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Melbourne

                                                                                                   

Physical Information

                             

This page provides details about the region, its water resources, land use and water-related infrastructure.

 

General Description

Area: 11,723 km²
Population: Approximately 4 million in June 2009 (Australian Bureau of Statistics, 2010)

The Melbourne region is located in the southeast of mainland Australia (Figure P.1). It is the second largest metropolitan area in Australia and is home to over 73% of Victoria's population (Australian Bureau of Statistics, 2010).

Figure P.1 Location map of the Melbourne region within Australia

Figure P.1 Location map of the Melbourne region within Australia

 

The Melbourne region, shown in Figure P.2, extends from the coastlines of Port Phillip Bay, Westernport Bay and Bass Strait to the south, the Yarra and Dandenong ranges in the east, and the Great Dividing Range to the north and west.

The Melbourne region includes the:

  • Yarra River catchment
  • Bunyip River catchment
  • Maribyrnong River catchment
  • Werribee River catchment.

Figure P.2 Contextual map of the Melbourne region

Figure P.2 Contextual map of the Melbourne region

 

Yarra River Catchment

Catchment area: 4,110 km2. The Yarra catchment begins on the southern slopes of the Great Dividing Range. It flows through Yarra Valley and metropolitan Melbourne into Port Phillip Bay. The upstream catchment is forested and is the source of much of the region's water supply.

 

Bunyip River Catchment

Catchment area: 4,078 km2. The catchment lies to the east and south of Port Phillip Bay, and takes in the south-eastern suburbs of Melbourne and the Mornington Peninsula. It extends from Western Port Bay in the south to the eastern highlands in the north. It contains several river systems: Patterson River; Cardinia and Toomuc Creeks; Bunyip and Tarago Rivers; and Yallock Creek and Lang Lang River.

 

Maribyrnong River Catchment

Catchment area: 1,452 km2. The headwaters are located approximately 70 km north of central Melbourne, near the towns of Lancefield and Macedon. The upstream catchment is primarily rural while the downstream reaches flow through suburban Melbourne before joining the Yarra River estuary just upstream of Port Phillip Bay.

 

Werribee River Catchment

Catchment area: 1,978 km2. It is located to the west of Melbourne. The Werribee River and Lerderderg River meet upstream of Melton Reservoir and the rivers flow through Werribee before entering Port Phillip Bay.

Figure P.3 Map of surface water catchments in the Melbourne region

Figure P.3 Map of surface water catchments in the Melbourne region

 

Description of region

The Melbourne region is physically defined in the General description. The region includes the Yarra River, Bunyip River, Maribyrnong River and Werribee River catchments as well as the 105 km² area of the Western Treatment Plant.

The region includes all water within and beneath the land described above excluding:

  • water in private reservoirs, such as landscape catchment reservoirs (also known as ‘farm dams’) and other private reservoirs used to harvest floodwater or collect rainwater, as this water is already abstracted and no longer available for sharing
  • water stored in the landscape, such as soil moisture
  • groundwater found outside defined management units. These management units are described in the Groundwater section below
  • water in the Thomson reservoir (to the east) and water in Lake Eildon (to the north). Any transfers of water from these stores into the region are treated as transfers, imports or inter-basin claims.

For more information regarding items in this water accounting report, please refer to the significant water accounting policies.

 

Land Use

Major cities within the region

The major cities and their populations within the Melbourne region (Australian Bureau of Statistics, 2010) are:

  • Melbourne – 3,371,888 (Urban centre)
  • Melton – 35,490
  • Sunbury – 29,566
  • Pakenham – 18,808
  • Bacchus Marsh – 13,261.

A number of smaller towns are interspersed throughout the region including Healesville, Drouin, Gisborne, Emerald and Wallan (Figure P.2).

Land use activities

Major land use activities in the Melbourne region are summarised in Table P.1, while Figure P.4 shows the distribution of these land uses.

 

Table P.1 Land use in the Melbourne region

Land use

Area (km2)

Area % of total

Conservation and natural environments

1,941

17

Grazing

4,196

36

Forestry

1,302

11

Dryland agriculture

513

4

Irrigated agriculture

350

3

Urban

2,801

24

Other intensive uses

362

3

Mining

71

1

Water

187

1

Total

11,723

100

 

Figure P.4 Map of land use in the Melbourne region 

Figure P.4 Map of land use in the Melbourne region

 

Land use activities that are major water users in the region are:

  • residential
  • manufacturing and industry
  • dairy
  • horticulture
  • viticulture.

Irrigated agriculture occupies less than 1% of land use in the region. The major irrigation districts are Bacchus Marsh and Werribee (Southern Rural Water, 2009) (Figure P.5).

Figure P.5 Map of irrigation districts in the Melbourne region

Figure P.5 Map of irrigation districts in the Melbourne region

 

Significant Aquatic Environmental Systems

Wetland systems of international and national importance occur in the Melbourne region. The region contains all or part of three wetlands that are Ramsar listed:

1. Edithvale-Seaford wetlands
2. Westernport Bay wetlands
3. the western shoreline of Port Phillip Bay wetlands.

 

It also contains five other wetlands of national importance:

1. Lerderderg River
2. Point Cook and Laverton Saltworks
3. Werribee-Avalon area
4. Yarra River wetlands
5. Mud Islands wetlands (occur within Port Phillip Bay).

Further information can be found at the Directory of Important Wetlands in Australia.

 

Water Resources

Surface water is the main source of water in the Melbourne region. Most of this surface water comes from mountain ash forest catchments in the Yarra Ranges in the east of the region. More than 15,700 km2 of native forest has been protected for the primary purpose of harvesting water and is closed to public access.

Groundwater and recycled water are also sources of water in the region.

 

Surface Water

Major storages
Table P.2 Major storage reservoirs in the Melbourne region

Reservoir

Total storage capacity (ML)

Dead storage capacity (ML)

Purpose of water supply from Reservoir

Upper Yarra

204,985

4,406

Urban supply

Maroondah

28,233

6,054

Urban supply

Silvan

40,581

136

Urban supply

O’Shannassy

3,123*

Unknown

Urban supply

Yan Yean

33,125

2,859

Urban supply

Sugarloaf

99,222

2,969

Urban supply

Greenvale

27,501

662

Urban supply

Cardinia

288,964

2,053

Urban supply

Tarago

37,580*

Unknown

Irrigation

Urban supply

Pykes Creek

22,119

1,770

Irrigation

Urban supply

Merrimu

32,215

335

Irrigation

Urban supply

Rosslynne

25,400

150

Irrigation

Urban supply

Melton

14,360

140

Irrigation

Urban supply

Total

857,408

* as "dead storage capacity" is unknown, it is not possible to calculate nor provide "total storage capacity." The figure should be considered as "accessible storage capacity excluding dead storage."

Note: Melbourne Water typically quote live storage volumes for reservoirs they manage. Live storage is the difference between total capacity and dead storage.

Other surface water infrastructure

The Werribee and Bacchus Marsh irrigation supply systems are located in the west of the region.
 
Rivers
There are four main rivers within the Melbourne region – Yarra, Bunyip, Maribyrnong, and Werribee. Seasonal flow characteristics of these rivers reflect the local rainfall pattern, which is relatively constant throughout the year, with a slight maximum in early spring (Figure P.6). The flows from each of these rivers, however, are affected by a reservoir or flow diversion structure. As such, streamflow is influenced by rainfall patterns, water supply needs, irrigation and environmental flow obligations. Figure P.7 shows the location of flow gauging stations along these main rivers used in Figure P.6.

Figure P.6 Mean monthly flows along the Yarra, Bunyip, Maribyrnong and Werribee Rivers; mean monthly spatially-averaged rainfall for the region is also shown
Figure P.6 Mean monthly flows along the Yarra, Bunyip, Maribyrnong and Werribee Rivers; mean monthly spatially-averaged rainfall for the region is also shown.

 

Figure P.7 Map of key flow gauging stations along the main rivers within the Melbourne region

Figure P.7 Map of key flow gauging stations along the main rivers within the Melbourne region

 

Streamflow summary
During 2009–10, annual flow in each of the four major rivers was well below the mean annual flow (Table P.3). The low flows in these rivers occurred despite close-to-average rainfall across the region in 2009–10. Low flows can be explained as storage operators responded to drought conditions by harvesting water rather than letting it flow downstream.

Table P.3 Mean annual and 2009–10 flow volumes along the Yarra, Bunyip, Maribyrnong and Werribee Rivers

River

Period of record

Mean annual flow (ML)

2009–10 flow (ML)

2009–10 as % of mean annual flow

Yarra

1975–2010

326,768

193,111

59

Bunyip

1962–2010

110,943

45,804

41

Maribyrnong

1985–2010

63,423

8,892

14

Werribee

1911–2010

52,849

558

1

 

Figures P.8, P.9, P.10 and P.11 show the total monthly flows for the Yarra, Bunyip, Maribyrnong and Werribee Rivers respectively.

Figure P.8 Total monthly flow in Yarra River at Chandler Highway during 2009–10 compared against long-term percentiles

Figure P.8 Total monthly flow in Yarra River at Chandler Highway during 2009–10 compared against long-term percentiles

Figure P.9 Total monthly flow in Bunyip River at Iona during 2009–10 compared against long-term percentiles

Figure P.9 Total monthly flow in Bunyip River at Iona during 2009–10 compared against long-term percentiles

Figure P.10 Total monthly flow in Maribyrnong River at Keilor during 2009–10 compared against long-term percentiles

Figure P.10 Total monthly flow in Maribyrnong River at Keilor during 2009–10 compared against long-term percentiles

Figure P.11 Total monthly flow in Werribee River at Werribee during 2009–10 compared against long-term percentiles

Figure P.11 Total monthly flow in Werribee River at Werribee during 2009–10 compared against long-term percentiles

 

Groundwater

Geology of the Melbourne region can be broadly split into two zones: the northern zone and the southern zone. The northern zone is about two-thirds of the total region. Geology of the northern zone is typically fractured bedrock. Smaller, local groundwater systems occur here. Geology of the coastal southern zone is unconsolidated sediments and basalts. Larger, regional groundwater systems occur in this zone.

On average, groundwater provides less than 10% of total water supply to the Melbourne region. It is mainly used to supplement surface water sources for high value agriculture, including production of vegetables, fruits, wine grapes, flowers and turf. It is also used for commercial, stock and domestic purposes.  In the metropolitan area, there is limited groundwater use with the extraction generally limited to the south-eastern sandbelt.

In Victoria, Groundwater Management Units are classified as either Groundwater Management Areas, Water Supply Protection Areas or Unincorporated Areas. Further information about each of these can be found at the Victorian Department of Sustainability and Environment website.

There are nine Groundwater Management Units in the region (Figure P.12); three are Water Supply Protection Areas and six are Groundwater Management Areas. The rest of Melbourne region is considered to be Unincoporated Area.

Figure P.12 Map of Groundwater Management Units in Melbourne region

Figure P.12 Map of Groundwater Management Units in Melbourne region

 

The Permissible Consumptive Volumes, which are the maximum extraction limit for each Groundwater Management Area, are listed in Table P.4.

 

Table P.4 Permissible consumptive volume for each groundwater management unit

River catchment

Groundwater Management Unit

Permissible Consumptive Volume

Werribee

Deutgam Water Supply Protection Area

5,100 ML/y

Cut Paw Paw Groundwater Management Area

3,650 ML/y

Merrimu Groundwater Management Area

450 ML/y

Maribyrnong

Lancefield Groundwater Management Area

1,485 ML/y

Yarra

Wandin Yallock Water Supply Protection Area

2,924 ML/y

Kinglake Groundwater Management Area*

n/a

Bunyip

Frankston Groundwater Management Area

3,200 ML/y

Moorabbin Groundwater Management Area

2,700 ML/y

Nepean Groundwater Management Area

6,013 ML/y

Koo Wee Rup Water Supply Protection Area

12,915 ML/y

* Approximately 19% of the Kinglake GMA lies within the Melbourne region. Values for Kinglake GMA are not included in this report as the majority of the groundwater extraction from licensed bores is north of the region and managed by Goulburn-Murray Water. 

Other water resources

Recycled water
Recycled wastewater is used for a range of activities such as the irrigation of agriculture, vineyards, market gardens, conservation areas, dual pipe (or third pipe) schemes and golf courses.

Western Treatment Plant
The major source of recycled water is the Western Treatment Plant. About one-third of the recycled water from the Western Treatment Plant is supplied to Lake Borrie wetlands. The rest is mainly used for:

  • pasture irrigation
  • horticulture irrigation
  • land and salinity management
  • a secure water supply to the Werribee Tourist Precinct including golf club, equestrian centre, open range zoo and Werribee Park and Mansion.

The Werribee Irrigation District Recycled Water Scheme delivers recycled water from the Western Treatment Plant to the Werribee irrigation supply system. The recycled water is mixed with water sourced from Pykes Creek, Merrimu and Melton surface water reservoirs.

Eastern Treatment Plant
Recycled water from the Eastern Treatment Plant is made available to South East Water to supply customers in the area. The main uses include:

  • horticulture irrigation
  • sportsfield irrigation
  • domestic dual pipe schemes.

Other wastewater treatment plants in the region are listed in Table P.5.

Table P.5 Wastewater treatment plants in Melbourne region grouped by managing authority

South East Water Yarra Valley Water
Blind Bight Aurora
Hastings (Somers) Brushy Creek
Koo Wee Rup Craigieburn
Lang Lang Healesville
Longwarry Lilydale
Mornington (Mt Martha) Monbulk
Pakenham (Deep Creek) Upper Yarra
Rosebud (Boneo ) Wallan
Whittlesea
City West Water Western Water 
Altona Bacchus Marsh

Sunshine Golf Course sewer mining plant

Gisborne
Melton
Riddells Creek
Romsey
Sunbury
Woodend

 


Stormwater
There are a number of stormwater harvesting schemes in operation throughout the Melbourne region. In comparison to recycled wastewater, the volumes of water involved are small.