Water Turbidity

AUS-TMS-URB-WTU General Moderate confidence

Benchmark Value

5 NTU

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

A study of tropical macroinvertebrate communities identified a substantial drop in the abundance of tegument-respiring invertebrates at turbidity levels beyond 5 NTU.

Metric Definition:

Water turbidity concentration in surface waters

Benchmark Definition:

Ecological tipping point for turbidity in tropical monsoonal savanna urban waters where significant harm to macroinvertebrate communities occurs beyond 5 NTU.

Justification:

Linked to a documented, community-level ecological impact indicating a significant decline in sensitive macroinvertebrate abundance.

Sources (1)

Preview of Clarity and colour - WetlandInfo, accessed August 12, 2025,

Clarity and colour - WetlandInfo, accessed August 12, 2025, Government

Determining Tipping Points and Responses of Macroinvertebrate Traits to Abiotic Factors in Support of River Management - PMC - PubMed Central

View Source

Supporting Sources (4)

Additional references from the underlying research that informed this benchmark.

Preview of A review of guideline development for suspended solids and salinity in tropical rivers of Queensland, Australia - ResearchGate, accessed May 11, 2025,

A review of guideline development for suspended solids and salinity in tropical rivers of Queensland, Australia - ResearchGate, accessed May 11, 2025,

Contextual Support Journal

Queensland Water Quality Guidelines (QWQG), accessed July 25, 2025,

View Source

Darwin Harbour water quality report 2020 | Department of Lands ...

Direct Evidence Government

Darwin Harbour water quality report 2020 | Department of Lands ...

View Source

Darwin Harbour water quality report 2020 | Department of Lands, Planning and Environment

Direct Evidence Government

Darwin Harbour water quality report 2021 | Department of Lands ...

View Source

Water Quality Guidelines Level of protection, accessed August 11, 2025,

Direct Evidence Government

Water quality objectives for the Darwin Harbour Region

View Source

Context

Region Australia
Biome Tropical Monsoonal Savannas
Land Use Urban & Developed Use
Assessment Not Stated
Evidence Type DegradationThreshold

Lifecycle

Status Active
Version 1
Effective From 5 Jun 2026

Notes

This 5 NTU value is a detrimental threshold indicating a tipping point beyond which aquatic macroinvertebrate communities are significantly harmed. It validates the protective nature of the <4 NTU benchmark. AssessmentContext defaulted to 'Not Stated' because the source document did not state one.

Related Benchmarks

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