Water availability

There is around 685 GL/yr of water available under allocation limits in the South West region, 60% of which is surface water and 40% groundwater.

There is a high proportion of resources fully allocated particularly in areas with the biggest population growth and economic development pressures. Most of the high-quality groundwater resources from the shallow (Superficial) and mid-depth (Leederville) aquifers along the Swan Coastal Plain between Myalup and Dunsborough are fully allocated or approaching allocation limits.

Groundwater from the deeper South West Yarragadee aquifer is mostly reserved to support the medium to long-term growth of the major urban centres including Greater Bunbury and Busselton. There is no groundwater available for licensing in the Collie groundwater area and only small volumes from the Blackwood groundwater area.

Surface water available in the major dams along the Darling Scarp, including Drakes Brook, Harvey and Wellington dams is fully allocated, and mostly used for the region’s irrigated agriculture districts. Water from Stirling and Harris dams is exported to the Perth-Peel and Great Southern regions respectively for public drinking water supplies. The full allocation limit generally can’t be taken each year from major dams in the South West due to the reduced inflows caused by climate change. The salinity of water from Wellington Dam also currently limits the volume that can be taken for use.

Individual irrigators also take surface water from on-stream dams or direct pumping from rivers in the higher rainfall areas of the South West including around Capel, Donnybrook, Busselton, Augusta–Margaret River, Manjimup and Pemberton. Water demand in these areas is currently focused on a few highly productive catchments and some surface water is available in less developed areas.

Some of the groundwater and surface water that is still available under allocation limits is poor quality, low yielding or is highly variable in yield due to a drying climate.

Call for action:

In some parts of the south-west land division we need to rebalance the volume of water allocated for use with actual groundwater recharge and surface water flows arising from less rainfall and higher temperatures associated with climate change.

Given water sources in the highly-developed areas of the South West are fully allocated and water availability is reducing in a drying climate, meeting the forecast population and economic growth will require improved demand management and/or alternative water sources.

Case Studies

Notes

  • There are approximately 3600 groundwater and surface water licences in the region.
  • The Department of Water and Environmental Regulation (DWER) authorises the taking of groundwater and surface water by granting a water licence under the Rights in Water and Irrigation Act 1914.
  • Not all water taken in the region is used in the region. Water is transferred from Harris and Stirling dams to Great Southern and Perth-Peel regions respectively.
  • Not all of the licensed water entitlement volume is used each year. This is because rainfall limits the amount of surface water available and the water needed for urban areas, mining, industry and agriculture changes from year to year due to seasonal conditions, phases of production and economic factors. In 2016 DWER estimated that around 250 GL of the licensed groundwater and surface water was taken in the South West region.

Data Source

  • Water allocation limit data is from the Department of Water and Environmental Regulation’s Enterprise Data Warehouse and accessed via the Enterprise Information Program reporting tools. Western Australia’s Water Inventory (2014).
  • Western Australia’s water demand by sector for planning regions 2016
  • Water for Growth: Urban (DoW, 2016)