Abstract
To improve borehole siting for rural water supply, an advanced resistivity method was adapted for developing country use and demonstrated in Malawi. The method was designed to be low cost, developing-country accessible, efficient. It allows single or multiple operators to acquire the multiple vertical electrical soundings (VESs) required that are inverted together in 2-D, to give a true cross-section of subsurface resistivity. Application at four sites generated true cross-sections of subsurface resistivity to around 100 m depth relevant to groundwater-resource investigation. A wide range of (hydro)geological features was identified, including fractured/weathered basement, gneiss domes, well-developed fault zones and several types of deltaic deposits. Imaging performance appears comparable to that of 2-D surface ERT (electrical resistivity tomography) that uses more expensive equipment, often unaffordable in developing countries. Based on the subsurface configurations determined and hydrogeological conceptualisation subsequently undertaken, the local aquifer potential could be evaluated, thereby providing a decision-making basis for future borehole siting at the sites surveyed. The technology is far superior to conventional 1-D VES, electromagnetic profiling or magnetic profiling currently used for borehole siting in Malawi. Technology adoption currently under consideration nationally would make use of existing VES capacity and permit much improved targeting of aquifer resource, more sustainable siting of boreholes and greater future resilience of Malawi’s rural water-supply infrastructure.
Highlights
Groundwater is the principal source of community drinking-water supply for Malawi’s predominantly rural population
Our wider programme of research has recently mapped over 120,900 water points in Malawi, of which 49% are boreholes predominantly drilled to provide community hand-pumped water supply (Climate Justice Fund, mWater data retrieval, August 2020)
This study contributes to the Climate Justice Fund (CJF) Water Futures Programme of research, funded by the Scottish Government, that aims to assist the Government of Malawi in achieving Sustainable Development Goal (SDG)
Summary
Groundwater is the principal source of community drinking-water supply for Malawi’s predominantly rural population. Our wider programme of research has recently mapped over 120,900 water points in Malawi, of which 49% are boreholes predominantly drilled to provide community hand-pumped water supply (Climate Justice Fund, mWater data retrieval, August 2020). Improving access to groundwater is pivotal to rural water supply across the developing world [1,2,3] and a priority means of enabling governments to meet. Amongst other factors, are commonly blamed [8,9], these can obscure poor hydrogeological siting and borehole design that may primarily drive persistent functionality problems [10,11]. Boreholes screened in less permeable or saline units, or else drilled too shallow and vulnerable to dry-season dewatering or contamination may fail to respond to increased maintenance
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