Water Turbidity

AUS-TMS-URB-WTU General High confidence

Benchmark Value

4 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 2 benchmarks together — the OptimalRange form drives the primary score, while 1 guard(s) constrain the result.

Contributing Benchmarks

OptimalRange Primary MaximumOnly Guard

Evidence & Context

The WQO for turbidity, applied across all zones of the estuary (Upper, Mid, and Outer), is set at <4 NTU.

Metric Definition:

Water turbidity concentration in surface waters

Benchmark Definition:

The ambient, dry-season Water Quality Objective (WQO) for Darwin Harbour representing a high ecological health state in a tropical monsoonal savanna urban estuary.

Justification:

Derived using the 80th percentile of ambient data from local reference sites, established by government environmental protection agency, and validated by long-term monitoring.

Sources (3)

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

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

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

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

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

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

Water quality objectives for the Darwin Harbour Region

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Supporting Sources (2)

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

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

Direct Evidence Government

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

View Source

Context

Region Australia
Biome Tropical Monsoonal Savannas
Land Use Urban & Developed Use
Assessment Pristine Reference
Season dry season
Evidence Type ReferenceCondition

Lifecycle

Status Active
Version 1
Effective From 5 Jun 2026

Notes

This benchmark represents the ambient, dry-season Water Quality Objective (WQO) for Darwin Harbour, a large, urban-influenced estuary in Australia's tropical monsoonal savanna that demonstrates 'very good' ecological health. It is selected as the best-on-offer real-world state for a well-managed urban system. The <4 NTU benchmark is protective against the known ecological harm tipping point at 5 NTU for macroinvertebrates. There is no evidence supporting a lower critical threshold for turbidity in managed urban systems.

Related Benchmarks

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