Groundwater provides most of the domestic water in rural Africa and supports poverty reduction through irrigation. Reliance on groundwater is likely to increase as rainfall becomes more variable and demand for water becomes greater.
However, African groundwater resources are poorly understood, and there is little knowledge about how resilient they are to climate change. This lack of knowledge is reflected in the small amount of information on groundwater presented in the IPCC 4th Assessment Report and Technical Paper on Water.
Progress and Impact:
Final list of outputs and documents
Main output – Final report, Research summary.
Project web pages – www.bgs.ac.uk/gwresilience. These summarise all components of the work and results. Links to the papers from the project will be inserted, once papers are published.
Maps – new robust, quantitative groundwater maps for Africa. Available from project web pages.
Documents – a series of data reports from each component of the study.
Papers - 5 peer-reviewed papers ; one submitted, four being finalised for submission in December 2011.
This research project has examined the resilience of groundwater to climate change in Africa; an area of science that has been under-researched, but has much relevance for the formulation of climate adaptation policies. There are several outcomes from the research:
A series of quantitative groundwater maps for Africa- the first of their kind. These indicate the wide variation in groundwater resources across the continent. For much of Africa, carefully sited and constructed boreholes will be able to sustain rural handpumps.The potential for shallow boreholes yielding greater than 5 l/s is not widespread across Africa, although smaller yields of 0.5 to 5 l/s will be easier to find. Large groundwater stores in the major sedimentary basins, which can accommodate high yielding boreholes, are often far from population centres and associated with deep water-levels.
New data from focused groundwater case studies. Three case studies were undertaken to gather new data on groundwater and climate change in Africa:
Detailed sampling in West Africa from hand-pumped boreholes abstracting shallow (less than 50 m deep) groundwater indicates significant resilience to climate variability across the range of climate zones sampled (mean annual rainfall 400–2000 mm). The mean residence of groundwater in shallow aquifers was approximately 20–70 years and therefore well buffered against short term variations in climate. The residence time of shallow groundwater in weathered basement rocks was found to be similar to the residence time in sandstones, indicating that weathered basement can contain considerable volumes of groundwater which moves slowly because of the low permeability.
A study of higher yielding supplies from crystalline basement rocks in Uganda and Tanzania indicates that sustainable larger supplies are often associated with a thick regolith (often including alluvium) over weathered basement rocks, and that yields of more than 1 l/s maybe available in approximately 35% of effectively sited boreholes in these areas. Enhanced groundwater storage in this aquifer environment is of particular importance in semi-arid regions (e.g. Dodoma, Tanzania) where significant recharge occurs episodically in association with extreme climate events a few times or less per decade.
Detailed analysis of data on water use in Ethiopia found that both wealth and the seasonality of water access are important drivers of domestic and productive water use, probably due to higher collection times in the dry season and the labour shortages faced by poor households. Policy responses in the water sector need to centre on: extending reliable services to reduce collection times, even where coverage statistics may look positive; safeguarding health and livelihood needs, especially at critical times of year; and enhancing the storage and transport facilities of poorer households.
It is clear from this research that groundwater possesses a high resilience to climate change in Africa and should be central to adaptation strategies. Increasing access to improved groundwater sources based on handpumps is likely to be highly successful. However, building strategies that depend on the availability of widespread higher reliable yields from groundwater is likely to be problematic.
- MacDonald AM, O Dochartaigh BE, Bonsor HC, Davies J and Key R. 2010. Developing quantitative groundwater maps for Africa, BGS Internal Report, IR/10/103, pp 34.
- Bonsor HC and MacDonald AM. 2010. Groundwater and climate change in Africa: review of aquifer properties data, BGS Internal Report, IR/10/076, pp 30.
- Bonsor HC and MacDonald AM. 2010. Groundwater and climate change in Africa: review of recharge studies, BGS Internal Report, IR/10/075, pp 30.
- Lapworth DJ, MacDonald AM, Darling WG, Gooddy DC and Bonsor HC. 2010. Case study note: Groundwater residence times for rural groundwater supplies across different climate zones, West Africa, BGS Internal Report, IR/10/100, pp 22.
- Maurice L, Taylor RG, MacDonald AM, Sanga H, Johnson P, Darling WG, and Gooddy DC. 2010. Case study note: Resilience of intensive groundwater abstraction from weathered crystalline rock aquifer systems to climate change in sub-Saharan Africa. BGS Internal Report, IR/10/105, pp 36.
- Lapworth DJ, MacDonald AM, Bonsor HC, Tjiani MN and Calow RC. 2011. Preliminary results from Water Economy and Livelihoods Survey (WELS) in Nigeria and Mali in sub-Saharan Africa, BGS Open Report, OR/11/018, pp.
- Tucker J and Yirgu L. 2011. Water in food security assessment and drought early warning: experience from sub-Saharan Africa with a special focus on Ethiopia, RIPPLE Working Paper 21, pp 45.
- MacDonald AM, Bonsor HC, and O Dochartaigh BE, Quantitative maps of groundwater resource for Africa, submitted to Nature, but not published; now being re-submitted to Environmental Research Letters (ERL).
- Lapworth DJ, MacDonald AM, Tijani MN, Darling WG, Gooddy DC, Bonsor HC, Aragus-Araguas LJ. The residence times of shallow groundwater resources across a West African transect: implications for hydrogeology and resilience to climate variability, submitted to Journal of Hydrology.
- Taylor RG, Kongola L, Nahozya E, Maurice L, Sanga H and MacDonald AM (in prep) Dependence of groundwater resources on extreme rainfall: evidence from East Africa. Nature Climate Change.
- Maurice L, Taylor RG, Sanga H, Johnson O, Darling G, Goody D, MacDonald AM, Owor M, Kaponda A and Tindimugaya C (in prep) Resilience of intensive groundwater abstraction from deeply weathered crystalline bedrock aquifers to climate variability and change: evidence from East Africa, Hydrogeology Journal
- Tucker J, Roger C, Coulter L, MacDonald AM (in prep) Exploring seasonal drivers of water use and their policy implications: quantitative findings from a highland to lowland transect, Ethiopia, Water Policy
Related outputs –
ODI Briefing note: Calow RC, Bonsor HC, Jones L, O’Meally S, MacDonald AM and Kaur N.2011. Climate change, water resources and WASH, ODI Working Paper 337, pp 58.