You are here

TasWater – Aquaculture Nutrients

Dr Rosalie Woodruff MP

Dr Rosalie Woodruff MP  -  Wednesday, 1 December 2021

Tags: TasWater, Water Quality, Fish Farms, River Health

Dr WOODRUFF - Dr Gumley, at the last hearings we had I asked a number of questions about the nutrient levels in the upper Derwent catchment and the Bryn Estyn upgrades. We had some correspondence with you and TasWater about those issues. Thank you for that exchange. As you accepted in your reply to my letter, a probable component of the nutrient algae overgrowth includes the intensification of aquaculture activities. You said, 'We know that aquaculture facilities contribute nutrients to the Derwent River, however, we don't directly measure nutrient outputs'.

There were five salmon hatcheries and two trout facilities that have flow-through processes and that contribute to that algal growth in hot summer conditions. Bryn Estyn isn't ready and it will take at least two more years. Is that a consideration in the Hobart water restrictions, accepting that there will be a warm summer and the potential for algal overgrowth, contributed to in part by these intensive aquaculture activities upstream?

Mr BREWSTER - We are always concerned about nutrients in the river. That's why we have critical control points. We're monitoring the nutrients. When the turbidity gets too high, for example, we will then slow down the plant. If we detect that there's algal blooms, we will introduce taste and odour. Regarding aquaculture, it's very difficult to determine what contribution is aquaculture, what contribution is other land management practices and what contribution is coming from heavy rainfall. The Derwent Estuary Program is undertaking further studies. We've contributed a small amount to that. That may produce more results but I can't sit here and say it's an aquaculture issue. The honest truth is that I don't know.

What we do is we deal with what we get, using those critical control points. So, we look at things that could affect drinking water that we monitor on a continuous basis and to the extent that if we see we were to exceed one of those critical control points, like turbidity and chlorine effectiveness going out of the plant, we slow down the plant to ensure water is safe for our customers. We have undertaken sanitary surveys of all of our catchments, including the Derwent Catchment. That's also part of the decision-making around how we run the plants.

Dr WOODRUFF - The Bryn Estyn Water Treatment Plant was two years ago slated to cost TasWater $160 million. Today we've heard it's $243 million. That's a substantial $83 million increase. It's a 50 per cent increase on the original cost. TasWater customers are paying for that and a large reason is because of over-nutrification in the Upper Derwent and a probable cause is flow-through salmon hatcheries. Would TasWater like to have salmon companies deal with their nutrients?

CHAIR - Dr Woodruff, before you go on, this will be much easier if you stick to asking questions rather than making statements and asking the members at the table to confirm or deny them.

Dr WOODRUFF - I was asking a question right at that point.

CHAIR - Before that you were making several assumptions and putting words in the TasWater representatives' mouths.

Dr WOODRUFF - With respect, Chair, I wasn't putting words in their mouths. I was making a preamble.

CHAIR - With respect, that was my ruling on what you were doing. I'm asking you to please keep it to questions.

Dr WOODRUFF - This is an uncomfortable space, no doubt about it. That's why I'm trying to be very clear and respectful about it.

CHAIR - Dr Woodruff, please don't speak over the top of me. I don't care what the topic is. That's not my job. My job is to make sure that all you're doing is asking questions of the representatives at the table.

Dr WOODRUFF - Has TasWater had conversations with the salmon companies that have the flow-through hatcheries upstream about ending that process and removing the nutrients that they put into Hobart's water supply?

Mr BREWSTER - I'll answer your earlier question so we are really clear on it.

There is no doubt a portion of the cost of Bryn Estyn is to bring it up to modern-day standards. That means being able to address any nutrients and any pathogens coming down the river based on our understanding of the catchment.

The majority of the cost - this is a 1968 plant. This plant is at the end of its life. It was designed for a much smaller supply. We are talking 40 years later so the vast majority of the cost is because we have to upgrade this plant. Then on top of that, standards have changed in 40 years around what's expected of us in terms of Australian drinking water guidelines, health-based targets. We are building a plant, as I said earlier, that will absolutely address the next 20 to 40 years but with the capacity to go beyond that.

I wouldn't want people listening to think that it's all about nutrients and pathogens. Yes, that is a component but fundamentally it is Hobart's drinking water supply and it needs replacing. That is where the majority of the money is going.

In terms of the flow-through catchments, we obviously talk to fish farmers. Our relationship in terms of what our requirements are put to the Environmental Protection Authority (EPA) through the process when plants are built. Would we prefer, like I am sure everyone else, close-through hatcheries? Of course, everyone would. But, at the end of the day, we don't control that. An assessment is made by the independent authority, being the EPA and we work to that. We've been on the record; we would prefer to see close-through hatcheries closed.