ACT State of the Environment 2007
Issue: Catchment quality
The drought had a significant impact on our catchments during this reporting period. The reduced rainfall (including the dry conditions that increased the intensity of the 2001 and 2003 bushfires) and hence water availability, has adversely affected the Territory's catchments. These impacts will provide ongoing challenges to our catchment managers.
The drought, resulting in shortage of water in the ACT water supply and ensuing water restrictions, has highlighted the importance of water and catchment management to the ACT community. Catchments are becoming more valued in their natural state and water is increasingly being viewed as a dynamic, limited and precious resource. The ACT Government's efforts to return the Lower Cotter Catchment to its natural state for water protection are applauded.
Land use in the urban and drinking water catchments has had impacts on water resources during this reporting period. Increased urban development on greenfield sites has altered the hydrology of previous environments, and needs to be continually monitored. Urban storm water runoff is a key part of this change and is high in a variety of pollutants, including pathogens, nutrients and heavy metals and has the capacity to degrade water quality in our lakes and rivers. Greater information on the impacts of the urban area on our catchments is needed to improve our future management of catchments and water supply.
Former land uses, particularly commercial pine plantations, significantly modified the Lower Cotter Catchment. The 2003 bushfire made the problems of water quality in the Cotter Dam worse, resulting in tens of thousands of tonnes of sediment from erosion entering the reservoir. Now that the Lower Cotter Catchment has become a significant future water resource for the Territory, there has been a major change to land use such that the focus now is on water and conservation. Recognition of the importance of the natural ecosystems and drinking water catchments will result in beneficial changes to the Lower Cotter Catchment and in the overall state of catchment management in the ACT. Rehabilitation of the catchment is, however, at an early stage. While some good works have been achieved, the result has been patchy with some highly degraded areas, still needing urgent attention some four years after the bushfires.
One major drinking water source for Canberra and the ACT region is the Googong reservoir, with an extensive catchment area in New South Wales. Urban and rural development in, and close to, this catchment will have had adverse effects on water availability and quality. Increasing urbanisation and intensification of rural activities in this area can be expected to compound existing problems.
How well do we know our catchments?
While we know that climate and population are key pressures on our catchments, only limited data exist that can be used to quantify how significant these pressures are or the full impacts they may have. There are also limited data on the effects of changes in catchment management practices. There is, for example, limited information on changes to soil, vegetation cover or diversity, effects on fauna or catchment hydrology, all of which are likely to have been affected by the drought and bushfires as well as urban intensification.
There is little knowledge or understanding of the basic properties and systems within our catchments. For example, information about the turbidity of the Lower Cotter River, the sources of the turbidity, the type and amount of soil that causes turbidity, and the state of the land condition that may protect the river is scarce. Available information is often narrowly focused, fragmented or incomplete.
High quality data are essential for evidence-based decision making and planning for our catchments. For example, during the reporting period, data were collected about the volume of groundwater available for use. This data informed an effective and equitable management strategy for groundwater use in the ACT. Lack of understanding of our catchments may have severe implications for sustainability, especially where pressures on catchments are diverse and include the effects of urban development and fire on water quality. Building a strong knowledge base to help us understand our catchments is vital to developing a sustainable Territory.
The ACT in the Murray–Darling basin
As the largest centre of urban population in the Murray–Darling basin, Canberra–Queanbeyan significantly affects waters downstream. During the reporting period between 52 and 55 GL of water was used by the Territory per year with 27 to 29 GL per year returned to the Molonglo River as treated effluent.
Both treatment plants generally meet the requirements for discharge, however substantial loads of salt – around 15,000 tonnes per year (40 tonnes per day) – are released into the river. This has downstream implications for towns and irrigation areas on the Murrumbidgee and to a lesser extent on the Murray River salt load in South Australia. Up to one-third (5000 tonnes per year) of the total salt exported from the Lower Molonglo Water Quality Control Centre is from domestic and commercial sewage. Salt in detergents and other washing products is a significant component of that. This could be partly addressed through simple actions such as consumers' choice of detergents. Effort should be made to increase the community's awareness of this issue and its role in reducing the Territory's contribution to the Murray–Darling basin salinity.
With valuable contributions from the Ginninderra, Sullivans Creek, Southern and Molonglo catchment groups, and government agencies we are better able to understand and monitor urban catchments. Storm water management continues to be a major challenge, with the ever-expanding area of urban dwellings and commercial development in Canberra and surrounding areas. The urban storm water that flows into our lakes encourages growth of toxic blue–green algal blooms which causes restrictions on recreational use of our lakes. Each year water contact sports have been cancelled periodically due to algal blooms. We need to increase our efforts to ameliorate the pollution loads entering our lakes as climate change, drought and urban growth exacerbate nutrient loads and resulting toxic algal growth.
Gross pollution traps, which collect much of the solid waste found in our waterways, are used in urban areas to help protect surface water quality. To ensure maximum protection of waterways, it is necessary to assess the gross pollutant trap network for its effectiveness and, where practical, take action to improve the system. Microbiological contamination of the lakes has also led to periodic closures when potential pathogens have reached concentrations above health guidelines.
Building a scientifically local and regional knowledge base is a significant part of catchment management. Vegetation monitoring programs have been established to assess the ecological impact of bushfires and hazard reduction burns. Similar programs are needed to determine the impacts of other fuel reduction and management activities (such as grazing, slashing and physically removing material for fire management) and to assess the effectiveness of land and water management programs. All such monitoring programs need long-term commitment to be effective.
The 2003 bushfire was a significant event affecting several ACT catchments. Catchments are dynamic and sensitive to any source of damage including road construction and land use changes, such as forestry or clearing to wildfires, or managed burns. The bushfire highlighted the dynamics and exposed both the strength and fragility of natural systems. The natural regrowth of the Upper Cotter Catchment vegetation was impressively rapid. In contrast, areas of burnt pines in the Lower Cotter Catchment, which suffered extensive erosion, have been slow to recover and need significant management effort (the extensive regrowth of weeds are a major problem in conversion to native vegetation). Restoration of the quality of the vegetation cover in the Lower Cotter Catchment will be a significant future management challenge.
ACT Government agencies and ACTEW play a key role in gathering knowledge and fostering new research. Monitoring and data on water and catchment health exist in various locations in the ACT; ACTEW is a primary source. A scientifically based approach should be the basis of planning and decision making. It is crucial to review and align indicators of catchment and water supply health to provide an integrated and cooperative approach to catchment management in the ACT. Communication between relevant parties and public access to information is important in progressing capable management of catchments. Web access and published summaries are important to keeping the public informed of progress. A greater effort to publish results, both good and bad, is needed so others can learn from and review the Territory's management efforts.
While there is a need to continue focusing on restoring the Lower Cotter Catchment, the issue of appropriate recreational activities also needs to be addressed. Given the proximity to Canberra and historical recreational uses before the 2003 bushfire, this is likely to be a sensitive issue requiring considerable public consultation.
The future of catchments
We need to broaden existing catchment knowledge. Effective management needs a strong science-based policy and implementation framework supported by a robust monitoring and assessment program. Structured data collection is an important part of such a program.
It is essential to integrate our knowledge, in an interdisciplinary manner, about urban and rural catchments. The ACT is a relatively small jurisdiction and has the opportunity to embrace interdisciplinary work and a holistic approach to catchment management. Key to this is effective communication within government agencies, between government and ACTEW and the wider scientific and general community.
Community groups contribute positively to monitoring and restoring catchment health. Major cooperative projects between community groups, ACT Government agencies and ACTEW have been successful; for example, willow removal at Ginninderra Creek and restoration in the Lower Cotter Catchment.
The ongoing challenge for catchment management is to adapt to future change, particularly climate change. To better understand any changes in the Territory's catchments and to provide a basis for managing them, ongoing research and monitoring is essential. Reducing the impacts of urban development and commercial intensification is also an important part of catchment management in the ACT.
The Territory's policies and strategies for various water supply catchments are embedded in management plans, and various agencies' policies and actions affect the Territory's water supply catchments. Integrated data is difficult to source. It would be beneficial to have a centralised source of information. As well, an overarching integrated water catchment policy and strategy would help meet ongoing challenges for the Territory's water supply catchments.
The following recommendations are made to the ACT Government with a commitment from the Commissioner to assist in advancing their implementation:
1. Improve catchment management by:
- Developing an ACT integrated water supply catchment management policy and strategy to guide, among other things, coordination of:
- scientific research,
- data collection,
- monitoring and reporting (including public information).
- Monitoring the effects of urbanisation on the ACT region's water catchment and using the information in developing and implementing strategies in response to specific issues (eg the development of greenfield sites).
- Monitoring the effectiveness of the Gross Pollutant Trap network (including its supporting maintenance program) to identify ways to improve its overall effectiveness in protecting surface water quality.
- Determining the sources and loads of salts entering the waste water treatment networks and using the information to develop strategies to reduce salt discharges to the Molonglo and Murrumbidgee rivers.
- Ensuring the key indicators in State of the Environment Report, Natural Resource Management Plans and other relevant ACT Government reports are reviewed and aligned.
2. Further progress restoration efforts in the Lower Cotter Catchment by:
- Continuing the science-based approach to management with an emphasis to be given to monitoring and publicly reporting on recovery of this catchment.
- Further reducing water turbidity in streams through targeting areas of greatest vulnerability that have high rehabilitation potential.
- Clearly defining recreational activities with protection of water being the highest priority.
The indicators drawn on for this issues paper were: