One third of African rivers fail to meet the ’good ambient water quality’ nutrient targets

• Published in: Ecological indicators 2024-09, Vol.166, p.112544, Article 112544
• Main Authors: Nkwasa, Albert, James Chawanda, Celray, Theresa Nakkazi, Maria, Tang, Ting, Eisenreich, Steven J., Warner, Stuart, van Griensven, Ann
• Format: Article
• Language: English
• Subjects: Africa; Nitrogen pollution; Phosphorus pollution; Sustainable Development Goal (SDG); SWAT
• ISSN: 1470-160X
• DOI: 10.1016/j.ecolind.2024.112544

•Limited African water quality data hinders SDG target 6.3 assessment.•Developed a continental water quality (sediment load, TN and TP) model for Africa.•44% and 15% of rivers fail to meet the thresholds set for TP and TN, respectively.•Polluted rivers linked with high fertilizer, manure, and wastewater inputs.•Targeted strategies are crucial to reduce nutrient pollution. The ambition of Sustainable Development Goal (SDG) target 6.3 is to improve global water quality by 2030. SDG indicator 6.3.2 monitors progress towards this target by assessing water bodies against ‘good’ ambient water quality criteria, with nutrients (nitrogen and phosphorus) as part of the key metrics. However, large data gaps present a fundamental challenge, especially for Africa on how to assess the progress being made with respect to both the current and desired future situations. Here, a continental water quality model for Africa is presented to simulate river sediment load, Total Nitrogen (TN) and Total Phosphorus (TP) loads and concentrations. Furthermore, critical areas and hotspots of TN and TP pollution are mapped for the period 2017 – 2019, in relation to the United Nations Environment Programme (UNEP) target thresholds used for the assessment of SDG indicator 6.3.2. Utilizing the UNEP’s criteria, which designates a water body as having “good ambient water quality” if 80% or more of its monitored values meet their targets, it is estimated that 44 % and 15 % of African rivers fail to meet the set water quality thresholds for simulated TP and TN, respectively. When synthesizing data for both TP and TN, 34 % of the rivers do not qualify as having “good ambient water quality”. Geographically, the most pronounced nutrient pollution hotspots were in North Africa, Niger River Delta, Nile River basin, Congo River basin and specific zones in Southern Africa. These areas correlate with regions characterized by high inputs of fertilizers, manure and wastewater discharge.