A recent research by scientists from the British Geological Survey and University College London have for the first time mapped the groundwater across the continent and concluded that the mapped water could provide a buffer against the effects of climate change for years to come.
"The largest groundwater volumes are found in the large sedimentary aquifers in the North African countries Libya, Algeria, Egypt and Sudan," the researchers said in their paper.
They estimate that reserves of groundwater across the continent are 100 times the amount found on the its surface, or 0.66 million cubic kilometres.
The research published in the Journal Environmental Research Letters, cautioned that not all the water reserves can be accessed. Where they can, small-scale extraction using hand pumps would be better than large-scale drilling projects, which could quickly deplete the reservoirs and have other unforeseen consequences.
Groundwater is no panacea for Africa's water shortages but it could form an important part of a strategy to cope with an expected sharp increase in demand for water as the continent's population increases.
Even now, some estimates put the number of Africans without access to safe drinking water at more than 300 million and only 5 percent of arable land is irrigated.
"It is not as simple as drilling big bore holes and seeing rice fields spring up everywhere," said Dr Stephen Foster, a London-based senior adviser for aid group Global Water Partnership and an expert in groundwater issues.
"In some places it could be economically and technically feasible to use groundwater to reduce crop loss, but I would question whether that is true everywhere. It will need detailed evaluation.
"In northern Nigeria there have been groundwater irrigation projects that have failed because of the rising cost of fuel - a major factor in drilling costs - and distribution difficulties."
The researchers say some of the largest deposits are in the driest areas of Africa in and around the Sahara, but they are deep - at 100 to 250 metres below ground level.
"Water levels deeper than 50 metres will not be able to be accessed easily by a hand pump," said the study, led by Dr Alan MacDonald of the British Geological Survey. "At depths greater than 100 metres the cost of borehole drilling increases significantly due to the requirement for more sophisticated drilling equipment."