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Hermanus harnesses water supply from record yield borehole

Judy Bryant

Several years after discovering one of South Africa’s highest yielding boreholes near Hermanus on South Africa's southwest coast the region has started using this underground water supply and there are plans to link it to a global satellite monitoring system to manage it scientifically.

Some 1.5 million m³/year of underground water have been added to the existing 2.8 million m³/year from the De Bos Dam, formerly the only water source for the Greater Hermanus area, including the villages of Fisherhaven, Hawston, Onrus and Sandbaai.

The new groundwater project, boasting cutting-edge technology, has cost some R5.5m, resulting in a price of R0.8/m³ of abstracted water.

Developing from a holiday town with a large seasonal variation in water consumption into the economic and administrative hub of the Overberg, the municipality faced a growing water shortage because of burgeoning residential, business and leisure demands. Accordingly, the municipality appointed Cape Town-based groundwater consultants Umvoto from 2002 to explore underground water resources to augment the municipal water supply.

Installation of telemetry system in Hermanus.

Umvoto Head: Water Systems Dr Kornelius Riemann said Umvoto focused on the Gateway wellfield target area, named after a nearby shopping centre. Several boreholes were drilled deep into the Peninsula aquifer, a layer of water-bearing, permeable rock capable of providing significant amounts of water.

A borehole was found to be one of the highest yielding in SA – blowing out at more than 100 litres/second – and infrastructure such as pumps, a pipeline and a pre-treatment plant (to ensure water quality) were constructed.

“We are now at the stage where we [can] put the aquifer and monitoring system to the test,” said Riemann. “We want to extract water from the aquifer continuously for at least several months to a year and see the response of the aquifer to measure the long-term sustainability. The water will be pumped into the reticulation system of the town.”

Riemann said the new system was noteworthy for its close monitoring of both the aquifer and the environment; the project had been completed swiftly and efficiently because all stakeholders, ranging from the Ratepayers Association to CapeNature, had been involved in setting up and overseeing the monitoring; and Umvoto had installed a telemetry system (remote monitoring and controlling) which ensures that real time data on the Hermanus project can be accessed by the municipal staff and from Umvoto’s offices in Muizenberg.

Dr Chris Hartnady taking a GPS co-ordinate of a Hermanus monitoring site.

Umvoto research and technical director Dr Chris Hartnady added that the Hermanus wellfield would also be monitored in a project involving the Hermanus Magnetic Observatory (HMO), the Chief Directorate: Surveys and Mapping (CDSM), the Water Research Commission (WRC) and the Department of Earth and Atmospheric Sciences at Purdue University in Indiana, USA.

The existing continuously-recording GPS station at the HMO will be supplemented with surplus GPS receivers on loan from the CDSM and equipped with new antennas bought with WRC funds. All the data that is recorded around the aquifer will be relayed to Eric Calais, Professor of Geophysics in Indiana. This will enable the scientists to precisely measure the aquifer properties and how the water resource fluctuates because of factors like seasonal rainfall and pumping extraction.

Umvoto also has longer-term plans to link this GPS monitoring to the Gravity Recovery and Climate Experiment (GRACE) mission that is measuring subtle changes in the gravity field all around the world on a monthly basis. Twin satellites, launched in March 2002, are making detailed measurements of the earth’s gravity field and these are leading to discoveries about the total amount of water stored in the earth’s crust.

“We want to link Hermanus into a bigger effort by using GPS,” said Hartnady.

“We at Overstrand are proud to be associated with such hi-tech developments, which underline our vision to be a centre of excellence to our community. This will make us part of a world-wide network of scientific research, which will help us to manage this valuable resource in the best way possible,” said Stephen Muller, municipal director of infrastructure and planning.

More information:

 Dr Kornelius Riemann (Head: Water Systems) or Ms Rowena Hay (Director Umvoto) at (021) 788 8031 or kornelius@umvoto.com
See www.umvoto.com

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