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Sub-Saharan Africa will increasingly become the dominant hotspot of surface water pollution

Nature Water volume 1, pages 602–613 (2023)Cite this article

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Abstract

Human activities greatly impact surface water quality, while being reliant upon it for water supply. Surface water quality is expected to change in the future as a result of alterations to pollutant loadings, surface water withdrawals and hydrological regimes, driven by both climate change and socio-economic developments. Here we use a high-resolution global surface water quality model to project water temperature and indicators of salinity (total dissolved solids), organic (biological oxygen demand) and pathogen (fecal coliform) pollution until 2100. The results show that while surface water quality, as indicated by these pollutants, will improve in most advanced economies, the outlook for poorer nations is bleak. The proportion of the global population exposed to salinity, organic and pathogen pollution by the end of the century ranges from 17 to 27%, 20 to 37% and 22 to 44%, respectively, with poor surface water quality disproportionately affecting people living in developing countries. Exhibiting the largest increases in both the absolute and relative number of people exposed, irrespective of climate change and socio-economic development scenario, we conclude that Sub-Saharan Africa will become the new hotspot of surface water pollution globally.

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Fig. 1: Future pollutant loadings by contributing water use sector.
Fig. 2: Change in surface water quality under uncertain climate and socio-economic change.
Fig. 3: Change in surface water quality at outlets of major river basins under uncertain climate and socio-economic change.
Fig. 4: Seasonal variability in surface water quality in selected African cities under uncertain climate and socio-economic change.
Fig. 5: Exceedance of BOD concentration thresholds under uncertain climate and socio-economic change.
Fig. 6: Population exposed to surface water pollution under uncertain climate and socio-economic change.
Fig. 7: Severe deterioration of surface water quality threatens populations across most of Africa, irrespective of future climate and socio-economic scenario.
Fig. 8: Geographic distribution of the global population versus the global population exposed to organic pollution under uncertain climate and socio-economic change.

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Data availability

Global hydrological and surface water quality output at 10 km resolution, per GCM and global change scenario (RCP–SSP), is available open-access at https://doi.org/10.5281/zenodo.7811612.

Code availability

The surface water quality model used in this study, DynQual, is available open-access through a GitHub repository (https://github.com/UU-Hydro/DYNQUAL).

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Acknowledgements

M.T.H.v.V. was financially supported by the Netherlands Scientific Organisation (NWO) by a VIDI grant (VI.Vidi.193.019) and European Research Council under the European Union’s Horizon Europe research and innovation programme (grant agreement 101039426). We acknowledge and thank the Netherlands Organisation for Scientific Research (NWO) for the grant that enabled us to use the national supercomputer Snellius (project: EINF-3999).

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Authors and Affiliations

  1. Department of Physical Geography, Faculty of Geosciences, Utrecht University, Utrecht, the Netherlands

    Edward R. Jones, Marc F. P. Bierkens, Ludovicus (Rens) P. H. van Beek, Niko Wanders, Edwin H. Sutanudjaja & Michelle T. H. van Vliet

  2. Deltares, Unit Soil and Groundwater Systems, Utrecht, the Netherlands

    Marc F. P. Bierkens

  3. PBL Netherlands Environmental Assessment Agency, The Hague, the Netherlands

    Peter J. T. M. van Puijenbroek

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Contributions

The research was designed by E.R.J., M.F.P.B. and M.T.H.v.V. The model runs, data analysis and paper writing were led by E.R.J., with feedback from M.F.P.B. and M.T.H.v.V. Data on wastewater scenarios and water use scenarios under the different SSPs were provided by P.J.T.M.v.P. and L.P.H.v.B., respectively. N.W. and E.H.S. aided in the development of the water quality model, and provided processed meteorological input data required for the model runs. All authors approved the paper.

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Correspondence to Edward R. Jones.

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Jones, E.R., Bierkens, M.F.P., van Puijenbroek, P.J.T.M. et al. Sub-Saharan Africa will increasingly become the dominant hotspot of surface water pollution. Nat Water 1, 602–613 (2023). https://doi.org/10.1038/s44221-023-00105-5

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