Canberra
Physical information

Area: 4202 km².

Population: 400,001 in 2010, consisting of total Australian Capital Territory (ACT) population plus Queanbeyan population (Australian Bureau of Statistics 2011a).

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

The Canberra region 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 ACT and extends into New South Wales (NSW). It was necessary to extend the Canberra region boundary beyond the ACT boundaries to reflect the extent of the water supply system to Canberra. 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 2011 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 (ABS 2011a), are:

• Canberra – 358,222 in 2010
• Queanbeyan – 41,430 in 2010.

Figure P4 shows that urban land use is concentrated within the Canberra and Queanbeyan metropolitan 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 areas, natural environment and grazing. Conservation areas and natural environment are extensive throughout the Canberra region and 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 percentage areas of each major land use 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, 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 12 nationally important wetlands, listed in the Directory of Important Wetlands in Australia.

In the Canberra region, most water used is surface water. In recent years, prolonged low streamflow conditions led to an increase in the demand for groundwater. However, use of groundwater is still low in comparison to 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 exaction 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. The monthly average rainfall for the Canberra region is similar from season to season, however, the 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 P6 shows the locations of the flow gauging stations (and their station number), whose flow data is plotted in Figure P5.

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

Figure P6. Map of key flow gauging stations used in the 2011 Account

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 (Australian Natural Resource Atlas 2009). These storages are listed in Tables P2 and P3, and shown in Figure P7.

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

• four surface water storages (detailed in Table P2)
• Mount Stromlo and Googong water treatment plants
• a water abstraction point on the Murrumbidgee River below the Cotter confluence.
• the Lower Molonglo Water Quality Control Centre
• Fyshwick and Queanbeyan wastewater treatement plant.

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 (ActewAGL 2011).

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 yielding 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 (Australian Natural Resource Atlas 2009).

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 to surface water. Two groundwater management areas (GMA) occur within the NSW part of the Canberra, the largest being the Lachlan Fold Belt GMA (shown in green in Figure P8) and the Yass Catchment GMA (shown in purple 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 P4. The majority of the water recycled at Lower Molonglo Water Quality Control Centre (LMWQCC) is reused within the treatment process.

NA – not available.

Source: ActewAGL (2011).

ACTEW Corporation is the ACT Government-owned statutory body that owns and manages the Canberra water supply system. ACTEW 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 River catchment, the Murrumbidgee River catchment and the Queanbeyan River catchment.

The Mount Stromlo Water Treatment Plant receives water from the Corin, Bendora and Cotter reservoirs, all located on the Cotter River, as well as water from the Murrumbidgee River at the Cotter pump station. Water diverted from Googong Reservoir receives treatment at the Googong Water Treatment Plant. Excess treated water can be released into the Googong Reservoir for storage (ACTEW 2007).

Intense bushfires in the Cotter River catchment in January 2003 resulted in poor water quality in the Cotter River system, requiring the Mount Stromlo water treatment plant to be upgraded to ensure adequate treatment whilst the Cotter catchment recovered. The upgraded plant was commissioned in 2004.

In order to secure water resources for Canberra and Queanbeyan's future, two main projects are in progress. The most significant is the enlargement of the Cotter Reservoir from 3.9 GL to 78 GL total accessible storage capacity. Construction of the new dam wall commenced in late 2009 (ACTEW 2011). 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 2011).

The Lower Molonglo Water Quality Control Centre is the largest wastewater treatment plant 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 Wastewater Treatment Plant 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 is discharged to the Molonglo River with only a small fraction used for on-site irrigation purposes.