Daina Mudimbu, from the University of Zimbabwe, presented the work in “Resource limitations to sustainability of groundwater well-points in basement complex regions of SSA” Catalyst Study.
In Malawi there is episodic recharge; there is sparse data in Malawi for looking at groundwater storage and long term water balances. The balances were done for different water resource areas in Malawi and in four of these areas it appears that there isn’t water available and boreholes in those areas are likely to run dry because abstraction exceeds recharge after long dry periods.
Zimbabwe, like Malawi, it is dominated by the Basement Complex geology. The study looked at micro-aquifers and tried to look at the overall flows of groundwater. Recharge doesn’t occur every year and when it is only intense rainfall that seems to have an effect, which supports the work done by other Catalyst projects on recharge thresholds.
WaterAid water point mapping data which indicated that demand is not exceeding supply. However, the lack of published borehole data makes it difficult to estimate aquifer properties. Furthermore, Zimbabwe boreholes cannot be identified in many cases, so it is hard to match new measurements with old records.
Monitoring rainfall is done quite well, but multi-annual monitoring is very sparse so hard to look at long term trends.
Crystalline basement areas are at high risk aquifers. Some settlements totally dependent on this groundwater. Population growth and greater agricultural use without monitoring and understanding the resource, then the risk increases of unheralded resource failure: there is no back up.
This work shows that there is a very urgent need to improve the groundwater monitoring network in both countries so that aquifer depletion can be detected before the wells run dry.
UPGro - African Groundwater 2020 