Scientists say the notoriously dry continent of Africa is sitting on a vast reservoir of groundwater.

科学家称，众所周知的干旱大陆非洲实际上坐落在一片广阔的地下水库之上。

They argue that the total volume of water in aquifers¹（蓄水层） underground is 100 times the amount found on the surface.

The team have produced the most detailed² map yet of the scale and potential of this hidden resource.

Writing in the journal Environmental Research Letters, they stress that large scale drilling might not be the best way of increasing water supplies.

Across Africa more than 300 million people are said not to have access to safe drinking water.

Demand for water is set to grow markedly in coming decades due to population growth and the need for irrigation to grow crops.

Freshwater rivers and lakes are subject to seasonal³ floods and droughts that can limit their availability for people and for agriculture. At present only 5% of arable⁴ land is irrigated⁵.

Now scientists have for the first time been able to carry out a continent-wide analysis of the water that is hidden under the surface in aquifers. Researchers from the British Geological Survey and University College London (UCL) have mapped in detail the amount and potential yield of this groundwater resource across the continent.

Helen Bonsor is from the BGS is one of the authors of the paper. She says that up until now groundwater was out of sight and out of mind. She hopes the new maps will open people's eyes to the potential.

"Where there's greatest ground water storage is in northern Africa, in the large sedimentary basins, in Libya, Algeria and Chad," she said.

"The amount of storage in those basins is equivalent to 75m thickness of water across that area - it's a huge amount."