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River networks and catchments

Earth Sciences New Zealand continues to publish the River Environment Classification (REC2) framework developed by NIWA. REC2 is a connected national river network with catchment attributes and topology used by many freshwater models.

The current downloadable revision described by ESNZ is REC2 version 5 (v2.5).

What REC2 is good for​

  • national river network
  • stream order
  • upstream/downstream traversal
  • reach identifiers
  • catchment attributes
  • linking national freshwater models and monitoring

What it is not​

REC2 is not a survey of every visible drain or small channel at LiDAR resolution. A 1 m DEM can reveal local drainage detail absent from the national network.

Use the two scales together​

Start with REC2 for network identity and catchment relationships. Use LiDAR terrain for local flow-path screening. Check culverts, stormwater and modified drains against council/local data because terrain-only hydrology will not see underground infrastructure.

Official source: Earth Sciences NZ / NIWA REC2.

Last reviewed: 26 August 2026

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