About the area
- The Maribyrnong flows from the foothills of the Great Dividing Range in central Victoria towards the south through Melbourne’s north-western suburbs, joining the Yarra 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.
2021-22 overview
Available water
Catchment inflow was higher than the previous year.
Licensed diversion restrictions
There were fewer restrictions on licensed diversions than the previous year.
Water use
A similar volume of water was used for consumptive purposes to the previous year.
When compared to the previous year, in 2021-22:
- about the same amount of rainfall was received
- catchment inflow and storage levels were higher
- there were fewer restrictions on licensed diversions from unregulated streams
- a similar volume of water was diverted from the basin for consumptive use.
Climate
Rainfall
In 2021-22, rainfall the in Maribyrnong basin was overall similar to the previous year. Rainfall was average in most areas, and above average in the centre from around Sunbury to Tullamarine.
River basin water balance
In 2021-22, 5,411 ML of water was diverted for consumptive uses: town, domestic and stock, irrigation and commercial supply. This was similar to the 5,889 ML diverted in the previous year.
Water balance table
The table below shows the total volumes of water available and supplied from water resources in the Maribyrnong basin in 2021-22.
Table 1: Water balance, Maribyrnong basin
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 64% on 30 June 2022.
Higher than the previous year
Storage levels in the Maribyrnong basin were 40% on 30 June 2021.
Table 2: Storage levels, Maribyrnong 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, the known inflows, and the net change in storage volume.
Below average inflows received
Catchment inflow was 98% of the long-term average of 92,800 ML.
More than the previous year
This is higher than the previous year (64% 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 the environment 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 Greater Western .
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 below.
Entitlement volumes represent a 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 actual 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 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 2021-22. The volume includes carryover from the previous year, seasonal allocations and net trade into the basin.
Water taken
There was 2,761 ML taken under entitlements in 2021-22, similar to the previous year (3,038 ML).
Restrictions on licensed diversions from unregulated streams
In 2021-22, there was a total ban on winter-fill licenses on the Maribyrnong River from November 2021 until the end of June 2022. The rest of the streams were unrestricted for the whole year; this is one less restriction than 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, a similar volume of water was taken under entitlements to the previous year.
Table 5: Available water and take, Maribyrnong basin
Compliance
Compliance against water entitlements is reported for this basin in three areas
- entitlement issued: the volume of entitlements issued in a basin does not exceed formal caps or 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
- bulk entitlement provisions: 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. See note below.
Total volume diverted
The total volume diverted (2,761 ML) was within the volume available for the year (13,743 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.
Note to total entitlement volume:
- A 9 ML registration licence for a small catchment dam was converted to a take and use licence for the same volume.
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 that which contains areas of intact streamside vegetation that provide important habitat for native fish including migratory short-finned eels, common and ornate galaxias, flathead gudgeon, tupong and Australian smelt
- waterbug populations that provide an abundant food source for a significant platypus population in several reaches in the Maribyrnong system.
Environmental water reserve
In 2021-22, water for the environment in the Maribyrnong basin comprised:
- 315 ML of water traded temporarily from rural customers to the VEWH for release to deliver low flows and freshes in the Maribyrnong River in summer and autumn.
- water set aside for the environment through the operation of passing flow conditions:
- on consumptive bulk entitlements held by Western 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 2021-22, a total of 315 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 |
|---|---|
| Melbourne Water |
|
| Greater Western Water (formerly City West Water and Western Water) |
|
| Southern Rural Water |
|
| Water supply system | 2021-22 (ML) | 2020-21 (ML) |
|---|---|---|
| Main integrated system | 1,570 | 2,166 |
