Enhancing Sustainable Groundwater Use in South Africa

Project summary

Groundwater is an increasingly important source of water supply for agriculture, households, and industry. With population growth and increasing climate variability, this water resource plays an increasingly important role in South Africa (RSA) to enhance water and food security. However, with increasing pressure on groundwater and intensive landuse, the resource is vulnerable to depletion and degradation. This is compounded by limited capacity and inadequate resources allocated to its protection and sustainable management. Managing groundwater resources for sustained uses requires knowledge of the aquifer systems, their replenishment and interactions with rivers, wetlands and terrestrial systems. It also requires knowledge of the human interaction with the resource to ensure a sustainable exploitation.

The replenishment, or recharge, of groundwater occurs as diffuse and focused fluxes. Diffuse recharge is recharge that occurs distributed over the catchment. Focused recharge, on the other hand, occurs from localized accumulation of water on the land surface such as ponds and from river segments. It varies much more in space and time than diffuse recharge, especially for ephemeral rivers, which are common in arid and semi-arid areas. Large uncertainties are related to focused recharge and this component can potentially be the major contributor to recharge in such environments. In this project, a suite of field experiments and data collection in conjunction with hydrological modeling will be carried out to investigate and quantify focussed recharge.

Sustainable groundwater exploitation requires consideration of the environmental, agronomic, and socio-economic conditions in the linked groundwater-surface water system. Integrated
hydrological models in combination with resource sustainability indicators will be used for making such assessments. Citizen science has been documented as an efficient manner to involve stakeholders in the management of their water and environmental resources. In this project the citizen science approach will be further developed and adapted for integrated surface groundwater systems.

Outputs

Extra midterm report
Two field sites for detailed hydrogeological observations have been established at Mamadila and Kalkfontein in the Hout catchment. Seven monitoring wells are equipped for automated logging/monitoring of groundwater levels, generating data on focused recharge. In February 2021, large rainfall events and associated river flow provided clear evidence of focused recharge. A study based on historical data has documented the important role of focused recharge to groundwater recharge.

An integrated hydrological model has been developed and calibrated for the Hout/Sand catchments. Reanalysis rainfall data products from the European Centre for Medium-Range Weather Forecasts (ERA5) and satellite data from the Tropical Rainfall Measuring Mission (TRMM) have been retrieved and analyzed for a more detailed spatial representation of rainfall in the model. This is important, as rainfall is the key driver for groundwater recharge.

The project developed and assessed a novel approach in RSA on citizen science that contributes in two integrated ways: (1) An improved scientific understanding of catchment hydrogeology and (2) Literacy and tools for local stakeholders to better participate in water resources management. Three sections in the Hout catchment have been identified as study areas in which volunteers have been equipped and trained in measuring rainfall, groundwater level and river flow. An online App has been developed, and volunteers record the data on the App via their cellphone.