Beneath the Surface - Africa's Aquifers

Africa's Aquifers

Groundwater, though not as clearly evident as surface water, still exists as a major source of water and constitutes the invisible half of the world's blue water resources. Groundwater exists as an indispensable freshwater resource, of the 2.5% of water on earth that exists as fresh water, 29.9% of that fresh water exists as groundwater (Shiklomanov 1999:4). Groundwater therefore dwarfs the total amount of fresh surface water which constitutes a mere 0.26% of fresh water resources on Earth. The parched continent of Africa does in fact contain relatively large groundwater resources. Total groundwater storage in Africa is estimated to be 0.66 million km3, this estimated volume is more than 100 times the estimates of annual renewable freshwater resources on the African continent (Macdonald et al 2012). Though Africa does have vast groundwater resources, these are unevenly distributed (see figure 1a and 1b) with the largest groundwater volumes found in large sedimentary aquifers in North Africa within nations such as Libya, Algeria, Egypt and Sudan such as the Nubian sandstone aquifer (See next Blog post). Another challenge which faces groundwater extraction is the fact many of these aquifers are ancient and take well over a millennia to fully recharge (Shiklomanov 1999:60). Irrigation in many nations has become reliant on groundwater and Africa is no exception, this has led to heavy depletion with 8 major aquifers in Africa having experienced little to no refilling of offset water withdrawals between 2003-2013 (NASA 2015).

The largest groundwater withdrawals within Africa are Africa's northern nations with total groundwater withdrawal in Egypt of 7km3, followed by Libya withdrawing 4km3. Though so far this groundwater withdrawal has been unsustainable with Egypt's groundwater withdrawal actually exceeding their total renewable groundwater resource by 350% whilst Libya's total groundwater withdrawal exceeds their total renewable groundwater resource by a massive 800% (FAO Aquastat as quoted in Giordano 2009:158). This exists as a great challenge not only to groundwater resources but also to surface water resources as there is clearly an intimate relationship between groundwater and surface water.  Groundwater storage works to complement surface water availability especially during periods of water scarcity in water stressed regions (United Nations World Water Development Report 2019, Savenijie and Van der Zaag 2008). It is also difficult for nations to switch to utilising groundwater resources due to extraction being more difficult and more expensive than use of surface water and issues relating to local groundwater problems such as pollution etc. (Giordano 2009). But despite these challenges the abundance of groundwater resources in comparison to surface water resources offers benefits for economic development and poverty reduction on the African continent. Giordano (2006) actually argues that underutilisation actually remains a problem for Africa, and there is great potential for groundwater utilisation within Sub-Saharan Africa. Groundwater therefore exists as a major blue water resource with successful utilisation offering great opportunity for development on the African continent. But groundwater's uneven distribution and long recharge time coupled with the technology and capital needed for it's utilisation makes it a contested and often difficult to access resource.

Figure 1a) African Groundwater storage and depth - Source

1b) African groundwater productivity - Source

As already discussed, Africa does sit upon a sea of great groundwater reserves which offer potential for water supply for the continent. It is argued that groundwater is the most affordable and sustainable way of improving secure access to water especially within rural Africa (Macdonald and Calow 2009). Great inter annual variability in rainfall across the African continent coupled with high evaporation and low recharge means water stored below the Earths surface which is recharged in the wet season can offer a relatively secure source of fresh water. Groundwater also generally has good quality due to protected cover provided by the soil and the unsaturated zone. But groundwater's relative reliability and long term viability in arid/semi-arid regions which exist across much of the African continent depends on replenishment of the resource by recharge (Taylor et al 2012). As evidenced earlier in this blog post, some African Aquifers are already under pressure and suffering from depletion. The depletion of great aquifers not only threatens the livelihoods of groundwater dependent communities but also the ecosystem functions of the environments also dependent on the groundwater. So though groundwater offer's great potential, utilisation of the resource must ensure it is sustainable and enables the aquifer's to replenish to ensure viability of the resource for the future not only for the communities that rely on it, but the ecosystem services also reliant on the resource. Therefore the need to tap into groundwater resources sustainably coupled with groundwater resources importance for both communities and ecosystems makes groundwater a contested resource. 

Now I have contextualised Africa's groundwater resource and it's importance, I will explore how African nations contest and cooperate in regard to Africa's transboundary groundwater resources within the next blog post.