PUMPING RESPONSIBLY THE ONLY WAY TO CONSERVE GROUNDWATER

As South Africa increases its use of boreholes to meet growing water needs, users must pay more attention to monitoring and controlling how much groundwater they pump or these resources could be rapidly depleted.

This is according to Stephan Venter, Grundfos product manager water utilities for India, Middle East and Africa, who has been extensively involved in providing pumping solutions for borehole users.

“The main risk when municipalities, businesses or households make use of groundwater resources is that their extraction from boreholes could exceed the recharge rate of the aquifer,” says Venter. “To avoid this, users need to gather a great deal of information from the start – it’s more than just drilling and pumping.”

An important aspect of ensuring the sustainability of a borehole, he says, is the correct sizing of the pumping infrastructure. This requires data including the borehole’s safe yield, the dynamic water level, the required lift above ground, discharge ratio, friction loss in piping, flow demand and well size.

He notes that while larger water projects will usually employ the services of a qualified hydrogeologist to generate the necessary data on the aquifer, many smaller users simply proceed with minimal information.

“This makes it difficult to put the borehole on a sustainable footing,” he says. “Lack of investment in the monitoring equipment also creates challenges in controlling the water abstraction adequately.”

He highlights the importance of taking a conservative view on what levels of extraction the aquifer can accommodate. Even when yield testing is conducted, for instance, there could be other users of that particular aquifer who are not pumping at the time of the tests – leading to an over-estimation of yield capacity.

“Just to be safe, I tend to advise the user to size their pumping equipment at only 50 to 60% of the borehole’s safe yield,” he says. “This reduces the risk of over-pumping, through which they could possibly even lose this valuable groundwater source altogether.”

There is no substitute for constant monitoring, however, and Venter emphasises the value of digital technology in collecting and transmitting data to keep users informed. Many users still use a manual inspection method to check the level of the borehole and the condition of the pump, but the most effective way is through electronic equipment linked to online platforms.

“This provides updated information at the click of a button, either through a SCADA system for larger users, on a standard computer or even on a mobile phone,” he says. “Monitoring and measuring our groundwater resources is vital in a dry country like South Africa, especially as we work towards becoming more responsible water users.”

Further challenges for borehole users include the unreliable power supply and the rising cost of the electricity required to pump water. Fortunately, solar power generation technology has improved in leaps and bounds, says Venter, and has been well leveraged by borehole pump manufacturers.

“Solar power now allows water to keep flowing even when mains power goes down,” he says. “The development of high-efficiency pumps – combined with technology like permanent magnet motors and variable speed drives – can reduce pumping costs and ensure constant supply.”

He says that specialised software developed by Grundfos – the world’s largest pump manufacturer – even allows users to go online and select the ideal pump model to suit their borehole specifications, helping to make the most responsible use of the country’s scarce groundwater resources.

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