South Gippsland

The major rivers of the South Gippsland basin are broadly south-flowing and include the Bass, Powlett, Tarwin, Franklin, Agnes, Albert and Tarra rivers. All of these rivers are unregulated, although the Tarwin and Powlett catchments have on-stream storages for domestic water supply.

The basin's rivers flow from the Strzelecki and Hedley ranges through productive agricultural land as well as areas of high conservation value, including Wilsons Promontory and Tarra Bulga National Park.

Mean annual rainfall ranges from below 600 mm in the east of the basin to above 900 mm across most of the basin.

The desalination plant near Wonthaggi produces desalinated water that is transferred into Cardinia Reservoir. The accounting for this is included in the Yarra Basin.

More information on water management and accounting is detailed in Water explained.

When compared to the previous year, in 2022-23:

• more rainfall was received, catchment inflows were higher and storage levels peaked and declined at higher levels
• there was a similar level of restrictions on licensed diversions from unregulated streams
• more water was diverted from the basin for consumptive uses.

Rainfall

In 2022-23, rainfall in the South Gippsland basin in some regions was above to very much above the long-term average, and higher than the previous year. Rainfall was:

• very much above average in the north-west around Candowie Reservoir
• above average in the central-north and central-west around Inverloch, Foster and Gunyah
• average across the rest of the basin.

Figure 1 displays the rainfall received in 2022-23 compared to the long-term average (1975-2023).

Wastewater treatment plants

Water treated at wastewater treatment plants can be used to supplement water available in the basin. Water discharged to waterways from treatment plants is included as an inflow to the water balance.

Information on treatment plants is reported in the water supply local reports for the water corporation responsible for managing the plant.

In this basin, wastewater treatment plants are managed by Gippsland Water, South Gippsland Water and Westernport Water.

Compliance

Compliance against water entitlements is reported for this basin in 3 areas:

• entitlement issued: that the volume of entitlements issued in a basin does not exceed formal caps, and has not increased without appropriate approvals
• water taken: that the volume of water taken during the year does not exceed the volume considered to be available for consumptive and/or in-stream use during that year
• bulk entitlement provisions: that holders of entitlements do not breach any provisions that are documented in their bulk entitlement orders.

Notes on the increase in entitlement volume:

• An update was made in the Victorian Water Register to the location of 31 ML of licensed small catchment dam volumes from the Bunyip to the South Gippsland basin.
• There was also 2 ML of take and use licensed volume cancelled during the year.

Environmental watering sites

There are no environmental entitlements in the South Gippsland basin, so no active environmental watering occurs. 

However, important sites and environmental values in the South Gippsland basin that depend on water for the environment include:

• the Bald Hills Wetland, which is a rehabilitated wetland complex of the once extensive floodplains of the Tarwin River system that supports rare and intact vegetation communities in a largely agricultural environment
• the Bunurong Coast wetlands, which provide habitat connectivity with the marine and estuarine systems
• Corner Inlet and Western Port, which are listed as internationally significant wetlands under the Ramsar Convention and rely on freshwater inputs from the South Gippsland basin to function ecologically
• the Australian grayling population, listed in the Commonwealth Environmental Protection and Biodiversity Conservation Act 1999 and the Victorian Flora and Fauna Guarantee Act 1988, whichalso relies on water for the environment.

Environmental water reserve

In 2022-23, water for the environment in the South Gippsland basin comprised:

• water set aside for the environment through the operation of passing flow conditions:
  • on consumptive bulk entitlements held by Gippsland Water and South Gippsland Water
  • on licensed diversions
• all other water in the basin not allocated for consumptive uses: this water also provides social, recreational and cultural benefits.

Management of water in the South Gippsland basin is undertaken by various parties