About the area
The Maribyrnong River flows from the foothills of the Great Dividing Range in central Victoria towards the south through Melbourne’s north-western suburbs, joining the Yarra River before flowing into Port Phillip Bay. Major tributaries include Jacksons Creek and Deep Creek.
Annual rainfall in the basin varies from almost 900 mm in the north and west to below 600 mm in the south.
More information on water management and accounting is detailed in Water explained.
2023-24 overview
Available water
Catchment inflow was lower than the previous year.
Licensed diversion restrictions
There were no restrictions on licensed diversions, the same as the previous year.
Water use
About the same amount of water was used for consumptive purposes as the previous year.
When compared to the previous year, in 2023-24:
- less rainfall was received
- catchment inflow and storage levels were lower
- licensed diversion restrictions were the same with no restrictions on licensed diversions from streams
- about the same amount of water was diverted from the basin for consumptive use.
Climate
Rainfall
In 2023-24, rainfall across the Maribyrnong basin was lower than the previous year. Rainfall was:
- below average in the south from Sydenham to Port Phillip Bay and in a small area in the north-west over Jacksons Creek
- average in the rest of the basin.
Figure 1 displays the rainfall received in 2023-24 compared to the long-term average (1975-2024).
Figure 1: Rainfall deciles, Maribyrnong 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, 72% flowed out into the Yarra River in 2023-24.
Water balance table
The table below shows the total volumes of water available and supplied from water resources in the Maribyrnong basin in 2023-24.
Table 1: Water balance, Maribyrnong basin
Major on-stream storages
Major - greater than 1,000 ML - on-stream storages in the Maribyrnong basin are included in the water balance.
Storage levels
Major on-stream storage levels in the Maribyrnong basin were 83% on 30 June 2024.
Lower than the previous year
Storage levels in the Maribyrnong basin were 95% on 30 June 2023.
Table 2: Storage levels, Maribyrnong 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. The long-term average inflow presented has been updated from the previous Victorian Water Accounts, as detailed in Water Explained. The updated long-term average inflow has been applied to this year and the previous year’s volume in this report.
Below average inflows of 47,399 ML were received (53% of the long-term average of 89,900 ML), less than the previous year (236% of the long-term average).
Below average inflows received
Catchment inflow was 53% of the long-term average of 89,900 ML.
Less water received than the previous year
Catchment inflow was lower than the previous year (236% 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 Greater Western Water.
Outflows
Diversions
In 2023-24, 6,177 ML of water was diverted for consumptive uses: town, domestic and stock, irrigation and commercial supply. This was about the same as the 6,424 ML diverted in the previous year.
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, Maribyrnong basin
Entitlements and compliance
Entitlements provide the basis for how water is shared in the basin.
Entitlement volumes
Rights to water in the Maribyrnong basin are shown in Table 4.
Entitlement volumes represent a maximum volume of water 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 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, Maribyrnong 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 2023-24. The volume includes carryover from the previous year, seasonal allocations and net trade into the basin.
Water taken
There was 4,369 ML taken under entitlements in 2023-24, more than the previous year (2,752 ML).
Restrictions on licensed diversions from streams
There were no restrictions on licensed diversions from streams in 2023-24, the same as during the previous year.
Available water and take table
This table shows the volume of available water and the volume taken under entitlements in 2023-24.
More information on available water and take has been detailed in How we account for surface water.
In 2023-24, more water was taken under entitlements than in the previous year.
Table 5: Available water and take under entitlements, Maribyrnong 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.
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 (4,369 ML) was within the volume available for the year (13,636 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. However, a compliance difficulty was reported. See note below.
Note to exceptions to compliance:
- Greater Western Water (GWW) experienced difficulties with one of their monitoring sites. GWW have worked with DEECA to review the Romsey monitoring program and a solution for the issue is currently being implemented.
Water for the environment
Environmental watering sites
Environmental watering sites and environmental values in the Maribyrnong basin that depend on water for the environment include:
- Australian grayling and the Jacksons Creek platypus population
- the upper Maribyrnong catchment, which contains areas of intact streamside vegetation that provide important habitat for native fish, including migratory short-finned eels, common and ornate galaxias, Yarra pygmy perch, flathead gudgeon, tupong and Australian smelt
- waterbug populations that provide an abundant food source for a significant platypus population in several reaches of the Maribyrnong system.
Environmental water reserve
In 2023-24, water for the environment in the Maribyrnong basin comprised:
- 262 ML of water traded temporarily from rural customers to the VEWH for release to deliver low flows and freshes in the Maribyrnong River during June 2024
- water set aside for the environment through the operation of passing flow conditions:
- on consumptive bulk entitlements held by Greater Western Water, Melbourne Water and Southern Rural Water
- on licensed diversions (regulated and unregulated waterways)
- all other water in the basin not allocated for consumptive uses: this water also provides social, recreational and cultural benefits.
Environmental water use
In 2023-24, a total of 262 ML of environmental water was delivered in-stream in the Maribyrnong basin.
Management responsibilities
Management of water in the Maribyrnong basin is undertaken by various parties.
| Authority | Management responsibilities |
|---|---|
| Greater Western Water |
|
| Melbourne Water |
|
| Southern Rural Water |
|
| Water supply system | 2022-23 (ML) | 2023-24 (ML) |
|---|---|---|
| Main integrated system | 1,413 | 3,313 |
