The potential of groundwater

When one thinks of the biggest sources of water, groundwater is maybe not at the top of the list, given the fact we can not even see it. In my first post I mentioned the Water Stress Index, which is used to define water scarcity and mentioned how mean annual river runoff is used to calculate water flow, which therefore assumes that groundwater storage changes are negligible (Damkjaer and Taylor 2017). Therefore, we can see how even official metrics can disregard groundwater. However, its potential, especially in the context of Africa must not be underestimated. Outside of Africa this potential is perhaps more recognised, with groundwater irrigating 14% of cultivated land in Asia, but for Africa the figure is just 1% (Altchenko and Vilholth 2015). The accuracy of this figure is questionable, since groundwater irrigation is often small scale and is sometimes not registered by published analyses, but it is nonetheless worth investigating, given Saharan Africa has more than 3 times the per capita groundwater availability of China, which is a major player in groundwater-fed agriculture (Giordano 2006).

One of the reasons as to why groundwater can be effective is due to its ability to produce higher quality water. This is firstly due to the fact that as the water is protected by the soil, it is not as vulnerable to contamination or pollution, as is the case with surface water. Furthermore, the movement of groundwater through geology can even help disinfect the soil. It must also be noted however, that certain types of geology can actually introduce contaminants to the water, with arsenic being one such example. 

Meanwhile groundwater is seemingly an especially viable option for Africa, due to the specific geology of the continent, in particular sub-Saharan Africa. Over 40% of sub-Saharan Africa is underlain by fractured or weathered rock aquifers (MacDonald et al. 2012). these aquifers have low transmissivity, which refers to the ability of the geology to transfer the water, as such meaning the yield of boreholes from this geology is low. However, what this also means is that the impact of drawing groundwater is low. Given the abundance of small-holder agriculture in Africa, with it supplying up to 80% of food consumed (FAO 2011), groundwater therefore appears to be a viable option for helping to improve food security. 

Nonetheless, in my first post I introduced the significance of variability within Africa and groundwater is no exception to this. Went we look at Africa an aggregate there is seemingly an abundance of groundwater, but in reality over half the annually renewable groundwater supplies are in just 4 countries: The Democratic Republic of Congo, The Republic of Congo, Cameroon and Nigeria (Giordano 2006). As such, we must view groundwater not as a solution to the water and food dynamic in the entire continent, but rather as an option when local conditions are particularly suited to its use. 

Groundwater certainly has potential in Africa, but more needs to be done for this potential to be realised in the same way that it has been elsewhere. This includes introducing groundwater monitoring systems and further research to assess the impact of groundwater abstraction all to ensure that we can have a better understanding of when and how groundwater is best utilised (Gaye and Tindimugaya 2019). Building on my last post, which highlighted the significance of the water and food relationship in Africa, this post has assessed a potential water supply that can help address food security, while further highlighting the importance of recognising variability when assessing strategies.