About the area
- The Corangamite basin is a landlocked basin in western Victoria. Rivers and streams within the basin terminate in a series of inland lakes, the largest of which is Lake Corangamite. Woady Yaloak Creek is the largest waterway.
- For the purpose of accounting in this basin, the terminal lakes are considered to be outside the basin; i.e. outflow from the basin ends up in the lakes.
- The basin’s annual rainfall ranges from 400-900 mm.
More information on water management and accounting is detailed in Water .
2021-22 overview
Available water
Catchment inflow was similar to the previous year.
Licensed diversion restrictions
There were fewer restrictions on licensed diversions than the previous year.
Water use
About the same amount of water was diverted for consumptive purposes than the previous year.
When compared to the previous year, in 2021-22:
- less rainfall was received, but catchment inflow was similar
- there were fewer restrictions on licensed diversions from unregulated streams
- about the same amount of water was diverted for consumptive purposes.
Climate
Rainfall
In 2021-22, rainfall in the Corangamite basin was average across the entire basin, lower than the previous year.
River basin water balance
The Corangamite basin received above average catchment inflows (227,057 ML received, 262% of the long-term average of 86,800 ML). This was similar to the previous year.
In 2021-22, 2,973 ML was diverted for consumptive uses: town, domestic and stock, irrigation and commercial supply; about the same as the previous year (3,077 ML).
Water balance table
The table below shows the total volumes of water available and supplied from water resources in the Corangamite basin in 2021-22.
Table 1: Water balance, Corangamite basin
Catchment inflow
Catchment inflow represents the volume of water flowing into the waterways of a basin. It is calculated to be the difference between the total outflows and the known inflows.
The amount of water flowing from the Corangamite basin into the Ramsar-listed Western District Lakes represented 99% of the total inflows in 2021–22.
Above average inflow received
Catchment inflow was 262% of the long-term average annual volume of 86,800 ML.
A similar volume of water received to last year
Catchment inflow was similar to the previous year (245,512 ML, 283% of the long-term average in 2020-21).
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 now 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 Barwon and Wannon .
Small catchment dams
Water harvested, used and lost by small catchment dams (farm dams) is included in the water balance.
Table 2: Small catchment dams, Corangamite basin
Entitlements and compliance
Entitlements provide the basis for how water is shared in the basin.
Entitlement volumes
Rights to water in the Corangamite basin are shown in table 3 below.
Entitlement volumes represent a maximum volume that can be taken in a one-year period. The volume available in a particular year is dependent on the rules for allocating water set out in the entitlement and the seasonal conditions in that year, which varies. The rules for allocating water under an entitlement can differ between entitlements and systems. This affects the ability and likelihood of water being taken in a particular year.
Table 3: Annual entitlement volumes at 30 June, Corangamite basin
Available water and take under entitlements
Total water available under entitlements represents the volume of water that was available to be taken by entitlement holders in 2021-22. The volume includes carryover from the previous year, seasonal allocations and net trade into the basin.
Water taken
There was 1,004 ML used in 2021-22, about the same as the year before (1019 ML).
Restrictions on licensed diversions from unregulated streams
There were no restrictions on licensed diversions from unregulated streams in 2021-22; one fewer restriction than in the previous year.
Available water and take table
This table shows the volume of available water and the volume taken under entitlements in 2021-22.
More information on available water and take has been detailed in the How do we account for surface section on the How do we account for water page.
In 2021-22, about the same amount of water was taken under entitlements as the previous year.
Table 4: Available water and take, Corangamite basin
Compliance
Compliance against water entitlements is reported for this basin in two areas:
- entitlement issued: the volume of entitlements issued in a basin does not exceed formal caps, and has not increased without appropriate approvals
- water taken: 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.
Total entitlement volume
There was no net increase in the total entitlement volume from the previous year.
Total volume diverted
The total volume diverted (1,004 ML) was within the volume available for the year (4,743 ML).
Water for the environment
Environmental watering sites
There are no environmental entitlements in the Corangamite basin, so no active environmental watering occurs.
However, important sites and environmental values in the Corangamite basin that depend on water for the environment include:
- the Western District Lakes, including lakes Corangamite, Gnarpurt, Milangil, Terangpom, Beeac, Colongulac and Cundare, which are internationally significant wetlands listed under the Ramsar Convention and which rely on freshwater inputs from the Corangamite basin to function ecologically
- wetlands of national importance including the Kooraweera Lakes, Lough Calvert, Lake Thurrumbong and Cundare Pool
- native fish populations and the Corangamite water skink.
Environmental water reserve
In 2021-22, water for the environment in the Corangamite basin comprised:
- water set aside for the environment through the operation of passing flow conditions on licensed diversions
- all other water in the basin not allocated for consumptive use: this water also provides social, recreational and cultural benefits.
Management responsibilities
Management of water in the Corangamite basin is undertaken by various parties
| Authority | Management responsibilities |
|---|---|
| Southern Rural Water |
|
| Barwon Water |
|
| Central Highlands Water |
|
| Wannon Water |
|
| Corangamite Catchment Management Authority |
|
