About the area
The West Port Phillip Bay groundwater catchment extends to the north and west of Melbourne, covering its western suburbs, part of Geelong, and the Bellarine Peninsula.
The West Port Phillip Bay groundwater catchment contains the Cut Paw Paw groundwater management area (GMA), Lancefield GMA, Merrimu GMA, and Deutgam water supply protection area (WSPA). The geographical area within the catchment containing licensed entitlement that is not covered by these is reported as outside management units.
Groundwater resources within the catchment supply licensed entitlements, domestic and stock use, and urban use to Blackwood, Lancefield, and Romsey.
More information on water management and accounting is detailed in Water explained.
2024-25 overview
Urban supply
Groundwater supplied to 3 towns in the catchment.
Water use
More water was used for consumptive purposes than the previous year.
Climate
Rainfall
Rainfall received in the West Port Phillip Bay groundwater catchment in 2024-25 varied but was overall similar to the previous year, ranging from close to very much below the long-term average across the catchment. Rainfall was:
- average in most of the catchment’s south around Geelong
- below average across most of the catchment
- very much below average along parts of the catchment’s northern boundaries.
Figure 1 displays the rainfall received in 2024-25 compared to the long-term average (1975-2025).
Figure 1: Rainfall deciles, West Port Phillip Bay groundwater catchment
Sourced from the Australian Bureau of Meteorology
Groundwater level trends
In the Accounts, groundwater level trends for groundwater management units (GMUs) have been determined by monitoring data from key bores in the State Observation Bore Network. Trend determinations are made quarterly by comparing each reading to a previous reading in the same season 5 years prior; for example, a summer record is compared to the summer record from 5 years earlier to account for seasonality. These trends are shown in Table 1 below.
Groundwater level trends reporting in the Accounts does not necessarily represent the status of the resource for management purposes. Groundwater resources are actively managed by rural water corporations. For more detail on management responses, go to Groundwater on the Southern Rural Water
In 2024-25, the groundwater level trends for the Merrimu GMA and Deutgam WSPA were stable towards the end of the year. Whereas the trend for the Lancefield GMA was declining towards the end of the year.
There are insufficient state observation bores in the Cut Paw Paw GMA to adequately define the groundwater resource or changes to the resource over time.
Table 1: Groundwater level trends, West Port Phillip Bay groundwater catchment
Response to water availability
Groundwater restrictions
In 2024-25, licence holders in the Deutgam WSPA were restricted to 50% of their licence volume, whereas no restrictions were in place during the previous year.
Entitlements and use
Groundwater licence and use volumes in the West Port Phillip Bay groundwater catchment are shown below. Domestic and stock use does not require a licence, so in the Groundwater availability and take table (Table 3), these rows only report water taken.
The licensed volume used under entitlements must not exceed the volume made available to individual licensed entitlement holders. We report on compliance in the GMU local reports and in the Statewide groundwater summary.
Water used
Use in the West Port Phillip Bay groundwater catchment was 3,346 ML, more than the 2,574 ML used in the previous year.
Entitlement volumes
Rights to water in the West Port Phillip Bay groundwater catchment are shown below.
Table 2: Groundwater entitlements at 30 June, West Port Phillip Bay groundwater catchment
Available water and take
The table below shows the total water available and taken under entitlements, and estimated domestic and stock use in 2024-25. Total water available under entitlements is calculated as the sum of: opening carryover from the prior year (where available), allocation issued during the reporting year, and the net trade in or out of water, across all entitlements. The level of allocation issued is reduced if there are any restrictions in place.
Estimated domestic and stock use is calculated based on an assumed usage per registered bore per year. In this catchment, the assumed usage is 1.5 ML per bore per year.
More information on groundwater use and availability has been detailed in How we account for .
In 2024-25, 3,346 ML of water was extracted for consumptive purposes, which was similar to the 2,574 ML extracted in the previous year. Of this volume, 1,707 ML was for non-urban (irrigation) use, 133 ML was for urban use, and 1,506 ML was estimated to be for domestic and stock use.
Table 3: Groundwater availability and take, West Port Phillip Bay groundwater catchment
Management responsibilities
Management of water in the West Port Phillip Bay groundwater catchment is undertaken by Southern Rural Water.
| Authority | Management responsibilities |
|---|---|
| Southern Rural Water |
|
