Water targets
Urban development and land management practices within and upstream of the ACT have caused the health of rivers and streams in the ACT to decline. Water quality has been diminished by increased sediment and nutrient loads, decreased oxygen concentrations, higher water temperatures, reduced flow, and increased algal concentrations. Most natural riverbank vegetation and habitat has disappeared. In recent years, extended drought and severe bushfires have combined to place enormous pressure on water supplies – for urban use, and for the natural environment:
- drought has reduced ground cover vegetation, river flows, water quality and the amount of water released for environmental flows
- bushfires have severely reduced water quality (from sediment and ash washing from the fire-denuded landscapes), and altered run-off – although run-off increased immediately following the fires it will gradually decrease over the next 15 years as re-growing plants place a higher than pre-bushfire demand on water.
Water is a precious resource – it is needed for urban and rural use and for environmental uses. Downstream users also need to be considered when calculating how much water the city of Canberra should be permitted to abstract. Currently it uses 1.3% of total water taken from the Murrumbidgee River system.
In the last few years urban water use in the ACT has been reduced following voluntary and mandatory restrictions. However, in some areas new water sources, particularly groundwater, have been tapped. Groundwater extraction in some areas is exceeding the acceptable limit of 70% of sustainable yield (ACT Government 2003). Run-off from suburban development continues to degrade water quality in rivers and streams.
In order to ensure that water quality in waterways is maintained or improved, and that long-term supply to all users is reliable, water use efficiency needs to be increased, and an integrated regional approach to water management needs to be developed and implemented.
Use 12% less water per person to 2013 and increase use of treated water to 20%
Use 25% less water per person to 2023
Reduce level of nutrients and sediments in runoff to no more than for a well-managed rural landscape
Reduce intensity and volume of urban run-off to no more than pre-development size
Figure 5. Movement of water into, through and out of the ACT
Figure 5. Movement of water into, through and out of the ACT.
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Water agreements
Water in the ACT needs to be managed within international, national, state/territory and local agreements, strategies and plans including:
- ACT legislation, strategies and plans for management of water quality, ecologically sustainable development, and conservation of biodiversity (e.g. Think water, act water, the National Capital Plan, the Territory Plan, the Canberra Spatial Plan, the Environment Protection Act 1997 [ACT] and theWater Resources Act (2007) [ACT]).
- the Murray-Darling Basin Agreement and other agreed strategies of the Murray-Darling Basin Ministerial Council
- Water Act 2007 (Cwlth), establishing the Murray-Darling Basin Authority to develop the Basin Plan under Commonwealth overarching control
- participation in the Council of Australian Governments’ Water Reform Framework, National Water Quality Management Strategy and National Water Initiative; and the National Resources Management and the Environmental Protection and Heritage ministerial councils
- agreements with China, Japan and the Republic of Korea concerning bird migration
- protection of Ramsar-listed sites (e.g. Ginini Flats wetlands) and
- the United Nations agreements on climate change, biological diversity and forestry.
Water supply catchments
The ACT collects and stores water from rivers arising in the Brindabella mountain range to the west of Canberra and has paramount rights to water in the Molonglo and Queanbeyan rivers – giving it an interest in a number of catchments that straddle the ACT border. Its current water supply system should be adequate until 2017. Supply is augmented from some water that is treated
and distributed, and domestic greywater.
Rainfall in the region is variable and, to ensure water security for urban use, dams have been built to capture and store water as security against dry years (e.g. during 2006, flow into the ACT catchments was reduced by 85% and dam levels dropped as stored water was used). Following severe damage to the catchments in the 2003 bushfires and low inflows due to the continuing drought from 2001, the ACT Government has been re-examining its water security options. Security to 2023 will be achieved by:
- enabling transfer of water from the Murrumbidgee and from dams in the ACT into the Googong Reservoir in NSW
- enlargement of the Cotter Dam to 20 times its current capacity
- water from Tantangara Dam bought from irrigators and allowed to flow down the Murrumbidgee River into the ACT
- water efficiency measures and stormwater re-use projects and possibly
- use of a water purification plant.
Dam storage
| Cotter Dam (1912) | 4 GL |
| Bendora Dam (1961) | 11 GL |
| Corin Dam (1967) | 71 GL |
| Googong Dam (1979) | 121 GL |
Until 2003, supply catchments to the west of Canberra were fairly pristine needing little treatment before distribution. More extensive treatment of this water has been needed since the 2003 bushfires. Catchments to the east of Canberra flowing into the Googong Reservoir are mainly rural and water from this source also needs treatment so that it meets Australian Drinking Water Guidelines (NHMRC 2004). Land management practices in the Googong catchment are monitored.
The water supply catchments target will protect and rehabilitate catchments that are used for potable water supply. Recovery of the catchments following the 2003 bushfires and efforts to improve groundcover to reduce sediment run-off from erosion are continuing to ensure that relevant water quality standards are met. Wherever possible, use will be made of natural processes. This work will complement efforts to increase biodiversity in these catchments. Measurement of targets will use holistic systems to assess the condition of the entire catchment not just water quality.
Water use
Residents of Canberra use 174 to 192 kL of mains water per person per year. More than half this water is used in detached homes and nearly half of that (43% or approximately 23% of the total) is used outdoors, mostly on gardens. A small amount of greywater and tank water is also used. Some 29 000 ML of effluent is treated each year. ActewAGL also re-uses some greywater in their plant (~2000 ML/y).
Rural and some commercial properties use non-reticulated supplies of water – rainwater collected in tanks and dams, and groundwater from bores. The amount of rainwater collected in tanks and dams is not monitored or recorded. Bore water is extracted only under licence and is limited to not more than 10% of the recharge rate.
This target is taken from the ACT plan Think water, act water. It aims to increase per capita water use efficiency of the ACT. Overall increasing demand for water means that active involvement from all sectors of the community in innovative and educated approaches is required.
Water-sensitive urban design is a way to counter the massive changes (e.g. loss of clean water, altered run-off patterns and volumes, and polluted stormwater) that urban development imposes on the natural water cycle. It includes:
- using water-efficient techniques and technology (e.g. triple A-rated water devices, rainwater tanks and greywater recycling)
- managing stormwater quality and quantity through ponds and wetlands, filter strips, and maximising permeable surfaces and
- re-using waste water through larger-scale sewage treatment schemes and recycled domestic greywater.
All new developments and redevelopments in the ACT must adhere to water-sensitive urban design principles. Where feasible (economic, social and physical), retro-fitting of existing properties also follows these guidelines.
Surface water quality
This target will protect and enhance riverine ecosystems across the ACT. Urban and rural waterways and ponds potentially provide ecological services (e.g. habitat and water quality) to the surrounding land. Rural and urban development may lead to loss of health and capacity unless intervention based on sound ecological and planning principles is undertaken.
Run-off from urban areas is probably as much as 13 GL more today than under previously rural land use. It contains significantly more pollutants (hydrocarbons, pesticides, nitrogen, phosphorus, salt and bacteria) and soil from erosion from building and development sites. Most, but not all, city drainages employ some sort of filter system to remove some of the pollutants before the water reaches an open river.
This target measures outcomes using physical and chemical methods (e.g. turbidity, oxygen concentration, nitrate concentration), and by scoring according to the AUSRIVAS method of monitoring water quality. AUSRIVAS monitors aquatic macroinvertebrates as a more integrative method of assessing the impact of water quality and habitat condition. Sites are given scores of A (good) to D (severely impaired). In the ACT the average score over the last four years was about half way between a B and a C.
The target recognises that heavy rain often results in water quality standards being exceeded for a short time. The number of times the standard is exceeded should decrease as a result of improvements in catchment health.
Riverine ecosystems and wetlands
Riverine ecosystems range from uplands through rocky gorges to lowland floodplains. They are often quite different to neighbouring countryside with distinctive habitats, plants and animals.
Riparian zones provide connectivity for migrating birds, as well as habitat and recreational values.
Wetlands provide environmental (e.g. biodiversity, habitat and ecological functions), social and economic values. ACT wetlands are under threat and continued monitoring and maintenance is required.
Two ACT wetlands have a plan of management – Jerrabombera has one through its status as a nature reserve; Ginini has one through its Ramsar listing. Updated planning expectations for Ramsar sites require ‘ecological characteristics’ to be sought for all sites.
Several wetlands projects have been funded including for rehabilitation works and pig control.
Achievement of this target will ensure long-term protection of internationally and nationally designated wetlands and integrity of ACT riparian ecosystems.
The Directory of Important Wetlands in Australia (EA 2001, third edition) lists 13 nationally important wetlands in the ACT (including Jerrabomberra). It includes one Ramsar site (Ginini and Cheyenne Flats). Only two are lowland wetlands, 10 are in Namadgi National Park.
The listing excludes the lakes – Burley-Griffin, Tuggeranong and Ginninderra – and associated ponds.
The ACT also has a large number of farm dams, many of which have considerable biodiversity value.
WORKING WATERWAYS
Creative ways of improving stream health with wetlands, native vegetation and improved management
Working waterways projects include control of riparian weeds and revegetation along the Molonglo, and a survey of vegetation and habitat in key riparian areas.
Photos Sarah Ryan
Environmental flows
Abstraction of supply water and run-off from disturbed surfaces (rural or urban) can place endangered and vulnerable aquatic species in and ecosystems of the ACT’s waterways at increased risk due to changed conditions.
Water quality and flow can be maintained by releasing ‘environmental flows’ downriver. Environmental flows often mimic the natural flow of rivers and streams. They generally consist of a base flow, smaller and larger floods, and special purpose flows (e.g. water released to maintain fish refuges during drought). They may comprise water released from dams or be a protected portion of the natural flow. Environmental flows are used for protecting aquatic habitats of plants (e.g. plants that require regular inundation on the floodplain) and animals (e.g. profiding flows for Macquarie perch breeding).
- In water supply catchments, emphasis is on ensuring a natural level of water is allowed to flow in the river and that this water has comparable temperature and chemical characteristics to a natural flow.
- In disturbed catchments (rural or urban), emphasis is on reducing pollutant levels (gross, fine and nutrient) and ensuring that streams do not suffer from excess of flood conditions. Design of urban impoundments in the ACT does not enable release of environmental flows and most are managed so that they are generally full with an equivalent amount of water to that entering being released downstream. Water released from the base of these pools is quite detrimental to the environment. Downstream flows are augmented by flows from urban tributaries.
More information is needed about the particular needs of some species and community education is required to help people understand the multitude of factors involved.
Achievement of this target will ensure that the environmental flows necessary to support water ecosystems are released. Existing environmental flow guidelines set objectives (with respect to macro-invertebrates, sediments and, in some cases, populations of endangered species) for rivers in the ACT depending on whether they are natural, modified or built by people.
Since introduction of managed environmental flows in the Cotter River, both Macquarie perch and the two-spined blackfish have successfully spawned.
All rivers, streams and created ecosystems
- To maintain healthy ecosystems, prevent degradation of habitat and loss of macrophytes
Corin Dam to Bendora Reservoir
- To maintain populations of the two-spined blackfish; and population numbers and distribution of the Cotter River frog
Bendora to Cotter Reservoir
- To maintain populations of Macquarie perch and the two-spined blackfish
Below Cotter Reservoir
- To maintain populations of Macquarie perch
Groundwater
Groundwater is an integral part of the water cycle and is linked directly with surface water. In the ACT, groundwater typically flows through fractured rock aquifers – currently thought to be relatively shallow and tending to mirror the topography of the catchments above them. Groundwater flows in a direction towards valley low points, with the water discharging into a stream. Aquifers represent an efficient water storage option because they do not lose water by evaporation as dams do.
Groundwater is used when bores are sunk. It can also be contaminated as pollution seeps into the soil and flows into the aquifers. Ecosystems that are dependent on groundwater need to be identified and managed.
Overuse of groundwater affects stream base flows. The time lag between pumping and detection of any effect presents a considerable risk for management and is the reason for ACT cautionary extraction limits and expanded groundwater monitoring.
The ACT groundwater monitoring program is a risk-based approach where aquifers with the most demand for abstraction and therefore at risk are afforded proportionally more resources for measuring and monitoring – aquifers in national parkland where no abstraction is occurring require minimal information to manage risk; aquifers in urban areas with higher use along with other changes to the catchment such as increased impervious surfaces require more information. More monitoring bores are located in aquifers in urban areas and a wide range of methods are used to determine sustainable yield.
biodiversity, recreation and aesthetic benefits.
