Southern Forests Irrigation Scheme

Page last updated: Thursday, 24 June 2021 - 2:34pm

Please note: This content may be out of date and is currently under review.

The Southern Forests Irrigation Scheme will improve water storage and distribution through a new dam, pipeline and infrastructure. This will allow for the movement and trading of water between farms, to ensure water is optimised productively. It will be owned and operated by the region’s growers.

The scheme follows on from the $3.6 million first stage Water for Food Southern Forests Water Futures project, which investigated new water supply options and increasing water availability to meet productivity expansion plans for the Southern Forests region.

Latest Update - Donnelly River Model Review

The Department of Water and Environmental Regulation (DWER) commissioned an external consultant (Hydrology and Risk Consultants - HARC) to build and calibrate a hydrological model in the Donnelly River area in South West of Western Australia.

The primary intention of the model was to predict the future available water from the Donnelly River to support the development of a proposal that aims to improve water security and water distribution to irrigators in the Manjimup-Pemberton area.

Concerns were raised regarding model methods and streamflow predictions under future climate scenarios.

As a result, the Department of Primary Industries and Regional Development (DPIRD) contracted the CSIRO to prepare the ‘Donnelly River model review’.

Key achievements

  • Southern Forests Irrigation Co-operative Ltd established to own and operate the scheme
  • Federal government has committed $1 million to finalise regulatory approvals and $40 million for construction
  • Over $10 million committed by local growers via the first round water sales complete
  • Department of Water and Environmental Regulation water modelling complete
  • Dam site geotechnical Phase 1 studies complete
  • Hydrological modelling and conceptual pipeline design complete

Irrigation Scheme

The proposed scheme will comprise a 15GL dam located on Record Brook and a 250km pipeline distribution network that will supply water to irrigators who have purchased a water entitlement for the scheme.

Water for the scheme will be of high quality and reliability and will be supplied from peak winter flows in the Donnelly River. The scheme will be designed to ensure that environmental flows within the catchment are retained.

The scheme will be owned and operated by the Southern Forests Irrigation Cooperative Ltd and all scheme water users will be members of the cooperative. Membership will allow for efficient buying, selling and trading of water between properties.

Funds for the $80 million scheme have been committed from three sources: $19 million by the State Government, over $10 million paid by local growers to be part of the scheme, and the almost $40 million by the Federal Government’s National Water Infrastructure Fund. The scheme’s design can be scaled and delivered in stages to accommodate available funding.

Water Efficiency Initiatives

Consideration of how to activate unused water allocations across the Warren-Donnelly area is underway with a draft concept focusing on the Manjimup Brook area being investigated.  If the concept proves feasible, it can potentially be replicated across other catchments providing additional water security and complementing the Southern Forests Irrigation Scheme.

The next steps to refine the concept include:

  • Evaluate water management options for effectiveness and cost
  • Confirm economic benefit of scheme
  • Confirm and resolve water policy and regulation issues with proposed scheme
  • Survey current users for use and storage in the catchment
  • Survey farmers in the catchment as to the potential to increase use and production if water made available
  • Review concept and recommend business case if proposal meets criteria

To view the full report, refer to the 'Preliminary investigation of Effective Licenced Water Use - Manjimup Brook Case Study' under the documents section.

For further information or to be provided with an alternative format please contact Eugene Carew at