Perspectives on African water resources with a focus on ambient river water quality

Clean water availability is crucial for ensuring sufficient water of appropriate quality to meet both human and ecosystem needs. Recent research underscores the significance of water quality as a critical factor limiting water availability for sectoral uses. Water quality is a cornerstone of the Sustainable Development Agenda, intersecting with nearly all Sustainable Development Goals (SDGs). Specifically, SDG Target 6.3 outlines an ambitious vision: “By 2030, improve water quality by reducing pollution, eliminating dumping, and minimizing the release of hazardous chemicals and materials; halving the proportion of untreated wastewater; and substantially increasing recycling and safe reuse globally.”

To monitor progress toward this target, SDG Indicator 6.3.2 serves as a key metric, tracking the percentage of water bodies that achieve “good” ambient water quality. This designation refers to levels of dissolved oxygen, salinity, nutrients (total nitrogen – TN and total phosphorus – TP), and acidity that do not compromise ecosystem or human health. However, significant data gaps pose a major challenge, particularly in Africa, where assessing both current conditions and future trajectories remains difficult, hindering efforts to fully understand the severity and extent of water quality deterioration across the continent.

The emergence of large-scale water quality models offers a potential solution to this challenge. These models provide extensive geographic coverage and sufficient spatial resolution to simulate water quality gradients along river networks. For instance, a continental-scale water quality model for Africa was developed to simulate TN and TP loads and concentrations at a daily time step. Using this model, critical areas and hotspots of TN and TP pollution were identified for the period 2017–2019, based on United Nations Environment Programme (UNEP) thresholds for assessing SDG Indicator 6.3.2. According to UNEP’s criteria, a water body is classified as having “good ambient water quality” if at least 80% of monitored values meet the specified thresholds. The model estimates that 44% of African rivers fail to meet the threshold for TP, while 15% fail to meet the threshold for TN. When both TN and TP are considered together, 34% of rivers do not qualify as having “good ambient water quality.” Geospatial analysis highlights pronounced nutrient pollution hotspots in North Africa, the Niger River Delta, the Nile River Basin, the Congo River Basin, and specific areas in Southern Africa. These regions are strongly associated with high inputs of fertilizers, manure, and wastewater discharge.

These findings, along with the generated data augment the UN Environment Global Environment Monitoring System for Freshwater (GEMStat) database, offering a tool to monitor SDG target 6.3 progress in Africa and project potential outcomes by 2030, especially in areas where little or no information are available on whether water quality is suitable to support sustainable development, despite its fundamental importance. For instance, by highlighting areas that do not qualify as having “good ambient water quality,” these results provide insights for African national policy and decision makers to prioritize remediation efforts, develop targeted policies, interventions, and regulatory frameworks to improve water quality.