About the area
The Wimmera basin covers a large area of western Victoria. The main river in the basin is the Wimmera River and its headwaters are near Mount Cole in the Pyrenees Ranges. The river flows westwards across the foothills of the Grampians, and at Horsham, it turns north and flows for about 150 km, terminating at Lake Hindmarsh. Other rivers in the basin include the Avon and Richardson rivers. Originating in the Pyrenees Ranges, the Avon River flows northwards and joins the Richardson River, which terminates in Lake Buloke.
Average annual rainfall varies across the basin from over 600 mm in the south to below 300 mm in the north. While rainfall is variable, winter is typically the wettest season.
Dryland broadacre agriculture is the main industry within the basin, with the production of cereal, oilseed and pulse grains. Dryland livestock production is also significant. A small amount of irrigation occurs for pasture production and there is some horticulture in the basin.
The Wimmera-Mallee Pipeline carries water across the basin for agricultural, environmental and domestic and stock uses.
More information on water management and accounting is detailed in Water explained.
2024-25 overview
Available water
Catchment inflow was lower than the previous year.
Licensed diversion restrictions
There were more restrictions on licensed diversions than the previous year.
Seasonal determinations
Allocations for the Wimmera-Mallee Pipeline Product reached 19%, lower than the previous year.
Water use
More water was diverted for consumptive purposes than the previous year.
When compared to the previous year, in 2024-25:
- less rainfall was received, catchment inflow was lower and storage levels were lower
- there were more restrictions on licensed diversions from streams
- seasonal allocations were lower, reaching 19% allocation
- more water was diverted from the basin for consumptive uses.
Climate
Rainfall
In 2024-25, rainfall received in the Wimmera basin was lower than the previous year. Compared to the long-term average (1975-2025), rainfall was:
- the lowest on record throughout most of the basin’s central regions, encompassing Horsham, Warracknabeal and Hopetoun
- very much below average over the remaining regions south of Underbool
- below average in the basin’s far north around Ouyen, and the eastern boundary near Wycheproof.
Figure 1 displays the rainfall received in 2024-25 compared to the long-term average.
Figure 1: Rainfall deciles, Wimmera 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, 17% were outflows to Lake Buloke and Lake Hindmarsh.
Water balance table
The table below shows the total volumes of water available and supplied from water resources in the Wimmera basin in 2024-25.
Table 1: Water balance, Wimmera basin
Major on-stream storages
Major — greater than 1,000 ML — on-stream storages in the Wimmera basin are included in the water balance.
Storage levels
Storage levels in the Wimmera basin were 43% on 30 June 2025.
Lower than the previous year
On 30 June 2024 storage levels were 66% full.
Table 2: Storage levels, Wimmera 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 27,319 ML were received (13% of the long-term average of 207,800 ML), lower than the previous year (30% of the long-term average).
Below average inflows received
Catchment inflow was 13% of the long-term average annual volume of 207,800 ML.
Less water received than the previous year
Catchment inflow was lower than the previous year (30% of the long-term average in 2023-24).
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 Grampians Wimmera Mallee Water.
Outflows
Diversions
In 2024-25, 26,154 ML of water was diverted for consumptive uses: town, domestic and stock, irrigation and commercial supply. This was more than the 19,531 ML diverted in the previous year, mainly due to the increase in urban diversions and water supplied to recreational lakes. Less water was estimated to have been used by small catchment dams.
An additional 293 ML was delivered to the environment, about the same as the previous year (269 ML in 2023-24).
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, Wimmera basin
Entitlements and compliance
Entitlements provide the basis for how water is shared in the basin.
Entitlement volumes
Rights to water in the Wimmera 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, Wimmera 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 carryover from the previous year, seasonal allocations and net trade into the basin.
Water available under entitlements
Seasonal allocations reached 19%, lower than the previous year (87% in 2023-24).
Water taken under entitlements
There was 50,779 ML taken under entitlements in 2024-25, more than the previous year (34,840 ML).
Seasonal allocations
The Wimmera Mallee Pipeline Product began the year with a 3% opening seasonal allocation in July 2024 and reached 19% in April 2025. This was lower than the previous year which ended at a final allocation of 87%.
Restrictions on licensed diversions from streams
- There was a ban on licensed diversions from the Wimmera River for the entirety of 2024-25.
- During the previous year the Wimmera River had a restriction on licensed diversions in July 2023 and was unrestricted for the rest of the year.
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, more water was taken under entitlements than the previous year.
Table 5: Available water and take under entitlements, Wimmera 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 (50,779 ML) was within the volume available for the year (227,197 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 except one. See note below.
Note to exceptions to compliance:
- Grampians Wimmera Mallee Water (GWMW) reported one compliance failure for the Willaura, Elmhurst and Buangor System Bulk Entitlement, due to water extraction outside the permitted period of take listed. Approximately 40 ML of surface water was extracted from Mt William Creek and Stony Creek between January and May 2025, as an emergency response and replacement of water used for firefighting.
Water for the environment
Environmental watering sites
Environmental watering sites and environmental values in the Wimmera basin that depend on water for the environment include:
- the regionally threatened populations of native fish — river blackfish, southern pygmy perch and mountain galaxias — and platypus (of which there are believed to be less than 10, with this the only population in the catchment) in the MacKenzie River
- the Wimmera bottlebrush (Melaleuca wimmerensis, formerly known as Callistemon wimmerensis) which is listed as threatened under the Flora and Fauna Guarantee Act 1988 (the FFG Act) and as critically endangered under the Environmental Protection and Biodiversity Conservation Act 1999; this species depends on flows in the MacKenzie River for its survival and recruitment
- the lower Wimmera River, which is listed under the Heritage Rivers Act 1992 and which flows into Lake Hindmarsh (listed as a nationally significant wetland) and Lake Albacutya (a Ramsar-listed wetland). It contains Victoria’s only self-sustaining population of freshwater catfish (which is an FFG-Act-listed species). The Wimmera River also contains stocked populations of Murray cod and silver perch, which are both FFG-Act-listed species.
Environmental water reserve
In 2024-25, water for the environment in the Wimmera basin comprised:
- the Wimmera and Glenelg Rivers Environmental Entitlement 2010 held by the Victorian Environmental Water Holder (VEWH), which includes 40,560 ML of high-reliability entitlement shared with the Glenelg basin, 1,000 ML of entitlement for wetlands supplied from the Wimmera Mallee Pipeline and 1,000 ML of unregulated flow in the Avon-Richardson Rivers to be used to maintain the weir pool at the Rich-Avon Weir
- water set aside for the environment through the operation of passing flow conditions:
- on consumptive bulk entitlements held by Grampians Wimmera Mallee Water
- on licensed diversions
- a supply by agreement with the Commonwealth Environmental Water Holder under Grampians Wimmera Mallee Water’s bulk entitlement, which includes 28,000 ML of low-reliability entitlement
- all other water in the basin not allocated for consumptive uses: this water also provides social, recreational and cultural benefits.
Environmental water use
A total of 13,317 ML of environmental water was used in the Wimmera basin in 2024-25 (including 1,301 ML of passing flows). 13,216 ML was delivered in-stream and the remaining 101 ML was diverted off-stream to wetlands.
Additional water supplied under the shared Wimmera and Glenelg Rivers Environmental Entitlement 2010 was used in 3 other basins:
- Glenelg basin: 13,406 ML (including 1,301 ML of passing flows)
- Avoca basin: 11 ML diverted off-stream to wetlands
- Mallee basin: 181 ML diverted off-stream to wetlands.
The breakdown per basin of the volume delivered to wetlands in the Wimmera, Avoca and Mallee basins is based on VEWH’s 2024-25 Seasonal Watering Plan and Reflections reports. The exact breakdown is not measured per basin and so this volume is an estimate. The total volume delivered to wetlands is known (293 ML).
Management responsibilities
Management of water in the Wimmera basin is undertaken by various parties
| Authority | Management responsibilities |
|---|---|
| Central Highlands Water |
|
| Goulburn-Murray Water |
|
| Grampians Wimmera Mallee Water |
|
| North Central Catchment Management Authority |
|
| Wimmera Catchment Management Authority |
|
| Water supply system | 2023-24 (ML) | 2024-25 (ML) |
|---|---|---|
| Ararat system | 1,642 | 1,869 |
| Borung | 3 | 4 |
| Buangor | 15 | 29 |
| East Grampians system | 194 | 231 |
| Elmhurst | 22 | 32 |
| Glenthompson system | 17 | 31 |
| Horsham system | 3,035 | 3,312 |
| Korong Vale - Wedderburn | 165 | 359 |
| Stawell | 1,261 | 1,694 |
| Wimmera Mallee Pipeline Supply System 1, 2 & 7 | 4,884 | 5,583 |
| Wimmera Mallee Pipeline Supply System 3 | 2,010 | 2,138 |
| Wimmera Mallee Pipeline Supply System 4 | 3,302 | 3,376 |
| Wimmera Mallee Pipeline Supply System 6 | 547 | 769 |
| Wychitella | 2 | 4 |
