Africa is sitting on a giant reservoir of groundwater, British scientists have discovered. But the new information might prove both a boon and a curse.

­Researchers from the British Geological Survey (BGS) and University College London collected all the available water information from governments and recent surveys. Their conclusion: there is 100 times more water underneath the surface than there is on it.

Among the countries with the richest reserves are some of the driest in the world like Libya, Tunisia and Egypt.

Three hundred million people in Africa already have no access to clean water, and the pressure on existing water resources is predicted to cause poverty, instability and even war within the next two decades.

But Dr Alan MacDonald from the BGS says that his team wanted to strike out against the "scaremongering" over water supplies, saying there is enough water – as long as it is used judiciously.