General

The water quality of Lake Burley Griffin has been extensively monitored since about 1978, by a number of organisations, including:

  • University of Canberra, CRC for Freshwater Ecology
  • ECOWISE Environmental (now ECOWISE Australia Pty Ltd, trading as ALS Water Resources Group)
  • ACT Environment and Sustainable Development Directorate
  • ACT Health Protection Service.

Water quality in the Lake and its tributaries has also been the focus of a number of research studies (including Honours, Masters and Doctoral projects), from:

  • Australian National University
  • University of Canberra
  • Australian Defence Force Academy.

Community groups, through Waterwatch ACT, have also collected water quality information on the Lake and its surrounding tributaries.

Collectively, these various efforts have provided a considerable amount of valuable information on water quality in the Lake, and have made the Lake one of the most studied lakes in Australia (Atech Group, 2002).

Consequently, it is possible to provide some good indications for benchmark water quality values within the Lake.

A summary of these benchmark values for the respective environmental values is provided below, with additional information in subsequent sections of the previous chapter:

Environmental value: Ornamental water

  • Turbidity values of 40 NTU in East Basin, and 20 NTU in West Lake.
  • Suspended solids values of 40 mg/L in East Basin, and 20 mg/L in West Lake.

Environmental value: Protection of freshwater aquatic system

  • Turbidity values of 40 NTU in East Basin, and 20 NTU in West Lake.
  • Suspended solids values of 40 mg/L in East Basin, and 20 mg/L in West Lake.
  • Total phosphorus concentration of 0.06 mg/L.
  • Total nitrogen concentrations of 1.4 mg/L in East Basin and 1.0 mg/L in West Lake.
  • Ammonia concentration of 0.1 mg/L.
  • Cyanobacteria cell concentration of 20,000 cells/mL
  • Chlorophyll-a concentration of 20 μg/L.
  • Conductivity of 400 μS/cm.
  • pH range of 6.5–8.5.
  • Metal concentrations as specified by ANZECC/ARMCANZ (2000).

Environmental value: Recreational water

  • Recreational benchmark values are based on the Guidelines for Managing Risks in Recreational Water (Australian Government, 2008).
  • Bacterial quality as specified by Australian Government (2008) preferentially using intestinal enterococci as indicators of the potential presence of pathogens. A concentration of <200 CFU/100mL is recommended.
  • Cyanobacterial toxin concentration of <4 µg/L (possible toxins include microcystins and cylindrospermopsins), or <20,000 cells/mL where known toxin producing species are dominant.
  • pH 6.5-8.5

Environmental value: Irrigation water for parks and gardens

  • Water quality as specified in Guidelines for Managing Risks in Recreational Water (Australian Government, 2008)

Methodology

The National Water Quality Management Strategy (NWQMS), which has provided the ANZECC/AMRCANZ (2000) guidelines, has suggested that communities develop their own water quality objectives in their local environment, based on a number of factors, including:

  • ecological information (either of a general nature or specifically related to the water body of interest);
  • economic affordability (and the willingness of the community to obtain a particular level of water quality).

This Lake Burley Griffin WQMP generally follows the above-mentioned NWQMS procedures. However, instead of using water quality objectives (based on the 80th percentile values), this WQMP uses water quality benchmark values (which are close to, but not necessarily exactly, at the 80th percentile value for each data set). Revised benchmarks in this updated WQMP also consider values in the Guidelines for Managing Risks in Recreational Water (Australian Government, 2008).

Because the Lake has been extensively studied, it is possible to establish benchmark values for the key water quality characteristics at levels that in the past have shown no adverse effects (in terms of either ecology or human health).

This approach is suggested, as it is unlikely that the community would be interested in paying for and providing a more stringent benchmark than one that showed no adverse effects on the environment or on human health. For example, it is unlikely that the community would be willing to pay for increased phosphorus removal at the Queanbeyan Wastewater Treatment Plant (upstream of Lake Burley Griffin), if current phosphorus concentrations showed no adverse effects. Limited financial resources would then be allocated to other, more needy water quality issues (or indeed to a range of other general issues such as schools, hospitals, roads etc).

It is important to balance the above approach (using specific information on the Lake) with:

  • a more general Australia-wide approach (using information from a range of sources including values generic for south-east Australian waterways) as outlined in ANZECC/ARMCANZ (2000);
  • a more general ACT-wide approach, using information from ACT Government (2011).

Furthermore, once a benchmark is established, it is nevertheless important to continue with its ongoing assessment (and if necessary, with its ongoing adjustment).

Turbidity and Suspended Material

The ANZECC/ARMCANZ (2000) guideline value for turbidity is 20 NTU. The corresponding value for suspended material is 25mg/L.

Other ACT water bodies have no specific turbidity standard for recreational areas, other than the requirement that the turbidity should not be objectionable. The corresponding value for aquatic habitats is <10–<30 NTU (ACT Government, 2011).

The Lake often exceeds these values, particularly in the shallower areas such as East Basin. Most of this is due to wind mixing, with turbidity levels in East Basin often being well above those in the Molonglo Reach (just upstream of the Lake).

Lake Burley Griffin has always been a relatively turbid lake, but these levels have shown no adverse effects in terms of ecology or human health.

Consequently, based on past information on the Lake, it is proposed that the benchmark level for Lake Burley Griffin turbidity should be 40 NTU and 20 NTU in East Basin and West Lake respectively.

It is proposed that the benchmark suspended solids values should be 40 mg/L and 20 mg/L in East Basin and West Lake respectively.

Phosphorus

The ANZECC/ARMCANZ (2000) guideline values for total phosphorus and filterable phosphorus are 0.1 mg/L and 0.05 mg/L respectively.

The corresponding value for other ACT waters is <0.1 mg/L total phosphorus. Filterable phosphorus concentrations are not specified, as total phosphorus concentrations appear to be the more important measure in terms olake management (ACT Government, 2011).

Consequently, a 0.06 mg/L benchmark total phosphorus value is proposed for Lake Burley Griffin.

Nitrogen

The ANZECC/ARMCANZ (2000) guideline values for total nitrogen and ammonia are 0.35mg/L and 0.1mg/L respectively.

There is no particular value for other ACT waters (ACT Government, 2011).

The Lake has higher than usual nitrogen values, but this has had no adverse effects in terms of ecology or human health. Consequently, based on past information on the Lake, it is proposed that the benchmark concentrations for total nitrogen be 1.4 mg/L in East Basin and 1.0 mg/L in West Lake.

It is proposed that for ammonia, the benchmark level should be 0.1 mg/L, which is the ANZECC/ARMCANZ (2000) trigger value.

Algae and Chlorophyll-a

Total algal counts and chlorophyll-a concentrations have remained in the same general range, despite phosphorus reduction measures implemented at the Queanbeyan Wastewater Treatment Plant. However, the intensity of late summer cyanobacterial blooms has generally increased since 2005.
Based on past information on the Lake, and from other sources, it is proposed that the benchmark level for cyanobacterial cell concentration is 20,000 cells/mL. This is based on national and ACT algal water quality standards (Australian Government, 2008; ACT Government, 2010).
A benchmark value of 20 μg/L chlorophyll-a is proposed for the Lake.

Conductivity and pH

Based on monitoring information on the Lake over the past 28 years, a conductivity value of 400 μS/cm is proposed as a benchmark value.

Similarly, based on monitoring information a pH range of 6.5–8.5 is proposed for Lake Burley Griffin. This is also the same range as that specified for water based recreation in other ACT waters (ACT Government, 2011).

Bacteria

Bacterial quality as specified by Australian Government (2008) preferentially using intestinal enterococci as indicators of the potential presence of pathogens. A concentration of <200 CFU/100mL is recommended. This testing regime has been undertaken since late 2009, therefore no trend information for intestinal enterococci is available for this updated Plan.

Prior to late 2009, faecal coliforms were used as the indicator for bacteria. Historically, bacterial counts in terms of faecal coliforms have been in the same general range, except in the late summer months, at which times they have increased.

The ANZECC/ARMCANZ (2000) faecal coliform guideline value is 150 CFU/100mL for primary contact recreation, and 1,000 CFU/100mL for secondary contact recreation. This is the same as water quality standards for other ACT waters (ACT Government, 2011). The ACT Guidelines for Recreational Water Quality (ACT Government, 2010) sets the intestinal enterococci guideline value for primary and secondary contact recreation at ≤200 CFU/100mL.

These are important health based guidelines, and are proposed as the Lake Burley Griffin benchmark values for primary and secondary contact recreational activities.

Based on previous faecal coliform levels in the Lake, it is likely that additional effort and resources will be required to ensure that the Lake meets these benchmark levels. Alternatively, if these levels are exceeded, appropriate action will be required to close the Lake (or parts of the Lake) to some types of recreational activities.

However, it will also be important to establish the cause of the increase in bacterial levels. Possible factors include:

  • increased urbanisation in the catchment;
  • possible sewage overflows;
  • in-lake regrowth of coliforms;
  • better and more accurate bacterial monitoring techniques;
  • some changes to monitoring methodology for faecal coliforms;
  • increased number of waterbirds using the Lake as their home.

Metals

Trace metal concentrations have generally decreased in the Lake since abandoned mining areas upstream of the Lake were rehabilitated in the 1970s.

Consequently, trace metal concentrations in the Lake are generally not regarded as an ecological or human health problem. This is further supported by results indicating that trace metal concentrations in fish caught from the

Lake are either extremely low or below detection values specified by the Australian National Food Authority.