TNCL irrigation infrastructure Modernisation Project

An Irrigation Infrastructure Modernisation Success Story

Trangie-Nevertire Co-operative Ltd

This modernisation and renewal project involved transfer of most of the saved water entitlements to the Australian Government – in return for funding to totally modernise the irrigation infrastructure of the Trangie-Nevertire Co-operative Ltd, both off-farm and on-farm. The results have seen channel conveyance losses reduce from as high as 50% to 7%. On-farm productivity has improved from greater availability of water and installation of a “state of the art” farm irrigation system.

Water previously lost both from the channel system and on-farm is now being used for environmental benefits. Furthermore, the irrigation farmers now have more water available at their farm offtake than pre-project.

Trangie-Nevertire Co-operative Ltd is a member owned Irrigation Scheme that pumps out of the Macquarie River in Central West NSW. Built in the early 1970s, it had reached its use-by date in the middle of the Millennium Drought. There was combined pressure from:

high conveyance losses
a series of low or zero water allocation years
the threat of losing water and members to government buy-backs
ever increasing costs

Subsequently, there was a general realisation among members that it had to modernise to survive.

The first step was to develop a strategic plan from our membership base. This quantified our issues, which led to an application for Commonwealth funds for a modernisation feasibility study.

Furthermore, this study allowed the Co-operative to be one of the initial applicants for Round 1 of the Private Irrigation Infrastructure Operators Program (PIIOP). In May 2010 the Co-operative was granted $115m to modernise its Irrigation Scheme in exchange for 29,889 ML of water savings. These were transferred from its members to the Australian Government for environmental use in the Ramsar listed Macquarie Marshes.

The Modernisation Project had 5 major elements:

1.

Reduction in the earthen channel system from 240 km down to 138 km and retiring 17 members permanently from irrigation.

2.

Rebuilding the remaining 138 kms of channel system, lining 108 kms with Firestone EPDM rubber membrane, and installing a complete Rubicon water gate system, all enclosed within electric exclusion fencing.

3.

Installing a 230 km Stock & Domestic pipeline from the river to all continuing and retiring members’ farms to replace the previous reliance on the channel system.

4.

Modernising the remaining members’ on-farm irrigation infrastructure, with 24 linear move or centre pivot irrigators installed, as well as upgraded field layouts, tailwater return systems and storages.

5.

The water savings in the project came from 4 main areas

1.

The reduction of the original earthen channel length by 40 percent, allowing 17 of our members on poorer irrigation soils to retire from active irrigation and reduce the footprint of the irrigation system substantially.

2.

The lining of 138 kms of rebuilt main channel with EPDM rubber led to a massive reduction in seepage losses, especially where the channel traversed porous soil types and paleo channels closer to the Macquarie River.
EM38 testing and ground truthing confirmed that up to 2 metres of water column per day was being lost to deep drainage in the worst of these prior streams.

Clay lining of such leaky areas had been trialed in the recent past, but the drying and wetting cycle of our summer dominant pumping regime meant the clay kept migrating downstream away from the leaks. The selection of Firestone GeoGard EPDM for the channel liner was a major leap of faith as the product had never been used before on such a large scale in irrigation channels worldwide, but the advice, backup and warranty from Firestone gave the Board the confidence to proceed.

The inclusion of the automated Rubicon Total Channel Control system has substantially increased the level of service of water delivery to the Members, allowing on time and accurate on-farm water supply and measurement.

The combination of the technologies has reduced the channel conveyance losses from a historical average of 25% (range 20% to in excess of 50%) to now 7%. Substantial volumes of rainfall are captured and held in the lined channel sections most winters, often providing the initial pool fills prior to the pumping season commencing.

This has all lead to the remaining members now having more water available to them at the farm gate now than pre-project.

The system can now operate to irrigate even in very low allocation years, as losses are stable and predictable whereas pre-modernisation 25% or greater water allocations were needed to reduce the wet-up loss to tolerable levels.

3.

The Stock and Domestic pipeline system has exceeded all expectations, with over 90% water savings achieved and clean pressurised river water is available to all our members every day of the year. This is in contrast to previously where stock and domestic water was supplied through the earthen channel system, and only when irrigation water was being supplied along each reach.

In years of low or no irrigation allocation such deliveries were either not available or with very high wet up losses that meant thousands of megalitres needed to be pumped to deliver only a couple of hundred megalitres into open dams. Some of these areas have no or only poor quality groundwater, so this has been a huge improvement in livestock health and human amenity especially in drought times.

4.

The on-farm infrastructure upgrades on the remaining member farms have led to both water savings and yield increases on both summer and winter crops grown. Most of these projects were based around replacing traditional furrow surface irrigation with overhead sprinkler centre pivot and linear move irrigators. Water use on the predominant cotton crop under these machines has reduced by around 1 ML per ha while crop yields have risen by 1-2 bales/ha, leading to Water Use Efficiency increases in the order of 30%.

Rotational winter crops have also showed WUE improvements, especially in chickpeas where a surface flood irrigation would often kill the crop from Phytophthora root rot but the sprinkler irrigation allows high yields to be achieved as the application rate can be controlled to prevent waterlogging and accompanying root disease.

Preparing for channel lining

As very few organisations worldwide had attempted a channel lining project of this scale, the Board and our Project Managers (Farrell Coyne Projects) visited other irrigation schemes both in Australia and Spain to assess the products that had been utilised in other projects. A short list of ten liner products and two control systems was drawn up, examined and ranked in a matrix considering longevity, ease and speed of laying, ease of infield repair, fire risk, overall cost and product availability etc. Two liners were chosen to trial lay on 500 metre prepared channel sections, leading to the final choice of the Firestone GeoGard product.

Once the earthworks were completed there were a number of liner installation issues to be solved in the field. These included systems to unroll and place the geofabric underlay and liner in the correct alignment, a system to compensate for the 5% shrinkage that would occur as the EPDM further cured over time, the development of tools to cut the side anchor trenches into the compacted channel bank and techniques to join the rolls and terminate the liner at each in stream control structure.

These issues were all solved over time and by the end of the project the laying team were able to achieve over 2 kilometres of liner laid, joined, anchor trenched and terminated in a day.

The nearby Narromine Irrigation Board of Management was impressed with our liner solution to similar seepage losses in parts of their system, and went on to apply Geo-Gard EPDM to a substantial length of their channel system using the TNCL developed laying system and team as part of their modernisation.

Leading the way for others

There is substantial scope for this channel lining system to be adopted across Australia and worldwide where ever seepage losses in open channels is a significant problem. TNCL has hosted many visits from directors and staff from major Australian irrigation corporations and smaller operators similar to ourselves. All have been impressed with the modernisation package TNCL has achieved, and particularly with the conveyance loss reductions now evident after five irrigation seasons.

The project was largely driven by TNCL Chairman James Winter and Treasurer Tony Quigley, but with strong support and backup from the rest of the Board. All directors completed site inductions which allowed prompt onsite inspections of works when challenges or problems arose to allow solutions to be developed without delaying the project. Strong support from our membership base, upon whose land the works were occurring, also contributed greatly to the project’s success.

An Irrigation Infrastructure Modernisation Success

Innovative Water Management Award

Tight supervision and a great project management team meant that the project was delivered on time and within budget constraints and total administration cost were held to less than 7 percent of the total budget.

The proof of the pudding is in the eating, and this project has exceeded the expectations laid out at its inception by not only reducing channel conveyance losses substantially, but also with a much higher level of service delivery of irrigation water, clean fresh pressurised stock and domestic water available 24/7/365 and increased crop water use efficiency across our members’ farms.

This project was recently recognised at the World Irrigation Forum and International Executive Council held in Bali in September 2019 where it received an ICID Watsave Innovative Water Management Award.