About the area
The Tarwin groundwater catchment is in south-eastern Victoria. Bass Strait forms the catchment's southern boundary.
The Tarwin groundwater catchment contains the Leongatha groundwater management area (GMA) and Tarwin GMA. The area 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 Leongatha.
More information on water management and accounting is detailed in Water explained.
2023-24 overview
Water use
More water was used for consumptive purposes than the previous year.
Climate
Rainfall
Less rainfall was received in the Tarwin groundwater catchment in 2023-24 than the previous year, being below the long-term average across most of the catchment. Rainfall was:
- average in eastern parts of the catchment around Waratah Bay to Gunyah, and the northern tip of Wilsons Promontory
- below average across the central parts of the catchment from Tarwin Lower and Wonthaggi to Leongatha, and the central portion of Wilsons Promontory
- very much below average around the upper reaches of the Tarwin River West Branch, near Kilcunda and southern parts of Wilsons Promontory.
Figure 1 displays the rainfall received in 2023-24 compared to the long-term average (1975-2024).
Figure 1: Rainfall deciles, Tarwin 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 resources are being actively managed. For more detail on management responses, go to on the Southern Rural Water website.
In 2023-24, groundwater level trends for the Leongatha and Tarwin GMAs towards the end of the year were rising and stable, respectively.
Table 1: Groundwater level trends, Tarwin groundwater catchment
Response to water availability
Groundwater restrictions
There were no restrictions on licensed groundwater use in 2023-24, the same as previous year.
Entitlements and use
Groundwater licence and use volumes in the Tarwin 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 Tarwin groundwater catchment was 833 ML, more than the 643 ML used in the previous year.
Entitlement volumes
Rights to water in the Tarwin groundwater catchment are shown below.
Table 2: Groundwater entitlements at 30 June, Tarwin 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 2023-24. Total water available under entitlements is the sum of opening carryover, allocation issued and the net trade in or out of water.
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 usage per bore per year.
More information on groundwater use and availability has been detailed in How we account for
In 2023-24, 833 ML of water was extracted for consumptive purposes, which was more than the 643 ML extracted in the previous year. Of this volume, 245 ML was for non-urban (irrigation) use, and 588 ML was estimated to be for domestic and stock use.
Table 3: Groundwater availability and take, Tarwin groundwater catchment
Management responsibilities
Management of water in the Tarwin groundwater catchment is undertaken by Southern Rural Water.
| Authority | Management responsibilities |
|---|---|
| Southern Rural Water |
|
