Water Turbidity

AUS-AKW-URB-WTU General Low confidence

Benchmark Value

5 NTU
Thresholds: Lower: —, Upper: 50
Direction: Higher 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 6 benchmarks together — the OptimalRange form drives the primary score, while 5 guard(s) constrain the result.

Evidence & Context

Therefore, a reference value of < 5 NTU is proposed. This value is: Protective: It sits at the most stringent end of the applicable national guideline ranges, representing a state of high water clarity.

Metric Definition:

Water turbidity as 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 a high ecological health state for water clarity in urban and developed areas of the Arid Karstic Woodlands & Shrublands biome, based on stringent national guideline values for water turbidity.

Justification:

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.

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 ..., accessed August 10, 2025

View Source

Context

  • Region Australia
  • Biome Arid Karstic Woodlands & Shrublands
  • Land Use Urban & Developed Use
  • Assessment Pristine Reference
  • Evidence Type ReferenceCondition

Lifecycle

  • Status Active
  • Version 1
  • Effective From 19 Mar 2026

Notes

A lower critical threshold is not applicable; lower turbidity consistently indicates better ecological health. The optimal range is considered < 5 NTU, reflecting the clear water conditions of natural refuge pools between rainfall events. An upper detrimental threshold is identified at 50 NTU; sustained turbidity above this level indicates a degraded state and potential for significant ecological harm.

Related Benchmarks

Other benchmarks in the AUS-AKW-URB-WTU family.