Is Africa really short of water? -- The Potential of Groundwater

Groundwater is an integrated component of the natural water cycle and can be found almost anywhere beneath our feet. This hidden source of water is important for drinking, livestock, and irrigation in Africa. Sustainable freshwater sources are critical in fulfilling the sustainable development goals (SDGs), particularly SDG 6 on water. According to the first quantitative map of groundwater resources in Africa produced by MacDonald et al. (2012), the volume of groundwater is estimated to be 0.66 million km³. To view this number in a more realistic manner, this is 100 times more than annual renewable freshwater resources and 20 times more than the freshwater present in African lakes. However, this gigantic pool of ‘hope’ to Africa has been widely ignored and misunderstood. Falkenmark’s study (1989) on the Water Stress Index only sees a definite measure of water scarcity that is based on the “hydraulic density of population”. This water metric disregards freshwater storage such as groundwater and misrepresents freshwater availability and demand in sub-Saharan Africa (Taylor,2009).

Distribution of Groundwater across Africa

Map of groundwater storage expressed as water depth in millimeters with modern annual recharge for comparison (MacDonald, 2012)

South Africa’s groundwater resources supply approximately 15% of the total volume of water consumed nationally (Knüppe, 2011), more than 280 cities and towns are dependent on groundwater (Van Tonder, 1999). Recorded by the most recent data, a total of 235,000 m. m³/a is available underground and between 10,000m and 16,000 m. m³/a are ready for direct use in an average precipitation year (Knüppe, 2011). It is worth noticing that South Africa’s unique aquifer system characterized by a wide range of geological structures and climatic circumstances alters hydrogeological settings and local extraction rates of groundwater (Braune and Xu, 2008). However, despite groundwater’s great potential, it is unequally distributed. Over half of the water supply ends up in only 4 countries, namely Nigeria, Congo, Cameroon, and the Democratic Republic of Congo.

Potential of Groundwater

The greatest potential of groundwater lies within the economic advantages of groundwater extraction. Found by Dittion and Kamwamba (2013), the value-added per area in irrigation zones supplied by groundwater is twice more than irrigation zones supplied by other irrigation methods. Furthermore, groundwater supplies various small-scale irrigation projects where these projects can have a greater return of capital investment in comparison to large-scale dam constructions. For Africa's local farmers, the adoption of groundwater irrigation allows them to plant a more diverse range of crop products. Farmers possess a greater sense of control in their hands than rain-fed agriculture which is highly dependent on seasonality and rainfall level.

Groundwater pollution

Overviewing the whole population of Africa, over 65% of the people rely upon the basic pit latrine sanitation and 10% have no sanitation systems, while 25% of the population is reported using a ‘flush toilet’ (Adelana and McDonald, 2008). The coverage of septic tanks is concentrated in larger cities where water-borne sewage systems exist, and even at these places, the dwellings in coverage are not connected to each other. What this reveal is the potential of large subsurface contaminant and the threat of groundwater pollution. The major sources of groundwater pollution come from high nitrate concentrations, sourced from industrial effluent disposal, and leachates from solid-waste tipping. Another source of groundwater pollution is fecal contamination. This remains a serious problem in Africa because of inappropriate sanitation unit designs and utilization of such facilities, there is no solid perimeter around each water supply well (Gaye and Tindimugaya, 2018).

Groundwater management challenges

Because of urbanization, substantial groundwater development for domestic water supply occurred throughout Africa in the twentieth century. Groundwater is widely scattered and generally of potable quality, it is widely used as a low-cost alternative to surface water in metropolitan water systems. However, the increased reliance on groundwater for urban water supplies and agriculture raises questions about the sustainability of groundwater resources and the scale of extraction. Sub-Saharan Africa is one of the world's most urbanizing regions (UN, 2007), and the rate of population increase puts further strain on the provision of safe drinking water and sanitation. In Africa, there is a scarcity of knowledge and technical institutions for the development of groundwater infrastructure at the national and regional levels. In addition, the development of effective institutions to manage transboundary groundwater resources is an added challenge, transboundary conflicts must be solved to ensure equitable use of non-renewable water sources.