River health is a term used to describe the ecological condition of a river. Health is more than just the plants and animals that live in a river or the quality of the water in it. It depends also on the diversity of the habitats, plant and animal species, the effectiveness of linkages and the maintenance of ecological processes.

Diversity of habitats and life

Rivers support an enormous diversity of life by providing a range of habitats between aquatic and land ecosystems. River habitats include the river channels, the vegetation on river banks, the floodplains and estuaries and lakes. (For more information, see how rivers work).

Each of these habitats includes a complex array of smaller habitats with different physical conditions. For example:

• river channels have pools, riffles, debris dams, rocks, woody debris, river banks and benches
• floodplains may have billabongs, intermittent lakes, swamps, chains-of-ponds, debris piles and channel systems
• river bank vegetation includes reeds, grasses, shrubs and trees.

Maintenance of this diverse range of habitats and the animals and plants depending on them is of key importance for healthy rivers.

Linkages

Maintaining linkages means making sure that a river is part of the total landscape, that it is not just regarded as a channel running though the land. Disruption of any of the linkages along a river, between a river and its banks and floodplains and between a river and groundwater sources will affect the health of a river.

Ecological processes

The ecological processes operating within a river are important for maintaining its health and biodiversity. They include:

• ensuring the river has enough energy and nutrients to sustain its food chain
• maintaining animal and plant populations through reproduction or regeneration, dispersal, migration, immigration and emigration (some species have quite specific requirements, for example: some fish need specific flows before they will migrate and/or breed, waterbirds need particular flood durations and temperatures before breeding, and many plant seeds require flooding prior to germination)
• maintaining natural interactions between species such as predator-prey, host-parasite and competition relationships (changes to flow, river bank vegetation or species composition such as through the spread of an exotic species such as carp (read a story about this) can affect species interactions by favouring some species over others.

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