Mapping groundwater recharge in Africa from ground observations and implications for water security

MacDonald, Alan M; Lark, R Murray; Taylor, Richard G; Abiye, Tamiru; Fallas, Helen C; Favreau, Guillaume; Goni, Ibrahim B; Kebede, Seifu; Scanlon, Bridget; Sorensen, James P R; Tijani, Moshood; Upton, Kirsty A; West, Charles

Abstract

© 2021 British Geological SurveyUKRI. Published by IOP Publishing Ltd. Groundwater forms the basis of water supplies across much of Africa and its development is rising as demand for secure water increases. Recharge rates are a key component for assessing groundwater development potential, but have not been mapped across Africa, other than from global models. Here we quantify long-term average (LTA) distributed groundwater recharge rates across Africa for the period 1970-2019 from 134 ground-based estimates and upscaled statistically. Natural diffuse and local focussed recharge, where this mechanism is widespread, are included but discrete leakage from large rivers, lakes or from irrigation are excluded. We find that measurable LTA recharge is found in most environments with average decadal recharge depths in arid and semi-arid areas of 60 mm (30-140 mm) and 200 mm (90-430 mm) respectively. A linear mixed model shows that at the scale of the African continent only LTA rainfall is related to LTA recharge - the inclusion of other climate and terrestrial factors do not improve the model. Kriging methods indicate spatial dependency to 900 km suggesting that factors other than LTA rainfall are important at local scales. We estimate that average decadal recharge in Africa is 15 000 km3 (4900-45 000 km3), approximately 2% of estimated groundwater storage across the continent, but is characterised by stark variability between high-storage/low-recharge sedimentary aquifers in North Africa, and low-storage/high-recharge weathered crystalline-rock aquifers across much of tropical Africa. African water security is greatly enhanced by this distribution, as many countries with low recharge possess substantial groundwater storage, whereas countries with low storage experience high, regular recharge. The dataset provides a first, ground-based approximation of the renewability of groundwater storage in Africa and can be used to refine and validate global and continental hydrological models while also providing a baseline against future change.

Citation

MacDonald, A. M., Lark, R. M., Taylor, R. G., Abiye, T., Fallas, H. C., Favreau, G., …West, C. (2021). Mapping groundwater recharge in Africa from ground observations and implications for water security. Environmental Research Letters, 16(3), Article 034012. https://doi.org/10.1088/1748-9326/abd661

• Journal Article Type: Article
• Acceptance Date: Dec 23, 2020
• Online Publication Date: Feb 16, 2021
• Publication Date: Mar 1, 2021
• Deposit Date: Feb 17, 2021
• Publicly Available Date: Feb 17, 2021
• Journal: Environmental Research Letters
• Electronic ISSN: 1748-9326
• Publisher: IOP Publishing
• Peer Reviewed: Peer Reviewed
• Volume: 16
• Issue: 3
• Article Number: 034012
• DOI: https://doi.org/10.1088/1748-9326/abd661
• Keywords: Renewable Energy, Sustainability and the Environment; Public Health, Environmental and Occupational Health; General Environmental Science
• Public URL: https://nottingham-repository.worktribe.com/output/5331678
• Publisher URL: https://iopscience.iop.org/article/10.1088/1748-9326/abd661
• Additional Information: Article Title: Mapping groundwater recharge in Africa from ground observations and implications for water security; Journal Title: Environmental Research Letters; Article Type: paper; Copyright Information: 2021 British Geological Survey © UKRI. Published by IOP Publishing Ltd; Date Received: 2020-09-29; Date Accepted: 2020-12-23; Online publication date: 2021-02-16