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In this section you will find detailed information, including national overviews and state and regional level assessments, from the 2000-2002 National Land and Water Resources Audit theme assessments.
Water resources - Overview - Victoria
Basin & Surface Water Management Area: Mitchell River (Vic)
Introduction
The Mitchell River Basin extends from the eastern highlands in the north, southwards to Lake Victoria on the coast. The basin is 120 km long and generally 40 km wide, covering an area of 4,873 km2(2% of the State). The Mitchell River originates in the Barry Mountains, and its headwaters are known as the Wonnangatta River. Major tributaries of the Mitchell River include the Wongungarra, Dargo and Wentworth Rivers. Below the confluence with the Wentworth River, the Mitchell River flows through a narrow gorge and into the undulating plains at Glenaladale. It then winds through alluvial flats and drains into Lake King near Bairnsdale. The area south of the eastern highlands to the foothills is heavily timbered and sparsely populated. The central and northern sections of the basin are, for the most part, naturally forested. There are no major storages in the Basin.
Average annual rainfall is greatest in the high country. At elevations of greater than 1,200 m on the Dargo Plains, between 1,200 mm to 1,600 mm of rainfall are received annually. The Wonnangatta River valley receives less than 700 mm and a rain shadow effect results in a mean annual rainfall of 659 mm at the junction of the Wentworth and Mitchell Rivers. Further south at Bairnsdale the annual average rainfall increases to around 702 mm. Snowfalls are a regular occurrence at elevations above 600 m.
The mean annual runoff from the basin is 1,100,000 ML, which represents 5.4% of the total runoff generated in the Stat
The alluvial plains are intensively farmed, the major activities including dairying, grazing and grain production.
Average annual water use within the basin is 11,640 ML; with urban and industrial use representing 22% of the total use, irrigation 75% and rural 3%.
It should be noted that this estimate of water use does not take account of the volume of reclaimed or returned water.
As the area is relatively well endowed with water resources, no water is imported into the Basin.
There are no surface water exports from the Basi
Vital Statistics:
| Area: | 4,873 Km2 |
|---|---|
| Total storage volume: | no data |
| Total surface water use: | 11,640 ML/yr |
| Development category: | MEDIUM DEVELOPMENT |
| Mean annual run-off: | 1,100,000 ML/yr |
A four-class classification system was developed to provide a simple method to communicate the status of the use and allocation of Australia's water resources in relation to sustainable water management.
It is important to recognise that adequately quantifying a sustainable flow regime or sustainable yield and consequent operating rules is a complex matter. State, Territory and scientific agencies continue to develop and apply methods and measures for determining sustainable flow regimes and sustainable yields.
This categorisation provides a general guide only. Please refer to the State and Territory Overview and Technical reports for detail on the analysis methods used.
| Category | Development status | ||
|---|---|---|---|
| 1 | <30% | Low development | |
| 2 | 30 - 70% | Moderate development | |
| 3 | 70 - 100% | Highly developed | |
| 4 | 100% | Overdeveloped |
* Water use as a percentage of sustainable flow regime (surface water) and sustainable yield (groundwater)
PLEASE NOTE:
Sustainable Yield:
While Victoria has a variety of programs under way aimed at identifying, improving and protecting environmental water requirements, the necessary investigations take considerable time and resources.
Given the short time frame of the Audit, it was necessary to make some broad assumptions, and use a variety of approaches, to derive estimates of the sustainable yield for surface water management areas (SWMAs) in Victoria. Consideration was given to environmental water requirements (known and likely), existing user rights, and related social and economic impacts. The reported allocations to the environment represent the water that can currently be maintained or made available in an attempt to meet environmental water requirements.
For surface water management areas in the southern part of Victoria where environmental values could potentially be threatened by further allocations, the sustainable yield was limited to the current allocation volume, pending the outcomes of further detailed investigations of environmental water requirements. In the case of the Mitchell River River, the sustainable yield was limited to the current annual allocation volume, pending the outcomes of the Gippsland Lakes environment study.
The allocation volume was determined as the average diversion that would occur when the existing entitlements within the basin are fully taken up.
In the longer term, there may be further scope for freeing up additional water to improve environmental regimes by improving distribution and water use efficiencies (other options for improving environmental regimes will be considered as part of the Victorian River Health Strategy). In SWMAs where a significant portion of the available resource is committed to a downstream SWMA, there is also potential for trading of entitlements between the two SWMAs. This will result in a change to both the sustainable yield and the environmental allocation in both SWMAs. Trade out of a SWMA would decrease the sustainable yield of the SWMA and a trade of water rights into a SWMA would increase the sustainable yield. However, the sum of the sustainable yields for the two SWMAs would remain unchanged.
PLEASE NOTE:
Categorisation:
The categorisation of SWMAs in terms of the current level of water resource development has been determined with consideration given to the level of allocation and actual diversion of the resource relative to the assessed sustainable yield.
Five development categories have been defined:
Category 1: Low level of development: 0-30% Category 2: Medium level of development: 31-70% Category 3: High level of development: 71-99% Category 3*: Fully developed: 100% Category 4: Over allocated/used resource: >100%
The development category for the Mitchell River Basin has been reported as fully developed (Category 3*) with respect to allocation and as a medium level of development (Category 2) with respect to diversion. The 3* rating for allocation has been assigned, pending the outcomes of the Gippsland Lakes environmental study.
How saline are the surface water resources in the Mitchell River (Vic) surface water management area?
Table: Surface water resource by salinity class.
| Total Volume, Divertible Yield (ML/Yr) | |
|---|---|
| Total volume (ML/yr), DIVERSION | 435,000 |
| <500 mg/l (ML/yr) | 435,000 |
| 500 mg/l (ML/yr) - 1500 mg/l (ML/yr) | no data |
| 1500 mg/l (ML/yr) - 5000 mg/l (ML/yr) | no data |
| 5000 mg/l (ML/yr) - 14000 mg/l (ML/yr) | no data |
| > 14000 mg/l (ML/yr) | no data |
Major water storages
Table: Major water storage areas:
There were no major water storages reported in this area as part of the assessment
Further Information
- View the Victoria Water Resources Assessment 2000 Report
- View the Victoria Water Resources Assessment 2000 Technical Report
- Link to data available for download on the:
- Surface Water Management Areas
- Data from the 1985 Review of Australia's Water Resources and Water Use
- Link to the Map Maker to make a map using this information.
- For more information about water and other natural resource issues link to www.dse.vic.gov.au