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Transboundary Aquifer (TBA) management in part seeks to mitigate degradation of groundwater resources caused either by an imbalance of abstraction between countries or by cross border pollution. Fourteen potential TBAs were identified within a hydrogeological mapping programme based on simple hydrogeological selection criteria for the Southern African Development Community region. These have been reassessed against a set of five data categories, of which (1) groundwater flow and vulnerability is perceived as the overarching influence on the activity level of each TBA, while other contributing categories are (2) knowledge and understanding, (3) governance capability, (4) social/demand and (5) environmental issues. These assessments enable the TBAs to be classified according to their need for cross-border co-operation and management. The study shows that only two of the fourteen TBAs have potential to be the cause of tension between neighbouring states, while nine are potentially troublesome and three are unlikely to become problematic even in the future. The classification highlights the need to focus on data gathering to enable improved understanding of the TBAs that are potentially troublesome in the future due, for example, to change in demographics and climate.

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in particular, has been blamed on a variety of causes. These include poor borehole design, badly sited boreholes, mechanical failure and even implementer ignorance of basic hydrogeological principles. Recent work in Malawi demonstrates that recharge and flow potential of the data-scarce basement aquifer can be investigated by deriving a variety of surrogate and secondary data. Investigation shows that the weathered Precambrian basement aquifer may not always be up to the job sustaining even modest abstraction sources indefinitely and that many new sources will fail in the short to medium term. Failure is the result of recharge being able to sustain abstraction within the limited capture zone of an abstraction source, there being little effective lateral inflow of groundwater on the African plateau savannah lands which have very low hydraulic gradients. If lateral groundwater flow does occur across source capture zone, for example towards the rift-valley escarpment, sources are more sustainable to a degree, depending on the volume of through-flow. Where surface water courses traverse the aquifer, albeit flowing ephemerally or largely as sub-river bed sand rivers, sustainability of borehole sources is increased provided there is hydraulic connectivity to the aquifer. Abstraction from the aquifer within a source capture zone may be as little as 25% of storage in isolated rural areas, more typically about 50% and as high as 70% in the more densely populated areas. If demographic growth requires an increase of just 1% in large areas of Malawi, source failure will occur within a 25-year to 35year period.