Enhancing Sustainable Groundwater Use in South Africa (ESGUSA)

Groundwater is an increasingly important source of water supply for agriculture, households, and industry. Generally, groundwater is naturally protected against pollution, can be exploited anywhere depending on the local conditions, and has a year-round availability. With population growth and increasing climate variability, groundwater plays an increasingly important role in the Republic of South Africa (RSA) to enhance water and food security. More than 50% of communities in RSA, especially living in the arid and semi-arid areas, depend on groundwater for their domestic and livelihood needs. However, with increasing pressure on groundwater and intensive land-use, the resource is vulnerable to depletion and degradation.

This is compounded by limited capacity and inadequate resources allocated to its protection and sustainable management. Intensification of use and poor management potentially leads to adverse impacts on ecosystems, water access, human health, and agricultural production.

Objectives - Expected outcomes and outputs - Methodology - References

Background

Groundwater is an increasingly important source of water supply for agriculture, households, and industry. Generally, groundwater is naturally protected against pollution, can be exploited anywhere depending on the local conditions, and has a year-round availability. With population growth and increasing climate variability, groundwater plays an increasingly important role in South Africa (RSA) to enhance water and food security. More than 50% of communities in RSA, especially living in the arid and semi-arid areas, depend on groundwater for their domestic and livelihood needs (DWS, 2016). However, with increasing pressure on groundwater and intensive land-use, the resource is vulnerable to depletion and degradation. This is compounded by limited capacity and inadequate resources allocated to its protection and sustainable management. Intensification of use and poor management potentially leads to adverse impacts on ecosystems, water access, human health, and agricultural production.

Denmark is one of only few countries in the world exclusively dependent on groundwater since historic times . This has provided significant challenges with both water quantity and quality, most prominently water quality, as Denmark has a relatively humid and temperate climate. This reliance has given rise to world-recognized expertise in pro-actively managing and protecting groundwater. Denmark has over the years developed advanced research expertise and evidence-based sustainable practices within groundwater management, integral to larger environment planning and protection.

Managing groundwater resources for sustained and high-value 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, potential adverse impacts, e.g. from excessive abstraction or from poor agricultural or land-use practices, and how to properly mitigate such and ensure a sustainable exploitation. This is in particularly important in arid and semi-arid regions where the groundwater resources are under relatively heavier pressure of intensive use. RSA is one such example, where such areas comprise about 30% of the country’s land mass, and within the Limpopo province specifically, 65% of the land area is under significant pressure to intensify groundwater use (Ebrahim, pers. comm.).

The replenishment, or recharge, of groundwater occurs as diffuse and focused fluxes (Healy, 2010). Diffuse recharge is recharge that occurs distributed over the catchment in response to precipitation. 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. Fractures or geological structures (like faults and dikes) in the subsurface may enhance and facilitate focused recharge (Scanlon et al., 2006). Although both components are difficult to estimate, particularly under arid and semi-arid conditions (Villeneuve et al., 2015), most uncertainties are related to focused recharge (Döll and Fiedler, 2008). This component can potentially be the major contributor to recharge in such environments (Scanlon et al., 2006).

Based on a modelling study, Ebrahim et al. (2017) found that groundwater replenishment through the riverbed during flooding in the Hout catchment in the Limpopo Province was the most uncertain component of the water balance, due to lack of process understanding and field evidence. Other studies in the Limpopo River Basin substantiate the significance of recharge through the riverbed (Riddell et al., 2014), also from a surface water perspective (Hughes and Sami, 1992). Focussed recharge through the riverbed is most important in lower catchment reaches and after a sequence of smaller rainfall events or following an intense event, which overcomes a certain saturation threshold for significant recharge (Riddell et al., 2014). Villeneuve et al. (2015) found in a study in a semi-arid part of Australia that deep groundwater recharge from rivers were constrained by less impermeable layers under the riverbed. Rather than replenishing the regional aquifers, the ephemeral rivers recharged a local shallow aquifer that supplied water to evapotranspiration of the riparian vegetation. Also, geological heterogeneities complicate and change the dynamics of river-aquifer interactions (Villeneuve et al., 2015). Such phenomena may also occur under RSA conditions, but they have never been documented. In addition, the geological settings in dry parts of RSA, dominated by weathered and fractured rock, may provide complex subsurface flow paths for infiltrating water via e.g. vertical dolerite dikes . Combining this with landscape-controlled focused recharge sites, like rivers, this may provide complex and time- and space-variable mechanisms and local zones of significant recharge.

In this project, we seek to clarify for the first time these critical processes in conjunction by using and further developing traditional and innovative field techniques. These include geophysics, hydraulic head measurements in the aquifer in and adjacent to the river, differential river gauging (McCallum et al., 2014), heat as a tracer (Roshan et al., 2012), and environmental tracers such as stable isotopes (Healy, 2010). The episodic and localized nature of groundwater replenishment, coupled with intensive use of groundwater in the Limpopo River Basin, means that groundwater may be significantly overexploited during periods and in areas, where recharge is not significant. It also implies that groundwater may be replenished on a cyclical basis dependent on climate and climate variability (Taylor et al., 2012). Understanding this spatial and temporal variability in the context of groundwater replenishment, storage and exploitation becomes central for sustainable management. In other words, groundwater may be replenished on an irregular basis, but if knowledge exists on the stochastic properties related to events and recharge processes, much better management can be put in place in these settings.

The distributed hydrological model MIKE SHE (Abbott et al., 1986) considers all-important and interacting hydrological processes including precipitation, evapotranspiration, unsaturated flow, river flow, subsurface flow and the interaction among these components. The model is usually parameterized based on knowledge of land surface and sub-surface characteristics, driven by climatic measurements and estimates, and calibrated against field measurements of groundwater heads and river discharges. This is a standard method in temperate regions (Henriksen et al., 2003), but is more challenging in arid and semi-arid regions with ephemeral rivers. In addition to field-based data, satellite platforms offer an increasingly wealth of remotely sensed hydrology-relevant data, which can be used to drive and validate integrated models (Stisen et al., 2008). New satellite platforms provide data of appropriate spatial and temporal scales, e.g. the Sentinel satellite (Yang and Chen, 2017), which offers unprecedented resolution of spatio-temporal information on free water surfaces (basically surface water occurrence). This is very useful for acquiring data on ephemeral flows in river stretches and flood plains during flooding that can be used for constraining the simulation of groundwater-river exchange in these systems with limited hydrometric monitoring networks. As such, the model to be developed, calibrated and validated as part of the project, will provide an innovative scientifically-based and tested tool for understanding and managing groundwater resources in these prevalent systems in RSA.

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 (Henriksen et al., 2008) can be used for making such assessments. In this study, the methodology will be adapted and further developed for conditions in RSA, especially with regards to the socio-economic drivers and environmental requirements, building on previous work on reserve determination (Ebrahim and Villholth, 2015; Seaman et al., 2016), seasonal forecasting (Fallon et al., 2017), and citizen science (Stuart-Hill, 2016).

Citizen science has been documented as an efficient manner to involve stakeholders in the management of their water and environmental resources, but mostly for surface water systems (Stuart-Hill, 2016). In the present project, the citizen science approach will be further developed and adapted for integrated surface-groundwater systems, enhancing data collection, empowering groundwater users in co-managing their resources as well as raising awareness and insights into best management practices, supporting and supported by the modelling approach.

Objectives

The overall objective of the project is to develop sustainable groundwater management in RSA.

This is achieved through:

1. Establishing an effective research partnership with Denmark.
2. Improving the understanding of hydrogeological conditions in typical geological settings and farming communities in RSA, exemplified by the Hout/Sand river catchment in Limpopo Province.
3. Development of modelling and resource indicator tools for integrated groundwater management.
4.  Stakeholder involvement in development and promotion of sustainable groundwater management options.
5. Increasing the research capacity in RSA within integrated groundwater resource assessment and management.

Our scientific hypotheses are:

1. Focused recharge in ephemeral rivers significantly contribute to groundwater replenishment during major rainfall events in semi-arid RSA. The complex sub-surface geology leads to large spatial and temporal variability in river-groundwater interactions, groundwater recharge and storage.
2.  Integrated hydrological models, making innovative use of new satellite data types and state-of-the-art field investigations and monitoring, results in a better understanding of the surface and subsurface water fluxes and storages and hereby provides an improved basis for development of sustainable groundwater management plans.
3. Involvement of local stakeholders via new developments of citizen science helps securing the implementation of management plans.

Expected outcomes and outputs

We expect to develop new and innovative research methodologies, findings, outputs, and outcomes related to the three hypotheses listed above. Results will be published in high-impact international journals and presented at national and international conferences, by both Danish and RSA researchers.

An important outcome of the project is strengthened research capacity in RSA. This is secured by assigning two RSA postdocs to the project. They will work closely together with a postdoc employed in Denmark, and the three postdocs will be supervised by a team of experienced and internationally recognized scientists with long research track-records. Furthermore, the two RSA postdocs will make research visits in Denmark where they will receive training in field techniques, integrated hydrological modelling, data management, and citizen science. Furthermore, they will be introduced to the Danish research-based and internationally recognized practices in integrated groundwater management, which have been developed and refined over many years.

In addition, the groundwater administration in RSA at national and district level will benefit from the project-developed knowledge and tools in the form of guidelines, monitoring tools and indicators for sustainable groundwater exploitation, and model concepts. Local stakeholders will benefit through the citizen science approaches and local management tools. Finally, broader stakeholder groups will be informed of the project outcome through public seminars and meetings.

Methodology

The research will be focusing on the Hout catchment (about 2500 km2), which is part of the Limpopo River Basin in RSA. The area may be expanded to the Sand catchment, to which Hout is a tributary, in order to better close the water balance using the only discharge station in the area, which is downstream of the confluence of the two rivers, see Figure 1.

The geological setting in the catchment is rather complex, as the upper horizon (down to approximately 50 m depth) is composed of weathered granite and the deeper horizon (down to approximately 120 m depth) consists of fractured rock (Ebrahim et al., 2017). Furthermore, the geology is characterized by local and regional features, like faults and dikes, which can significantly alter otherwise expected flow paths. The impact of these features on water flow and particularly on the recharge and exchange between groundwater and surface water is unknown and hampers the management of the groundwater resources in the region. Moreover, this offers challenges to field investigations and modelling of subsurface water flow, requiring specialised field and modelling approaches. Flow in the rivers is intermittent and the surface water resources are limited. Thus, groundwater is used extensively in the region for irrigated agriculture (potatoes and other vegetables), livestock as well as for water supply. Evidence of cyclical long-term declining groundwater levels (Fallon et al., 2017) emphasizes the need for better management of groundwater resources.

 
Figure 1. Hout/Sand catchments
In order to ensure sustainable development as well as protection and management of the groundwater resources, better knowledge of the water circulation and the spatial and temporal availability in the catchment is required, including rainfall variability, diffusive and focused recharge, flow processes in the geological materials, and water exchange between groundwater and surface water. This requires dedicated hydrogeological field investigations, collection of geological and hydrological data, retrieval of surface characteristics from remote sensing platforms as well as integrated and distributed hydrological modelling. The field investigations will be supported by involvement of local stakeholders (farmers, ranchers, municipality) in structured processes (citizen science) to both generate important knowledge and data for the modelling as well as empowering the stakeholders to better understand the groundwater systems and take up recommendations on local management from the modelling.

The research will be organized into five work packages and include the following activities:

WP1: Data collection and hydrogeological field investigations

1. Collection of existing spatial data and time series from the catchment(s), including climate data, geological data and maps, hydraulic head measurements, water abstractions and transfers, soil maps, digital elevation data for ground surface and river topography, land-use maps, and river discharge.
2. Hydrogeological investigations and borehole logging of existing wells including pumping tests, slug tests, gamma logging, flow logging, and resistivity logging.
3. Identification of three river segments representing typical geological and hydrogeological processes for focused recharge.
4. Geophysical mapping in the riverbed and in transects across the river using multi-electrode profiling (MEP) and electromagnetic measurements (EM).
5. Drilling of one horizontal well and four vertical wells at each segment, well testing, and installation of transducers and data loggers for continuous monitoring.
6. Monitoring of hydrogeological conditions from new and existing field installations.
7. Water collection from wells for analyses of stable isotopes.
8. Temperature stick-probing for measurements of vertical profiles of temperature.
9. Analysis of dynamic processes using the FEFLOW code, which can handle complex 3D flow and transport processes as well as temperature transport, in order to improve the process understanding.

WP2: Development and calibration of integrated hydrological model(s) for the Sand/Hout catchments

1. Identification of relevant remote sensing products to obtain spatial and temporal data for land-use, vegetation characteristics (NDVI, albedo), precipitation, evapotranspiration, surface temperature, free water surfaces (rivers/wetlands).
2. Development of scripts for retrieval and use of remote sensing data.
3. Retrieval of remote sensing data.
4. Development of a conceptual geological model.
5. Development of an integrated and distributed hydrological model for the entire catchment based on the MIKE SHE code, which can make use of historical and project-generated data and information.
6. Calibration of the model using state-of-the-art calibration techniques based on pilot points and regularization (Doverty, 2015) to allow for incorporation of spatial heterogeneity in the model and for performing uncertainty analyses.
7. Model analyses of water balances and flow dynamics.

WP3: Citizen science and capacitating local stakeholders

1. Designing approach and process for citizen science, conducting stakeholder identification and assessment and actor networks, identifying and selecting key stakeholders and a champion to lead the stakeholder group, based on previous engagement (Fallon et al, 2017), conducting sensitisation and induction sessions and joint field visits.
2. Training and equipping local stakeholders to collect essential temporal data for the assessments, like groundwater levels, stream flow and rainfall.
3. Monitoring via citizen science.
4. Capacitating local stakeholders in the management of groundwater and conjunctive use of surface and groundwater, and adapting to climate change. This will be partly based on modelling results and done in an interactive manner, encouraging lesson sharing and development of joint management solutions (overlap with WP4.2 and WP4.4).
5. In discussion with DWS and other authorities identifying best institutional (formal/informal) mechanism(s) and incentives to extend the citizen science activities beyond the project lifetime.

WP4: Development of integrated groundwater management options for present and future climate conditions

1. Identification of resource sustainability indicators.
2. Development of groundwater management schemes using resource sustainability indicators and various future scenarios of water demand, water use, climate variability and change and management options (overlap with WP3.3).
3. Model simulations and analysis of consequences of alternative management schemes.
4. Presentation and discussion of results with stakeholders (overlap with WP3.3).

WP5: Capacity strengthening

1. Three postdocs will form the base of the planned research, as they will be fully dedicated to the project. The postdocs will spend time both in the North and South. They will work closely together on fieldwork, journal papers and exchange of knowledge and data.
2. Capacitating national and local stakeholders in groundwater understanding, monitoring, integrated model tools in decision making, and co-development of improved management options under future uncertainty in the Hout/Sand catchment.

References

1. Abbott, MB, Bathurst JC, Cunge JA, O’Connel PE, Rasmussen R., An introduction to the Eupean Hydrological System – System Hydrologique Eupeen, SHE, 2. Structure of a physically-based distributed modeling system, J. Hydrol., 87, 61-77, 1986.
2. Anderson SP, Bales RC, Duffy CJ, Critical Zone Observatories. Building a network to advance interdisciplinary study of Earth surface processes, Mineral. Mag., 72(1), 935–944, 2008.
3. Cuthbert MO, Acworth RI, Andersen MS, Larsen JR, McCallum AM, Rau GC, Tellam JH, Understanding and quantifying focused, indirect groundwater recharge from ephemeral streams using water table fluctuations, Water Resour. Res., 52, 827–840, doi:10.1002/2015WR017503, 2016.
4. Dept. of Water and Sanitation (DWS), National Groundwater Strategy, Dec 2016, 110 pp, 2016.
5. Doverty J, Calibration and uncertainty analysis for complex environmental models, Watermark Numerical Computing, 2015.
6. Duque C., Caovache ML, Engesgaard, Investigating river-aquifer relations using water temperature in an anthropized environment (Motril-Salobreña aquifer), J. Hydrol., 381, 121-133, 2010.
7. Döll P, Fiedler K, Global-scale modeling of groundwater recharge, Hydrol. Earth Syst. Sci., 12, 863–885, 2008.
8. Ebrahim GY, Villholth KG, Boulos M. Supporting sustainable agricultural groundwater use in the Dendron Area, Limpopo Province, South Africa - Application of an integrated hydrogeological model. Hydrogeol. J., 2017 (accepted).
9. Ebrahim GY, Villholth KG. Estimating shallow groundwater availability in small catchments using streamflow recession and instream flow requirements of rivers in South Africa. J. Hyd. doi:10.1016/j.jhydrol.2016.07.032.
10. Fallon A, Villholth KV, Ebrahim G, Conway D, Lankford B. Agricultural groundwater management strategies and seasonal climate forecasting: Perceptions from Dendron, South Africa. J. Water and Clim. Change. Submitted.
11. Healy R., Estimating Groundwater Recharge, Cambridge University Press, 245 pp, 2010.
12. Henriksen HJ, Troldborg L, Nyegaard P, Sonnenborg TO, Refsgaard JC, Madsen B, Methodology for construction, calibration and validation of a national hydrological model for Denmark, J. Hydrol., 280, 52–71, 2003.
13. Henriksen HJ, Troldborg L, Højbjerg AL, Refsgaard JC, Assessment of exploitable groundwater resources of Denmark by use of ensemble resource indicators and a numerical groundwater–surface water model, J. Hydrol., 348, 224-240, 2008.
14. Hughes DA, Sami K, Transmission losses to alluvium and associated moisture dynamics in a semiarid ephemeral channel system in Southern Africa, Hydrol. Proces., 6, 45-53, 1992.
15. Jensen KH, Illangasekare TH, HOBE – a hydrological observatory in Denmark. Vadose Zone J., 10, 1-7, doi:10.2136/vzj2011.0006, 2011.
16. McCallum AM, Andersen MS, Rau GC, Larsen JR, Acworth RI, River-aquifer interactions in a semiarid environment investigated using point and reach measurements, Water Resour. Res., 50, 2815-2829, 2014.

• Establishing an effective research partnership with Denmark.
• Improving the understanding of hydrogeological conditions in typical geological settings and farming communities in RSA, exemplified by the Hout/Sand river catchment in Limpopo Province.
• Development of modelling and resource indicator tools for integrated groundwater management.
• Stakeholder involvement in development and promotion of sustainable groundwater management options.
• Increasing the research capacity in RSA within integrated groundwater resource assessment and management.

Lindle J, Jensen KH, Villholth KG, Taylor R (2019), Inferring groundwater recharge associations to climate, land use and geological structures using multi-decadal groundwater level observations from the semi-arid Limpopo basin of South Africa. International Association of Hydrogeologists 46th Congress, Malaga, September 2019, http://www.iah2019.org/.

Kanyerere T, Pietersen K, Goldin J, Villholth KG, Levine AD (2019), Using citizen science in groundwater data generation research to improve decision-making support on water information. 2nd  SADC-GMI Groundwater Conference, Johannesburg, September 2019, https://www.un-igrac.org/agenda/2nd-sadc-gmi-groundwater-conference.

Muchingami I, Pietersen K, Kanyerere T (2019), Framework for assessing aquifer-river interaction for crystalline basement formations in semi-arid areas, with case study in Hout River catchment, Limpopo basin, South Africa. 2^nd  SADC-GMI Groundwater Conference, Johannesburg, September 2019, https://www.un-igrac.org/agenda/2nd-sadc-gmi-groundwater-conference.

Muchingami I, Pietersen K, Kanyerere T (2019), Groundwater exploration in crystalline basement Aquifers with a case of Houtriver Gneiss Formation, Limpopo, South Africa. Proceedings of the 13th Biannual GSSA Groundwater conference, 21-23 October 2019, Port Elizabeth, South Africa, https://gwd.org.za/event/2019-groundwater-conference-conservation-demand-surety-gwd/.

Report on 1^st Multi-Stakeholder Workshop, Citizen Science Component, Polokwane, March 7-8 2019.

Report on 2^nd Multi-Stakeholder Workshop, Citizen Science Component, Makhado Agricultural Office, Louis Trichardt, July 31 2019.

Report on 3^rd Multi-Stakeholder Workshop, Citizen Science Component, Polokwane, November 22 2019.

Time series analysis of Sentinel 2 data for the years 2016 & 2017 in the Hout river catchment, Limpopo Basin, South Africa.

Training Manual on Field Data Collection for Water Resources Management.

Training Manual on field data collection for groundwater water level measurements.

ESGUSA report on Work Package 1: Data collection and hydrogeological field investigations.

Questionnaire on Household Water Security.

University of Copenhagen

• Professor Karsten Høgh Jensen (project leader), khj@ign.ku.dk
• Postdoc Rena Meyer, reme@ign.ku.dk

Geological Survey of Denmark and Greenland

• Professor Torben Sonnenborg, tso@geus.dk
• Senior researcher Hans Jørgen Henriksen, hjh@geus.dk

University of Western Cape

• Senior Lecturer Thokozani Kanyerere, tkanyerere@uwc.ac.za
• Senior Lecturer Kevin Pietersen, kpietersen@mweb.co.za
• Professor Yongxin Xu, yxu@uwc.ac.za
• Postdoc Innocent Muchingami, 2967580@myuwc.ac.za

Ekosource

• Managing Director Jason Hallowes, jhallowes@ekosource.co.za
• Reseacher Bruce Robert Eady, BEady@ekosource.co.za

International Water Management Institute – South Africa (IWMI)

• Principal Researcher Karen Villholth, K.Villholth@cgiar.org
• Regional Researcher Girma Y. Ebrahim, g.ebrahim@cgiar.org
• National Researcher Manuel Magombeyi, m.magombeyi@cgiar.org

Collaborating Partners

• Department of Water and Sanitation
• Capricorn District Municipality
• South African Water Research Commission