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This GIS layer has been produced by using the Northland river water quality current state predictive model developed by NIWA using Random Forest statistical method. The uncertainty of model prediction is high for DRP, suspended fine sediment and E.coli, particularly in Aupouri, Herekino and Bream Bay Freshwater Management Unit (FMU) area. For any water quality attribute this predictive model should always be viewed together with the current water quality state at the SOE monitoring sites.

Attribute field  Field description

streamOrde - Stream order

nzsegment - UID for river segment based on REC (River Environment Classification model)

NH4medState - Ammonia median - NPSFM band

NH4maxState - Ammonia max concentration (95th percentile) - NPSFM band

NO3medState - Nitrate median - NPSFM band

NO3maxState - Nitrate max concentration (95th percentile) - NPSFM band

DRPmedState - DRP median concentration - NPSFM band

DRPmaxState - DRP max concentration (95th percentile) - NPSFM band

ClarityState - Horizontal visual clarity (Suspended fine sediment) - NPSFM band

EcolMedState - E.coli median - NPSFM band

EcolMaxState - E.coli max concentration (95th percentile) - NPSFM band

Shape_Length - River segment length

The details of NIWA water quality model with its methodology, accuracy level and uncertainty can be found in the Northland water quality model by NIWA - Draft report.