2.6 Modern Managed Aquifer Recharge in Southern Africa
In South Africa, following a period of serious water shortage, modern MAR technologies took their rightful place when systematic water research was initiated with the promulgation of the Water Research Act (Act number 34 of 1971) and the establishment of the Water Research Commission. Some of the first projects addressed the storage of river run-off, stormwater, and reclaimed water (treated sewage effluent) in the sand deposits of the Cape Flats aquifer for later abstraction and augmentation of fresh water supplies of the Cape Peninsula.
South Africa’s oldest MAR scheme was inspired by the above-mentioned pilot-scale testing of artificial groundwater recharge in the Cape Flats. Indirect recycling of water at the newly established industrial town, Atlantis, on the arid South African west coast started shortly after development of the town commenced in the mid-1970s, Tredoux and others (2002). Treated domestic effluent (from maturation ponds) is blended with urban stormwater runoff and discharged into recharge basins in the coastal dune area.
A surge of research commissioned by the Water Research Commission in the late 1990s and early 2000s (Murray and Tredoux, 1998; Murray and Tredoux, 2002) laid a foundation for the practical implementation of MAR in the region. Among others, it led to the construction of a major borehole injection scheme for the City of Windhoek, Namibia (Murray, 2002; Murray, 2016). Windhoek’s MAR scheme is of particular interest because it involves large-scale borehole injection and recovery in a highly complex, fractured quartzite aquifer. Prior to this scheme, MAR had not been practiced anywhere in the world at a large scale in complex geological environments. The risk of losing water was generally considered too high. By undertaking a comprehensive feasibility study, it was demonstrated that water losses would be negligible if the scheme was designed and operated correctly (Murray, 2002).
Importantly, in 2007, the South African government, through its Department of Water Affairs and supported by the Water Research Commission, developed and rolled out a national Artificial Recharge Strategy (DWAF, 2007). Its purpose was “to use natural sub-surface storage as part of Integrated Water Resource Management wherever technologically, economically, environmentally and socially feasible.”
The strategy had three main thrusts:
- increasing awareness of artificial recharge;
- incorporating artificial recharge into relevant planning documents; and,
- developing successful demonstration sites.
A comprehensive list of site-specific areas for potential artificial recharge for each of the 19 Water Management Areas was produced as a follow up to the strategy (DWAF, 2009). A website is maintained by the Department as a resource for research and education and as an information hub for water practitioners in government and the private sector (https://www.artificialrecharge.co.za/).
Implementation has been slow since then. Apart from the larger schemes of Windhoek and Atlantis mentioned above, some small to medium scale MAR schemes have been implemented in South Africa and feasibility studies have been conducted with the intention of implementation in the near future. One major feasibility study was undertaken for the Botswana government with the aim of assessing the value of MAR for the more populated eastern part of the country (Groundwater Africa, 2012; Lindhe, et al., 2014).
While the main purpose of MAR in Southern Africa is to augment water supplies and to enhance water security, two schemes are for mine water disposal to comply with environmental regulations. In these cases, it is not permitted to dispose of surplus water from the mines’ dewatering processes on the land surface, so aquifer recharge has become the chosen alternative and local farmers benefit from it (Murray, 2016).
The total MAR volume in Southern Africa by 2015 was 10.3 Mm3/year, or 0.2 percent of groundwater use, compared to a global average of 2.4 percent (Murray, 2016; Dillon et al., 2019). While the volume is small, it remains an important aspect of groundwater development on the African continent. The vast majority of African countries have not implemented MAR. MAR is practiced most commonly in South Africa (17 reported cases), followed by Tunisia (11 cases), Kenya (8 cases), and Algeria (5 cases). Of the South African cases, 12 represent open well, shaft and borehole injection, four are the surface spreading/infiltration method, and one is in-channel modification (Ebrahim et al., 2020).
While MAR activities in Southern Africa are limited, it is evident that MAR practices on a greater scale could substantially enhance the region’s water security (Murray, 2016).