Water supply and services

Wungong Catchment Trial

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Project goal:

To determine if we can restore streamflow and surface water runoff in the Wungong catchment area

Status:

Trial

Delivery Date:

N/A

About the trial

The Wungong Catchment Trial, which began in 2005, has been conducted to determine if we can restore streamflow and surface water runoff in the Wungong catchment while maintaining a healthy forest environment.

The treatments used include selectively removing crowded trees, controlling re-growth and, in some areas, gradually replacing introduced species of trees with native species.

The original proposal for the trial estimated that an extra 4-6 billion litres of water could be produced each year.

Where is the trial being done?

The trial is being carried out in the Wungong catchment area, which is about 60km south-east of Perth in the Shire of Jarrahdale. The catchment is in the high rainfall zone, and consists mainly of jarrah, marri and sheoak trees.

The forest in the catchment area has been significantly affected by past forestry practices, the introduction of dieback disease and bauxite mining. It was chosen because it is now mostly regrowth forest and because there are comprehensive rainfall and streamflow records.

How is the catchment managed?

 Forest management work undertaken as part of the Wungong Catchment Trial is done in line with Department of Environment and Conservation's (DEC) interim silvilculture (forestry) guidelines, which were prepared specifically for the trial and are consistent with the Conservation Commission's Forest Management Plan 2004-2013.

Silviculture guidelines follow best practice forest management for environmental and water values, and use a range of treatments.

To date, we have worked with DEC to develop three interim silviculture guidelines for on-the-ground operations of the Trial. These guidelines are published as part of DEC's Sustainable Forest Management series and include:

Interim Guideline 1 - Silvicultural Practice in the Jarrah Forest of the Wungong Catchment, 2007

Interim Guideline 2 - First Thinning of Bauxite Rehabilitation Areas Established After 1988 with Native Species in the Wungong Catchment, 2007

Interim Guideline 3 - First Thinning of Bauxite Rehabilitation Areas Established Before 1988 with Exotic Species in the Wungong Catchment, 2007

Following a community consultation process, the draft Silviculture Guideline 4 (for Treatment Area 4) is currently with DEC for its consideration.

Who is conducting the trial?

We are conducting the Wungong Catchment Trial in collaboration with the Department of Environment and Conservation (DEC). DEC implements all on-the-ground operations.

What happens after the trial?

At the end of the trial, the findings will be reviewed and may be used to inform the management of other water supply catchments in high rainfall zones. DEC will continue to maintain the forest according to their guidelines.

We are committed to ensuring our stakeholders and community understand the aims of the Wungong Catchment Trial.

More than 1,000 people have toured the catchment area with members of the project team, and we have consulted with the community on various aspects of the trial.

Community Consultation

We asked the community to comment on our latest draft Silviculture (Forestry) Guideline between 5 June and 17 July 2012. The aim of the guideline is to restore soil moisture, groundwater levels and streamflow to approximately 70% of the levels experienced in the 1990s.

In the first decade, this is expected to produce an extra 7 billion litres of water to flow into the Wungong Dam, which is enough to supply over 26,000 households for one year.

Since 2005 when the trial commenced, continued reductions in rainfall have reduced groundwater levels to such a degree that the original proposal will no longer recover groundwater levels enough to impact streamflows. The draft guideline proposes a more intense level of thinning, over about 15% of the original trial area (referred to as Treatment Area 4) for the continuation of the project.

The draft guideline was informed by:

  • Comprehensive streamflow monitoring and research
  • Thinning trials in Chandler and Cobiac sub-catchments
  • Hydrological process modelling

As a result of your feedback, we revised the draft Silviculture Guideline to include specific references to dieback, chemicals, burning, soil movement, erosion and compaction, and salinity.

Below you can read the revised draft Silviculture Guideline, Response to Public Submissions and the Streamflow and Groundwater Enhancement Report, which provides more information about the proposed guideline. 

The revised draft guideline is currently with the Department of Environment and Conservation for consideration.

Draft Silviculture Guideline 4 – Revised September 2012 

Response to Public Submissions

Streamflow and Groundwater Enhancement report

More information

You can find out more about the Wungong Catchment Trial through our project newsletter, Wungong Whispers. In our last newsletter we reported on the draft Silviculture Guideline 4, Dr Robert Humphries provided a case study on the bio-physical environment and we discussed the cockatoo research that has been carried out as part of the trial.

Wungong Whispers - April 2012

Wungong Whispers - November 2011

Wungong Whispers - May 2011

The Wungong Catchment Trial has assessed the effect of different forest management treatments on streamflow and supports a comprehensive range of research and monitoring projects to understand the interaction between water, land and biodiversity.

There are 18 research projects in the areas of water, forest and biodiversity. Our latest reports on these projects are available below.

Aquatic Fauna Biodiversity Assessment

This report, prepared by consultants Wetland Research and Management, forms part of the Wungong Catchment Trial's monitoring and research program for biodiversity.

Read the report

Demonstration plots in native forest and rehabilitated mine pits

These two reports by consultant Frank Battini discuss the various demonstration plots set up in the northern jarrah forest as part of the Wungong Catchment Trial. The demonstration plots provide a first-hand view of the results for different silviculture prescriptions for native forest areas and rehabilitated mine pits.

Read the report for native forest

Read the report for mine pits

Modelling of forest management options for 31 Mile Brook catchment

Water and Environmental Consultants undertook a modelling study at 31 Mile Brook, near Jarrahdale, to assess the potential hydrological benefits from managing the forest vegetation cover.  The need for the study arose from the below-average rainfall we have been experiencing over recent years, and the effects it is having on groundwater and streamflow declines in the jarrah forest.

Read the report

Future streamflows from the northern jarrah forest: Learnings from the Wungong Catchment Trial

Prepared by A Reed, K Barrett and J Croton, this report summarises the trial's hydrological research findings and builds on the extensive research undertaken in the region since the late 1960s.  The research uses the latest monitoring data and sophisticated computer modelling techniques to help us understand the historic changes that have taken place in the catchment, and how streamflow and groundwater may respond under various rainfall and forest management scenarios.

Read the report

Past reports

A list of all reports produced during the trial is provided below. To request a past report please email wungong@watercorporation.com.au or call the Community Engagement Officer on (08) 9420 2912.

List of all Wungong Catchment Trial reports