Assessing the ecological value of NSW Rivers

High Ecological Value Aquatic Ecosystems

Ecological value is how we perceive the importance of an ecosystem. We use the High Ecological Value Aquatic Ecosystems (HEVAE) national framework to assess the ecological value of rivers. This tool assigns an instream value to a length of river to determine the importance of each river relative to others. Identifying rivers of high importance or high value allows for their protection and enhancement. This is essential for water sharing rules in NSW rivers.

We rely on information and data from across government agencies for the HEVAE tool. Over time the tool has improved due to technology and new contemporary data. Our assessment has gone from a water source scale approach to a single reach approach. You can find the instream value of inland freshwater rivers and coastal rivers above the tidal limit using our HEVAE mapping tool.

Figure 1 shows the four HEVAE criteria used in our assessment of NSW river values. Due to lack of data we do not include vital habitat in our assessment of coastal rivers. As more information becomes available we will include it. We also will include the fifth criteria, representativeness, for inland and coastal rivers as more information becomes available.

Overall HEVAE (instream value)


  • Threatened species
  • Endangered populations
  • Endangered ecological communities
  • Geomorphic rarity

Vital habitat

  • Wetlands
  • Dissolved organic carbon
  • Large woody habitat


  • Fish
  • Macroinvertebrates


  • Geomorphic recovery
  • Hydrologic stress
  • National Park Estate
  • Observed vs expected macroinvertebrates
  • Catchment disturbance

Figure 1. The four HEVAE criteria and associated attributes used by the department in the assessment of NSW Catchments.

Download a high resolution version of Figure 1 JPG, 1560.86 KB.

We use the HEVAE in our water sharing plan risk assessment work to describe the instream values that may be at risk from surface water extraction. We also use the HEVAE in combination with other tools to assess change in river condition. A detailed technical report outlines how the HEVAE framework has been applied in NSW.