Water in the landscape
As part of the Regional Estuaries Initiative, streams will be revegetated and fenced to deter stock. Drainage upgrades, water sensitive urban design and prioritised infill sewerage will reduce nutrients entering estuaries.
Clearing for agriculture has often removed riparian vegetation (vegetation on the banks of rivers and streams) and stock have unimpeded access to streams and drains. This can lead to degradation, sedimentation and infilling of rivers, wetlands and estuaries.
Re-establishing functional rivers and streams enhances the uptake and removal of nutrients and improves ecological and amenity values. Healthy riparian zones are the most effective measure of improved river health and water quality.
Together with catchment groups, community members and land holders, the Regional Estuaries Initiative will fence 60 kilometres of priority waterways to exclude stock and plant 20 hectares of foreshore. Outreach and extension programs will enhance farmer knowledge and skills for managing land use around waterways.
Restoring stream function through stock exclusion fencing and revegetation reduces soil erosion and organic loading while also enhancing the uptake and removal of nutrients.
Almost all of the at-risk estuaries receive water from extensive engineered drainage networks originally designed to drain the vast wetlands of the Swan Coastal Plain for urban and agricultural development. These drainage networks are still used for lowering high groundwater levels and preventing flooding of farmland and urban centres. While they usually do a good job of keeping our feet dry, drains can move water through the landscape so quickly that they pick up organic matter, sediments and nutrients along the way and discharge them to our estuaries. This can lead to algal blooms, low oxygen, and fish deaths.
Drainage waters can be treated to improve the quality of water delivered to our estuaries. It is challenging to treat large volumes of water carrying high nutrient and organic loads, especially in the winter when the landscape can be waterlogged. Drains can also have complex ownership arrangements and management responsibilities, with multiple landowners, service providers, local and State Government agencies involved.
The Regional Estuaries Initiative will treat five major drainage sites with innovative science to trap nutrients and improve water quality. The works are focussed on Peel Main, Punrak, Dirk Brook, Nambeelup and Gull Road drains, which flow to the Serpentine River, and Mayfield Drain, to the Harvey Estuary. These catchments need a 53 per cent reduction in their nutrient loads to meet their water quality objectives. The Initiative will target phosphorus load and work to reduce sediment and organic matter transport.
The works will be delivered in partnership with the Peel-Harvey Catchment Council, Water Corporation, farmers and landholders. Clear, catchment-specific guidelines for water quality improvement in constructed drains will also be developed.
Water sensitive urban design
Nutrients and organic matter from urban areas contribute significantly to poor water quality, especially in waterways with restricted circulation. Stormwater runoff can carry contaminants from industry and fertilisers from urban areas to our estuaries. For healthy estuaries, stormwater from urban areas often needs treatment.
Water sensitive urban design is a land planning and engineering design approach that integrates the urban water cycle – including stormwater, groundwater, wastewater management and water supply – into urban design to minimise environmental degradation and improve aesthetic and recreational appeal. In Western Australia, Better Urban Water Management provides a framework for how water resources should be considered at each planning stage.
The Regional Estuaries Initiative will encourage and support local governments to develop and implement best practice urban water management by providing support and matching funding for activities such as:
- Stormwater retrofits and upgrades to reduce nutrients and organic matter in Albany and Bunbury
- Collaboration with developers and local government to expand the use of water sensitive urban design in new urban areas
- Urban fertiliser behaviour change programs to promote efficient fertiliser use in home gardens, and
- Garden workshops for the community and industry.
The focus will be on reducing point source pollution and nutrient and organic matter inputs to the Leschenault, Wilson Inlet and Oyster Harbour estuaries.