South Africa has a looming water supply crisis, with 98% of its surface water already developed, demand outstripping supply in most catchment areas (WRC, 2015). Based on current usage trends, South Africa is expected to face a water deficit of 17% by 2030, and this shortage will only be worsened by climate change (WWF, 2017) which is mainly characterized by prolonged period of drought. There are many challenges facing the sustainability of groundwater, among others there are issues such as climate change, human errors in data handling, over abstraction due increasing water demand, damage of borehole infrastructure in remote areas and poor groundwater management systems.
Groundwater resources within the D41L quaternary catchment occurs in abundance. Aquifers in the area are classified as karst and fractured dolomite aquifers with a median yield of >5 L/s. These aquifers are compartmentalized by several impervious dykes that sub-divide the D41L area into sub-catchments and smaller sub-compartments. With the probable impacts of extended drought period in the Gasegonyana Local Municipal area, increased water demands and density of abstraction points in some sub-catchments/sub-compartments the water resources have become stressed and at risk of being over-exploited. To sustainably and secure future water supply in the region, it has become essential that a comprehensive assessment is undertaken of the sustainable water supply potential of the D41L and delineate various groundwater resource units (GRU's).
The paper highlights why is it imperative to conduct the groundwater feasibility studies on a regional scale in order to protect the sole aquifer resource for semi-desert areas such as Gasegonyana municipal zone. Secondly, the importance use of appropriate geophysical techniques which include regional gravity surveys on dolomitic aquifers with emphases to sustainability on exploitable resources as these karst aquifers are highly vulnerable to over-abstraction if not properly investigated.
Groundwater water potential and large aquifer zones were delineated explicitly with the regional gravity results and exploration drilling of these zones proved to be sustainable compared to existing boreholes that were drilled in limited/smaller dolomitic compartments. The predictive scenario of the groundwater assessment confirms that the water demand could be achieved with half of the simulated abstraction rates while an increase in water demand should be managed accordingly by distributing the yields of the borehole between the existing boreholes and the newly drilled production boreholes.
The study results will ensure sustainability of water supply in the region and the document will assist the town planners and stakeholders to manage high population growth in a groundwater secure zone, and it will mitigation against climate change impact for the municipality.