Groundwater exploration

September 21, 2018

Alongside its role in assisting Cape Town’s future water augmentation planning, Umvoto Africa has been instrumental in establishing key aquifer sources within the broader Western Cape region.

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Hydrogeologists and scientists at Umvoto Africa have been in the business of finding, testing and delivering groundwater in various parts of the country and on the continent for decades.

At the onset, Umvoto Africa was instrumental in siting and drilling one of the first boreholes for the Citrusdal Municipality in 1998 to access the groundwater potential of the Peninsula aquifer of the Table Mount Group (TMG), which yielded up to 100 l/s.

As the millennium began, Umvoto Africa was appointed under the Deep Artesian Groundwater Exploration initiative for the Oudtshoorn Supply (DAGEOS) project. They subsequently managed the Oudtshoorn Groundwater Project (OGP) from 2011 onwards, drilling numerous high yielding artesian boreholes. A particularly memorable moment was seeing strong artesian groundwater flow from deep (600 metres plus) boreholes at the Blossoms Wellfield as part of the OGP, which is currently on hold.

Overstrand

Umvoto Africa are the current groundwater specialists for the Overstrand Municipality and assisted in developing and monitoring wellfields within the primary Stanford aquifer, as well as the fractured Peninsula Formation aquifer of the TMG at Hermanus.  

The Stanford Aquifer is highly productive and is thought to be comprised of the lower part of the Waenhuiskrans Formation. Palaeochannels, such as the Kouevlakte and Klein River Palaeochannels along the base of the Stanford Aquifer are hydrogeologically important due to their potential for high yields.

Development of the Kouevlakte Wellfield at Stanford has made the town water-secure for decades to come. In turn, the Camphill and Volmoed wellfields helped Hermanus survive the 2009-2011 Southern Cape drought and now ensures that the town is water-secure during the current Western Cape water crisis.

Landfills

In 2015 Umvoto was engaged by the City of Cape Town‘s Solid Waste Management to undertake the assessment of monitoring borehole infrastructure at operational landfill sites (Coastal Park, Bellville South, and Vissershok),  old landfill sites (Brackenfell, Faure, Gordon’s Bay, Kraaifontein and Tableview) as well as transfer stations and historical landfills (Athlone Refuse Transfer Station, and Kraaifontein).

Hydrogeologists surveyed and assessed the groundwater monitoring borehole infrastructure, cleared and desilted the existing infrastructure and installed new boreholes where required.

Risk mitigation

 

Umvoto’s approach presents ideas to build resilience against future water crises through projects that complement or support existing strategic plans and interventions already underway, but not ignoring innovation options. A prime example is the work undertaken by Umvoto Africa with the city of Cape Town.

Local scale schemes abstracting from the unconfined portion of the TMG aquifer, e.g. in the Southern Planning District and Helderberg Basin, can cumulatively contribute to augmenting bulk water supply, and permit increased flexibility in the reticulation system in times of severe shortage.

These schemes also provide an opportunity to train, empower and build capacity in local communities to support aquifer monitoring, water sampling and water resource management, as well as wellfield operations and maintenance.

These thoughts underpinned the water resilience strategy for the City of Cape Town which included (amongst other augmentation plans):

  • Local groundwater development in the Southern Planning District,
  • Horizontal drilling in the Helderberg Basin,
  • Groundwater abstractions from the Cape Flats Aquifer (CFA),
  • Optimisation of the Atlantis Water Supply Scheme, and
  • Construction of a desalination plant at Saldanha to free allocation from Voelvlei Dam.

The geomorphology and aquifer geometry/hydrostratigraphy facilitate an approach of Managed Aquifer Recharge (MAR) in the CFA through use of wetlands, making it possible to reclaim storm water and treated effluent, while contributing toward aquifer rehabilitation where groundwater contamination is prevalent. These same factors address the issues of sewerage management and winter flooding in the Kuils River catchment and licensing of the wastewater effluent from the Zandvliet treatment plant/discharge from the Bellville treatment plant (and or treatment to potable drinking water standards).

Umvoto Africa made use of various geophysical techniques and technologies to identify and refine drilling locations for the Cape Town resilience plan. This included aerial surveying, a non-invasive technology used to determine the thickness of the aquifer by identifying conductive basement clay layers underlying the sandy aquifer. The results of these various studies will help shape the city’s future planning.

The drought may break, water restrictions may be relaxed, but the recent appreciation and understanding of the value and scarcity of water resources in Cape Town, and the Western Cape as a whole, will remain.