Pipeline to Prosperity: building infrastructure for Tasmania’s irrigation future

Irrigated agriculture contributes more than 50 per cent of the value of Tasmania’s agricultural production from eight per cent of the land, with the State Government aiming to further grow the farm gate value of the agricultural sector to $10 billion by 2050 through investment in irrigation infrastructure. The Pipeline to Prosperity program is the third tranche of irrigation schemes being delivered by Tasmanian Irrigation consisting of ten proposed projects – eight new schemes and two scheme augmentations. Here, we take a look at the projects, what infrastructure they are proposing and at what stage of development they’re at.

The Pipeline to Prosperity program is looking to deliver ten irrigation projects in the agricultural areas of Tasmania, delivering up to 78,000ML of irrigation water at an estimated capital cost of $496 million.

Phase one includes four new schemes: Don, Fingal, Northern Midlands and Tamar, and one project to augment the existing Sassafras-Wesley Vale scheme. Collectively, the ten potential schemes of the Pipeline to Prosperity program comprise:

• 78,000ML
• 479km pipelines
• Seven dams
• 23 pump stations
• Four power stations

Tranche three builds on Tasmanian Irrigation’s successful delivery of tranche one (ten schemes across 2010-2015) and tranche two (five schemes over 2016-2019). It is jointly funded by the Federal Government, Tasmanian Government and Tasmanian farmers.

Pipeline to Prosperity is expected to create:

• $114 million per annum net present value at the farm gate
• A total of $783 million in economic benefit over the life of the project
• A farm gate benefit to cost ratio of 2.4
• 2,600 full-time jobs
• $150 million on-farm private investment

Tranche three projects: infrastructure and timelines

Don Irrigation Scheme

The Don Irrigation Scheme is the most progressed scheme in tranche three, with the business case now approved. The preferred option is for a 4,750ML/p.a. irrigation scheme in the state’s north-west, providing high reliability water to the area from West Kentish and north to Don Heads, which is famous for its cropping and dairy enterprises. The Forth River Catchment is regarded as the best water source in the area and provide the 95 per cent reliability required for Tasmanian Irrigation schemes.

The scheme has a capital cost of $29.02 million and the design includes two pump stations (one on Lake Barrington and one downstream of Paloona Dam at Forthside) which will pump to balance tanks with distribution to irrigators via a 67km distribution pipeline. The peak flow rate is 41.7ML/day for a 180-day summer irrigation season, with a winter delivery option available in the future if demand is adequate.Water sales closed in June 2020 and 3,225ML worth of contracts have been issued.

The scheme is now in the approvals phase after the preferred option was launched in March 2020 and the tender for design support was expected to be awarded in mid-March 221 to prepare the design to be ready to put out the construction tender. Efforts in early 2020 have been focused on gaining all required approvals to commence construction.

The approval process involves the finalisation of ecological and heritage surveys, geotechnical investigations and local government approval. Once these tasks are complete tenders will be issued for construction. Construction is expected to commence in the first half of 2021, with scheme water available to irrigators for the 2022/23 irrigation season.

Detention Irrigation Scheme (DEIS)

The DEIS proposed for the Waratah-Wynyard Council region is part of the Future Irrigation Project which will inform the development of the Pipeline to Prosperity suite of schemes proposed by Tasmanian Irrigation. The Waratah-Wynyard Council region has a small number of land holdings that provide a range of agriculture products that support dairying, including pasture and cereal crops for stock.

The proposed design for the scheme assumes a minimum 3,000ML of water sales and includes approximately 12-15km of distribution pipeline and a pump station with a 0.4km rising main from the Detention River pumping winter flows to a dam to be constructed on the Alarm River.

This design will provide flexibility to supply irrigators through either a piped supply or riparian release into the Detention River or Wilsons Creek. The concept scheme incorporates an uplift in costs to reflect current pricing and to allow for additional pump stations and pipelines to be installed.

To date there has been insufficient demand expressed to develop a detailed engineering concept design report with the proposed scheme assuming the minimum water sales to proceed. Furthermore, a preliminary water assessment suggests that there may be insufficient water available to support delivery of 3,000 ML in accordance with Tasmanian Irrigation’s irrigator service charter. Further water monitoring will take place to confirm this.

Fingal Irrigation Scheme

The Fingal Irrigation Scheme is proposed for the area along the South Esk River, downstream of Fingal. As one of the state’s drier areas, agriculture is focused primarily on fodder crops, potatoes, seed and poppy production. A major impediment to the expansion of irrigation is the limited availability of water and lack of security supply during the summer months.

The current preferred design option for the scheme is a 12,600ML riparian delivery, South Esk only scheme to allow for future demand and potential augmentation of the scheme to include piped sections (such as St Marys and Royal George) in the future if there is sufficient demand and water availability.

The scheme has a capital cost of $53.6 million and includes a 14,000ML dam located about 12km north of Fingal, a pump station on the South Esk River and 2.3km of dual supply pipeline. It will have a 150-day irrigation season nominally from November through to March annually with water being able to be taken over a 120-day delivery period within this. It is possible that the delivery period can be decreased in order to allow increased flexibility as the scheme progresses through the detailed design phase.

The preferred option was presented for public consultation in September 2020, and development is progressing with flora and fauna and transmission loss assessments taking place in addition to the initial geotechnical investigations conducted in late 2020. Flood modelling and heritage assessments were expected to be conducted in the first half of 2021.

Works for the concept dam design and preliminary geotechnical investigations were conducted in late 2020, with no major issues at the proposed site being found. These works have provided guidance as to the next steps of work required. Additional investigations are underway to confirm quantities of specific construction materials, and will provide greater clarity around the constructability of the dam with the field work portion scheduled to commence in April 2021.

The transmission loss assessment for the South Esk River was completed in early 2021. The aim of having an adaptive model that allows for varying losses dependent on time of year, release volume, base flow and distance from the offtake point will be achieved through a simplified model which is currently being worked through.

The model will likely have set loss rates on a per kilometre basis within each management zone of the river, allowing for simplified seasonal variation. Relevant surveys will be conducted on the pipeline, pump station and any borrow pit areas once better understood in addition to potential gauging weir site investigations which will monitor flows upstream of the proposed pump station site.

Flowerdale Irrigation Scheme

The Flowerdale Irrigation Scheme is proposed for the Waratah-Wynyard Council region and is part of the Future Irrigation Project. The region proposed for the Flowerdale scheme has a moderate number of land holdings that provide a range of agricultural products that support dairying, as well as a number of boutique agricultural services including nurseries and flower farms.

The proposed design includes a pump station with a 0.3km rising main from the Flowerdale River which will pump winter flows to a 4,000ML dam to be constructed on a tributary of the river, and approximately 25km of distribution pipelines. The design has been developed to allow for further development in the region and is sized at 3,000ML/season.

Demand for 1,865 ML/season was indicated from initial Expressions of Interest (EOI) sought in March 2018. The current scheme design indicates an upfront irrigator capital contribution in excess of $2,200/ML and operational charges varying from $195-$295/ML. There is a concern that the scheme costs may impact the viability of the scheme, however, given the extent of uncertainty about the project in its current formative stage, it is considered that additional investigation and design still be pursued.

Harcus Irrigation Scheme

The Harcus Irrigation Scheme is proposed for the Circular Head Council region and is part of the Future Irrigation Project. The region has a small number of large land holdings that provide a range of agricultural products to enable and support dairying. The proposed design includes a pump station with a 5.6km rising main from the Welcome River which will pump winter flows to a 9,000ML dam to be constructed at Jims Plains, and approximately 28.4km of distribution pipelines.

Northern Midlands Irrigation Scheme

The Northern Midlands Irrigation Scheme is proposed for the lower Isis Valley and Macquarie River region to provide additional high reliability water for cropping and will be underpinned by large Hydro Tasmania storages in the state’s central highlands.

The project capital cost is $73.29 million and the proposed design includes three pump stations, two balance tanks, approximately 30 property outlets and 99.7km of HDPE pipe to deliver 76ML/day. The main line is proposed to be constructed from Poatina to short of Ross, and connecting branch lines east of Campbell Town, Powranna, Conara and the Lower Isis Valley.

The scheme will utilise outflows from the Poatina Power Station during the summer months, providing water during the 180-day summer period from October to March. Construction is expected to begin in 2022 with water available in early 2024 and the scheme fully operational by summer 2024-25.

Sassafras Wesley-Vale Irrigation Scheme Augmentation (SWISA)

SWISA will expand the existing Sassafras Wesley-Vale Irrigation Scheme (SWIS) which was developed by Tasmanian Irrigation and commenced operations in the 2011-12 irrigation season. SWIS is committed to supplying 5,660ML to 99 irrigators over a 150-day irrigation season from November to March. In a survey conducted in 2019, 28 existing and 33 new irrigators expressed interest in an additional 5,785ML.

To meet this interest, the proposed SWISA will allow the SWIS to meet the contracted plus requested total water demand of 11,445ML at 76.3ML/day. The capital cost for the project is $57.5 million and condition assessment have been completed on the now 50-year-old ex-Wesley Vale Paper Mill assets, which include the Great Bend pump station and reservoir, and the Wesley Vale rising main and main pipeline, to determine what assets are degraded and need repairs or replacements.

Following assessments, the SWISA project has been split into two distinct interrelated projects: one to rectify and, where necessary, replace the degraded assets, and the other to expand the scheme to meet the demand for new water.

The preferred design option is expected to be approved by August 2021, with water sales to follow soon after. Construction is expected to begin in July 2022 and the first full irrigation season is anticipated to begin in November 2024.

South East Integration Project (SEIP)

The SEIP is part of the Future Irrigation Project and is proposed for the region that is currently serviced by three existing schemes: South East 1 – services by riparian delivery into the Coal River from Craigbourne Dam; South East 2 – takes water from TasWater potable supply or riparian release from Craigbourne Dam into the Coal River and pumping from Richmond into Daisy Banks Dam; and South East 3 – supplied exclusively from TasWater potable supply with an offtake located near Granton.

The existing schemes lack the capacity to cater for the continued growth and increasing demand in the region, prompting concerns about future availability and cost of water from TasWater, and concerns around water quality from the Coal River. The Coal River Valley has a large number of smaller land holdings that generally provide a range of high value agricultural products, typically viticulture, fresh fruit and vegetables etc..

SEIP is investigating options for increasing irrigation water availability in the existing area including new raw water supplies and the potential expansion of the existing irrigation districts into the Derwent and Jordan River Valleys. The project also includes a 7.5km pipeline from the Tea Tree Road Pump Station along Middle Tea Tree Road into Daisy Banks Dam to allow for the interconnection of South East 2 with South East 3.

An expression of interest process for additional irrigation demand for the SEIP concluded in March 2020 and around 300 expressions of interest were received, totalling approximately 33,500ML of water (20,400ML of summer irrigation water, 6,100ML of winter irrigation water and 7,000ML of resume water). Concept designs have been developed to service a majority of expression of interest for raw water.

Preliminary costings indicate a standalone scheme for the Gretna area may be the best option to deliver around 7,000ML. The design for the main South East area is progressing, with the preferred water source appearing to be the lower River Derwent catchment upstream of New Norfolk and a new trunk main extending east to Forcett.

It also includes connections to the existing South East 2 and 3 schemes, and possibly new pipelines in the South East 1 area. Up to 200km of pipelines will potentially be installed. Engineering assessments are underway and the preferred design option is expected to be released for public comment in July with water sales following in December.

Southern Midlands Irrigation Scheme (SMIS)

The SMIS is part of the Future Irrigation Project and will be situated across the Central Highlands and Southern Midlands Council regions. These regions have a significant number of land holdings providing a range of agricultural products including livestock, broadacre cropping, wool, dairy, fruit and wine grapes.

The concept design is based on 30,000ML for a 180-day summer irrigation season and includes a low lift pump station sourcing water from Hydro Tasmania’s upper Derwent catchment supplying the Bothwell region with a lift pump station near Shiners Hill to Jericho and Kempton. There is also potential to supply the Hollow Tree, Elderslie and Broadmarsh areas with additional branch lines.

It also provides an interconnection with the existing Southern Highlands Irrigation Scheme and the potential for connections to the South East Irrigation schemes. Based on expressions of interest sought in March 2018, there is demand for 31,500ML during the summer season. As over 200km of pipeline would be required to service this demand, multiple pipeline routes are being investigated.

Tamar Irrigation Scheme

The Tamar Irrigation Scheme is proposed to service the area east and west of the Tamar River, from Lake Trevallyn to Westwood, Beaconsfield, and from Hillwood, Lilydale, Pipers River and Pipers Brook. Agricultural production in this region includes a range of high quality products such as pasture and cereal crops for stock through to fruit and wine production from orchards and vineyards, as well as boutique agricultural services including nurseries and flower farms.

The preferred design option has a capital cost of $146.2 million for a 12,000ML piped delivery through approximately 240km of pipe based on a 180-day irrigation system with water source from Lake Trevallyn. The design proposes East Tamar irrigators will be supplied via booster pumps for those east of East Arms Road, with a second smaller booster pump planned near Second River Road; West Tamar irrigators will be supplied under gravity pressure from a balance tank; and irrigators on Pipers River to be supplied by riparian deliveries north of Karoola.

Constructability assessments were undertaken in early 2021 and construction is expected to start in September 2022.

Tenders for tranche three works are posted on Tasmanian Irrigation’s website at www.tasmanianirrigation.com.au/contractors-notices.