Waterwise Guide to Irrigation

Edited by John Colwill - Local gardening expert

Your Lawns

No matter whether you are watering your lawn from the mains water scheme or by a private bore, it is important to apply the water as efficiently as possible through a well designed and maintained reticulation system. A properly designed automatic reticulation system will use less water than a manually operated system.

Private Bores

Many areas of Perth are suitable for private bores. Contact one of the major irrigation companies who can advise on the depth and availability of water in your area.
Consider sharing a bore and the associated capital cost with neighbours. A legally binding agreement is essential.
Contact Synergy to find out more about 'smart' meters which will cut running costs of a bore dramatically.
Most members of the Irrigation Association of Australia offer a free, no obligation design service.

Choice of equipment

Use sprinklers that produce coarse sprays of large droplets. These are less prone to wind drift.
Use good quality sprinklers which have matched precipitation rates. Cheap sprinklers will vary enormously in their output.
Use a good quality controller which has the ability to run separate programmes for lawn areas and garden.
Gutter mounted rain sensors can be used to disable watering after summer rain storms.

Design principles for lawn watering systems

Sprinklers should be placed so that the spray from one sprinkler touches the next sprinkler.
Rows of sprinklers should be staggered.
Use good quality part circle sprinklers on the edges to prevent water being thrown onto hard surfaces such as driveways or paving.
Never mix different types of emitters on the same line.
Always water your lawn separately from garden areas.
Solenoid valves should be covered by a valve box, not buried beneath the soil.
The controller should be placed under cover in an easily accessible site.

Operating pressure

Too much pressure causes misting and high evaporative loss.
Too little pressure causes uneven application rates.
Irrigation specialists can conduct pressure and flow testing.

Calibration

Use 'Catch-cups' to calibrate your system accurately. These come with full instructions and are available from specialist irrigation suppliers.

Operation

Set your controller to deliver a 'standard drink' of 10mm per application. Then follow the guidelines below, changing your schedule as indicated. During water restrictions only water on your rostered days.

Month	Frequency
January	Twice a week
February	Twice a week
March	Twice a week
April	Every fifth day
May	No watering
June	No watering
July	No watering
August	Once a fortnight (if needed)
September	Once a week (if needed)
October	Every fourth day
November	Twice a week
December	Twice a week

In exceptionally hot weather the frequency may have to be increased slightly but it should be returned to the recommended rates once conditions return to normal.
Water early in the morning (5am to 8am). Never water during the heat of the day.
Visually check your system once a week.
Calibrate your system once a year, replacing worn nozzles or broken seals as necessary

Your Garden

Private Bores

Many areas of Perth are suitable for private bores. Contact one of the major irrigation companies who can advise on the depth and availability of water in your area.
Consider sharing a bore and the associated capital cost with neighbours. A legally binding agreement is essential.
Contact Synergy to find out more about 'smart' meters which will cut running costs of a bore dramatically.
Most members of the Irrigation Association of Australia offer a free, no obligation design service.

Sprinklers

Overhead sprinklers should only be used on broad areas which are densely planted.
Use sprinklers that produce coarse sprays of large droplets. These are less prone to wind drift.
Use good quality sprinklers which have matched precipitation rates. Cheap sprinklers will vary enormously in their output.

Micro-irrigation

Micro-irrigation is suitable for most areas of the garden, especially general garden beds, shrubberies, pot plants and hanging baskets.

These systems are flexible, low cost and easy to install, and allow for precision delivery and placement of water to the root zones of individual plants.
Various types of emitters are available including a full range of micro-sprays and fixed and variable drippers.
For consistent performance it is best to use recognised brand name products.
Most members of the Irrigation Australia offer a free, no obligation design service.

Choice of equipment - general

Use a good quality controller which has the ability to run separate programmes for lawn and garden areas.
Gutter mounted rain sensors can be used to disable watering systems after summer rain storms.

Design principles for garden watering systems

Never mix different types of emitters on the same line.
Always water your garden areas separately from the lawn.
Solenoid valves should be covered by a valve box, not buried beneath the soil.
The controller should be placed under cover in an easily accessible site.

Operating pressures

Too much pressure causes misting and high evaporative loss.
Too little pressure causes uneven application rates.
Irrigation specialists can conduct pressure and flow testing.
Micro-irrigation systems must begin with a pressure or flow regulating device.

Watering Shrubs and Perennials

Micro-irrigation is ideal for these plants. If you have improved soil that is well mulched even the thirstiest of plants can be maintained on a watering schedule of twice a week in the heat of summer. This can be extended as the weather cools down.

Very tough, water efficient plants may only need a drink every month or so during their first summer after which the micro-irrigation system can be disconnected and re-cycled elsewhere in the garden.

Other advantages are

Only the soil around the plant root zone is watered, not the area between plants. This minimises nitrogen draw-down problems, weed germination and the number of slaters.
The pipes can be hidden under the mulch.
Adjustable emitters can be used to deliver variable quantities of water to the right locations. Emitters should be exposed to allow for inspection.
The system can be linked to either an automatic controller or a tap timer.
Even when the water is being delivered precisely to the plants at ground level, it is still desirable to water early in the morning to minimise evaporation losses.
Your irrigation supplier can give you more details on designing a micro-irrigation system for the shrubs and other parts of your garden.

Watering Fruit Trees

If the soil has been improved and a good mulch is present, all fruit trees in the home garden, even tropical species like mangoes, avocadoes and custard apples can be kept growing healthily and productively by watering only on alternate days during the heat of summer.

Where applicable, once the crop has been harvested the water may be cut back further.
Flat throw, low pressure micro-irrigation sprinklers are the most efficient means of watering fruit trees. They can be set close to the ground and since they have a flat trajectory they can easily be adjusted to wet the entire drip zone area without being affected by wind.
A simple technique to ensure the most efficient use of water is to shape the mulch like a saucer with the highest part immediately below or just outside the drip line. Place the sprinkler in the middle and adjust the height until it just throws out to the rim of the saucer. The water is then caught and directed down to the roots.
Drippers are generally not satisfactory for fruit trees in sandy soils. They only wet a limited surface area and lead to wastage as most of the water is lost to the deeper soil. Drippers are slightly better in heavier soil where they have a flatter wetting pattern but even then they are not as efficient as micro-sprinklers.
Overhead watering of fruit trees is extremely wasteful due to high evaporation losses. It is not recommended for the home gardener.

Maintenance

Run the entire system in early spring to check that it is working properly.
Visually check your system once every week or two. Do not wait for plant deaths to discover a fault.
Calibrate your sprinklers once a year, replacing worn nozzles or broken seals as necessary.
All maintenance should be carried out on your specified watering day before 9 am and after 6 pm. If this is not possible you may be eligible for an exemption by calling 13 10 39.

No matter whether you are watering your garden from the mains water scheme or by a private bore it is important to apply the water as efficiently as possible through a well designed and maintained reticulation system. A properly designed automatic reticulation system will use less water than a manually operated system.

Watering Pot Plants

Micro-irrigation systems can be installed to deliver water to individual pots around the verandah or patio. Adjustable drippers allow for different pot sizes and plants.

Terracotta is a porous material which allows moisture to escape comparatively quickly. Before planting up you should make it moisture proof by either using a liquid sealant painted on to the inside of the pot or lining the inside of the pot with polythene. (Make sure that a hole is cut in the polythene to coincide with the drainage hole of the pot.)
Self watering pots come in many styles. These pots are very water efficient as long as they are maintained correctly.
Hydroponic systems are also water efficient. Though they may use a large liquid mass, the fluid is retained and recycled in the hydroponic process with very little waste.
Slow release fertilisers release their nutrients gradually over the growing season and are the best way to feed pot plants.

Watering Hanging Baskets

icro-irrigation systems can be adapted to deliver water to individual hanging baskets. Adjustable multi outlet emitters ensure a large area of the surface is moistened.

Protect hanging baskets from the drying winds.
Porous basket liners such as coconut fibre or wool should be lined internally with polythene to reduce excess moisture loss (make sure that a hole is cut in the polythene to allow for drainage).
Slow release fertilisers release their nutrients gradually over the growing season and are the best way to feed hanging baskets.

Prepared with the support of the:

Nursery Industry Association,
Irrigation Australia,
Australian Institue of Landscape Architects,
Turf Growers Association,
Landscape Industry Association,
Independent Lawn Mowing Contractors.