Water Nitrate

AUS-TGP-AQU-WNI General Moderate confidence

Benchmark Value

0.5 mg/L

Direction: Lower is desirable ↓

Form: Point

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 10 benchmarks together — the OptimalRange form drives the primary score, while 9 guard(s) constrain the result.

Contributing Benchmarks

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

Evidence & Context

Water Nitrate 0.5 mg/L (as NO3−) Derived from the Australian and New Zealand Guidelines for Fresh and Marine Water Quality (2000) default trigger value for Total Nitrogen in lowland rivers of the Murray-Darling Basin, synthesized with CSIRO reports on best-practice aquaculture and ecological studies of the target biome.

Metric Definition:

Water nitrate concentration in discharge from best-practice freshwater aquaculture facilities

Benchmark Definition:

This benchmark represents the best available water nitrate concentration achievable under sustainable aquaculture practices in the Australian Temperate Grassy Woodlands & Plains biome, reflecting a low-nutrient discharge condition protective of aquatic ecosystems.

Justification:

This benchmark is derived from the ANZECC (2000) default trigger value for Total Nitrogen (TN) (0.5 mg/L) for lowland rivers in the Murray-Darling Basin, which is the most relevant, scientifically-endorsed standard for protecting aquatic ecosystems in the specified biome. It is set as a nitrate (NO3−) value for indicator specificity, assuming nitrate is the dominant, stable component of TN in treated discharge.

Sources (3)

Preview of Aquaculture viability. A technical report to the Australian Government from the CSIRO Northern Australia Water Resource Assessme

Aquaculture viability. A technical report to the Australian Government from the CSIRO Northern Australia Water Resource Assessme Journal

Living in polluted waters: A meta-analysis of the effects of nitrate and ...

View Source

Toxicant default guideline values for aquatic ecosystem protection ...

Water Quality Objectives - Murray River catchment (NSW)

View Source

Preview of Water resource assessment for the Southern Gulf catchments - CSIRO

Water resource assessment for the Southern Gulf catchments - CSIRO Journal

(PDF) Identifying ecological barriers to restoration in temperate ...

View Source

Supporting Sources (2)

Additional references from the underlying research that informed this benchmark.

Preview of Identifying ecological barriers to restoration in temperate grassy woodlands: soil changes associated with different degradation states - ResearchGate, accessed August 5, 2025,

Identifying ecological barriers to restoration in temperate grassy woodlands: soil changes associated with different degradation states - ResearchGate, accessed August 5, 2025,

Contextual Support GreyLiterature

(PDF) Identifying ecological barriers to restoration in temperate grassy woodlands: soil changes associated with different degradation states - ResearchGate, accessed August 4, 2025,

View Source

Preview of Living in polluted waters: A meta-analysis of the effects of nitrate and interactions with other environmental stressors on freshwater taxa - PubMed, accessed August 17, 2025,

Living in polluted waters: A meta-analysis of the effects of nitrate and interactions with other environmental stressors on freshwater taxa - PubMed, accessed August 17, 2025,

Direct Evidence Journal

Living in polluted waters: A meta-analysis of the effects of nitrate and ...

View Source

Context

Region Australia
Biome Temperate Grassy Woodlands & Plains
Land Use Aquaculture
Assessment Not Stated
Evidence Type ReferenceCondition

Lifecycle

Status Superseded
Version 1
Effective From 2 Jun 2026
Effective To 2 Jun 2026

Notes

Upper Detrimental Threshold: Evidence is strong that concentrations above this benchmark are suboptimal. Levels approaching 10–50 mg/L cause demonstrable sub-lethal harm (reduced growth, impaired performance) to sensitive native freshwater fauna like Silver Perch. Therefore, any discharge significantly exceeding the 0.5 mg/L benchmark indicates a degraded state, not a best-practice condition. Lower Critical Threshold: For the receiving ecosystem, which is naturally nutrient-poor, a lower critical threshold for nitrate is not ecologically meaningful. The management goal is minimization towards the natural background state to support native biodiversity. Optimal Range: The optimal range for discharge to maintain ecosystem health is ≤0.5 mg/L, reflecting the natural character of the receiving environment. AssessmentContext defaulted to 'Not Stated' because the source document did not state one.

Related Benchmarks

Other benchmarks in the AUS-TGP-AQU-WNI family.