Resource limitations to sustainability of groundwater well-points in basement complex regions of sub-Saharan Africa

Lead Research Organisation: NERC British Geological Survey
Department Name: Groundwater

Abstract

35% of Africa, 40% of the sub-Saharan Africa land surface and almost 37% of the member states of the Southern African Development Community (SADC) is underlain by weathered and fractured 'basement complex' bedrock which contains groundwater within its weathered mantle (most significant under the 'African erosion surface') and to a lesser extent within rock fractures (most significant under the 'post-African erosion surface'). Achievement of the Millennium Development Goals (MDGs) in Africa (MDG Target 7.C: to halve, by 2015, the proportion of the population without sustainable access to safe drinking water and basic sanitation) is therefore fundamentally reliant on the long-term sustainability of groundwater abstractions from these crystalline basement complex aquifers (BCAs).

The incentive for our proposal is a recent reconnaissance analysis of the sustainability of groundwater resources of the BCAs in Malawi (the 'Malawi analysis' of Robins et al 2013). The reconnaissance method for estimating groundwater resource limitation compares estimates of groundwater throughflow and storage depletion with actual abstractions at a coarse scale (100s km2). The analysis raises concern that groundwater abstractions exceed long-term recharge in 4 of the 15 'water resource areas' (WRAs) of Malawi, in parts of both the 'weathered' and 'fractured' BCA environments. This controversial conclusion contrasts with the long and widely held view that resource development from BCAs is limited by low transmissivity, hence through low yield of wells, compounded by widespread technological failure of the well-points themselves. Also, it provides a cautionary perspective on a continent-wide assessment of groundwater 'volumes in place' in Africa by MacDonald et al (2012) who have estimated the BCA resource at 500,000 m3/km2 on the basis of published geological maps and estimates of hydrogeological parameters. Availability and sustainability of the groundwater resource, however, fundamentally require ground-truth measurements and process-based analyses (Edmunds 2012). Cumulative groundwater abstraction has greatly increased across much of SSA over the past 30+ years following numerous rural water development and drought relief programmes. Therefore the Malawi experience could be indicative of groundwater resources sustainability in BCAs more widely throughout SSA. If the Malawi analysis is correct, one important implication is that additional, un-recoverable well-point failure will be expected in the affected regions. This expectation forms the basis for the test we will apply to the Malawi analysis.

This proposal therefore addresses the concern that the Malawi experience is indicative for groundwater in BCAs throughout SSA. The principal objective is to test the Malawi analysis, by examining the implications for well-point failure using independent data on well-point occurrence and status (available through WaterAid and the Malawi Ministry of Water Development and Irrigation). Concurrently, we will explore the links between well-point failure, health, poverty and gender issues where resource limitation to sustainability of groundwater well-points has been proposed, using census and aggregated heath data.
We will carry out field investigations to refine the analysis of groundwater resource limitation over a smaller area and to develop a preliminary analysis for a selected region in southern Zimbabwe. We will develop a methodology for application to water-use policy and local resource/well-point monitoring. We will stimulate awareness and adoption of the methodologies at a regional Workshop. Hence we will support national mitigation measures, and local management of groundwater use. The project will lead to new estimates of resource limitation in Zimbabwe, new collaborations, and form the basis for wider investigation of resource-limitation across SSA basement complex regions.

Planned Impact

IMPACT SUMMARY
This proposal addresses a major question posed by UPGro (what is the state of the groundwater resource?) and contributes across the three UPGro themes of understanding the resource, providing tools for decision makers, and with relevance to possible future trends (the changing relationship of demands to limits of groundwater abstraction).
1. Our research will support national managers to focus mitigation measures to guard against groundwater resource depletion, and local community leaders to manage and regulate groundwater use.
We will develop as an outcome of the research a methodology for application to water-use policy (for use by national and regional authorities) and local resource/well-point monitoring (for local users). The borehole design commonly installed within Malawi precludes access for a water level measuring/monitoring device. Yet the relationship of abstraction quantity to water level is a fundamental determinand required for effective management of the limited Crystalline Basement groundwater resource. The methodology provided will include a simple illustrated statement, and assessment tools and monitoring protocols for Government, and also for village elders and NGOs. Tools developed for us in the SADC central Limpopo belt will be applied to sites located in Malawi and Zimbabwe.
These, the national and regional water authorities and NGOs, (in their development of water use policies), and local users (in local resource/well-point monitoring) are the ultimate users of the research, with the beneficiaries being the groundwater-dependent poor of rural Malawi and Zimbabwe. Work in the Limpopo area demonstrated that effective management of the limited but vitally important groundwater resources requires the user population to be fully informed of and conversant in the required skill sets.
2. Application of these methodologies will support the achievement of the Millennium Development Goals across the large regions of Africa which are fundamentally reliant on the long-term sustainability of groundwater abstractions from these crystalline basement complex aquifers. Our research will have an impact in optimising the achievement of MDG Target 7.C: to halve, by 2015, the proportion of the population without sustainable access to safe drinking water. A major impact will be informing the national controlling bodies and local population groups alike of the major problems the user group face if they reach a state of aquifer failure. In this scenario national government institution and NGOs responsible for water supply provision would be forced to realise the importance of Integrated Water Management Methods if their communities are to survive during prolonged dry periods and drought.
3. The project will lead to new estimates of resource limitation in Zimbabwe, and initiate the translation of the Malawi reconnaissance method (Robins et al, 2013) to Zimbabwe. In Malawi, the new estimates of groundwater resource limitation will contribute to the National Water Master Plan study currently being compiled. The methodologies would be available for application to similar hydrogeological environments and hence to improve resource estimation and promote sustainable groundwater usage nationally.
4. Development of a new partnership with and between researchers in southern Africa and the UK will have a long-term impact on the research capability of the Southern African hydrogeological and water management community. Former strong links between the hydrogeological communities in the UK and those in Malawi and Zimbabwe are being resurrected especially with the provision of groundwater data and grey information via the www.sadcgwarchive.net web site that is currently hosted by the BGS who conduct regular updates of its content. This website will provide a real information dissemination conduit for ideas and methodologies developed by the project to adjacent countries in the SADC region and elsewhere in Africa.

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