Australian Natural Resources Atlas

Natural Resource Topics

Rivers - Assessment of River Condition - Western Australia

Location Map

Western Australia River Assessment

King Edward River Drysdale River Pentecost River Keep River Ord River Prince Regent River Isdell River Lennard River Cape Leveque Coast Fitzroy River Sandy Desert Mackay Port Hedland Coast De Grey River Fortescue River Onslow Coast Ashburton River Lindon-Minilya Rivers Gascoyne River Wooramel River Murchison River Greenough River Yarra Yarra Lakes Ninghan Salt Lake Warburton Nullabor Esperance Coast Avon River Moore-Hill Rivers Swan Coast Murray River Busselton Coast Blackwood River Warren River Frankland River Albany Coast

Assessment Results

Western Australia covers an area of 2,525,500. km2, has a coastline of 12,500 km, and is 32.9 percent of the total Australian area. It extends approximately 2,400 km north-south and 1,600 km east-west. A little more than one third of the state lies within the Tropics. Western Australia has three climatic zones, the north has a predominantly summer rainfall pattern, the south a Mediterranean-type climate with winter rainfall, and a large region in between in which there is extreme variation of rainfall both annually and seasonally. Most of the State is a plateau between 300 metres and 600 metres above mean sea level and is extremely old geologically.

The biological assessment of Western Australian rivers showed that 35% of the river length assessed had impaired biological communities; in most of these rivers 20-50 percent of the animal types have been lost. The environmental assessment found that around over 93% of the assessed river length was modified, the majority of these rivers moderately. This degradation was attributed to catchment disturbance, changes to the hydrological regime and to water quality.

Seventy six percent of the river length assessed had disturbed catchments, with degradation largely attributable to land use activities. Disturbance from infrastructure was a relatively minor contributor to the overall catchment disturbance. There has been no significant change to the hydrological regime of the assessed river length in Western Australia.

Riverine physical habitat has been altered in 66% of the river length assessed in Western Australia. Changes to the bedload condition (64% modified) contributed the most to altered physical habitat followed by changes to the riparian vegetation (52% degraded). Around 23% of the river length assessed had severely modified riparian vegetation sub-index indicating that there is very little riparian vegetation left along these stretches of river.

Over 95% of the river length assessed in Western Australia had altered water quality with elevated loads of suspended solids (86%), total phosphorus (92%) and total nitrogen (85%).

Comparison of the Biota Index and the Environment Index

Ideally, scores for the two main indices would be similar for each basin. In general, the Biota Index does not demonstrate the same degree of degradation as the Environment Index. Reasons for this may include:

Environment Index scores compared to Biota Index scores for all basins.

Environment Index scores compared to Biota Index scores for all basins.

Further Information

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