JG Afrika facilitates sustainable groundwater development in Laingsburg

JG Afrika facilitates sustainable groundwater development in Laingsburg
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JG Afrika facilitates sustainable groundwater development in Laingsburg

JG Afrika, a leading engineering and environmental consultancy, is helping Laingsburg Municipality optimise the use of groundwater resources in its jurisdiction.

The Sustainable Development Groundwater Project for Laingsburg Municipality is being undertaken on behalf of the Western Cape DLG. JG Afrika was appointed to work on the project shortly after completing similar work for the Western Cape DLG in the City of Cape Town Metropolitan Municipality when the city was in the throes of the worst drought in more than a century. While conditions in the City of Cape Town Metropolitan Municipality have since normalised, many other areas of the province are still experiencing an acute dry spell. This includes towns located in the Great Karoo where drought conditions have persisted for the past seven years.

“JG Afrika is part of a consortium of four consulting engineering firms that was appointed by the Western Cape DLG to help municipalities in the Great Karoo improve the management and use of their groundwater resources to help alleviate drought conditions. Our area of focus is on Laingsburg Municipality which is among those municipalities in this area that have been experiencing water shortages,” Regan Rose, an Executive Associate of JG Afrika, says.

His team commenced working on the project in 2019. It includes monitoring the municipality’s existing groundwater resources, namely a few shallow wells in dry riverbeds. As part of the process, JG Afrika also assessed the municipality’s own groundwater monitoring strategy and proposed various solutions to overcome existing constraints, which are mainly logistical in nature. The municipality is gradually implementing them to improve its own groundwater resource monitoring capabilities as and when it receives financing. These interventions are expected to improve water service delivery to constituents of Laingsburg Municipality, considering that monitoring is just as important as the maintenance and repair of borehole infrastructure for the sustainable use of groundwater resources. JG Afrika will continue the monitoring function until such time that the municipality is ready to assume these duties on its own. This process has been ongoing since the project came to an end in 2019 and subsequently extended by the Western Cape DLG.

As a specialist in the field geohydrology, JG Afrika has helped to significantly bolster Laingsburg Municipality’s skills and experience in the field. For example, the firm’s geohydrologists have been able to share important insights with the municipality that it has identified since it commenced monitoring the groundwater resources. This includes overextraction in certain areas whereas ideally groundwater use needs to be spread over a larger area in the Great Karoo to ensure sustainable use.

Another component of the project entails finding and assessing other available groundwater resources within the jurisdiction to bolster existing supplies.

Notably, JG Afrika used state-of-the-art Danish technology to significantly improve the accuracy of its geohydrology investigations on this project. The technology has also been successfully deployed on a few of the company’s other geohydrological projects, including in KwaZulu-Natal.

Known as a towed transient electromagnetic (tTEM) system, the technology enables the detailed investigation of the top 20m to 50m of the subsurface. While traditional technologies can image this zone, they are unable to create high-resolution full three-dimensional (3D) images over extremely large areas. The tTEM system can image a subsurface up to a depth of 70m at a high resolution both horizontally and vertically. Towed by an all-terrain vehicle, such as a quadbike in this instance, the technology uses a 2m × 4 m transmitter coil and a z-component receiver that is placed at a 9m offset from the transmitter. It uses a dual transmitter low and high moment measurement sequence to obtain the early and late time gates that correspond to shallow and deep information about the subsurface layers. The technology provides the first bias-free gate is as early as 4μs from beginning of the ramp. Data are then processed and inverted using methods directly adopted from airborne electromagnetics.

“We managed to achieve very good results using this technology, with two of the drilling sites that we presented to the municipality producing very high yields. Notably, one of these sites provided yields of up to 36 000l/hour. There is a strong possibility that we may not have located it without this state-of-the-art technology which has significantly improved the precision of our borehole siting methods,” Rose says.

The geohydrologists’ experience using this technology has broadened JG Afrika’s understanding of aquifer systems. Using the technology, they are also able to more accurately explore weathered rock that is often very thick and overlies granite, gneiss and other crystalline bedrock. Groundwater flowing through this bedrock could produce low to moderate yields of water, which is often the only form of potable water supply in rural areas.

A total of 14 drilling sites were presented to Laingsburg Municipality for testing and 10 were drilled during the hard lockdown that was implemented by national government to curtail the spread of the Covid-19 virus in 2020. They are sited on a farm that is located north-west of Laingsburg that was acquired by the municipality. The two holes that were already located on this site will also be tested as part of the next phase of the project. This is to determine if there is sufficient water to supply demand in Laingsburg.

There is probability that this supply could be augmented from groundwater resources from an area located west of the existing site. While it still needs to be explored further by Rose and his team, the area already has infrastructure to support groundwater supply schemes.

As part of the project, JG Afrika will also develop a borehole management plan on behalf of Laingsburg Municipality.

Rose concludes that he is proud of JG Afrika’s participation in another geohydrological project for the Western Cape DLG that is providing the company with ample opportunity to again demonstrate its leadership in the field.

 

 

 

 

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