Groundwater/surface-water interaction is receiving increasing focus in Africa due to its importance to ecologic systems and sustainability. In South Africa’s 1998 National Water Act (NWA), water-use licenses, including groundwater, are granted only after defining the Reserve, the amount of water needed to supply basic human needs and preserve some ecological integrity. Accurate quantification of groundwater contributions to ecosystems for successful implementation of the NWA proves challenging; many of South Africa’s aquifers are in heterogeneous and anisotropic fractured-rock settings. This paper reviews the current conceptualizations and investigative approaches regarding groundwater/surface-water interactions in the context of South African policies. Some selected pitfall experiences are emphasized. The most common approach in South Africa is estimation of average annual fluxes at the scale of fourth-order catchments (∼500 km2) with baseflow separation techniques and then subtracting the groundwater discharge rate from the recharge rate. This approach might be a good start, but it ignores spatial and temporal variability, potentially missing local impacts associated with production-well placement. As South Africa’s NWA has already been emulated in many countries including Zambia, Zimbabwe and Kenya, the successes and failures of the South African experience dealing with the groundwater/surface-water interaction will be analyzed to guide future policy directions.

The infamous drought of 2015–2017 in Cape Town (South Africa) provides important lessons on water governance. While it is undeniable that an unprecedented sequence of two record-low rainfall years instigated the ‘water crisis’, this essay argues that the severity of the drought may have been mitigated by good governance, both in terms of diversifying water sources and managing existing supplies. Historically, water authorities have focussed on surface-water resources for Cape Town’s water supply. Cape Town’s ample groundwater has not been utilised to any notable extent. It is concluded that the crisis, once passed, may be viewed as auspicious, for not only did it provide the impetus to adapt Cape Town’s water supply, thereby better incorporating its groundwater resources, but the crisis stands as a case in point to justify future investments in water security, not only for Cape Town, but for other cities as well.

Water storage assessment is an important component of feasibility studies for prospective mining areas. As required by national mineral resources and environmental Acts, this may include assessment of both exploitable and sustainable storage; the former relates to the amount of groundwater stored within the exploitable aquifer depth and the latter is defined as the groundwater that can be sustainably extracted without producing unacceptable environmental and economic problems. A simplified method is proposed to assess the groundwater storage in a typical mine area, Tugela in South Africa. In the area, five aquifers (Natal Group, Coastal plain deposits, Basement aquifer, Ecca Group and Dwyka Group) have better harvest potential compared with others on the basis of borehole yield. The study area was divided into four subareas (A, B, C and F) based on proposed mining boundaries. Both exploitable and sustainable groundwater storage were estimated. The estimated exploitable groundwater storage for subareas A, B, C and F are 20.66, 5.78, 43.12, 36.90 Mm³, respectively, on the basis of current median exploitation depths of each aquifer or geological formation. The calculated sustainable groundwater storage for subareas A, B, C and F are 3.31, 0.89, 6.67 and 6.01 Mm³, respectively, with a total of 16.88 Mm³. Groundwater recharge of the subareas was also estimated for subareas A, B, C and F as 31.92, 11.44, 43.38 and 29.78 Mm³/annum, respectively, with a total of 116.53 Mm³/annum. The assessment method can be applied to other areas with similar hydrogeological settings with the available datasets.

A feasibility assessment was undertaken on the application of water-sensitive urban design (WSUD) for the Cape Flats Aquifer in Cape Town, South Africa, at the local scale. The study contributes towards the planning of water-sensitive cities in the future. A three-dimensional steady-state groundwater flow model was applied to the Cape Flats Aquifer to predict WSUD scenarios by incorporating managed aquifer recharge (MAR). Analysis of the scenarios of varying recharge estimates and groundwater abstraction rates, predicted using the model, indicated that the water-table distribution and outflows from identified groundwater balance components show direct proportionality to the varying recharge scenarios. A notable increase in these outflows was observed when the recharge rate was increased by 50%. Varying groundwater abstraction scenarios indicated that with increasing abstraction rates, water levels and outflows from groundwater balance components also decreased accordingly. A notable decline in water levels and outflows was established at an abstraction rate of 2.5 and 5 L/s, respectively. Similar to the previous regional studies in the area, the results from the predicted scenarios show that there is a potential for applying WSUD, particularly MAR, at site-specific scale within the Cape Flats Aquifer. However, shallow groundwater levels during wet seasons limit the opportunities for application of WSUD in the area. This finding would provide an important reference to the ongoing debate on the Cape Town water crisis and similar environmental conditions where WSUD is considered.

Improved groundwater flow conceptualization was achieved using environmental stable isotope (ESI) and hydrochemical information to complete a numerical groundwater flow model with reasonable certainty. The study aimed to assess the source of excess water at a pumping shaft located near the town of Stilfontein, North West Province, South Africa. The results indicate that the water intercepted at Margaret Shaft comes largely from seepage of a nearby mine tailings dam (Dam 5) and from the upper dolomite aquifer. If pumping at the shaft continues at the current rate and Dam 5 is decommissioned, neighbouring shallow farm boreholes would dry up within approximately 10 years. Stable isotope data of shaft water indicate that up to 50 % of the pumped water from Margaret Shaft is recirculated, mainly from Dam 5. The results are supplemented by tritium data, demonstrating that recent recharge is taking place through open fractures as well as man-made underground workings, whereas hydrochemical data of fissure water samples from roughly 950 m below ground level exhibit mine-water signatures. Pumping at the shaft, which captures shallow groundwater as well as seepage from surface dams, is a highly recommended option for preventing flooding of downstream mines. The results of this research highlight the importance of additional methods (ESI and hydrochemical analyses) to improve flow conceptualization and numerical modelling.

Over the past few years groundwater has been recognized as an important contributor of freshwater to Lake St Lucia, South Africa during periods of prolonged drought. This has led to a management strategy aiming at increasing the groundwater recharge and minimizing groundwater use through active manipulation of the vegetation. For the Eastern Shores on the edge of Lake St Lucia, the replacement of vast areas of pine (Pinus elliottii) plantations with grassland over the past decade, combined with a strict burning regime, has led to a general rise of the water table, which has increased the groundwater seepage to Lake St Lucia. A numerical groundwater model has been applied to assess the effects of local management strategies on the mass balance of a shallow aquifer and these are compared to the effects of predicted climate and sea-level change for this area. The simulations indicate that local management actions that are being applied to the Eastern Shores have positive effects on the groundwater flux into Lake St Lucia and that they outweigh potential negative effects of future climate and sea-level change predicted for this area.

Groundwater recharge estimation in arid and semi-arid southern Africa is reviewed based on four decades of recharge investigation in the region. This paper updates an earlier review by incorporating emerging and grey literature from a wide range of research sectors in southern Africa, collected during the past decade. For ease of comparison, methods commonly used are critically reviewed with a rating provided in terms of accuracy, application and costs. These include, but are not limited to, the methods of chloride mass balance (CMB), rainfall infiltration breakthrough (RIB), Extended model for Aquifer Recharge and moisture Transport through unsaturated Hardrock (EARTH), water-table fluctuation (WTF), water balance in the saturated zone (including equal volume spring flow (EVSF) and saturated volume fluctuation (SVF)), and groundwater modelling (GM). As the methods based on mass balance and relationships between rainfall, water-level fluctuations and abstraction are proven to have the potential to simulate and forecast groundwater recharge, the EVSF and CMB methods are highly recommended for use in the southern African region according to this review. Caution on the uncertainty associated with error input and propagation for all the methods is advised, based on a case study in South Africa. The review provides an updated source of references related to recharge estimation in arid and semi-arid regions of Sub-Saharan Africa in general and to ongoing projects for the implementation for Resource Directed Measures (part of the National Water Resources Strategy) in South Africa in particular.

This study investigates whether increased use of the Ostrom design principles could improve groundwater governance research. The principles relate to self-organizing governance systems of common-pool resources, which are more likely to be sustainable if all eight design principles—e.g. clear resource and user boundaries, collective-choice arrangements, monitoring, sanctions, conflict-resolution mechanisms—are present. Empirical studies have proven the relevance and effectiveness of the Ostrom design principles for a range of common-pool resources. However, the application of the design principles to groundwater has been limited. The South African institutional landscape was therefore chosen as a case study to investigate the relevance of the design principles. The case study involved (1) comparing the design principles with established global governance benchmarking criteria, (2) assessing how implementable the design principles would be in South Africa, and (3) comparing the aims of the design principles and the broad aims of groundwater governance in South Africa. It was found that the Ostrom design principles provide researchers with a common ‘language’ for learning about the specific issues of a particular setting, learning from experiments in that setting, and learning from the experience of others. The Ostrom design principles and associated adaptive management, social learning, use of the diagnostic approach, and more specific hydrogeological principles are not mutually exclusive and can be complimentary. The implementation of groundwater governance in South Africa has been poor and few Ostrom design principles have been adopted. More use of the Ostrom design principles could improve groundwater governance in South Africa and globally.

Sustainable yield is defined as the amount of groundwater abstraction that can be maintained for an indefinite time without causing unacceptable environmental, economic and social consequences. It is usually determined by monitoring the water-table depth, without the need for costly pumping exercises and subsequent deterioration of the groundwater and ecological environment. Groundwater numerical modelling provides an effective way to determine the yield by analysing the responding water levels to various pumping scenarios. In this study, the natural flow system and flow with pumping scenarios were simulated using FEFLOW for the fractured-rock aquifer in Table Mountain Group, South Africa. Results for different pumping rates show the distinct impact of groundwater abstraction on hydraulic head, which indicates that long-term abstraction slowly increases the well drawdown, but it would stabilize at a level that is dependent on pumping rate and induced recharge. To estimate the aquifer sustainable yield, a relationship between simulated drawdown and pumping rate was established, namely an exponential function with parameters that may change value between sites. This empirical relation, derived from this site-specific study, provides an option for informed decision-making. The issue of how to sustainably abstract groundwater might rely on a compromise between the groundwater user and the governmental authority.