Inputs into the NSW River Condition Index
This innovative River Condition Index approach will provide a consistent riverine condition assessment method incorporating biodiversity, geomorphic condition, riparian vegetation, catchment disturbance and hydrological stress into a single measure based on the National Framework for Assessing River and Wetland Health.
Riparian vegetation condition
A riparian zone or riparian area is the boundary between land and a river or stream. The plants occupying the riparian zone are called riparian vegetation, and are characterised by a higher diversity and abundance than nearby terrestrial habitats. Healthy riparian zones provide habitat for native birds, reptiles, frogs, mammals and insects, assist with shading and moderating water temperature, contribute organic input to the waterway, stabilise the banks and trap land-based sediment and nutrients. The River Condition Index uses riparian zone width and measures of native versus exotic plants species, along with the extent of native woody vegetation to assess riparian vegetation condition.
River styles geomorphic condition
Geomorphic condition is a measure of natural stream channel function, and how it changes in response to human-induced change in a catchment. Rivers in good geomorphic condition are important for instream biodiversity and ecological diversity, and overall catchment condition. Rivers in poor geomorphic condition are unlikely to favour aquatic biodiversity due to a reduction in available habitats and geomorphic stability, and are indicative of stressed catchments. The River Styles approach scores river reaches according to their river type, behaviour, condition, fragility and recovery potential, relative to a reference condition.
Hydrologic stress is a measure of alteration to natural flow regimes in catchments, and is calculated as the amount of water extracted relative to river flow. It is used to indicate the risks posed to instream values by extraction and as an indicator of the degree of competition between extractors.
River biodiversity condition
Aquatic biodiversity is the variety or species richness of plants and animals that live in aquatic habitats such as rivers and streams. An aquatic species (e.g. fish, macroinvertebrates, frogs, reptiles, aquatic and riparian vegetation) rely on healthy rivers and access to diverse habitats for their survival and reproduction. These biotic indicators can be incorporated into river condition assessments, with reduced river condition associated with loss of species.
Catchment Disturbance Index
The type and extent of land-use change, habitat modification, infrastructure and land management activities in a catchment affect river health and resilience. The Catchment Disturbance Index is a catchment summary of the type and extent of infrastructure, land-use and land cover change (loss of woody vegetation) in a catchment. The infrastructure index measures the extent of roads, unsealed roads, railways, utilities (e.g. power, pipes) and walking tracks. The land-use index measures the extent of horticulture, orchards, cropping, cotton, rice, transport, production forests, grazing and wilderness/National park areas. The land cover change index measures the loss of woody vegetation using Landsat imagery.
Water quality is a key driver of aquatic ecosystem condition. Both natural characteristics (e.g. geology) and human activities (e.g. pollution, water extraction, land-use) in a catchment influence water quality, and ecosystem condition. A water quality measure is currently being developed for inclusion in The River Condition Index. It will use data generated from routine monthly water quality sampling conducted throughout NSW as part of the NSW State Water Quality Assessment and Monitoring Program. The data includes turbidity, temperature, total nitrogen, total phosphorus dissolved oxygen and pH.
The diagrams within this gallery show how these factors can have an impact on our rivers.