A garden irrigation system is a fixed installation usually consisting of pop-ups in the lawn and standpipes in beds. It is often controlled by a computer that switches the system on and off at appropriate times. A properly designed and installed irrigation system gives even precipitation and applies exactly the right amount of water where it is required. A sprinkler that you attach to the end of your hosepipe and move around the garden is not considered an irrigation system.

In Johannesburg, in summer, the average garden requires about 25mm of water per week, assuming that it has no special watering requirements and no rain falls. If we take a 400m² garden as an example, this amounts to 10 000 litres of water per week, spread evenly across the landscape. It sounds like a lot, but remember we have assumed no rainfall and this is not a water-wise garden.

If one was to water by hosepipe it would take approximately 5 hours to put down 10 000 litres. You can imagine how difficult it would be to spread all of that water evenly across your garden. To avoid dry patches most people would over water by as much as 50%. That means they would be wasting about 5000 litres a week, or 20 000 litres a month – a lot by anyone’s standards. Using the latest maximum tariff in Johannesburg that amounts to R208 of wasted water per month. Of course, using a watering can is far less wasteful than a hosepipe, but it is clearly impossible to water a large garden in this manner. A 5 litre watering can would require 2000 refills!

A well-designed irrigation system will be able to apply exactly 10 000 litres per week, without waste. The modern irrigation computers are quite sophisticated and will allow you to control exactly when to start the system and how long to run it for. You can ensure that your garden is watered during periods of low evaporation such as early morning or late afternoon. When it rains the system will switch off to save water and one can even install a weather monitor that will control daily run times to further reduce the watering bill. Best of all, you can rest assured that when you come back from your three-week holiday your garden will be lush and green instead of a dry desert.