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Legislative Council - Fifty-Third Parliament, Second Session (53-2)
2015-03-25 Daily Xml
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River Torrens

The Hon. S.G. WADE (14:45): I seek leave to make a brief explanation before asking the Minister for Sustainability, Environment and Conservation questions relating to the River Torrens at Athelstone.

Leave granted.

The Hon. S.G. WADE: Each year during spring, Athelstone residents witness the severe deterioration of the quality and level of water of the River Torrens in the area, leaving native flora and fauna vulnerable. A concerned resident writes:

The water level is so low that the river can be crossed on foot in a number of places and it smells like an open sewer. The low water quality and level is also causing problems for the local duck population, as there is no water barrier to prevent predators attacking them, especially at night…

Further discussions raised deep concerns with regard to the yearly movement of young koalas that come down from the hills and the impact the quality of water and increased number of feral animals will have on their survival. Last year, this particular resident was personally involved in six koala rescues, with only one koala surviving; the koalas were unable to access sufficient water. This resident has contacted the Department of Environment, Water and Natural Resources directly, with no response. My questions are:

1. Is the minister aware of the decline in the quality of water at Athelstone and the resultant threats to local flora and fauna?

2. Can the minister advise whether water will be released to allow water flow through the area, restoring health to the river as well as to the local flora and fauna?

3. What further actions will be taken to ensure the protection of local flora and fauna in the area?

The Hon. I.K. HUNTER (Minister for Sustainability, Environment and Conservation, Minister for Water and the River Murray, Minister for Climate Change) (14:47): I thank the honourable member for his very important and very serious questions about the health of the River Torrens in the upper reaches from the city. Of course, the honourable member may be aware of the River Torrens and its upstream dam at Kangaroo Creek Dam and how that is an important part of SA Water's reservoir system and our catchment system for supplying drinking water to Adelaide.

That necessarily means that the water flow is not as it would have been in its wild state. It means that water is, in fact, restricted and let down the river only when there is either spill-over or some other environmental purpose. To have unrestricted spill-over would have severe implications, I would imagine, for SA Water's planning for the water needs of Adelaide.

However, we do, in fact, release water from the dam from time to time to enhance environmental conditions in the river, certainly as it applies to the Torrens Lake, and I might take the opportunity in a moment to take the council through some recent events in relation to how we are managing the Torrens Lake.

In terms of localised impacts, I think I am right in saying that I have, in fact, been in correspondence with a local resident in the area who has raised some of these issues with my office, and I have, to the best of my knowledge at least, responded to those issues with him, but I will check that. The honourable member, in his question, didn't indicate who that person might be, but if he would like to privately provide me with that gentleman's name, I will be able to use that to cross-reference my correspondence files in the office.

In relation to the Torrens Lake and our trials, from memory we haven't had a closure of the Torrens Lake since about February 2013. We have been trialling various responses to blue-green algae occurrences in the Torrens Lake since about 2011 with no great impact in the first couple of years but, as I have said, we haven't had a need to close the lake. Essentially, what we have been doing there is releasing pulses of water down the Torrens from Kangaroo Creek Dam and flushing out either the blue-green algae cells themselves or, in fact, the nutrient build-up which would lead to a blue-green algae explosion.

The initial pulses weren't particularly successful. They did, of course, ameliorate any huge blooms of blue-green algae. There were some blooms but not sufficient for us to actually close the lake. What has been happening in recent times is that the pulsing has been synchronised and we've had higher flows for shorter periods to really flush out of the system the nutrient build-up which leads to blue-green algae exploding over a period of time in summer when we often have the most international and interstate visitors in the city enjoying all of the festivals and fringes that are on offer through the summer period and, of course, March, which we have just experienced.

Having the Torrens Lake closed at those times is not particularly attractive. Having these flushes down the system and releasing water for environmental purposes, particularly clearing out the Torrens Lake and the build-up further upstream of nutrients that come in from stormwater inflows, has proved to be a very good method of controlling blue-green algae blooms over the summer period.

However, recently—and this has been an issue for some time—we have sought and obtained approval from the federal government's agency to trial the use of hydrogen peroxide in the control of blue-green algae. We have done that in ponds associated with the Torrens, but not directly connected to the Torrens. We have dumped Torrens water and blue-green algae into those ponds and treated them with various concentrations of hydrogen peroxide. My understanding is that those trials have worked incredibly well, to the point where we have established a dilution factor for the hydrogen peroxide which will kill off the blue-green algae cells but not harm the native vegetation that grows in the Torrens or, indeed, the invertebrates or small fish as well.

So, balancing those two, the flows of water and pulses down from Kangaroo Creek Dam and the use of hydrogen peroxide, appears to be a good way forward, giving us two weapons in our armoury to control blue-green algae. The next step in this program will be to trial hydrogen peroxide directly into the lake and see how we can control that. That is dependent on the weather conditions being appropriate for us to do that (i.e. it would be suitable to encourage blue-green algae growth). There is no point in dumping hydrogen peroxide into the lake if the blue-green algae isn't going to be cooperating with us and multiplying.

We have, as I said, two weapons now in our armoury to control blue-green algae: pulsing flows down the River Torrens and hydrogen peroxide, which is looking to be a very positive second weapon, but that needs to be determined on a larger scale directly into the lake itself. I am expecting that, as I say, weather conditions permitting, to be trialled over the next couple of weeks, and I eagerly await the results of that scientific trial.

In terms of the other aspects the honourable member asked about in terms of native vegetation and animals further up the river below Kangaroo Creek Dam, these are areas where I understand the Adelaide and Mount Lofty Ranges NRM board has been putting in a lot of effort and expenditure. I will seek an updated response on their latest environmental programs and bring it back to the honourable member.

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