Canberra
Physical information

Area: 4,202 km²

Population: Approximately 400,000 (Australian Bureau of Statistics 2012)

The Canberra region is located in the southeast of Australia (Figure P1) and within the Murray–Darling Basin (Figure P2).

It is characterised by forested mountains in the south and west of the region, and plains in the north of the region (Australian Bureau of Statistics 2007). The Canberra region boundary (Figure P3) encompasses the Australian Capital Territory (ACT) and extends into New South Wales (NSW). The boundary of the Canberra region captures the whole of the water supply system in the ACT. The ACT and NSW governments administer the part of the region that is within their respective jurisdictions.

Figure P1  Location map of the Canberra region within Australia

Figure P2  Location map of the Canberra region (in the context of the Murray–Darling Basin)

Figure P3  Contextual map of the Canberra region

The geographic boundaries of the Canberra region include:

• Upper Murrumbidgee River catchment downstream of the junction of the Michelago to downstream of the Ginninderra Creek (just upstream of Halls Crossing gauge) 
• Cotter River catchment
• Gudgenby River catchment
• Molonglo River catchment
• Queanbeyan River catchment.

The headwaters of the Upper Murrumbidgee catchment were not included in this region as the majority of the rainfall runoff from this catchment is diverted to the Snowy River scheme in NSW.

For the 2012 Account, the Canberra region includes the following water assets: the surface water and groundwater administered under the ACT and NSW water legislation, and the urban water system.

The following elements are not considered water assets of the Canberra region:

• water in off-channel water storages, such as landscape catchment storages (also known as farm dams) and other off-channel water storages used to harvest runoff, floodwater or collect rainwater, as these constitute water that is already abstracted and no longer available for sharing
• water stored in the landscape, such as soil moisture.

The major urban centres in the region, along with their population (Australian Bureau of Statistics 2012), are:

• Canberra: 355,596
  
• Queanbeyan: 35,878
  

Figure P4 shows that land use is concentrated within the Canberra and Queanbeyan urban areas of the region. Land use classifications were derived from the National Scale Land Use Mapping Technical Specifications.

In addition to urban land use, major land uses in the Canberra region include conservation and natural environments areas and grazing. Conservation and natural environment areas are extensive throughout the Canberra region and are particularly dominant through the forested mountains in the south and west of the region. Grazing occurs across much of the plains within the region (Figure P4).

Table P1 shows the major land use activities within the Canberra region (Australian Bureau of Rural Sciences 2010).

Figure P4  Map of land use in the Canberra region

The Canberra region contains the Ginini Flats Wetland Complex Ramsar-listed Wetland, that are located in the Namadgi National Park. It consists of a series of interconnected flats known as the Ginini Flats and the Cheyenne Flats.

The Canberra region also contains 13 nationally important wetlands that are listed in the Directory of Important Wetlands in Australia (see Table P2).

In the Canberra region, most water used is surface water. In recent years excluding the last two years, prolonged low streamflow conditions led to an increase in the necessity of groundwater, however, groundwater use is still low in comparison to that of surface water. Recycled wastewater is also used in the region.

The Water Resources Determination 2007 of the Water Resources Act 2007 (ACT) set an allowable surface water and groundwater abstraction limit of 273 GL. The current level of abstraction in the ACT is well under this limit,  however, future levels of water extraction and abstraction will be limited by the Murray–Darling Basin cap (refer to Water rights: Operating rules and constraints: Murray–Darling Basin cap).

The water resource in the NSW portion of the Canberra region is already incorporated under the current long term cap for the Murray–Darling Basin (refer to Water rights: Operating rules and constraints: Murray–Darling Basin cap).

The Murrumbidgee is the major river system that flows through the Canberra region within the Murray–Darling Basin. All rivers and creeks in the ACT drain into the Murrumbidgee River. Three of the main rivers which begin in the Canberra region and flow into the Murrumbidgee are the Molonglo, Cotter and Queanbeyan rivers.

Figure P5 shows mean monthly flow in the three main rivers of the Canberra region, along with rainfall. While there is little seasonality in the rainfall of the region, streamflow in the three main rivers does vary seasonally, with flows being lowest in autumn and highest in winter and spring.  Evaporation increases in summer causing the catchments to dry out. In autumn and winter, the catchments typically become saturated, leading to higher runoff in spring. Streamflow in the Cotter River in spring is also influenced by snowmelt and sphagnum moss bog release. The moss acts like a sponge, holding water from rainfall events and releasing it slowly over time.

Figure P5 shows the flow data at the gauging stations; station numbers are shown in Figure P6.

Figure P5  Graph of mean monthly flows along the Molonglo, Cotter and Queanbeyan rivers and mean monthly rainfall for the Canberra region

Figure P6  Location map of key flow gauging stations along the main rivers within the Canberra region

The Canberra region contains a number of major storages used for urban water supply and others that are used for pollution control and recreational purposes (ACTEW Water 2011a). These storages are listed in Tables P3 and P4.

The urban water supply network for Canberra and Queanbeyan consists of:

• four surface water storages (detailed in Table P3)
• Mount Stromlo and Googong water treatment plants (WTPs)
• a water abstraction point on the Murrumbidgee River below the Cotter confluence
• the Lower Molonglo Water Quality Control Centre (LMWQCC)
• Fyshwick and Queanbeyan wastewater treatment plants (WWTPs).

The layout of the supply system is shown in Figure P7. Water from the surface water storages in the Canberra region is supplied to 45 service reservoirs (tanks) in the region's water supply system (ACTEW Water 2011b).

Figure P7  Locations of key components of the urban water supply network

The Canberra region falls within the Lachlan Fold Belt geologic formation. The region encompasses low-yield fractured volcanic aquifers overlain in places by minor, high-yield aquifers in superficial, unconsolidated alluvium/colluvium. The alluvial aquifers can be a locally significant source of water, but groundwater is a small resource in the Canberra region .

Within the ACT, groundwater is managed as a combined resource with surface water as part of the water management areas. In NSW, groundwater is managed separately from surface water. Two groundwater management areas (GMAs) occur within the NSW part of the Canberra region, the Lachlan Fold Belt GMA and the Yass Catchment GMA as shown in Figure P8.

Figure P8  Map of groundwater management areas in the NSW part of the Canberra region

Three wastewater reuse schemes operate in the ACT. These schemes are listed in Table P5. The majority of the water recycled at LMWQCC is recirculated within the treatment process.

ACTEW Corporation is the ACT Government-owned statutory body that owns and manages the Canberra water supply system. ACTEW Water controls surface water diversions, operates water treatment plants, maintains Canberra's reticulation system and delivers water to Queanbeyan where the infrastructure is managed and maintained by Queanbeyan City Council.

Figure P7 illustrates the major components of the Canberra and Queanbeyan urban water supply system. The key components of the system are four water storages, two water treatment plants and four wastewater treatment plants. Water is sourced from three catchments: the Cotter, Murrumbidgee and Queanbeyan river catchments.

The Mount Stromlo WTP receives water from the Corin, Bendora and Cotter reservoirs, all located on the Cotter River, and water from the Murrumbidgee River at the Cotter pump station. Water diverted from Googong Reservoir receives treatment at the Googong WTP. Excess treated water from the Mount Stromlo plant can be released into the Googong Reservoir for storage (ACTEW Water 2011a).

In order to secure water resources for Canberra and Queanbeyan's future, two main projects are in progress. The more significant is the increase in the total accessible storage capacity of the Cotter Reservoir from 3.9 GL to 78 GL. Construction of the new dam wall commenced in late 2009 and is now scheduled for completion in 2013. The second project is a 13 km underground pipeline that will transfer water from the Murrumbidgee River at Angle Crossing to Burra Creek, where it will flow into the Googong Reservoir. Construction on the pipeline commenced in January 2011 (ACTEW Water 2011b).

The LMWQCC is the largest WWTP in Canberra. The plant treats more than 90 ML/day of wastewater before discharging it to the Molonglo River or providing it for irrigation purposes at nearby vineyards and golf courses. The Fyshwick WWTP collects and treats industrial and domestic sewage from Fyshwick and surrounding suburbs. Treated wastewater from this plant is then discharged back into the sewer or delivered to the North Canberra Water Reuse Facility where it undergoes secondary treatment before it is used for irrigation purposes. A sewer mining facility at Southwell Park also supplies recycled wastewater for irrigation purposes when operational. Wastewater treated at the Queanbeyan Sewage Treatment Plant (STP) is discharged to the Molonglo River with only a small fraction used for on-site irrigation purposes.