Automatic Irrigation

What is automatic irrigation?

SCADA automation on a pipe and riser outlet

Automatic irrigation is the use of a device to operate irrigation structures so the change of flow of water from one bay, or set of bays, to another can occur in the absence of the irrigator.

Automation can be used in a number of ways:

• to start and stop irrigation through supply channel outlets,
• to start and stop pumps,
• to cut off the flow of water from one irrigation area – either a bay or a section of channel and directing the water to another area.

These changes occur automatically without any direct manual effort, but the irrigator may need to spend time preparing the system at the start of the irrigation and maintaining the components so it works properly.

What are the benefits of automatic irrigation?

Reduced labour:

As the irrigator is not required to constantly monitor the progress of an irrigation, the irrigator is available to perform other tasks – uninterrupted.

Improved lifestyle:

The irrigator is not required to constantly check the progress of water down the bays being irrigated. The irrigator is able to be away from the property, relax with the family and sleep through the night.

More timely irrigation: Irrigators with automation are more inclined to irrigate when the plants need water, not when it suits the irrigator.

Assists in the management of higher flow rates: Many irrigators are looking to increase the irrigation flow rates they receive through installing bigger channels and bay outlets. Such flow rates generally require an increase in labour as the time taken to irrigate a bay is reduced thus requiring more frequent change over. Automation allows for these higher flows to be managed without an increase in the amount of labour.

More accurate cut-off: Automation of the irrigation system allows cut-off of water at the appropriate point in the bay. This is usually more accurate than manual checking because mistakes can occur if the operator is too late or too early in making a change of water flow.

Reduced runoff of water and nutrients: Automation can help keep fertiliser on farm by effectively reducing run off from the property. Retaining fertiliser on farm has both economic and environmental benefits.

Reduced costs for vehicles used for irrigation: As the irrigator is not required to constantly check progress of an irrigation, motor bikes, four wheelers and other vehicles are used less. This reduces the running costs of these vehicles and they require less frequent replacement.

What are the disadvantages of automatic irrigation?

Cost:

There are costs in purchasing, installing and maintaining automatic equipment.

Reliability:

Can the irrigator trust an automatic system to work correctly every time? Sometimes failures will occur. Often these failures are because of human error in setting and maintaining the systems. A re-use system is good insurance to collect any excess runoff when failures occur.

Increased channel maintenance:

There is a need to increase maintenance of channels and equipment to ensure the system works correctly. Channels should be fenced to protect the automatic units from stock damage.

What automatic irrigation systems are available?

Pneumatic system:

A pneumatic system is a permanent system activated by a bay sensor located at the cut-off point. When water enters the sensor, it pressurises the air, which is piped to a mechanism that activates the opening and closing of irrigation structures.

Portable timer system:

A portable timer system is a temporary system which uses electronic clocks to activate the opening and closing of the irrigation structures. Because of its portable nature, landowners usually buy 4 or 5 units to move around the whole property.

Timer/ Sensor Hybrid:

As the name suggests, this system is a hybrid of portable timer and sensor systems. Like a portable timer, it uses an electronic device to activate the opening and closing of the irrigation structures. However, this system has an additional feature of the irrigator being able to place a moveable sensor down the bay, which when comes in contact with water, transmits radio signals to the timer devices at the outlets to open or close the structures and sends a radio message to a receiver to let the landowner know water has reached the cut-off points down the bay.

SCADA:

Automation systems that use Supervisory Control and Data Acquisition (SCADA) consist of a personal computer and software package to schedule and control irrigation via a radio link. Signals are sent from the computer to control modules in the paddock to open and close irrigation structures with linear actuators. Bays are opened and closed on a time basis, some systems have the capacity to automatically alter the time a bay outlet is open if the channel supply is inconsistent.

SCADA based systems have the additional benefit of being able to start and stop irrigation pumps and motors.

How can an irrigation layout be automated?

An irrigation layout can be automated at one of two places; in sections of channel or at individual bay outlets.

Automation of channel sections

In this system the channel structures are automated allowing the channel level to be changed. The bay outlets do not have opening or closing structures rather each set of outlets is set at a specific level eg a set of sills.

This method of automation requires a larger amount of fall to be available in the channel system to allow for a change in water level between different areas. This change in water level is required to prevent water flowing onto bays previously irrigated, when another section is to be irrigated. On many farms this fall is not available, so this method of automation in many cases is not suitable.

Automation of individual bay outlets

This method of automation involves control of the bay outlets to change the flow of water onto the areas being irrigated. This system of automation is the most frequently used in areas where there is insufficient fall to automate channel sections.

The same type of automatic devices available can be set up to operate either automation of channel sections or automation of bay outlets.

Which system is best?

All systems of automation have advantages and disadvantages that need to be considered when deciding which system will suit the irrigation layout for a particular property. There is no system that will be the “best” system for all properties.

The methods of irrigation used by the irrigator need to be considered. If a system that can be moved around the property and perhaps used on other properties is required, then the irrigator needs to consider those systems that are portable. If the irrigator wants a system where the components are fixed and can follow the same irrigation sequence each irrigation, then a fixed system would be more appropriate.

In determining the best system for a property, the irrigator will need to consider the cost of the system, back up servicing of the system and which system will best suit the property and irrigation layout.

Where do I start?

SCADA actuator attached to a farm channel bay outlet

Development of a whole farm plan for the property is a good way to start preparing for automation. During the development of a whole farm plan, landholders should consider automatic irrigation in the planning process so they can incorporate some of the features required for automation from the start. This might involve design of the channels for channel automation if that is possible or it might be the use of bay outlets and other channel structures that will suit automation at a later stage.

When it comes to starting to install automation there are a number of ways of getting started. One way is to start by automating those areas irrigated at night, so appropriate irrigation flow rates can be acheived, without disrupting the irrigator’s sleep. Another is to automate those areas that are difficult to irrigate – areas of short steep bays that require the irrigator to be present more often or require frequent changes.

Automation is not only suited to areas of the farm that have been laser graded. Non-lasered areas can also be automated. This can include automation of the channel structures to irrigate sections of the non-lasered areas.

With the information from a whole farm plan, channel structures that will be used when the development works are carried out, can be purchased and used to automate these non-lasered areas. This can be done with the knowledge the structures will be suitable for use after the development work is carried out.

Acknowledgments

Irrigation Survey and Designers Group