Myalup–Wellington: Water for Growth
Economic development initiative
The Myalup-Wellington project is an industry-led initiative, proposed by Collie Water to reduce salinity in Wellington Dam, Western Australia’s second largest reservoir with a capacity of 185 gigalitres (GL).
It is a significant economic development project involving private proponent Collie Water, the State Government and the Commonwealth, to substantially increase production capacity, create jobs and economic uplift in the under-developed Collie River Irrigation District and Myalup Irrigated Agricultural Precinct.
The project is a major opportunity to help diversify Western Australia’s regional economy through irrigated agriculture. Currently, just 6557 hectares of the available 34 600 hectares of the Collie River, Harvey and Waroona districts are irrigated.
It is proposed that saline water flowing into Wellington Dam be diverted from the Collie River East Branch to a mine void, with that water then treated in a new desalination plant located near Collie. A new, smaller Burekup Weir will be built upstream to enable water delivery to be powered by gravity. Irrigation channels will be replaced with a new pressurised pipe network.
Existing open irrigation channels created in the 1960s will be replaced with a closed pipe network, saving an estimated 15 GL of water per year, currently lost through seepage, leakage or evaporation. The pipe network will replace the open channel system and allow expansion of the area presently under irrigation.
Harvey Water has experience in managing infrastructure projects having completed a $90 million project in 2008 to replace old, leaking channels in the Harvey and Waroona irrigation districts, where over 250 kilometres of networked pipe now delivers water under gravity pressure to irrigators, saving an average of 17 GL per year.
The Myalup-Wellington project also proposes a closed pipeline system from the Collie River Irrigation District to Myalup Irrigated Agricultural Precinct that will reinject water from Wellington Dam into aquifers in the Myalup area to address volume and salinity concerns. Reinjection of stormwater collected in the Harvey Diversion Drain is also proposed.
The Myalup-Wellington project will be subject to all statutory approval processes.
• Up to 14 GL per year of saline water in Collie River East Branch to be diverted into a disused mine void for storage. This will prevent between 60 000 to 110 000 tonnes of salt entering Wellington Dam per year.
• Stored water to be pumped to a newly-constructed 20 GL per year privately-owned desalination plant near Collie with disposal of brine pumped to an ocean outfall using an existing pipeline.
• Up to 10 GL per year of potable water from the desalination plant will be sold into Water Corporation’s Great Southern Towns Water Supply Scheme and stored in Harris Dam.
• New Burekup Weir to be constructed upstream of its current location to provide increased head pressure to enable Wellington Dam water to reach the majority of the Collie River Irrigation District and Myalup Irrigated Agricultural Precinct without the need for staging pumps.
• A closed pipeline system to be built from the new Burekup Weir to replace existing open channels to maintain pressure, prevent seepage, leakage and evaporation and enable monitoring of water usage. The pressurised pipe network will enable the use of high efficiency centre pivots and other technologies instead of flood irrigation.
• Up to 10 000 hectares of commercial softwood reforestation to be targeted in the Collie River South catchment.*
* As part of its Softwood Industry Strategy the Forest Products Commission is targeting Wellington catchment for plantation expansion with 600 hectares already established in 2015-16.