TMG

GWD Western Cape Networking Event

University of Cape Town, Geological Sciences Building
  • scientific networking
  • municipal water supply
  • TMG

Event description



About this event

GWD Western Cape Networking Event

University of Cape Town, Geological Sciences Building

Sponsors / Engagement Partners

Are Farmers Drying Out The Cederberg? Deep Groundwater Flow And Isotopes In The Table Mountain Group.

The Table Mountain Group is a major fractured rock aquifer system throughout the Western Cape, with many interconnected but semi-independent parts, each having its own recharge area, flow paths and discharge area. Groundwater is known to travel long distances and reach great depths, including through the Olifants River syncline, such as at The Baths hot spring near Citrusdal. Stable isotope compositions of rain and groundwater in the Cederberg and Olifants River Mountains were measured over a period of 2-3 years.

An innovative approach to dealing with elevated iron concentrations at the Knysna Hospital

In response to the drought which started in 2017, the Western Cape Government set about securing water supplies to key facilities across the province, including the Knysna Hospital. Drilling and testing of two boreholes at the facility indicated it to be viable to establish a groundwater supply of 66 KL/d from the underlying Table Mountain Group Aquifer. Iron concentrations were low and the initial water chemistry analyses pointed to concentrations below the SANS 241 aesthetic limit.

Groundwater Development Of The Table Mountain Group Aquifers As Part Of The City Of Cape Town's New Water Programme

The original City of Cape Town (CCT) Table Mountain Group (TMG) Aquifer Feasibility Study and Pilot Project was initiated in 2002, the purpose being to evaluate the feasibility of augmenting the CCT's bulk water supply using groundwater from the TMG (specifically the fractured Peninsula and Nardouw Aquifers). CCT TMG groundwater exploration/development was fast tracked under the "New Water Programme" (NWP; from 2017-present) as a result of two interrelated water scarcity/demand factors, namely periodic drought (including the major 2015-2017 1:590-year event) and rapid urban growth.

Groundwater development for Municipal water supply in response to drought of 2015 to 2019.

The geographic positioning of the Western Cape results in a Mediterranean climate - receiving majority of its rainfall during the winter months. A demand on the water supply throughout the year is typically met by storing water from winter rainfall in large dams. The Western Cape experienced a significant drought between 2015 and 2019. As a result, the supply dams have not been filled to capacity and drastic water restrictions had to be implemented. In the search for alternative water sources, groundwater exploration became a priority.

Intraplate tectonic setting of the southwestern Cape, South Africa: Analysis of the TrigNet geodetic record

In response to the serious 2015-2018 “Day Zero” drought, the City of Cape Town implemented large-scale augmentation of the Western Cape Water Supply System from deep groundwater resources within the Table Mountain Group (TMG) fractured aquifers. Several planned TMG wellfields target the Steenbras-Brandvlei Mega-fault Zone (SBMZ), the northern segment of which hosts the Brandvlei hot spring (BHS) – the hottest (~70°C) and strongest (~4 million m3/yr) in the Western Cape.