery could change the life of the 800,000 Namibians (40 percent of the country's population) who live in these very poor regions. The extraction of this 10,000-year-old pure water would replace the brackish liquid transported by an old canal and limit the spread of diseases.
Cattle would have more water to drink and the development of crop irrigation would favor food security all the while slowing down rural exodus. The several thousand Himba people could also ask that the project for a dam near the Epupa waterfalls be abandoned once and for all - it risks flooding the grounds where their ancestors are buried.
On a bigger scale, the Namibian discovery echoes the publication in April of the first maps indexing all underground water reserves. According to scientists from the British Geological Survey, the total volume of aquifers in the African sub-soil (660,000 km3) is one hundred times superior to the amount of water that falls on the surface every year and represents 20 times the volume of fresh water in all African lakes.
“Hydro geologists suspected that there was a lot of water still largely unexploited underground,” says Alan MacDonald, the head of the study. “But we had to make it “visible,” most notably to show governments and humanitarian organizations that there was also this solution for the 300 million Africans who still don’t have any access to drinking water.”
Even if this blue gold is unequally spread out over the continent (Libya, Algeria, Egypt and Sudan are the best endowed), most Africans can have access to smaller water sheets thanks to manual pumps.
In the future, these aquifers will be an asset in the fight against climate change, says Mr. MacDonald: “Underground water will more easily resist a string of droughts on the ground level.”
Contrary to the aquifers present under the Sahara desert, which enclose fossil water, most of the subterranean sources in Africa can renew themselves at a variable rhythm depending on how impermeable the soils are.
Not a “miracle solution”
Like his British colleague, Quinger says there are still risks of depleting reserves. “The Namibian aquifer could meet the current needs of the population for four centuries, but it would be technically difficult to extract more than 30 percent of the water,” he says. “And the level of pumping would depend on the renewal rate of the reserves, because we need to insure sustainable development.”
In some African countries, the commercial exploitation of underground water to develop agricultural irrigation projects (pumping over five liters per second) is therefore “not recommended,” according to the British scientists. One risk would be a destabilization of the local ecosystem because of the drying out of ground on the surface.
Even for small-scale use, underground water isn’t a “miracle solution,” say the scientists, because of extraction costs that vary depending on the depth of the source.
“In Zimbabwe, you have to spend between $4,000 and $5,000 to install a hand pump that will supply 500 inhabitants,” says Richard Owen, the network coordinator for the Africa Groundwater Network. Approximately 30 percent of African wells aren’t operational anymore because they lack maintenance financing. Collecting and stocking rainwater in better ways is still an interesting alternative for many experts.
The continent also lacks hydro geologists, who would be able to locate the best spots to drill and would recommend the best practices. “If we dig anarchically, there is a risk of contaminating the Namibian aquifer with the salt water contained in a smaller aquifer located just above,” says Quinger.
The German scientist also fears uncontrolled drilling. “We led an awareness campaign with the population,” he says. “The traditional chiefs know the value of this water and will know how to protect it.”
Like more and more African governments, the Namibian authorities could introduce new legislation on water by the end of the year. Permits setting up environmental constraints would then be required to drill in the protected zone.
But the lack of means to control this large country is worrying, as is the increasing demand by the mining industry for water. Two years ago, French group Areva inaugurated the first seawater desalinization factory in Namibia to supply its uranium mine.
The Namibian aquifer, which was discovered along the border, could extend to the Angolan neighbor. “It might even be larger on the other side!” says Martin Quinger. This isn’t a unique case. Approximately forty cross-border aquifers have been identified in Africa, which could be potential hotspots for a resource that is increasingly strategic.
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