It's not all bad...

Throughout this blog I've tried to stress the huge diversity there is within SSA, and whilst trying to make statements note that over-simplification can be misleading. One of my colleagues also writing a blog, Lulu (see here for her blog: Africa H2O under environmental impacts), commented on an earlier post that actually some areas of Africa, particularly in East Africa groundwater recharge may actually increase under climate change rainfall impacts. 

As discussed by Allan and Soden, one of the largest predicted changes in rainfall patterns is that rainfall events will become less frequent but more intense, an 'Amplification of Precipitation Extremes'. This is because when air is warmed it can hold more water. For example, a given volume of air 'at 20°C can hold twice the amount of water vapour than at 10°C' (NASA). The correlation between how much water air can hold at given temperatures is relative humidity, when it is 100% the air is saturated. When you heat up air, the relative humidity drops. So when the whole Earth gets warmed (given a few relatively localised exceptions) the air holds more water before it reaches a given relative humidity where it would start to rain. This is why rainfall events will become less frequent, but heavier (see Trenberth et al. for a more detailed explanation). Trenberth et al. go on to discuss how too rarely the frequency, intensity and duration of rainfall events is studied, instead just the quantity of rain is often modelled. As temporal variability in rainfall is key to analysing impacts, such climate change modelling can miss key aspects.

Source

As explained by Taylor et al., groundwater recharge in East Africa is largely dependant on extreme rainfall. Therefore, these changes in rainfall pattern could potentially increase the quantity of groundwater that is available for use in East Africa.