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Water resources - Overview - Victoria

Specify a region: -- select region -- Avoca River Barwon River Broken River Bunyip River Campaspe River East Gippsland Glenelg River Goulburn River Hopkins River Kiewa River Lake Corangamite Latrobe River Loddon River Mallee Maribyrnong River Millicent Coast Mitchell River Moorabool River Murray-Riverina Otway Coast Ovens River Portland Coast Snowy River South Gippsland Tambo River Thomson River Upper Murray River Werribee River Wimmera - Avon Rivers Yarra River Gippsland Lachlan Murray Otway Highlands Otways Port Phillip Westernport Avon River East Gippsland (Vic) Glenelg River (Vic) Mallee (Vic) Mid-Murray River (Hume to SA Border) (Vic) Millicent Coast (Vic) Mitta Mitta River Snowy River (Vic) Thomson-Macalister Rivers Upper Murray River (Vic)

Basin & Surface Water Management Area: Portland Coast

Introduction

The Portland Coast Basin encompasses the south western coastal region of Victoria from east of Port Fairy to west of Portland, and covers an area of 3,963 km² (2% of the State). The southern border is formed by the Southern Ocean, into which the many stream systems drain. The major stream networks include the Surry River, Fitzroy River and Darlot Creek, Eumeralla River, and Back Creek and Moyne River. The terrain is generally flat, interrupted now and then by volcanic outcrops.

Rainfall in the basin is generally greater around the coast, averaging 851 mm annually at Portland, but declines to around 750 mm in the north.

The mean annual flow of the basin is 231,000 ML, which is 1.1% of the States total discharge.

The Basin has been mostly cleared for agricultural activities, the dominant ones being sheep for wool and cattle for dairy and beef. Potatoes and orchards are particularly common in the south-east of the SWMA and at Cashmore, to the north of Portland. There are also some areas of cereal cropping, vegetables and vineyards.

Of the 18,200 ML of water used in the Portland Coast Basin, 94% is drawn from the Basins groundwater resources. The remaining 6 % is drawn from the Basins surface water resources and is self extracted for irrigation and rural use.

It should be noted that this estimate of water use does not take account of the volume of reclaimed or returned water.

There are no surface water imports or exports.

Vital Statistics:

Area:	3,963 Km2
Total storage volume:	no data
Total surface water use:	1,100 ML/yr
Development category:	LOW DEVELOPMENT
Mean annual run-off:	231,000 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.

The sustainable yield of the Portland Coast Basin was determined by calculating the total volume of water that can be extracted from the river system (during May to November) such that the degree of change to the natural flow regime is not unacceptable, as defined by the achievement of a rating of 5 for the Hydrology sub-index of the Index of Stream Condition (ISC). This method is described in further detail in the Victorian Technical Report. The yield that was estimated using this approach exceeded the divertible yield of the Portland Coast basin. In recognition of the infrastructure, water quality and financial constraints taken into account in the assessment of the divertible yield, the sustainable yield was limited to the divertible yield of the basin.

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).

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 Portland Coast Basin has been reported as a low level of development (Category 1) with respect to both allocation and diversion.

How saline are the surface water resources in the Portland Coast surface water management area?

Table: Surface water resource by salinity class.

	Total Volume, Divertible Yield (ML/Yr)
Total volume (ML/yr), DIVERSION	11,100
<500 mg/l (ML/yr)	no data
500 mg/l (ML/yr) - 1500 mg/l (ML/yr)	3,996
1500 mg/l (ML/yr) - 5000 mg/l (ML/yr)	7,104
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.