This country is drought-prone and with an ever-growing population and more and more factories, office blocks, shopping malls and what have you, the demand on our already scarce water resources is simply going to grow.

Some systems however are waterwise. Drip irrigation systems, in particular, can deliver precise amounts of water very accurately and with virtually no evaporation loss and hence are very efficient and waterwise.

They are ideal, for example, if a precise amount of water needs to be delivered to a specific plant, but they do have their limitations. For example, they are not suitable for watering large areas such as lawns, where pop-up sprinklers are the better option.

Common mistakes

If you would like to save water then make sure you use your watering system efficiently. The following is a basic list of where many owners of irrigation systems go wrong. In many cases, correcting the mistakes will cost nothing, and bring substantial benefits.

  • Problem:
    They drown their plants by watering too often and/or for too long. This results in a lot of the water being wasted as much of it isn't absorbed by the plants or runs off.

    Solution:
    Rather water more often, but for shorter periods each time, with a 15-30 minute break between each session. Runoff will be minimised and the plants will have time to absorb the water.

  • Problem:
    They water irrespective of what the plants actually need by positioning plants for aesthetic appeal, rather than according to water needs. The result is often that while one plant gets too little water, the one next to it gets too much. This is a classic case where the average is anything but right.

    Solution:
    Group plants as much as possible for water needs, with aesthetic appeal taking second place if necessary. A garden can also be divided into zones, and the system can incorporate different applications such as pop-up and drip, placed appropriately, for optimum results and water usage.

  • Problem:
    They ignore soil and shade conditions, with the result that sandy soils might be starved of water while clay and loam, which retain moisture much better than sand, can end up being waterlogged. Likewise, soil in a shaded area will tend to retain moisture for longer than areas in full sun.

    Solution:
    Take the soil type into account, and bear in mind that different areas of a garden might have very different roil characteristics, either thanks to nature, or the deliberate importation of topsoil, for instance, in particular areas. Likewise, take account of shady versus sunny areas and adapt accordingly.

  • Problem:
    They water at the wrong times of the day — when the sun is high.

    Solution:
    The best time to water is between about 5am to 10am in the morning when the air is cool, there is little wind to promote evaporation, and the sun is not yet high in the sky, which again, would promote evaporation.

    Watering in the morning also gives the plant foliage time to dry during the rest of the day so that they are dry by nightfall and the risk of disease is reduced.

  • Problem:
    They water things that don't grow and hence don't need water. How often have you seen paved drives being watered, or tarred pavements, or concreted areas? Often, right?

    Solution:
    The irrigation applicators need to be adjusted to put the water where it is needed and nowhere else.

  • Problem:
    They apply a mist rather than droplets, which also leads to wastage as the mist is blown this way and that in even a light breeze, whereas droplets are heavier and more likely to remain more or less where directed. Spray heads begin misting at a pressure of two bars (200 kPa or 30 psi), causing excessive water consumption and erratic coverage as a result of the action of the wind.

    Solution:
    Reduce the pressure applied to the spray heads. Note that a spray head operating at four bars will use 60 percent more water than one operating at a pressure of 1.5 bars. Hence the incorporation of a pressure regulator, pressure-compensating nozzle or screen filter will achieve significant water savings and greater efficiency.

  • Problem:
    They use inappropriate applicators and this wastes water.

    Solution:
    Drip systems are very efficient near non-grassed areas such as paved areas and are used to apply water directly to the roots of pot plants, shrubs, trees and so on. Runoff is reduced or virtually eliminated, as is evaporation. The spin-off is that the spread of weeds on paved areas, for instance, is reduced since the only water those areas receive will be rain water. Use a range of applicators, as appropriate, for optimum results.

  • Problem:
    They keep the system operating while it's raining, which not only wastes water, but can also result in too much water being delivered to the plants with the danger of damage to the plants and more runoff .

    Solution:
    Connecting an electronic rain gauge to the controller will cost in the short-term, but can more than make up for it over time. They serve not only to avoid irrigating the garden when the rain is already bucketing down, but they also help on the public relations front: few things annoy people more than seeing a garden being watered during a fall of rain.

  • Problem:
    They don't monitor the soil's moisture content with the result that again, water is wasted. An electronic rain gauge, as mentioned above, is a very sensible addition to an irrigation system. It has a drawback, however, in that it cannot measure the soil moisture content, which can result in the irrigation system either being turned on when it's not strictly necessary, or remaining off when it is.

    Solution:
    A soil moisture sensor linked to the controller will determine whether or not the system needs to operate. The system usually comprises one or more adjustable sensors, which are buried as specified by the manufacturer in positions appropriate in the situation.

    When the timer on the controller schedules a session, the moisture sensors, according to its setting, will allow or block the irrigation session. A further refinement is a system based only on moisture content of the soil.

    In this case the buried sensor checks the soil's moisture content according to a preset program — say every hour — and will automatically trigger a session when the soil's moisture content falls below a selected level, which can be selected.

    Once an irrigation session starts, the sensor can then check the roil moisture content level every couple of minutes or so and then terminate the session when the level achieves the optimum level.

  • Problem:
    They don't inspect or maintain the system with the result that heads become blocked, filters clog up, and punctures in pipes result in wastage.

    Solution:
    Systems should be inspected at regular intervals, components cleaned, repaired or replaced and leaks and punctures in pipes made good.




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