Source: Richie Southerton



This section provides an assessment of aquatic ecosystem health, river flows and water quality in the ACT. The following indicators are assessed:

For background information on water in the ACT see Background: Water

Threatened aquatic biodiversity and ecosystems are discussed in Biodiversity. Water resources and consumption are discussed in Human Settlements.

The Orroral Valley bushfire had severe impacts on the ACT’s aquatic ecosystems, including significantly degraded water quality, mortality of aquatic species and the loss of riparian vegetation. These impacts are discussed in 4. Bushfires in the ACT and should be considered in conjunction with the assessments of ACT waters presented in this section.

Assessments of the ACT’s groundwater systems are not included in this report. Groundwater is a minor component of total water use in the ACT and typically restricted to non-potable supply. There is also a lack of comprehensive data on groundwater resources and quality data in the ACT making difficult to assess their condition.

In 2022, the Office of the Commissioner for Sustainability and the Environment undertook an investigation into the State of the Lakes and Waterways. This investigation assessed the environmental health and management of Canberra’s urban lakes, ponds and wetlands, and waterways. This Water section should be read in conjunction with the Investigation to obtain a more detailed understanding of urban waters and their management.

That the ACT Government: 


Identify opportunities to develop water sensitive urban design measures to reduce the impact of urban land use on aquatic ecosystems.


Re-establish riparian vegetation in both urban and rural areas to improve habitat and protect lakes and waterways from pollutant run-off.


Establish a government reporting framework for the assessment of aquatic ecosystem health. This should include the selection of key monitoring sites that provide comprehensive coverage of land use types, sub-catchments and ecosystems across the ACT; incorporate work undertaken for the Catchment Health Indicator Program; incorporate all relevant condition parameters; and produce public reports at appropriate intervals to provide meaningful assessments.


Improve knowledge on water quality through more frequent monitoring, as well as events-based monitoring, to better assess periods of high pollutant loads.


Produce an annual recreational water quality report that includes monitoring results; investigations into the main sources of pollutants; recommended actions to improve water quality; and assessments of management effectiveness.


Identify opportunities to collaborate with the NSW Government on management activities to improve aquatic ecosystem health upstream and downstream of the ACT, including the management of native and alien fish, re-establishing riparian zones and reducing catchment erosion.


Seek to increase water releases to the upper Murrumbidgee River under the Snowy 2.0 project to improve aquatic ecosystem health in the Murrumbidgee River.


Include findings from the Aboriginal Water Assessments in the annual Catchment Health Indicator Program Reports.

W1: Aquatic ecosystem health




Aquatic ecosystem health is variable across the ACT and strongly influenced by land use. Aquatic health is mostly good in conservation areas but condition is poorer in urban and rural areas. Riparian condition is a concern with over half of the assessed river reaches having poor to degraded riparian condition. Although there has been a small improvement in aquatic ecosystem health in response to the wetter conditions since 2020, the preceding drought conditions placed significant stress on aquatic health and biodiversity. Alien fish populations continue to thrive in the Murrumbidgee River, greatly outnumbering native species.

The 2020 Orroral Valley bushfire has greatly impacted aquatic ecosystems in Namadgi National Park, including native fish populations in the Cotter River upstream of Corin Dam.

W2: River flows




The ACT’s rivers experienced flows well below the long-term average during the drought conditions from 2017 to 2019. Annual river flows were lowest in 2019 with cease-to-flow periods occurring for the Murrumbidgee and Molonglo rivers. These extremely low flows impacted on aquatic ecosystem health as well as the amenity of the ACT’s waterways. The high rainfall years following the drought period resulted in very high flows that were significantly greater than the long-term average from 2021 to 2022. Despite these wetter conditions, the ACT’s annual river flows remain at risk from severe drought periods.

Over the 2019 to 2022 period, annual flows downstream of all ACT water supply reservoirs were greater than the environmental flow requirement despite the significantly reduced rainfall and river flows in 2019.

W3: Water quality




Whilst water quality was generally good across the ACT, including for sites in urban and rural areas, turbidity and nutrient pollution significantly impact on aquatic ecosystems following high rainfall events. Good water quality results for some urban areas demonstrate the effectiveness of constructed wetlands and other water sensitive urban design approaches, although further urban development is degrading water quality in some catchments, especially in the Molonglo Valley. The 2020 Orroral Valley bushfire caused severe water quality impacts in Namadgi National Park.

Except for turbidity and electrical conductivity, water quality in the Murrumbidgee River is comparable upstream and downstream of the ACT. In high rainfall years, turbidity was higher downstream of the ACT as a result of additional sediment and other particles flowing into the Murrumbidgee River via Canberra’s urban waterways.

W4: Recreational water quality




Recreational water quality is poor in the ACT for both lakes and rivers. All of Canberra’s lakes experienced closures in every recreational season due to the exceedance of enterococci and/or blue-green algae guidelines. Lake Tuggeranong has by far the most closures, regularly suffering from cyanobacterial blooms and high levels of faecal contamination. These are often accompanied by odours and highly turbid water, reducing the recreational and aesthetic value of the lake and surrounds. The 2022–23 recreational season had the highest total closures across the ACT since 2015–16, with Lake Tuggeranong closed for 80% of the recreational season. The Murrumbidgee, Cotter, and Paddys rivers experience closures in every recreation season due to high enterococci concentrations.


Environmental condition is healthy across the ACT, OR pressure likely to have negligible impact on environmental condition/human health.

Environmental condition is neither positive or negative and may be variable across the ACT, OR pressure likely to have limited impact on environmental condition/human health.

Environmental condition is under significant stress, OR pressure likely to have significant impact on environmental condition/ human health.

Data is insufficient to make an assessment of status and trends.



Adequate high-quality evidence and high level of consensus.

Limited evidence or limited consensus.

Evidence and consensus too low to make an assessment.

Assessments of status, trends and data quality are not appropriate for the indicator.


Aquatic ecosystem health Catchment Health Indicator Program

This is the second ACT State of the Environment Report to use data from the Catchment Health Indicator Program. The program assessed 71 reaches in the Ginninderra, Molonglo and Southern ACT catchments. Main findings for the 2019 to 2022 period (averaged scores) are below.

Macroinvertebrate condition Catchment Health Indicator Program

Riparian condition Catchment Health Indicator Program

Pelicans at Jerrabomberra Wetlands. Source: Richie Southerton

Native fish

River flows

Water quality Catchment Health Indicator Program

Main findings for the 2019 to 2022 period (averaged scores) include:

Water quality in the ACT’s urban waterways

Lake Tuggeranong

Lake Ginninderra

Lake Burley Griffin

Urban rivers

Water quality entering and leaving the ACT

Recreational water quality 201516 to 202223


The ACT’s waterways are expected to be increasingly subject to extreme and variable climatic conditions in coming years. Within this context, management of waterways is especially challenging. In particular, balancing anthropocentric outcomes such as flood protection and domestic water supply with providing habitat and high-quality water for native species will be increasingly difficult.

Refer also to Human Settlements for information about water consumption and supply.

Policy framework

The Water Resources Act 2007 aims to ensure that management and use of the water resources of the Territory sustain the physical, economic and social wellbeing of the people of the ACT while protecting the ecosystems that depend on those resources. The ACT Water Strategy 2014–44:  Striking the Balance provides long term strategic guidance to manage the Territory’s water resources. It is intended to guide the development, integration and implementation of activities undertaken by ACT Government and its partners, developers, the ACT community, natural resource management groups and other stakeholders involved in planning, water management and water use. Four-year implementation plans are developed to provide detail about how the ACT Water Strategy 2014–2044 is put into practice, with the most recent of these plans ending this year. 

The Aquatic and Riparian Conservation Strategy and Action Plans 2018 provides guidance on the conservation of aquatic and riparian areas and component species. They include recommendations to address a range of key threats to aquatic and riparian species and ecosystems as well as action plans for threatened aquatic species. The management and enhancement strategies identified within it aim to increase the resilience of aquatic and riparian areas to threats such as climate change. However, urban lakes, ponds and waterways are not specifically covered in the strategy.

Aquatic habitat in the ACT’s rivers is also supported by the Environmental Flow Guidelines 2019 (No 2), an instrument under the Water Resources Act 2007 that sets out the flow requirements (quantity and timing) needed to maintain freshwater ecosystems. Among other things, the guidelines seek to maintain the minimum volume of water that a river needs to support the fish, plants, insects and protect water quality. The volume of this base flow is determined for each month for each stretch of stream or river, taking into account environmental conditions. Larger ‘flood’ flows are also built into management guidelines to mimic natural periods of higher flow and reduce the likelihood of sediment build-up in waterways.

During this reporting period, work has commenced on developing Aboriginal Water Assessments in collaboration with Ngunnawal Traditional Custodians. These assessments offer a way for Ngunnawal cultural and ecological knowledge to be incorporated into the management of waterways in the ACT region.

The Nature Conservation Act 2014, Environment Protection Act 1997 and Planning Act 2023 also contain elements which govern the management of water and aquatic habitats in the ACT.

Policy effectiveness

The State of the Lakes and Waterways in the ACT report published by the Office of the Commissioner for Sustainability and the Environment in 2022 discusses urban water management in the ACT in detail. This report found arrangements for urban water management in the ACT are complicated, with many different agencies playing a role in water management. This can lead to undesirable outcomes as responsibilities and communications between different entities are not always clear. The establishment in 2022 of the Office of Water to coordinate policy and management approach is a positive step but its work so far is still confined to the Environment, Planning and Sustainable Development Directorate, which has limited responsibility for water management within the urban area. An overarching framework for water management in the ACT which also includes Transport Canberra and City Services, the Environment Protection Authority and ACT Health is lacking.

The State of the Lakes and Waterways in the ACT report made 12 recommendations regarding water management in the ACT, of which 11 were agreed to by the ACT Government. Implementation of the recommendations is still at an early stage.

Since the publication of the State of the Lakes and Waterways in the ACT, a number of Territory Plan General Codes — frameworks which guided the sustainable use of water in the ACT — have ceased to have effect under the new Territory Plan. Different mechanisms will be in place under the new Territory Plan to guide water management in urban areas and it remains to be seen what effect these will have on Canberra’s approach to Water Sensitive Urban Design.

Greenfield developments continue to be a major contributor to sediment and nutrients entering the Molonglo and Murrumbidgee rivers. There is evidence from the recent past that erosion and sediment control measures put in place during the land clearing and construction phases have not always been adequate to prevent high sediment loads entering the rivers. It is essential to address this for future developments planned within river catchments.

Current knowledge about the detailed ecology of many native aquatic species is incomplete and this makes it challenging to know which targeted management interventions are needed. Therefore, protection of aquatic and riparian habitats through broadscale actions for water quality and habitat improvement, such as prevention of sedimentation and removal of invasive species, is likely to offer the best option for the conservation of surviving native aquatic species.