Introduction
Coleambally Irrigation Co-operative Limited (CICL) is wholly owned by its farmer members and is Australia's fourth largest irrigation company. CICL delivers irrigation water via a modern open-channel system across an area of approximately 400,000ha. The Co-operative's irrigation delivery system relies solely on gravity across 518 km of supply channels and 734 km of drainage channels. Delivery is managed via a Total Channel Control (TCC) system which is solar powered and fully computerised using broadband communications. TCC allows water orders to be satisfied within 2 hours; providing precise regulation of flows; accurate measurement; and the automation of water ordering and water accounting. This world-class technology is Australian designed, Australian built and Australian owned.
There are 491 irrigation farms in the Coleambally Irrigation Area, which are typically 220ha in size across 98,000 ha of intensively irrigated land. These farms employ very sophisticated layouts and recycling systems to ensure a high level of water efficiency. The major crops produced are rice, wheat, corn, cotton, barley, soy beans and canola. A variety of fruit, nuts and vegetables are also grown as well as mixed grazing operations.
Gogelderie Weir, credit Mattinbgn
Water is diverted to the Coleambally Irrigation Area (CIA) from the Gogelderie Weir on the Murrumbidgee River, approximately 26km upstream from Darlington Point. WaterNSW (formerly State Water) release water ordered by CICL, from Burrinjuck and Blowering Reservoirs, which takes seven days to flow down to the weir. The ordered water is diverted by gravity to the Coleambally Main Canal in the irrigation season, allowing farmers’ down stream irrigation requirements to be fulfilled. The Main Canal has a capacity of 6,100ML/day and runs for 47 km, with 430km of smaller supply channels taking the water to the farm boundaries.
The irrigation industry is highly regulated by both Federal and State regulation. CICL’s licensing obligations also require monitoring of soil and water quality to continually ensure chemicals are not discharged from farms into our supply and drainage systems. CICL works closely with the local community to protect local biodiversity and manages 1,700ha of crown land in its own right, to protect both flora and fauna. Species, which are highly endangered elsewhere, thrive in the local area e.g. Southern Bell Frog, Superb Parrot, Australasian Bittern.
What is a Water Bailiff?
Water Bailiff
A person who operates and monitors channel systems within a designated area, assists with water orders within the constraints of channel capacities and resource availability, and provides support with irrigation infrastructure maintenance. In later years called a Channel Attendant, and affectional known as a ‘Channely’.
The first water bailiffs were very patient and understanding men who had to educate the new pioneers who were using Dethridge wheels for the first time as well as controlling those who thought they knew all the tricks of the trade. Ralph Thompson, one of the first water bailiffs, lived at the Weir, rowed across in a boat daily to a ute parked on the south side, then set out on the dirt tracks to the farms to perform his duties. Even a shower of rain made it difficult, but like the Royal Mail, he always got through.
Water Card Box and Flag
In the early days the farmer ordered his water via the water card box and flag system. Water for the irrigation area was made available on a ‘rotation’ or ‘roster’ system. The water card provided an indication when the farmer wanted to take water within his rostered time. When the farm up-stream finished watering, the next farm down-stream was started by the channelly and so on down-stream till the water reached the end of the channel or escape.
When the farmer put the water card in the card box, he raised the flag so that the water bailiff knew to stop to pick up the card, and this information would be used to calculate the next run of water to be released. Usually the bailiff traveled his run once a day, every day of the irrigation season. Having to do the water run on Christmas Day often involved more than just a card at the card box, often receiving something cool to drink under a wet wheat bag or later on ice in an Esky.
One of our water bailiff’s remembered that “Some times the notes were written on masonite or fibro scratched with a nail or whatever the farmer could get his hands on! We had more personal contact with the farmers. In those days they would even flag you down to give you the orders, and have a chat, rather than driving to their water card box.”
One channelly told of how he had received a love letter instead of a water order mistakenly placed in the water card box. No doubt this was a cause for great laughs back at the office.
Historically the ‘Tail Ender Problem’ caused issues for the water bailiff where the upstream irrigators tend to receive all the water that they ordered while the farmers at the tail end of the system often suffered flow shortfalls during high crop demand and then flooding due to rainfall rejections following widespread significant rain.
History
Drop Boards
Drop boards were used to regulate water levels and flows, and were within the reinforced concrete regulator structures. Red gum drop boards, running in vertical red gum slots, were bolted to the upstream face of these openings and called ‘Cells’ or ‘Bays’ which had standard opening widths of 4ft, 5ft and some even bigger at 6ft. The size of gate installed was dependent on the width of the channel and quantity of water required to pass through.
Flow over the boards was measured using a ‘dip stick’ which had painted red and white stripes that directly read the flow over the boards.
The channelys used “board hooks” to lift out and replace the drop boards to regulate the flow through the regulator. At high flows, it required skill and strength to remove the drop boards without losing them. Being saturated red gum they sank and would be lost till they could be recovered the next winter.
The 6ft drop boards were phased out due to WH&S risks in the late 1990’s.
Drop Boards
The Early Days
The Coleambally Irrigation Area was designed to make use of water diverted westward across the Great Dividing Range by the Snowy Mountains Hydro-electric Scheme. In 1952 The Blowering Dam Investigation Committee advised “it would be feasible and more economic to develop from Gogelderie Weir, a very substantial and fertile area south of Spillers Creek….the area which the name Coleambally Irrigation Area has been given.” The land, formerly held as large grazing properties was resumed by the crown, gazetted as an irrigation area and subdivided into farms. The initial group of 26 farms was allocated via a ballot in 1960 and first delivery of water to the farms was in February of that year. Continued development was carried out in stages up until 1971. The town of Coleambally is one of New South Wales’ newest towns. It was established in 1968 for the sole purpose of supporting those who established irrigated farms in the area.
When the pioneers first moved onto their farms they mostly lived in sheds, tents and caravans. The irrigation channels served as a bathroom. A local pioneer recalled that “Many times after a hard day we would get into the overflow for our evening shower. What a business it was hanging on to the soap. Often we didn’t and off it went down the pipe. Don’t ask how many cakes of soap ended up in our rice crop that year! The channel water was crystal clear in the early days. As well as being our domestic supply the channel became our swimming pool.”
The Dethridge Wheel
Dethridge Wheel
The Dethridge Wheel was invented by John Stewart Dethridge in 1910. He was a Commissioner of the Victorian State Rivers and Water Supply Commission. Another widely adopted Australian invention, it was never patented and therefore never commercially promoted.
During the construction of the CIA, one large Dethridge Wheel was installed per farm. Some horticulture farms had the ‘half wheels’ installed. At first glance, some might think this wheel pushes the water but in actual fact the water flow, being gravity fed, is measured by the number of revolutions recorded by the wheel.
The original counter mechanism on the Dethridge Wheel was based on the pushbike odometer. This was replaced by the pendulum counter that was riveted to the inside circumference of the barrel. The pendulum counters were originally in acre-feet of volume and later converted to megalitres. Davies Shephard manufactured a pendulum counter mostly used in NSW.
Dethridge Wheel, credit Victoria State Rivers and Water Supply Commission photographer
Finley Police Station Dethridge Wheel, credit: Mattinbgn
Flow Fact 1 - Water volume was measured in acre-feet. An acre-foot is an area of one acre, one foot deep with water. A megalitre is 1,000,000 litres, which is the same as a hectare 100 mm deep. There are 1.23 megalitres in an acre-foot.
Flow Fact 2 - The rate of flow was in Revolutions per minute, or ‘Revs’, of the Dethridge Wheel. The water bailiffs had a stopwatch to measure the flow rate. There are 8 fins on the Dethridge Wheel. Counting the number of fins in 15 seconds and dividing by 2 gave the flow rate in ‘Revs’ of the wheel. The clever water bailiff worked out that you could just count the fins in 7.5 sec, for example, 5 fins would be 5 ‘Revs’.
A prototype cage to cover the exposed rotating Dethridge Wheel proved to be very unwieldy.
To overcome the rusting of fins and wheels, fibreglass wheels were tried but the fins fatigued at the join with the wheel barrel. The Dethridge Wheels were phased out to be replaced by more accurate meters that had less Workplace Health & Safety issues.
Flow Fact 3 - The long wheels were capable of 20 ML/day flow rate. They had 6 pointed and tapered fins for smoother entry into the water.
Gates
Gates
On 30 April 1976 the Water Conservation and Irrigation Commission was reconstituted as the Water Resources Commission with additional responsibilities and functions for water management in NSW. The following gates were recommended by the Water Conservation and Irrigation Commission as a standard gate for all irrigation areas in NSW and VIC.
Tilt Gates
Drop boards were replaced with tilting gates; Armtec designed, built and installed by Rubicon. When a channel had peak flow constraints, a two bay regulator was enhanced by removing the centre pier and increasing the opening width by installing wider aluminium tilting gates.
Tilt gates are generally flat rectangular panels hinged horizontally from the floor of the regulator and raised and lowered by cables attached to the top edge.
Drop boards and tilt gates are ‘overshot’ type regulators where the level of the up-stream water pool remained relatively stable but the flow over tended to vary depending on the flow passing down from upstream.
It took a lot of effort to raise up the taller tilt gates due to the force of water flowing over the gate. The Main Canal tilt gates were only installed where the head difference was relatively small.
Vertical Lift Gates
The offtake for the smaller channels had a vertical lift gate to try to achieve a more constant flow into the channel. These had an ACME threaded riser shaft with a brass nut in a thrust assembly. Water bailiffs had a big ‘handle’ that fitted the brass nut. The number of turns of the handle to deliver the number of ‘Revs’ or megalitres was known for each offtake.
Radial Gates
Radial gates were installed where the head was too big for tilt gates.
Radial gates were also known as Tainter gates (after the structural engineer who popularised them). It is classified as an undershot gate because water flows under the gate and tended to be relatively stable but the upstream level varied quite a bit compared to the ‘overshot’ type gate. Radial gates consist of a curved skin plate supported by a structural steel frame. A hoist system is used to raise or lower the gate.
Although relatively easier to lift, thanks to the ‘winch box’ worm drive reduction gearing, it still required the water bailiffs to be very fit. A rainfall rejection cut back required pairs of men to manage the winch box handles. The 240 Volt electric ‘torque leader’ was used instead of the manual handles when bigger changes were required at the regulators with winch boxes.
Channel pools with a radial gate all had an over flow ‘escape’. The ones in the bigger channels are named ‘glory hole escapes’ while the medium size channels had long crest, overflow type escapes. The end of every channel had an escape drain with a vertical lift gate.
Privatisation & Modernisation
History & Modernisation
In 1993, the NSW Government decided to allow irrigators to take over the management and ownership of the local schemes. It took until 1997 for privatisation to take place and ownership was handed over to Coleambally Irrigation Co-operative Limited in 2000.
CICL has participated in many water reform initiatives which have contributed to the modernisation of CICL’s infrastructure and that of its members, to the point where it now attracts international attention. These have included the following programs:
The Land and Water Management Plan commenced in 2000 which placed an emphasis for any on-farm works to increase water efficiency on-farm, water table and salinity monitoring, and to protect local biodiversity.
The next step in the modernisation process saw the introduction of Total Channel Control (TCC) commencing in 2001 to replace Dethridge wheels. TCC promoted accurate flow measurement, flow control, in-built diagnostics, connection to SCADA network, water tight seals, low maintenance, and enhanced monitoring.
The last of the TCC was installed in 2015 and CICL is the only irrigation entity in Australia to have the benefit of a fully operational, computerised system with in-built precision metering and automated water accounting systems.
WaterSmart was the next phase with the primary objective to increase efficiency of irrigated water usage and crop productivity to realise water savings on-farm.
Further investments and improvements have been ongoing under the government funded Private Irrigator Infrastructure Operators Program (PIIOP).
Water Meters
ANCID “Know The Flow” Project
There are a variety of technologies to measure water flow including: MACE Doppler ultrasonic components Open Flow Propeller Meter diagram Gauge poles were initially used where the level was read by eye from the bank. The flow was then read off the Discharge Chart derived from stream gauging by Hydrographers.
Pressure sensors were introduced which read the water pressure on a submerged sensor. They are subject to drift when they fail and so can give an undetected false reading. “I remember when one drifted at the main offtake and the reading said there was not enough water coming in and the big radial gates were raised. Within a couple of days there was far too much water in the channel system and water spilled over escapes and over banks” a water bailiff recalled.
Accusonic Ultrasonic Time-of-Flight flow measurement is currently used by CICL at its Main Offtake and Tombullen Storage inlet channel.
Propeller Meter
Closed flow propeller meters were fitted into the pipes for the horticulture farms. Suppliers included Badger and Davies Shephard.
Open flow propeller meters were the first device tried to replace the Dethridge Wheel.
These meters were adopted as part of our modernisation upgrades.
Propeller Meter
MACE Doppler Ultrasonic
MACE Doppler ultrasonics use sensors that continuously measure the speed of dirt, bubbles and other particles in the stream flow. MACE Doppler ultrasonic velocity sensors, utilizing MACE Advanced Signal Processing (MASP) technology, look across the entire stream profile to give a true average velocity. These are mostly for use in full pipes or partially full pipes (when used in conjunction with an EchoFlo ultrasonic depth sensor).
Combined Instruments Mag Flow
Combined Instruments Mag Flow utilise the Faraday Effect of when a conductor moves through a magnetic field it results in a current being produced. The amount of current produced is proportional to the velocity of the water flowing through the body of the Mag Flow.
Initial prototypes were a rectangular body that fitted neatly into a Dethridge Wheel concrete emplacement (body). Later versions were a 600mm Internal Diameter (I.D.) round body that bolted on the downstream end of a 600mm I.D. pipe.
Automation and the Future
FlumeGates®
Coleambally introduced the FlumeGate in 2000-2001 as a replacement to the Dethridge Wheel. The Dethridge Wheel replacement works program was completed in 2011.
The FlumeGate is a combined flow measurement and control gate designed to regulate flow in open channels. Accurate flow measurement, precise flow control, power supply and radio telecommunications are fully integrated in a single device.
It is at this point, the FlumeGates measure and control the volume and flow rate of water diverted from the Main Canal onto farms. Solar panels power the FlumeGates and radio communication links each gate in the system to our office. The TCC system has about 1,500 alarms built into it and if one of these are triggered, it results in an SMS message sent to our Channel Technicians. If an alarm occurs after hours, they log onto their computer at home to identify the problem and take appropriate action.
The FlumeGate evolved from the research of internationally renowned in-channel flow researcher, Dr John Replogle. Dr Replogle worked for the US Department of Agriculture and worked out methods to shorten the length of the traditional Parshal Flume, while still retaining the accuracy, and thus reduce the cost of the Parshal Flume.
Coleambally Irrigation is committed to investing in new and improved technologies for both our farmers and the environment.