Research
Pre-existing projects Considerable environmental work has already taken place in the catchment. A number of demonstration sites exist, foreshore surveys have been carried out, and CSIRO has carried out two studies in the Lake Powell/Torbay Inlet area.

Making research count
A conference paper prepared by Louise Duxbury: Communication Consultant to the Watershed Torbay Project. An extract from this paper was presented at the Watershed Torbay Technical Advisory Committee meeting June 2002 by Louise.

Research Projects

Watershed Torbay research projects were selected based on the following criteria:

  1. What is the capacity of the research to answer the key community questions?
  2. Will the research provide information to influence the selection and implementation of actions? (This criterion has double weighting)
  3. How transportable is the research to other catchments throughout Australia?
  4. How urgent is the research in terms of influencing actions (this is the priority), or is it addressing a long term issue?
  5. What is the likelihood of obtaining other potential funding sources instead of Watershed Torbay funding?
  6. What is the direct cost of the proposal and the extent to which there is matching funding for it?
  7. What is the research proposal's potential to give results that lead to low cost land-use management change (behavioural change)?

Environmental flows
These projects will look at the likely demands for water from the waterways in the catchment, and the requirements of the major waterways:


Algal blooms: processes and drivers
Sources of nitrogen to Lake Powell and Torbay Inlet

In September 2004, CENRM developed a costed project proposal to use Del-N values (N14/15 ratios) to identify relative sources of nitrogen to Lake Powell and possibly Torbay Inlet. This will require an analysis of aquatic plants to determine if the ultimate source of nutrients in plants (algae) is from sewage, agricultural fertilisers or through nitrogen fixation. The outcome from this research will also help clarify community perceptions about the impact of the WWTP on Lake Powell. This project proposal was accepted, with the work in Lake Powell to be undertaken initially. If successful, and dependent upon funding, the research may be expanded to Torbay Inlet.

Research update, February 2005: Craig Russell, CENRM:

1: Sources of nitrogen to Lake Powell - N isotope study

After securing this proposal Craig Russell was approached by Simon Brett (4th year Centre for Water Research student) to conduct an honours project on triggers to algal blooms across the Torbay waterways. Simon's proposal was developed through consultation with Anas Ghadouanni (UWA), Malcolm Robb and Helen Astill. The first part of Simon's research will involve characterising the nutrient status of Lake Powell. While this opportunity has held up the execution of the project, which was originally to be conducted with casual labour, it will lead to a far greater overall achievement and interpretation. Funds from the consultancy will be used to support Simon's scholarship and operating expenses. Simon finished his lake water and phytoplankton collections the week ending 25th February 2005, his project finishes in October 2005 with the submission of a research thesis. So far 40 samples of algae have been collected from across Lake Powell and its catchment. These have been processed and sent to Griffith University for N-15 analysis.

2: Sediment nutrient load and mineralisation potential

The aim of this project is to determine the nitrogen potential contained in the sediments within Lake Powell and Torbay Inlet. Sediments would be collected, incubated under anaerobic conditions to release ammonia, then analysed. While this does not provide any information on available nitrogen, it provides information on the potential for nitrogen release from sediments should anaerobic conditions prevail. While low oxygen is not an issue for Lake Powell at the water interface, anaerobic sediments may be contributing to high pore water values found by AGSO in 2002, and may be contributing significantly to nutrient cycling in Lake Powell.

Duplicate composite samples of sediment (surface organic, 0-5 cm and 5-10 cm depths) were collected from Lake Powell early December 2004. These samples were described in the field, dried, ground and weighed. Sub samples were incubated anaerobically for 21 days at 30°C and the biologically released ammonium and phosphate extracted. Incubation extracts and sediments will be analysed for nitrogen and phosphorus in April 2005.

Sediment-Water Interactions and Nutrient Release

Understanding the interaction between sediments and the water column in Lake Powell and Torbay Inlet is critical to understanding the overall nutrient balance, and role of sediments in providing nutrients to support algal blooms in summer. Lake Powell does not get anoxic because of its shallow depth and strong mixing. Some areas of Torbay Inlet and Marbellup Brook (below 'the plug') do experience anoxic conditions on a seasonal basis.

Ideally, investigations of nutrient cycling using benthic flux measurements would be undertaken. Geoscience Australia have the best capability to do this, and would replicate similar work undertaken in Wilson Inlet.

Malcolm Robb has advised there may be some potential to access Geoscience Australia to do some additional work at minimal cost. Dave Weaver has advised of some alternative methodologies developed by Murdoch University. Options to be further investigated.

Outcome: Geoscience Australia (previously AGSO) provided a project proposal and completed the study in April 2005. The project proposal included AGSO 2002 report summary.
Report due: GA's report on this latest study is due June 2005.

Environmental Criteria for Lake Powell, Lake Manarup and Torbay Inlet

To enable further development of the decision criteria for assessment of the drainage scheme, an expert panel and desk-top study approach is proposed to refine the water level criteria required, to protect the environmental values of the systems and minimise algal bloom frequency and other impacts. In particular advice would be sought about:

  • Appropriate water level regimes to protect and aid recruitment of fringing vegetation, provide water-bird habitat, and protect other values (fish, invertebrates etc).
  • Appropriate water regimes to aid nutrient cycling (for example bed drying to aid denitrification?)
  • Appropriate water regimes to manage typha invasion in Lake Powell

The approach to this task is:

  • Field trip of range of experts to undertake an ecological snapshot of Lake Manarup.
  • Compilation of other information on values and condition of Lake Powell and Torbay Inlet (DoE)
  • Literature review (CENRM)
  • Convene expert panel to discuss and develop water regime recommendations (CNRM and DoE)

DoE and CENRM to jointly develop a proposal for the expert panel, to identify appropriate participants and roles. The field trip to Manarup Lagoon has been completed (30th September 2004).

Phytoplankton drivers in Torbay Inlet and Lake Powell, South-Western Australia

A report has been completed by Helen Astill, Aquatic Sciences Branch, Department of Environment. Its reference is: DOE (2004). Background Document to determining Phytoplankton Drivers in Torbay Inlet and Lake Powell, South-Western Australia Department of Environment, Western Australia (unpublished).

The annual toxic algal blooms experienced in Lake Powell, Torbay Inlet, and the associated waterways are the focus of the following research projects for Watershed Torbay:

Report available: Background document to determining phytoplankton drivers in Torbay Inlet and Lake Powell, south-western Australia (2005).

Managing the lower drainage system
The lower catchment has been extensively drained by a very complex system which is an integral part of local agriculture. The project will look at how the drainage system works and how it may better meet the requirements of the people who use the area.

Report available: Foreshore Condition Survey and Management Recommendations for Drains and Waterways in the Torbay Inlet Subcatchment (2003).

Report available: Source Document for the Watershed Torbay Drainage Committee (480K). This report also has a separate Appendix (84K)

Catchment nutrient sources
Groundwater Investigations

Groundwater interactions with Lake Powell, Lake Manarup and Torbay Inlet:

Analysis of groundwater monitoring and analysis from 26 piezometers around the three water bodies to determine:

  • How closely linked the shallow aquifer is to the surface water system.
  • Estimates of quantity of water exchange between GW and SW and times of year this occurs.
  • Estimates of nitrogen and phosphorous contributions to or losses from the waterways.
  • Evidence of other issues such as acidity and further research required to better understand the system.

Data analysis and report completed by Steve Appleyard, Land and Water Quality Branch, DoE. Draft Report: DOE (November 2004). What Lies Beneath... Impact of groundwater and subsoil geochemical processes on the health of waterways in the Lower Torbay catchment, South Coast Region, Western Australia Unpublished report, Department of Environment, Western Australia.

Groundwater Hydrology and Nutrient Transport

This was identified as a research need at Technical Group meetings. Dave Weaver sent around some thoughts on this based on a recent study by Song Qui of Murdoch Uni. Steve Appleyard proposed a link to acid sulphate soils. Gerard Edwards has enrolled with CENRM to do an honours research project in this area. Dave Weaver, Adam Lillicrap, Andrew Maughan, Steve Appleyard and Craig Russell will assist Gerard with a project proposal. The project will require the installation of several peizometers into Lake Powell and its surrounds, and will make use of the existing network of peizos and their hydro and nutrient status data. Whilst Gerard is required to finalise his research and thesis by end of October, it is proposed that the experimental set-up he uses will be available for long term monitoring.

Nutrient discharge from Potato Farms to Lake Powell via flooding and or surface drainage

The aim of this research is to determine the level of surface water interaction between potato farms and Lake Powell, through both inundation due to lake flooding, or localised surface water drainage to the lake. The first step is to use land survey information and local inspection to determine the flooding potential of Lake Powell. To be undertaken by DoE (Andrew Maughan).

If surface water flows to Lake Powell, or if flood water recedes into Lake Powell, then CENRM with assistance from David Weaver to develop project to undertake sampling to determine potential nutrient inputs.

Initial Investigations in November 2004 included discussions with landowners and site assessment carried out by Andrew Maughan and Julie Pech, which determined that surface water runoff from potato farms is via feeder drains into North Creek drain. There appears to be no surface drainage or flooding of surface waters from potato farm from the south into Lake Powell. Sample sites in North Creek drain and feeder drains have been identified by Andrew Maughan, and will be included in a nutrient snapshot following a high rainfall event, to give preliminary indication of nutrient loads running off potato farms into Manarup Lagoon via North Creek Drain.

This is a critical part of Watershed Torbay, and the following projects have been set up to investigate the sources of nutrients in the waterways and methods to prevent movement of nutrients from the land to the water.

  News item: Dutch input on nutrients - Hugo van der Meer, a Senior Scientist with Plant Research International at Wageningen Agricultural University in the Netherlands, provides some eye opening insights into the management of nutrients in Holland. Hugo's Powerpoint presentation is also available on-line.
Social and Economic Issues
These projects will look at the social issues involved in managing the catchment waterways.