Swan Canning Estuary System

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About the catchment

The Swan Canning catchment comprises the 2126 km2 coastal plain section of the Swan Avon system (the total of which is approx 141 000 km2 in area).

The catchment runs north-south between Gingin and Byford, is bordered to the east by the Darling Range, where it incorporates Mundaring and Mount Helena, and to the west by the dunal system that is mostly 5 to 15 km inland from the coast.

The Perth metropolitan area spills across most of the catchment and beyond. However it does not extend far into the largest sub-catchment, Ellen Brook, which occupies most of the northern catchment and is peri-urban or rural in character. While this site encompasses part of the Forrestdale and Thomsons Lakes Ramsar site, the more western of these lakes (Thomsons Lake) falls outside the water quality hotspot boundary.

The Swan Canning catchment does not include the almost 140 000 km2 Avon River catchment upriver from Walyunga National Park (where 67 km from the river mouth the Swan River changes name to the Avon River). Also excluded are the upper reaches of the Canning River above the Canning reservoir and the upper reaches of the Helena River above the Mundaring Weir.

Values to be protected

The Swan Canning Estuary System is connected to the Swan River to the north-east and the Canning River system to the south-east. The estuarine system has a range of important environmental values in its riparian vegetation and diverse aquatic ecosystems. Notable fauna in the estuary include bottlenose dolphins, sea horse colonies, sea stars, Perth Herring and Mullaway.

The river is used extensively and is highly valued by the community for its aesthetic, recreational, commercial and environmental importance. The Swan Canning has significant cultural heritage values and is home to the endangered Western Swamp Tortoise.

Ramsar site

Thomsons and Forrestdale Lakes are situated in the Perth Basin, on the Swan Coastal Plain, and are the best remaining examples of brackish, seasonal lakes with extensive fringing sedgeland typical of the region. The Lakes provide important habitat for waterbirds on the Swan Coastal Plain with 84 species of waterbird occurring at the two lakes and 21 of them breeding.

The Becher Point Wetlands Ramsar Site comprises approximately 200 discrete, very small wetlands located between Becher Point (Indian Ocean coast) and the Perth Mandurah Road.

Water quality issues

Rapid population growth and increased urban development in the Swan Canning catchment, has led to a decline in water quality, dwindling water resources and native vegetation. The Swan Canning river system has shown symptoms of eutrophication, especially algal blooms and fish kills, over a number of years. In January 2000 a major toxic blue-green algal bloom occurred in the Swan Canning Estuary System, resulting in unprecedented closure of the whole estuary and its rivers to fishing and recreation for twelve days.

A reduction in nutrients entering the system is vital to the long term health of the waterway.

Key water quality improvement projects

  • Water Quality Improvement Plan (Final December 2009)
  • WSUD - Achieving better urban water management in Western Australia
  • Swan Coastal Catchment Predictive Modelling Data
  • Support system for phosphorus and nitrogen decisions
  • BMP Scenarios for Ellen Brook Catchment
  • Ecological Character Description for the Thomsons and Forrestdale Lakes Ramsar Site (Draft 2008)
  • A nutrient offset contributions scheme for the Swan Canning Catchment

Key stakeholders / Agencies

  • Swan River Trust
  • Department of Water
  • Department for Planning and Infrastructure
  • Department of Agriculture and Food
  • Department of Environment and Conservation
  • Western Australian Local Government Association
  • Perth Region NRM
  • Water Corporation

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