Assessing river health allows us to determine the system’s ecological integrity, which is its ability to support and maintain a community of organisms which is comparable to natural habitat* and resistant to disturbance.
The ecological integrity of a river system is represented by all the major components of the environment that constitute the aquatic ecosystem, including both the dynamics of the inhabitants and the abiotic environment that supports them (for example water quality, physical form, catchment and climate). As such, an assessment of river health must encompass a significant diversity of information to capture ecological integrity.
In Western Australia, the assessment of river health is made more difficult as our systems are poorly understood and information relating to conditions prior to European settlement (used to compare against current condition) is limited. The Department of Water is investing significant effort to increase the understanding of river processes incorporating increased diversity of information to assess river health, including analysis of chemical, biological and physical components of the environment.
The Department is currently involved in two programs which take a whole-of-system approach to assessing river health, these are:
River Health Assessment Scheme (RHAS)
The RHAS examines the health of rivers and drains entering the Swan and Canning Rivers in Perth.
Framework for Assessment of River and Wetland Health in Western Australia (FARWH-SWWA (excluding Rangelands)
The FARWH SWWA project examines river health throughout the southwest of Western Australia and is part of a national initiative to develop a river health assessment framework which is applicable across Australia.
Within each of these programs information is collected under a number of themes, which are combined to provide an overall assessment of river health. For FARWH-SWWA the major themes include:
- catchment disturbance (i.e. effects of land use, vegetation cover and infrastructure change)
- fringing zone (i.e. structure and condition of vegetation
- physical form (i.e. sediment, bank stability)
- hydrological disturbance (i.e. water flow change)
- water quality and soils (i.e. dissolved oxygen, temperature, pH, turbidity)
- aquatic biota (invertebrates, fish and crayfish).
The goal of the department is to promote ecological integrity of our rivers, where systems are both healthy and stable whilst maintaining the significant economic and social values that are linked to all waterways throughout Western Australia.
*Natural habitat is typically related to the form and function that existed prior to significant human disturbance (pre-European settlement).