Climate Change and Groundwater: Looking to the Future (Part 1)

 As the population of Africa continues to grow (Wada & Bierkens, 2014) causing a projected 30-40% increase in demand on water resources, climate change also continues to impact the regions within the continent. Understanding the variables and factors affecting groundwater is vitally important, especially for developing regions as this knowledge can be applied to build adequate resilience to climate change and variability.

 Due to the regional disparities and lack of congruent research, there are contrasting views about the ability for groundwater resources to provide sufficient 'buffers' to climactic events. To provide a holistic view about this debate, the potential impacts of climate change on groundwater in Africa can be assessed through limits, barriers and opportunities for adaptation.

The distribution of groundwater across the African continent is extremely uneven and is dependent on a number of variables such as climate patterns and geology. This is shown in Figure 1.

Figure 1: Interpolation/estimation of groundwater storage from a number of in-situ studies across the African continent. The black lines reflect recharge rates, also interpolated (MacDonald et al, 2012).

In some regions, the either the climate or the underlying geology will be the primary variable determining the access and volume of groundwater. This is exemplified by comparing the arid sub-saharan region with the temperate Congo basin. The sub-saharan region experiences extremely low levels of rainfall however the sandstone creates perfect conditions for aquifers (Nofal et al, 2015). In contrast, in parts of the Congo basin that experience heavy volumes of rainfall throughout the year the basement rock results in comparatively lower levels of groundwater storage (MacDonald et al, 2012), even though this central region receives 37% of all rainfall across the continent whilst only occupying 18% of the land area (Goulden et al, 2009). Accurately mapping the differences in regional distribution of groundwater as a resource is vital in order to assess where it can be used as a resilience method to combat climate change.

Figure 2: Groundwater productivity and estimated depth to groundwater across the African Continent (MacDonald et al, 2012).

The disparities shown in figure 1 are further emphasised in figure 2, showing that aquifer and groundwater productivity is highly dependent on geology and bares little to no relationship to the estimated depth to groundwater, which is clearly related to climate and biome (MacDonald et al, 2012). This is logically and scientifically congruent as evapotranspiration rates dictate that the groundwater level must be deeper in arid regions compared to temperate and tropical regions. 

Building Resilience to Climate Change:

As climate change accelerates, Africa will experience more variability, particularly with regard to extreme weather events in the sub-saharan region. This was outlined in the third blog-post where the details about the impact of temperature increases were examined. Possibly the most serious impact is the increased likelihood of catastrophic drought and increased desertification along the periphery of the Sahara Desert. This region has historically been of great economic and agricultural value, however it is also extremely vulnerable to rapid change. To combat the effects of climate change, groundwater resources can be managed and exploited in order to support the industry and communities of this region (Calow et al, 2009). As figures 1 and 2 show, groundwater resources are in abundance on a scale that is almost 100 times larger than the total annual rainfall and 20 times larger than the freshwater stored in lakes across Africa, with much of that abundance being situated in arid regions that would suffer extreme water scarcity (MacDonald et al, 2012).

Whilst this seems like a quick and easy fix, the situation is more nuanced and it should be stressed that the groundwater resources can be used as a 'buffer' and not a permanent solution due to a variety of issues (Goulden et al, 2009). These range from geopolitical issues due to the transboundary nature of groundwater and finding a balance between management and exploitation of what is ultimately a fragile resource that has been built up over hundreds or thousands of years. 

These specific problems and potential adaptations will be discussed in the following blog-post.