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. While these rivers are unregulated, 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 2024-25:

• less rainfall was received, catchment inflows were lower, and storage levels peaked and declined at lower levels
• there were more restrictions on licensed diversions from streams
• less water was diverted from the basin for consumptive uses.

Rainfall

In 2024-25, rainfall received in the South Gippsland basin was lower than the previous year. Rainfall was:

• very much below average across the western half of the basin
• below average across most of basin’s east past the Albert River
• average along the basin’s north-eastern tip.

Figure 1 displays the rainfall received in 2024-25 compared to the long-term average (1975-2025).

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.

Key points on compliance against entitlements in 2024-25

Note to increase in total entitlement volume:

• In 2024-25, 550 ML of take and use licence entitlement volume was issued as part of winterfill water set aside in the Central and Gippsland Region Sustainable Water Strategy. There was also 38 ML of licence entitlement volume surrendered.

Note to exceptions to compliance:

• South Gippsland Water reported that the Foster bulk entitlement was non-compliant with passing flow requirements from 31 January to 3 February 2025. Due to infrastructure maintenance operations at Deep Creek Reservoir and the need to protect wildlife within the reservoir at that time, no passing flows were released. Passing flows resumed after this period and no long-term impact on the environment was observed.

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 2024-25, 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