Water Turbidity

AUS-AKW-URB-WTU General Low confidence

Benchmark Value

5 NTU
Thresholds: Lower: —, Upper: 50
Direction: Lower is desirable ↓
Form: MaximumOnly

Scoring Curve

This curve shows how a field measurement for this indicator would score across all available benchmark forms in this context. The scoring engine uses 13 benchmarks together — the OptimalRange form drives the primary score, while 12 guard(s) constrain the result.

Contributing Benchmarks

OptimalRange Primary MaximumOnly Guard MaximumOnly Guard MaximumOnly Guard MaximumOnly Guard Point Guard OptimalRange Guard MaximumOnly Guard MaximumOnly Guard MinimumOnly Guard MaximumOnly Guard MaximumOnly Guard MaximumOnly Guard

Evidence & Context

An upper detrimental threshold is identified at 50 NTU; sustained turbidity above this level indicates a degraded state and potential for significant ecological harm.

Metric Definition:

Water turbidity is a measure of water clarity, quantifying the degree to which light is scattered by suspended particles such as silt, clay, organic matter, and microorganisms.

Benchmark Definition:

This benchmark represents the maximum turbidity level of 5 NTU for water clarity in urban and developed areas of the Arid Karstic Woodlands & Shrublands biome, indicating high ecological health. Sustained turbidity above 50 NTU signals ecological degradation and harm.

Justification:

The low confidence rating reflects the derivation from national guidelines rather than direct site measurements.

Sources (1)

Preview of Water Quality Objectives - Border Rivers - NSW Government, accessed August 12, 2025
Water Quality Objectives - Border Rivers - NSW Government, accessed August 12, 2025 Government

(PDF) Impact of mitigated forestry activities on turbidity: assessing ...

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Context

  • Region Australia
  • Biome Arid Karstic Woodlands & Shrublands
  • Land Use Urban & Developed Use
  • Assessment Not Stated
  • Evidence Type DegradationThreshold

Lifecycle

  • Status Active
  • Version 1
  • Effective From 4 Jun 2026

Notes

This benchmark is a derived proxy representing a state of high ecological health. It is based on the lower-bound trigger values from the ANZECC (2000) guidelines for high-value aquatic ecosystems (lowland rivers: 6–50 NTU) and aligns with the objectives of Water Sensitive Urban Design (WSUD) to treat stormwater to a very high quality before discharge. AssessmentContext defaulted to 'Not Stated' because the source document did not state one.