Thomsons Lake A Class Reserve Rehabilitation

 

 

 

 

 

 

 

 

 

 

 

 

Water Corporation

The Water Corporation of Western Australia (Water Corporation) constructed the Perth Seawater Desalination Plant, a $387 million plant and $125M of assets to deliver water to the Integrated Water Supply System (IWSS) and supplement Perth’s public supply by 17 percent.  Among the thirteen proponent and seven Ministerial and legally binding environmental commitments were key measures to manage flora and fauna.  360 Environmental worked directly with the Water Corporation and the Department of Environment and Conservation (DEC) to restore native vegetation between Thomsons and Kogolup Lakes within the A Class reserve and surrounding areas after the main desalination pipelines were installed.

Rehabilitation

Restoration and rehabilitation efforts commenced in the winter of 2006.  From mid-July, seed was spread and seedlings planted and fertilised.  The key areas that required restoration included:

• Pipeline route between Kwinana and Thomsons Lake
• Thomsons and Kogolup Lakes, Beeliar Regional Park
• Bartram Road Buffer lakes, Success
• Mather Reserve, Banjup
• Wetland Area near Bartram Road and within Jandakot Regional Park
• Wetland at the Nicholson Road Pump Station in Forrestdale

The seed spreading, seedling planting and fertilising was undertaken by a not-for-profit organisation, who competitively won the tender.  The rehabilitation areas were extremely diverse, ranging from the coastal primary dune in Kwinana to inland wetland areas, including an area within Thomsons Lake Nature Reserve, an internationally recognised wetland providing a habitat and refuge for water birds.

Seedlings were supplied from five different nurseries.  Seed was collected and sourced for specific areas.  Provenance-correct seed was collected from the A Class Reserve (with DEC approval).  This seed was then used to grow provenance seedlings for the restoration between Thomsons Lake.  The 2005/2006 cool summer prevented a generous seed set.  Therefore, in order to sustainably collect the required volumes of seed, collection occurred over two seasons.

Weed control programs were implemented prior to the planting seasons to help eliminate any competition for native seedlings. To further increase the survival rates of the green stock, mulch composted to Australian Standards (AS 4454), certified weed and dieback free was spread throughout the rehabilitation sites at an optimal depth of 100 mm before planting commenced.  The idea of utilising mulch is that it not only suppresses weed growth, it also helps to retain moisture content and provides nutrients for the seedlings when it biodegrades into the topsoil and soil layers.

All seeding was carried out prior to the planting and mulching programs. Native provenance seed was collected and broadcast in June with a bulking agent (to ensure an even coverage of seed). Seedlings for the reserve were grown from locally collected seed to ensure the provenance was maintained (and seedlings were endemic to the area). There has also been some natural recruitment of native species germinating throughout the sites, which may be partly attributable to good topsoil management. Green stock used outside of the A Class Reserve was sourced from dieback accredited nurseries.

 All seedlings were planted with an appropriately-sized, slow-release native fertiliser tablet to supply nutrients to the seedling over a period of time.  Rabbit proof fences were installed at the entrance to the A Class Reserve and within the reserve to protect the seedlings.  All green stock planted in areas outside the fences were protected with tree guards, which are maintained monthly until they can be removed.

Site meetings were held regularly for the duration of the project to ensure quality control measures and timelines were kept.  Weekly toolbox meetings were established to improve project quality and efficiencies.  All specifications for the project were followed and the planting program was completed successfully within the timeline given.

Rehabilitation Outcomes

A Rehabilitation Management Plan was finalised with input from the (then) Department of Conservation and Land Management and the Wetlands Conservation Society.  Ongoing monitoring was incorporated to ensure compliance criteria were met. 

The 2006 plantings have progressed remarkably well both inside the reserve and the Buffer Lakes, showing a high density and a large diversity.  Priority 4 species Dodonaea hackettiana has progress exceptionally well, even dominating some planted areas.  Areas where the success rate was not as positive, infill planting was undertaken as a part of the 2007 program. This successful rehabilitation project has been the subject of ongoing maintenance and monitoring.  Weed control throughout the site has been instrumental in producing a rehabilitation area that has a high diversity and density of vegetation, is self sustaining and aesthetically pleasing.

Contact

Email: admin@360environmental.com.au

Telephone: +61 8 9388 8360