Abstract
Achieving universal drinking water and sanitation access by 2030 (SDG 6) remains uncertain under future socioeconomic and climate conditions. This study projects access to improved services using a logit-based model that incorporates income distribution, settlement structure, governance, and hydroclimatic indicators along SSP–RCP scenarios and estimates the associated water and energy footprint of closing the access gap. Results show that universal access is not achieved by 2030 in any scenario, with about 296 (±10%) million people lacking drinking water access. By the end of the century, access improves but remains incomplete, with about 250 million people without sanitation and 85 million without drinking water. Long-term projections reveal persistent regional disparities: access gaps remain concentrated in Sub-Saharan Africa and South Asia throughout the century. Scenarios characterized by persistent socioeconomic inequality (SSP3) show stagnation or increasing gaps, whereas more prosperous pathways (SSP1 and SSP5) achieve substantially faster progress but do not fully eliminate disparities. Closing remaining gaps implies substantial regional infrastructure expansion and additional water and energy demand—on the order of several km³ of water per year and up to 19.6 TWh/year globally by mid-century—highlighting the need for long-term, region-specific planning strategies.
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Acknowledgements
M.A., A.V., and E.B. acknowledge funding from the Horizon Europe PRSMA project (grant agreement no. 101081604). M.M., E.R.J., and M.T.H.v.V. are financially supported by the European Union (ERC Starting Grant, B-WEX, Project 101039426) and the Netherlands Scientific Organisation (NWO) by a VIDI grant (VI.Vidi.193.019). The authors acknowledge the support of Lisah Ligono in uploading model outputs to the SSP Extension Explorer.
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Vinca, A., Andrijevic, M., Byers, E. et al. Limited progress in drinking water and sanitation access when accounting for inequality in long-term projections.
npj Clean Water (2026). https://doi.org/10.1038/s41545-026-00594-3
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DOI: https://doi.org/10.1038/s41545-026-00594-3
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