A NSW Government website

Monitoring changes in surface water environments

NSW River Condition Index

A consistent riverine condition assessment method.

The NSW River Condition Index (RCI) is the primary long-term reporting tool for assessing change in riverine condition. The tool uses inputs from a range of indicators.

The RCI was developed using the Framework for the Assessment of River and Wetland Health (FARWH) approach. The FARWH is an accepted approach applied throughout Australia. This approach is based on a hierarchical model of river function. The FARWH recognises the effects of catchment disturbance, physical form of the landscape, hydrologic regime, water quality, riparian zone and aquatic biota as measures of river health. The FARWH method uses existing data collection activities across Australia. It converts them into a standardised and nationally comparable representation of river health.

The River Condition Index: method development and application provides a detailed explanation of the index and how it has been applied across NSW, a summary of the RCI indices is explained below.

Inputs into the NSW River Condition Index

The River Condition Index approach provides a consistent riverine condition assessment method. It includes riparian vegetation, geomorphic condition, hydrologic stress, biodiversity, catchment disturbance and water quality.

Riparian vegetation condition

A riparian zone or riparian area is the interface between land and a river or stream. Riparian vegetation are the plants occupying this zone. Riparian vegetation is more diverse and abundant than nearby terrestrial habitats. Healthy riparian zones provide many benefits, including:

  • habitat for native birds, reptiles, frogs, mammals and insects
  • shade to help moderate water temperature
  • organic input to waterways
  • bank stability
  • a filter for runoff that trap land-based sediment and nutrients.

The River Condition Index assesses riparian vegetation condition using:

  • riparian zone width
  • a measure of native versus exotic plant species
  • the extent of native woody vegetation.

Figure 1. Good versus poor riparian vegetation condition

Figure 1. Good versus poor riparian vegetation condition.

Geomorphic condition

Rivers are diverse in their physical character and behaviour. Human-induced changes in a catchment affect river processes.

Geomorphic condition measures natural channel function against its response to change. Rivers in good geomorphic condition are important for instream biodiversity, ecological diversity, and overall catchment condition. There is a strong connection between healthy floodplain, channel and groundwater. Rivers in poor geomorphic condition are indicative of stressed catchments. These rivers are unlikely to favour aquatic biodiversity. This is due to a reduction in geomorphic stability and available habitat. The connection between floodplain and groundwater is lost as the channel incises into its bed.

The River Condition Index uses the River Styles Framework  to assess geomorphic condition. The River Styles approach scores river reaches according to their river type, behaviour, condition, fragility and recovery potential, relative to a reference condition.

Figure 2. Good versus poor geomorphic condition

Figure 2. Good versus poor geomorphic condition

Hydrologic stress

Hydrologic stress is a measure of change to natural flow regimes in catchments. It is the amount of water extracted relative to river flow. Hydrologic stress shows the risks posed to instream values from extraction. It is an indicator of the degree of competition between extractors. Hydrologic stress helps to assess river condition.

Figure 3. Hydrologic stress in low flow conditions and water extraction in low flow conditions.

Figure 3. Hydrologic stress in low flow conditions and water extraction in low flow conditions.

Figure 4. Hydrologic stress in no flow conditions and water extraction in no flow conditions.

Figure 4. Hydrologic stress in no flow conditions and water extraction in no flow conditions.

River biodiversity condition

Aquatic biodiversity is the variety of plants and animals that live in aquatic habitats such as rivers and streams. Aquatic species include fish, macroinvertebrates, frogs, reptiles, aquatic and riparian vegetation. Aquatic species rely on healthy rivers and diverse habitats for survival and reproduction. These biotic indicators can help assess river condition. Reduced river condition is associated with loss of species.

Figure 5. Good versus poor river biodiversity condition.

Figure 5. Good versus poor river biodiversity condition.

Catchment disturbance

Many activities in a catchment affect river health and resilience. These include land-use, habitat modification, infrastructure, and land management practices.

The Catchment Disturbance Index is a catchment summary of the type and extent of change in a catchment. It helps to assess river condition and includes the following features:

  • infrastructure
  • land-use
  • land cover change.

Infrastructure measures the extent of roads, unsealed roads, railways, utilities (e.g. power, pipes) and walking tracks. Land-use measures the extent of horticulture, orchards, cropping, cotton, rice, transport, production forests, grazing and wilderness/National park areas. Land cover change measures the loss of woody vegetation using satellite imagery.

Figure 6. Good versus poor catchment disturbance.

Figure 6. Good versus poor catchment disturbance.

Water quality

Water quality is a key driver of aquatic ecosystem condition. Both natural characteristics and human activities can influence water quality and thus ecosystem condition. For example, local geology can influence salt and nutrient inputs while climate, riparian vegetation extent and health, and stream flow influence sediment and nutrient loads. There are a wide range of human activities that can impact water quality. These include water extraction, pollution and changed land use.