A major fish kill event occurred in Marbelup Brook at the Grassmere Road penstock at the end of January 2013, coinciding with an algal bloom in the waterway between the "plug" and the penstocks. The two species obviously affected were black bream and mullet. The fish deaths and the problems arising from the smell of the rotting algae has had a substantial impact on local residents.

The penstock, together with the "plug" (a valve) were placed in the Marbellup Brook and a man-made connecting channel to divert water from the brook into a new channel which allowed water to flow directly into Torbay Inlet (see map below). The aim was to minimise flooding on the horticultural land and rural properties around Lake Powell. This created a backwater, and with little or no flow below the plug toxic algal blooms regularly occur through the summer months. Under the Land Drainage Act 1925/1990 the Water Corporation is responsible for managing the drainage in the lower Torbay catchment.

The Torbay Lakes page has more information on the drainage system.

On the 1st of February, in response to the algal bloom and the fish deaths the Department of Water took water samples from the fish kill site and from a location on the section of Marbellup Brook downstream from the "plug", and tested them for a range of phytoplankton species. The results are summarised below:

Their conclusions as a result of this sampling were:

• No microalgal species that are toxic to fish were observed in the samples.
• The fish deaths appear to have been caused by fish trapped in deoxygenated body of water as a result of a collapsing bloom of Nodularia spumigena.
• The oxygen values will be restored as healthy microalgae increases.

At the end of January the TCG were made aware that the Department of Water has applied for funding to investigate the feasibility of moving the penstock gates to the entrance of Lake Powell so the flows are shared between the two Marbelup channels (see map above). They were also aware that the Water Austhority had plans to carry out repairs to the penstock in February 2014. The TCG emailed the Water Corporation Regional Manager David Hughes-Owen outlining their concerns that expenditure on upgrading the penstocks would divert funding which might otherwise contribute to their possible relocation.

David Hughes-Owen replied:

I visited the affected area on Monday while the clean-up of the fish kill was under way and can understand the impact the result of the algae outbreak may have had on the local community. The Water Corporation has been actively involved in assisting the Department of Water (DoW) in the management of the outbreak for several days now. I assure you that we will continue to work closely with the DoW (which is the lead agency for management of the natural watercourse between Marbellup Plug and the junction between Marbellup Brook and the drain that leads to the penstock at Bridge 45.

Initially, our operators opened a valve at the Marbellup Plug that controls the water level between the upper and lower drainage areas. This action increased the water flow and it is noticeable that there has been a marked reduction of algae along the affected area. Following discussions between the DoW and ourselves we agreed to operate a pump in the natural waterway (just downstream from the Plug) to break up the remaining algae bloom in the affected area. This pumping operation will continue to improve circulation of the water which in turn should help minimise the likelihood of the large algae bloom that was the cause of the recent unfortunate incident. The DoW will monitor water quality in the area which should provide the agency with useful information on the effectiveness of the pumping operation.

I refer also to the location of the penstocks. There are a number of operational and management issues that need to be carefully thought through by the Water Corporation and the DoW before penstocks could be moved the location suggested on your plan. I understand your concern on the Corporation starting repairs at the existing penstock site. However, I may be required to initiate some work if an assessment of the current condition of these assets demonstrates that there could be a safety risk either to our operators who work at the site or to the general public.

I would appreciate if you could circulate this email to members of the Torbay Catchment Group.

On the 7th of February, when these pictures were taken, fish were apparently still dying at the penstock.

Water Corporation – Responsible for the management of flood gates, water flows and Torbay Inlet breach
David Hughes-Owen
Regional Manager Great Southern Region
215-217 Lower Stirling Terrace
Albany Western Australia 6330
Phone: (08) 9842 4243
[email protected]

Department of Water – Responsible for water quality monitoring
Brett Ward
South Coast Regional Manager
5 Bevan Street
Albany Western Australia 6330
Phone: (08) 9842 5760
[email protected]

Department of Environment and Conservation – Responsible for management of Lake Powell (A Class Reserve)
Mike Shepherd
Albany District Manager
Albany Regional Headquarters
120 Albany Highway
Albany Western Australia 6330
Phone: (08) 9842 4500
[email protected]

City of Albany – Responsible for signage - warning the public of toxic algal blooms on Marbelup Brook Graham Foster
Acting Chief Executive Officer
City of Albany
PO Box 484
Albany Western Australia 6331
Phone: (08) 9841 9301
[email protected]

Department of Health – Environmental health including food safety and handling, pesticide, poison and radiation safety, mosquito-borne diseases, wastewater management and water quality
Susan Kay
Great Southern Regional Director
WA Country Health Service
PO Box 165
Albany Western Australia 6331
Phone: (08) 9892 2662
[email protected]