About the area
- The Wimmera basin is the largest landlocked river basin in Victoria. The Wimmera River’s 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.
- Average annual rainfall varies across the region from up to about 900 mm in the south to 300 mm in the north. While rainfall is variable, winter is typically the wettest season.
- Dryland broadacre agriculture is the main industry of the region, 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 catchment.
- 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 .
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.
Seasonal determinations
Allocations for the Wimmera-Mallee Pipeline Product reached a higher level than the previous year.
Water use
A similar volume of water was diverted for consumptive purposes to the previous year.
When compared to the previous year, in 2021-22:
- more rainfall was received, catchment inflow was higher and storage levels were slightly higher
- seasonal allocations were higher, reaching 63% allocation
- licensed diversions from the Wimmera River remained unrestricted for the whole year
- a similar volume of water was diverted from the basin for consumptive uses.
Climate
Rainfall
Rainfall in the Wimmera basin was above average in most areas, much higher than the previous year. Rainfall was:
- above average throughout the entire north of the basin down to around Nhill, Horsham, and Navarre
- average in the Grampians National Park and other southern regions.
River basin water balance
In 2021-22, 22,648 ML of water was diverted for consumptive uses: town, domestic and stock, irrigation and commercial supply. This was similar to the 20,607 ML diverted in the previous year. An additional 121 ML was delivered to the environment, about the same as the previous year (124 ML in 2020-21).
Water balance table
The table below shows the total volumes of water available and supplied from water resources in the Wimmera basin in 2021-22.
Table 1: Water balance, Wimmera basin
Storages
Major — greater than 1,000 ML — on-stream storages in the Wimmera basin are included in the water balance.
An estimate of rainfall and evaporation for Green Lake in the Wimmera basin has not been made, as data for this site is not available.
Storage levels
Storage levels in the Wimmera basin were 37% on 30 June 2022.
Higher than the previous year
On 30 June 2021 storage levels were 34% full.
Table 2: Storage levels, Wimmera 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 40% of the long-term average annual volume of 223,100 ML.
Higher inflows received
More inflows received than in the previous year (19% of the long-term average in 2020-21).
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 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 Grampians Wimmera Mallee .
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.
Under GWMWater’s Wimmera and Glenelg rivers bulk entitlement, the water corporation operates the Wimmera–Glenelg system headworks to supply water to towns and customers connected to the Wimmera Mallee Pipeline and to supply entitlements held by Coliban Water, Wannon Water and the VEWH.
The Wimmera–Glenelg system is unique because the headworks harvest water from both the Glenelg and Wimmera river systems, and the volumes supplied to entitlement holders cannot be disaggregated between the two basins. The entitlement volumes and diversions are presented in this Wimmera basin report and are not presented in the Glenelg basin report.
Under GWMWater’s Willaura system bulk entitlement, the water corporation operates the Mt William system in the Wimmera basin to supply water to Willaura and to supply water to Wannon Water for Glenthompson.
Entitlement volumes
Rights to water in the Wimmera basin are shown in table 4 below.
Entitlement volumes represent a maximum 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 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, 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 2021-22. The volume includes carryover from the previous year, seasonal allocations and net trade into the basin.
Water available under entitlements
There was 185,238 ML made available under entitlements in 2021-22, similar to what was available the previous year (170,385 ML).
Water taken under entitlements
There was 41,035 ML taken under entitlements in 2021-22, more than the year before (33,614 ML).
Seasonal allocations
Seasonal allocations for the Wimmera-Glenelg system were higher in 2021-22 than in the previous year. The Wimmera Mallee Pipeline Product began the year with a 0% opening seasonal allocation in July 2021, which reached 57% in December 2021 and ended with a final allocation of 63% in June 2022.
Restrictions on licensed diversions from unregulated rivers
There were no restrictions on licensed diversions from the Wimmera River for 2021-22. In 2020-21, licensed diversions from the Wimmera River were banned for the whole 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, more water was available and taken under entitlements than the previous year.
Table 5: Available water and take, Wimmera 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, and 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.
Total volume diverted
The total volume diverted (41,035 ML) was within the volume available for the year (185,238 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.
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 Wimmera River, a heritage river
- platypus, freshwater catfish and river blackfish
- 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 2021-22, water for the environment in the Wimmera basin comprised:
- the Wimmera and Glenelg Rivers Environmental Entitlement 2010 held by the VEWH, comprising 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 GWMWater
- on licensed diversions
- a supply by agreement with the CEWH under GWMWater’s bulk entitlement comprising 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 27,207 ML of environmental water was used in the Wimmera basin in 2021-22. This volume includes 7,039 ML of passing flows delivered in-stream.
Management responsibilities
Management of water in the Wimmera basin is undertaken by various parties
| Authority | Management responsibilities |
|---|---|
| GWMWater |
|
| Central Highlands Water |
|
| Coliban Water |
|
| Goulburn-Murray Water |
|
| Wimmera Catchment Management Authority |
|
| North Central Catchment Management Authority |
|
| Water supply system | 2021-22 (ML) | 2020-21 (ML) |
|---|---|---|
| Ararat system | 1,607 | 1,745 |
| Borung | 3 | 4 |
| Buangor | 5 | 15 |
| East Grampians system | 195 | 204 |
| Elmhurst | 25 | 18 |
| Glenthompson system | 28 | 40 |
| Horsham system | 3,044 | 3,010 |
| Korong Vale - Wedderburn | 239 | 233 |
| Stawell | 1,394 | 1,432 |
| Wimmera Mallee Pipeline Supply System 1 | 1,744 | 2,078 |
| Wimmera Mallee Pipeline Supply System 2 | 2,936 | 3,071 |
| Wimmera Mallee Pipeline Supply System 3 | 2,071 | 2,153 |
| Wimmera Mallee Pipeline Supply System 4 | 3,221 | 3,426 |
| Wimmera Mallee Pipeline Supply System 6 | 532 | 519 |
| Wimmera Mallee Pipeline Supply System 7 | 265 | 274 |
| Wychitella | 4 | 3 |
