About the area
The Otway Coast basin is in south-west Victoria. It encompasses the numerous small creeks and rivers that flow to the coast from the Otway Ranges, the largest being the Gellibrand and Curdies rivers.
Annual rainfall in the basin ranges from below 600 mm in the eastern-most extent to over 1,200 mm in the elevated south around Cape Otway.
The moderate to steep forested Otway Ranges dominate the centre of the basin, while the remainder is largely covered by cleared farmland.
More information on water management and accounting is detailed in Water explained.
2024-25 overview
Available water
Less water was available than the previous year.
Licensed diversions restrictions
There were more restrictions on licensed diversions than the previous year.
Water use
A similar amount of water was diverted for consumptive purposes to the previous year.
When compared to the previous year, in 2024-25:
- more rainfall was received; however, catchment inflow was lower
- storage levels ended the year higher
- there were more restrictions on licensed diversions from streams
- a similar amount of water was diverted from the basin for consumptive uses.
Climate
Rainfall
In 2024-25, rainfall received in the Otway basin was higher than the previous year. Rainfall was:
- very much below average across most of the basin’s western half
- below average near Port Campbell and across most of the basin’s north-east
- average in the basin’s far north-east towards Geelong.
Figure 1 displays the rainfall received in 2024-25 compared to the long-term average (1975-2025).
Figure 1: Rainfall deciles, Otway Coast basin
Sourced from the Australian Bureau of Meteorology
River basin water balance
This section describes the known and estimated inflows, outflows and change of storage volumes in the basin.
More detail on major on-stream storages, catchment inflows, diversions and small catchment dams can be found in the sections below the water balance.
Of the total inflows in 2024-25, 93% flowed out to the Bass Strait.
Water balance table
The table below shows the total volumes of water available and supplied from water resources in the Otway Coast basin in 2024-25.
Table 1: Water balance, Otway Coast basin
Major on-stream storages
Major - greater than 1,000 ML - on-stream storages in the Otway Coast basin are included in the water balance.
Storage levels
Storage levels in the Otway Coast basin were 57% on 30 June 2025.
More than the previous year
Storage levels were 34% on 30 June 2024.
Table 2: Storage levels, Otway Coast basin
Inflows
Catchment inflow
Catchment inflow represents the volume of water flowing into the waterways of a basin. It is calculated as the total outflows and change in storage minus the known inflows.
Below average inflows of 343,009 ML were received (45% of the long-term average of 764,200 ML), less than the previous year (71% of the long-term average).
Below average inflow received
Catchment inflow was 45% of the long-term average of 764,200 ML.
Less water received than the previous year
Inflows received were lower than the previous year (71% of the long-term average).
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 Barwon Water and Wannon Water.
Outflows
Diversions
In 2024-25, 18,645 ML of water was diverted for consumptive uses: town, domestic and stock, irrigation and commercial supply, similar to the previous year (19,601 ML).
Small catchment dams
Water harvested, used and lost by small catchment dams (farm dams) is included in the water balance.
Table 3: Small catchment dams, Otway Coast basin
Entitlements and compliance
Entitlements provide the basis for how water is shared in the basin.
Entitlement volumes
Rights to water in the Otway Coast basin are shown in Table 4.
Entitlement volumes represent an indication of a maximum volume of water that can be taken or allocated in any one year depending on the rules of the entitlement. The volume available in a particular year is dependent on the rules for allocating water set out in the entitlement, the seasonal conditions in that year and how much water was carried over from the previous year, which can vary. The rules for allocating water under an entitlement differ between entitlements and systems. This affects the ability and likelihood of water being taken in a particular year.
Table 4: Annual entitlement volumes at 30 June, Otway Coast 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 2024-25. The volume includes seasonal allocations and net trade into the basin.
Water taken
There was 16,320 ML used in 2024-25, similar to the previous year (17,043 ML).
Restrictions on licensed diversions from streams
- There were 4 stream sections with bans or restrictions on licensed diversions in 2024-25.
- Carlisle River and Curdies River both had bans on licensed diversions between January and May 2025, with licensed diversions from Love Creek also restricted between March and May 2025.
- Kennedys Creek had a ban on licensed diversions only in July 2024.
- During the previous year, there was a peak of 2 bans in place in Feburary 2024 for Kennedys Creek and Curdies River.
Available water and take table
This table shows the volume of available water and the volume taken under entitlements in 2024-25.
More information on available water and take has been detailed in How we account for surface
In 2024-25, a similar volume of water was taken under entitlements to the previous year.
Table 5: Available water and take under entitlements, Otway Coast basin
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
Total entitlement volume
There was no net increase in the total entitlement volume from the previous year.
Total volume diverted
The total volume diverted under entitlements (16,320 ML) was within the volume available for the year (34,842 ML).
Individual bulk entitlements
No individual bulk entitlement holder took more than the annual volume made available to them.
Exceptions to compliance
Individual bulk entitlement holders complied with all provisions in their entitlements.
Water for the environment
Environmental watering sites
There are no environmental entitlements in the Otway Coast basin, so no active environmental watering occurs.
However, important sites and environmental values in the Otway Coast basin that depend on water for the environment include:
- Aire River (a heritage river) including the nationally significant Lower Aire wetlands and the state-significant Aire River estuary, Elliot River, Parker River, Grey River, Carisbrook Creek and Smythes Creek, which are ecologically healthy waterways, and lakes Costin and Craven
- native fish communities (such as river blackfish and Australian grayling) and their habitats (such as river reaches with remnant riparian vegetation); endangered, flow-dependent ecological vegetation classes including estuarine wetland and swamp scrub; the native bird population including the great egret (a Victorian endangered species), Cape Barren goose and Australasian bittern; native mammals including platypus and swamp antechinus; and macroinvertebrate communities in Elliot River, St Georges River and Wye River.
Environmental water reserve
In 2024-25, water for the environment in the Otway Coast basin comprised:
- water set aside for the environment through the operation of passing flow conditions:
- on consumptive bulk entitlements held by Barwon Water and Wannon 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 responsibilities
Management of water in the Otway Coast basin is undertaken by various parties
| Authority | Management responsibilities |
|---|---|
| Barwon Water |
|
| Corangamite Catchment Management Authority |
|
| Southern Rural Water |
|
| Wannon Water |
|
| Water supply system | 2023-24 (ML) | 2024-25 (ML) |
|---|---|---|
| Apollo Bay | 476 | 273 |
| Colac system | 3,958 | 3,272 |
| Lorne | 384 | 397 |
| Otway system | 9,651 | 10,055 |
