Advice and Opinion

Property developers must consider groundwater for irrigation

Water generic

Large residential and retail developments face a growing constraint in their use of water for irrigation purposes – as the drought in the Western Cape and Northern Cape leads to sterner water restrictions and rising water prices, part of the answer lies under the ground.

“Using treated municipal effluent for irrigation of parks in residential developments – or green areas in retail malls – is not always feasible due to quality and quantity constraints,” said Leon Groenewald, principal hydrogeologist at SRK Consulting. “Property developers and managers now need to be considering the judicious use of groundwater to augment their supplies; in fact, we find many already are.”

According to Groenewald, growing use of groundwater for irrigation helps to ensure that all water sources are used in a more appropriate and sustainable manner. For example, by utilising untreated – and therefore potentially cheaper – groundwater for irrigation, the dwindling supply of potable water can be more efficiently distributed for drinking and household purposes.

When used for irrigation, groundwater can also be blended with treated effluent to improve the quality and increase the quantity of treated effluent available for irrigation.

“At the same time, care must be taken in how groundwater use is managed, as this is not an infinite resource,” he said. “To establish whether groundwater is an option for any residential or retail development, a detailed feasibility study needs to be conducted to determine if groundwater is available, and whether yields and quality are appropriate for the intended use.”

The boreholes have to be correctly sited using scientific geophysical methods, and a competent contractor must be appointed to drill and test each borehole.

“When groundwater is intersected during drilling, correct pumping tests and scientific methods need to be employed to analyse the test data to establish the sustainable yield of the borehole,” said Groenewald. “If the decision to proceed is positive, the groundwater resource must be correctly managed within the parameters of its yield and water level in the borehole. This requires that groundwater levels and abstraction volumes be monitored, so that these levels are kept within the recommended limits.”

Also important are compliance requirements: the Department of Water and Sanitation (DWS) is tasked with the responsible management of the nation’s groundwater resources, so its usage must be monitored and controlled as prescribed by regulations.

If the daily use of the borehole is between 10 and 20 cubic metres, then the groundwater use must be registered with the DWS; if the daily abstraction exceeds 20 cubic metres, then a Water Use Licence – also from the DWS – must be obtained.

“The various stages in developing, managing and protecting groundwater resources demand a range of specialised skills which are well established at SRK Consulting,” he said. “Our specialist teams of geologists, hydrogeologists, hydrochemists, environmental practitioners and engineers undertake all aspects of groundwater studies, from liability assessments, site works, project management, impact assessment, licencing, design and implementation, to numerical modelling.”