TRANSCRIPT Inquiry into flood mitigation infrastructure in Victoria Lakes Entrance — 18 October 2011 Members Mr T. Bull Ms L. Wreford Mr D. Koch Chair: Mr D. Koch Deputy Chair: Mr J. Pandazopoulos Staff Executive Officer: Dr G Gardiner Research Officer: Dr I Zwart Office Manager: Ms K Taylor Witnesses Mr C. Rodda, Managing Director, Southern Rural Water 18 October 2011 Environment and Natural Resources Committee 246 The CHAIR — We now call upon our last presentation from Southern Rural Water and the Managing Director, Clinton Rodda, will be joining us at the table. On behalf of the Committee I welcome you this afternoon to our public hearing, you are our seventh and last making a presentation here in Lakes Entrance and we thank you for that. I’d just like to add that all evidence taken at this hearing is protected by parliamentary privilege as provided by the Constitution Act 1975 and is further subject to the provisions of the Parliamentary Committees Act 2003. Any comments you make outside the hearing may not be afforded such privilege. All evidence given today is being recorded. You will be provided with proof versions of the transcript in the next couple of weeks. Sorry, not hopefully, within the next couple of weeks. We now look forward to your presentation. Mr RODDA — Thank you. Thanks for the opportunity. I’ve put together a bit of a presentation to address the terms of reference. Try to provide a little bit of context around what Southern Rural Water does. Our main focus is on flood management is around our storages, in particular Lake Glenmaggie. Talk about the role that we take in flood management, give you a couple of case studies, because you talked about in the terms of reference, your practices around managing floods, so a couple of case studies of the most recent flood that we had and the biggest flood that we had, which was June 2007. Talk about the instruments or the framework that we have around managing floods and then talk about some of the issues and challenges in flood management. So, a number of the areas in the terms of reference are not relevant to us, things like levees, we don’t hold levees or those sorts of things, so I will focus on the areas which are relevant for us. Overheads shown. Just a little bit of context, we have three businesses in Southern Rural Water, we are a rural water provider and we look after rural water management in the south of the state. So we look after 37 per cent of the state, right from the South Australian border, to the New South Wales border, and effectively below the Great Dividing Range. We have three main businesses, an irrigation business, including the Macalister Irrigation District, not too far from here, Werribee and Bacchus Marsh in the west, we’ve got what we call ‘Headworks’, which are our large dams, we have seven of those and I will touch on those in a moment. We have what we call our Groundwater and Rivers Business, which is around licensing and regulated extractions from rivers and streams and ground water across the south of the state. So there our role there is more akin to a regulator rather than a water supply, but we manage to licence conditions. We make our allocations. We also manage farm dams, as well, beyond a certain scale. We have about 10,000 customers or licence holders, about 170 staff spread across those locations, where you can see the little yellow triangle and revenue of around $30 million, in capital, between about $8 and $18 million, so that give a sense of our business. In terms of our storages, we have seven what we call ‘large dams’ so these are over about 5,000 megalitres capacity, up to about 200,000 megalitres. In the western part of our business, this is the central west area, not too far from Melbourne, we have Lake Merrimu, Melton Reservoir, Pykes Creek, and Rosslyn Reservoir in the Werribee and Maribyrnong systems. They’re all between about 15,000 and about 35,000 megalitres. None of those have floodgates, so they are all what we call fixed crest storages so they just fill and spill naturally, as the water come through. Most of those reservoirs were empty for three or four years and in the last 12 to 18 months, just about all of them are now spilling, which is rather nice. On the eastern side of our business, we have one small reservoir called Lake Narracan, that’s only a capacity of about 7,000 megalitres and its on the Latrobe system so you can’t really play any role in flood mitigation, because it’s so small. Blue Rock dam is quite a large storage, it’s around 200,000 megalitres and it’s again a fixed crest storage, it provides natural flood mitigation so because of it’s area and size, flows coming in could be up to 15,000 megalitres a day, what will come out might only be about 8,000 megalitres a day, just because it naturally attenuates flows. Lake Glenmaggie is the one that has the most interest for the community around flood mitigation. It’s the only storage with floodgates and some capacity to mitigate, what we would say minor or moderate floods. To give you a sense of Lake Glenmaggie and one of the things that we try and do a lot, is educating the community around how big the storage is and how big the catchments are. So we use this concept of the funnel, so you can see the funnel representing the size of the catchment. So you can see Lake Wivenhoe there on the far end, it’s got a very very large catchment. Thompson Reservoir has actually a very small catchment compared to both 18 October 2011 Environment and Natural Resources Committee 247 Wivenhoe and Lake Glenmaggie. Lake Glenmaggie’s catchment actually is about four times the size of the Thompson Reservoir’s catchment. As you can see, the size of the dam which we represent by the beakers, Lake Glenmaggie’s size is about one fifth the size of the Thompson Reservoir, whereas Wivenhoe is very large, both compared to the Thompson and Lake Glenmaggie and Wivenhoe has, as you would know, more than 50 per cent of it’s capacity dedicated to flood mitigation. Whereas, Lake Glenmaggie is solely constructed for irrigation use. So that gives a bit of sense of the scale. What that says is, if we get a lot of rain, then Lake Glenmaggie will fill and spill, that’s just the natural behaviour. It’s a fairly small storage on quite a large catchment. So we have two primary roles, around floods, one is managing releases and managing the storage level of the reservoir, before, during and after rainfall and also, very importantly, making and managing notifications to various emergency bodies, that happen while floods are actually occurring. So, we have a policy that is on our website about how we manage levels in Lake Glenmaggie. There are three key things that we think about in managing water levels in Lake Glenmaggie. Firstly, the structural integrity of the dam is our prime focus, because the consequences of the dam failure and the water coming down in one rush would be disastrous. So that’s always our number one priority. The CHAIR — That’s been strengthened though hasn’t it? Mr RODDA — That has yes, the floodgates were put in about 50 years ago and there is also very strong anchors. So that dam meets the, what we call ANCOLD standards, the Australian New Zealand Dam Safety Guidelines installed in 1987. The CHAIR — One in 100? Mr RODDA — Oh, far greater than that. It would be a one in million type floods. So it’s a very well structured, well managed dam. When we had the big flood it performed as we would have hoped. There was no structural issues at all with that. I’ll come back to that. Secondly, we also want to harvest water on behalf of the entitlement holders who pay the cost of operating, maintaining the storage. So the storage costs are paid by fundamentally the irrigation district, so there’s about 700 customers that pay for the storage and where possible, mitigate the impacts of high flows on downstream farmland, properties, roads and towns. Mr BULL — In that order, Clinton? Mr RODDA — Not particularly. What typically happens in a flood is that when we get to around 7,000 or 8,000 megalitres coming out of Lake Glenmaggie, the first farmland starts to become inundated around the river. As more flows go you start to get more and more inundation of land, you then, when you start to get up to around about 30,000 megalitres a day, start to see properties in Tinamba becoming inundated and historically, when you get above 60,000 megalitres a day, the township in Newry starts to get inundated. So that’s the history but Newry might have only flooded a handful of occasions so it’s very hard to be specific about the level that the river will break out and the flooding will happen. But, in November 2007 we kept flows to, and this was after the big flood, to about 59,000 megalitres and the river didn’t break out and Newry didn’t get flooded. Now, that’s now to say it might not happen lower than that or it might be higher than that in the future.