Introduction

The NCA is responsible for the management of the National Capital's Lake Burley Griffin to ensure its sustainable use and to protect and enhance its water quality.

This section covers:

  • Recommended benchmark values for key water quality indicators.
  • Overview of the water quality monitoring programs.
  • Actions arising from the management of pollutants.
  • Communications.
  • Use of legislation.
  • Roles and responsibilities.

Recommended Benchmark Values for Key Water Quality Indicators

The recommended benchmarks for water quality in Lake Burley Griffin are as follows:

Recommended benchmarks for water quality in Lake Burley Griffin
Environmental Values Benchmark Values
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
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.Cyanobacterial cell concentration of 20,000 cells/mL.Chlorophyll-a concentration of 20 µg/L.Conductivity of 400 µS/cm.pH range of 6.5-8.5Metal values as specified by ANZECC/ARMCANZ (2000).
Recreational water Recreational benchmark values are based on the NHMRC 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 <4µg/L (possible toxins include microcystins and cylindrospermopsins), or <20,000 cell/mL where known toxin producing species are dominant.pH range of 6.5-8.5
Irrigation water for parks and gardens Water quality based on the Guidelines for Managing Risks in Recreational Water (Australian Government, 2008)

Benchmark values are provided only as a guide. The values for East Basin can be used generally for the eastern sections of the Lake (i.e Central Basin) whereas the values for the West Basin can be used generally for the western sections of the Lake (i.e West Lake to Scrivener Dam).

Although the development of a benchmark value in this Water Quality Management Plan (WQMP) generally follows the Australia-wide National Water Quality Management Strategy procedures, it nevertheless includes some local adaptations.

Instead of defining water quality objectives based on 80th percentile values, this WQMP proposes water quality benchmark values. These benchmark values are close to, but not necessarily exactly, at the 80th percentile values for each data set. The benchmark values as used in this WQMP are based on a combination of statistical analysis and scientific judgement. The benchmark values in this updated WQMP also take into consideration the values of the Guidelines for Managing Risks in Recreational Water (Australian Government, 2008).

The benchmark values will be reviewed from time to time, as new information and research on water quality becomes available.