Water wise

Mike de Kock, Emeritus Professor of Civil Engineering

The City of Cape Town recently revealed that the building industry was being allowed to use potable water for building works (“Developers allowed to use potable water”, CapeTowner, November 9).

Councillor Matthew Kempthorne said construction companies had been given permission to use potable water and that “because of the chemical make-up of concrete and mortar, potable water is needed in the process”.

According to Xanthea Limberg, the City’s mayoral committee member for informal settlements, water and services and energy, developers “have to” use potable water.

The City’s management has either been misled or is poorly informed. The claim that potable water is necessary for construction work is incorrect.

Borehole water which is not muddy is perfectly adequate for mixing concrete and building work, as is water out of the river.

The City should stop builders using potable and require builders and readymix concrete manufacturers to switch to using borehole and run-off water immediately.

There is very little preventing the City from establishing boreholes at strategic points in the city and charging builders for water.

Careful management of extraction from the boreholes will be necessary, but wasting potable water mixing concrete is unwise.

Accessing and managing water from boreholes on private property needs to happen.

Knowing how much water you (personally) use is important. It is easy to imagine that you are saving water and making an effort, but the proof is in the evidence.

For homeowners it is important to check the water meter once a week, because without monitoring actual consumption during the month it is impossible to know if you are on target.

The water crisis Cape Town is facing is incredibly serious and only with the co-operation of everyone will we avoid a major disaster. The residents of the city need to use less water.

The City has identified a target of 87 litres per person per day, however, many people are still not meeting this target. Saving water requires effort and some personal sacrifices.

Saving methods:

Collecting grey water and using it for flushing toilets. Collecting grey water is not difficult, however, it is best filtered. The odour of unfiltered grey water is unpleasant. Adding a small amount of Jik to the grey water also reduces the noticeable odour. Flushing away our human waste with drinking water is an unwise use of a scarce resource. If it’s yellow let it mellow, if it’s brown flush it down.

Daily showering is a pleasure which many people are not willing or wanting to compromise on.

Showering less often results in a large saving. Further savings can be made in the shower, by not having the water run while lathering with soap and shampoo.

Rain water harvesting is a extremely useful in our predicament and this should be used for keeping swimming pools full, water gardens, and flushing toilets.

The greater the reserves of fresh water the citizens collect and use, rather than relying on the City’s water supply the less the pressure will be on the current supplies.

The Cape Floristic Region in which we live is the smallest floral kingdom, yet Cape Town’s gardens are filled with imported plants, many of which require watering. Planting indigenous plants which are perfectly adapted for local conditions is both environmentally friendly and waterwise.

The City should change its building requirements that all new toilets being installed be dual flush/low-flow toilets. Personal experience, and the water records themselves, shows that with some effort and making some sacrifices water consumption can be cut a large amount. The 3.5 kilolitres water we use monthly supports three people, which amounts to 39 litres a person a day. The City’s stated water augmentation plans will at a minimum be providing 150 megalitres from desalination, effluent treatment and aquifer extraction, amounts to 37.5 litres a person.

Having lived the past five months using 39 litres a day, I can confirm it is possible. If everyone co-operates, no one needs to go without (and that is a big if).

The City should consider rewarding those who save water, rather than only focusing on punishment, as the carrot and stick is better than just the stick.

Mike de Kock, Emeritus Professor of Civil Engineering, lectured at UCT for many years and is an honorary life member of Concrete Society of South Africa.