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 condition for aquaculture discharge in Australian Temperate Grassy Woodlands & Plains, based on scientifically endorsed standards and ecological studies.

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 (1)

Toxicant default guideline values for aquatic ecosystem protection ...

Water Quality Objectives - Murray River catchment (NSW)

View Source

Supporting Sources (4)

Additional references from the underlying research that informed this benchmark.

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

Direct Evidence Journal

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

View Source

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

Water resource assessment for the Southern Gulf catchments - CSIRO

Direct Evidence Journal

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

View Source

Context

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

Lifecycle

Status Superseded
Version 2
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.