Water Nitrate

AUS-AMR-AQU-WNI General Moderate confidence

Benchmark Value

11.5 mg/L

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 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

For moderately hard water (30–150 mg/LCaCO3), a common condition in many surface waters, the upper limit for 95% species protection is 11.5 mg/L NO3− (2.6 mg/L as NO3−-N). Concentrations exceeding this level are expected to cause direct toxic harm to aquatic life and represent a state of severe degradation.

Metric Definition:

Upper detrimental threshold for nitrate concentration based on toxicity guidelines for aquatic life protection.

Benchmark Definition:

This benchmark represents the maximum nitrate concentration in moderately hard water typical of the biome, above which direct toxic harm to aquatic life is expected.

Justification:

Based on ANZG default guideline values derived from laboratory toxicity tests and species protection levels.

Sources (1)

(PDF) Water quality parameters and population characteristics for the Flinders Ranges Gudgeon - ResearchGate

Toxicant default guideline values for aquatic ecosystem protection ...

View Source

Supporting Sources (2)

Additional references from the underlying research that informed this benchmark.

Preview of Establishment of reference conditions and trigger values for chemical, physical and micro-biological indicators in New Zealand streams and rivers - Ministry for the Environment, accessed August 11, 2025,

Establishment of reference conditions and trigger values for chemical, physical and micro-biological indicators in New Zealand streams and rivers - Ministry for the Environment, accessed August 11, 2025,

Direct Evidence Journal

Australian and New Zealand Guidelines for Fresh and Marine Water Quality (2000)

View Source

SA Arid Lands Landscape Regional Summary 2022 Aquatic ..., accessed July 30, 2025,

Direct Evidence Government

(PDF) Effects of increasing salinity on freshwater ecosystems in ...

View Source

Context

Region Australia
Biome Arid Mountain Ranges & Uplands
Land Use Aquaculture
Assessment Not Stated
Evidence Type DegradationThreshold

Lifecycle

Status Active
Version 4
Effective From 4 Jun 2026

Notes

This threshold represents the maximum nitrate concentration before direct toxic harm occurs in moderately hard water typical of the biome. AssessmentContext defaulted to 'Not Stated' because the source document did not state one.

Related Benchmarks

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