FIGURE 7.9 Newly exposed water resources. It was long thought that Africa had only shallow and sparse deposits of groundwater. But recent research has revealed that for the African continent, the quantity of water stored in aquifers is nearly 100 times that of previous estimates. Some is near the surface and relatively accessible, but because much is fossil water deposited as many as 5000 years ago, it cannot be recharged (replenished) quickly under present drier climate conditions. Also, many densely populated areas have only small deposits. Compare this map of the depth of groundwater deposits and number of years needed to recharge with the population map (see Figure 7.22). Adapted from A. M. MacDonald et al., Environ. Res. Lett. 7 (2012), Fig. 2. © IOP Publishing Ltd; CP13/082 British Geological Survey © NERC 2011. All rights reserved. Boundaries of surficial geology of Africa, courtesy of the US Geological Survey; Country boundaries sourced from ArcWorld © 1995–2011 ESRI. All rights reserved.