Introduction
The Africa Use Cases provide an initial testbed that puts the quality of surface and groundwater into the context of the local Agenda 2030 and its multiple linkages across the Sustainable Development Goals. UNEP is working with relevant organizations and convenes the UN-Water Expert Group on Water Quality and Wastewater in the World Water Quality Alliance. The objective is to provide an evidence base that links water-quality hotspots to solutions and investment priorities.
The aim of the Africa Use Cases is twofold. The first is to evaluate availability and accessibility of data in selected locations/systems, and to test them in-situ to derive the best possible current state of water quality (baseline). Second, the Use Cases explore how to carry local engagement of water stakeholders with external experts - here represented by members of the World Water Quality Alliance - beyond the assessment of state and causal chains of water quality. The goal is to identify priority water-quality issues and hotspots and to co-design, pilot and demonstrate innovative information services and their application for water-quality improvement with the potential for upscaling and operational use.
Three locations in Africa were selected focused on urban groundwater (Cape Town); a lake of ecological and economic importance (Lake Victoria and associated basin); and a watercourse with pathogen risks (Volta River). In the mid- to long-term, the Alliance shall build on experience here to provide further services at scale to shift the water-quality needle, engage with UN Country Teams, and to enable upscaling to other locations.
Cape Town groundwater
Three aquifers are being targeted by the City of Cape Town for potable water supply: Atlantis, Cape Flats, and the Table Mountain Group.
Cape Flats is a sedimentary primary aquifer that underlies most parts of the city and is highly vulnerable to pollution from land-use activities, including small-scale agriculture, landfill sites, cemeteries, various industrial areas, sand mining, and informal settlements without proper sanitation. Its urban setting (and to an extent Atlantis) results in salinization and anthropogenic contamination with nutrients, microbiological and industrial contaminants, hydrocarbons and contaminants of emerging concern (see Figure 4.1a indicating the exceedances of water-quality guideline limits). The Table Mountain Group Aquifer, on the other hand, occurs in relatively pristine areas with good water quality, except naturally occurring elevated concentrations of iron and manganese.
The extensive in-situ monitoring data collected in the past three years for the city's groundwater development projects was supplemented with remote-sensing/earth-observation data, to provide a detailed land-use map identifying potential pollution sources, and a range of modelling from GIS-based vulnerability mapping to numerical flow and transport modelling to assist with the assessment (i.e. through the use of the Assessment triangulation approach).
The Cape Town Aquifer Use Case built on the existing stakeholder network and structures that were established as part of the groundwater development projects by the City of Cape Town. At the committee meetings, the Department of Water and Sanitation, as the regulatory authority, suggested the development of a groundwater management plan for each aquifer. Based on the presented water-quality data, Scientific Services (a department of the City of Cape Town) and the agricultural users of Cape Flats suggested that an aquifer protection plan be developed to address water quality concerns in the area.
As a result, a scheme was developed for Cape Flats (Figure 4.1b) to ensure the protection of groundwater quality to abstraction boreholes. The Groundwater Protection Scheme has several components, namely Groundwater Protection Zones, vulnerability mapping and ranking (using DRASTIC-model Specified Vulnerability Index), potentially contaminating activities, and a remediation plan (to be developed separately for each identified pollution). The vulnerability mapping indicated a very high (orange) to extreme high (red) vulnerability of the aquifer to pollution sources on surface. To reduce the risk of pollution entering the proposed abstraction boreholes, protection zones limiting certain land-use activities were proposed, depending on the expected residence time of pollutants entering the aquifer (modelled as lifetime expectancy). Zone II (purple) and Zone III (dark green) require strict restrictions on land-use activities that can potentially pollute the aquifer.
Lake Victoria Basin
The stakeholder engagement concept and data acquisition context for the Lake Victoria Use Case was shared with local people and groups at a symposium and workshop in Kenya and Uganda. Central aims were to collectively assess water-quality challenges and associated impacts at Lake Victoria and its catchment, develop a stakeholder network, and assess data sources and types associated with the lake, and any limitations to the sharing of such data. Subsequent virtual workshops were organized with the riparian fisheries organizations Kenya Marine and Fisheries Research Institute (KMFRI), Uganda's National Fisheries Research Institute (NaFIRRI), and the Tanzanian Fisheries Research Institute (TAFIRI). The goal of these meetings was to discuss water-quality data and information products and services to be co-developed to target hotspots. In-country direct engagement was not pursued because of pandemic travel restrictions.
The potential co-designed water-quality products and services agreed upon were:
Coastal Eutrophication
Available data sources are being assessed to indicate the possible coastal eutrophication, including the identification of hotspots and any seasonal patterns. This demand-driven tool is being developed to characterize the potential of algal blooms to impact fisheries, or to identify links between aquaculture and coastal eutrophication. This includes the joint use of:
- Remote-sensed earth observation (provided by EOMAP), including turbidity and chlorophyll-a values for the lake.
- Water-quality modelling to determine total phosphorus inputs into the lake from identified sources such as the domestic sector, agriculture, background loadings etc. (provided by Ruhr-University Bochum, Germany).
- In-situ measurements provided to date (river/lake measurements of nutrients such as nitrate, phosphate etc.) via GEMStat and in-country partners. This information is being used to validate the model and remote-sensing/earth-observation data.
Outcomes envisioned include the identification of nutrient hotspots, their drivers, and their temporal and spatial dynamics (Figure 4.2) so that priorities can be defined and management strategies can be efficiently directed. Further, scenario modelling can be used to evaluate the effectiveness of a range of management alternatives.
Water temperature and stratification dynamics
Monitoring activities by different research institutions of the adjacent countries generated a valuable record of water temperatures in Lake Victoria over past years, including data jointly collected by TAFIRI, NaFIRRI and KMFRI under the coordination of the Lake Victoria Fisheries Organization, which was shared with the Alliance. The aim is to use a freely available lake model (GLM 3.1, General Lake Model) to simulate temperature dynamics in Lake Victoria to inform the extent of stratification and vertical mixing in the water column. At the same time, this initiative brings together monitoring results from different countries and institutions and generates not only the required data for the modelling but also provides data for many other applications in research and development. Directly interfacing with the World Water Quality Assessment, the following research topics are being targeted by the Helmholtz Centre for Environmental Research (UFZ) and the Lake Victoria Fisheries Organization:
- Model-based reconstruction of water temperatures of Lake Victoria for the past 30 years at daily resolution.
- Water temperature projections for Lake Victoria until 2100 based on different climate scenarios (Representative Concentration Pathways) RCP 2.6, RCP 6.0, RCP 8.5.
- Potential effects of water temperature dynamics and mixing events on phytoplankton dynamics (derived from satellite-based remote sensing provided by EOMAP).
Sediment chemistry
UFZ has offered to collaborate with KMFRI on collected sediment chemistry, water profile physico-chemical quality parameters in the Nyanza Gulf, Kenya, and sediment and water samples near Kampala, Uganda. There is a potential for the joint assessment of sediment release of nutrients, turnover, and indication through algae blooms obtained from remote sensing (EOMAP).
Volta Basin
To assess the Volta water-quality challenges and associated impacts, and to assess data sources and types and any limitations to the sharing of such data, Alliance members attended various conferences in Ghana. In addition, a Stakeholder Engagement Workshop was held in Accra to assess the water-quality hotspots and the data and information products and services that may be of interest, and to initiate a bottom-up social engagement process.
The key challenges identified by the workshop participants were poor sanitation resulting in elevated bacterial contamination; mining activities and heavy metal and turbidity impacts; industrial effluent (including plastics and microplastics); agricultural runoff of fertilizers and pesticides, leading to increased aquatic alien plants; and water-quality impacts to and from aquaculture. A further challenge is there is not a consolidated national government department mandated to do water quality monitoring, with this role currently split.
Discussions towards potential water-quality product and services are continuing, in part due to ongoing development of in-country partnerships and collaboration. The initial products and services being considered to take forward include:
- The Ghana National Disaster Management Organization proposed an innovative tool that translates poor water-quality severity (measured through a water-quality index) into poor water-quality impact (expressed in terms of vulnerability of affected populations). The water-quality index would be derived in collaboration with Alliance partners. The vulnerability profiling would include the Volta Basin baseline household survey (which includes data on households' water sources and poverty status, as well as population data and administrative boundaries).
- University of Fada N'Gourma, Burkina Faso, proposed a groundwater quality assessment based on the DRASTIC vulnerability mapping method and remote-sensed data. The DRASTIC acronym is based on the major hydrogeologic factors that affect and control groundwater movement (Depth to groundwater, Recharge, Aquifer type, Soil media, Topography, Impact of vadose zone, and hydraulic Conductivity). The university's methodology incorporates land-use data with the DRASTIC parameters to assess groundwater pollution risk at a pan-African scale, including the Volta River basin.
Way forward
Below we summarize the key findings and lessons learned in the Use Case approach so far. These underpin the relevance of bringing interdisciplinary expert competence into dialogue and co-design at country and system level to advocate for stepping from data to solutions.
- Ongoing development of in-country partnerships and collaboration, especially with water resource decision makers to solve real-world problems for real impact, thereby benefiting in-country stakeholders and data providers to break the north-south divide. This needs sustainable funding and long-term investment. Initial exchanges with UN Resident Coordinators are encouraging and suggest, in future, to regularly engage UN Country Teams in this process if possible.
- There is a need to investigate options for integrating data derived from the World Water Quality Assessment triangle approach into a single dataset that can be used for water-quality decision making. The Cape Town Use Case successfully combined these three data types to develop aquifer protection zones and a risk analysis that are implementable by the in-country stakeholders. This was achieved through an integration team with overlapping experience in the data types.
- A need to improve the impact of research through a more effective science-policy interface, as well as better communication of the science via impact stories.
- A standard protocol for data sharing to ensure providers retain ownership and recognition. An example to use is the GEMS/Water Data Policy which allows data providers to select from three different levels of sharing.
- Development of a common data-management system, with agreed data types and formats, that allows for better collaboration between organizations/institutions/countries. This database option should have ownership by the data providers to ensure maintenance and longevity.
- In-country capacity building in the collection and assessment of data (in-situ data, citizen science, modelling and remote-sensing/earth-observation).
- Further development of the Africa Use Case concept to cover various water resource types and scales. This may include linking headwater protection to recharge (Cape Town Use Case), transboundary aquifers, the surface water/groundwater interface (e.g. wetlands).
Adapted from World Water Quality Alliance (2021). World Water Quality Assessment:
First Global Display of a Water Quality Baseline .