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The Middlemarch fire and Dunedin’s water supply

Written By: - Date published: 1:17 pm, November 11th, 2019 - 39 comments
Categories: climate change, Conservation - Tags: , , ,

Dunedin City encompasses a very large area and draws a significant portion of its water supply from catchments further inland.



The Otago Daily Times is reporting that the Middlemarch tussock fire over the past few days has impacted Dunedin’s water supply, possibly for months.

About three-quarters of Dunedin’s main water supply could be out of action for up to a year after a massive blaze engulfed an area near Middlemarch at the weekend.

At a media briefing in Dunedin yesterday, Mayor Aaron Hawkins said the fire had eliminated the use of the main water catchment for Dunedin, the Deep Stream Reservoir.

Water from the catchment was contaminated by ash and a small amount of run-off containing fire suppressant chemicals.

Both the Deep Stream Reservoir and Deep Creek Reservoir were of strategic importance for the Dunedin City Council, he said, as they were the only reservoirs that could supply water to all suburbs in Dunedin.

Dunedin residents were asked to voluntarily conserve water while the severity of the impact to the Deep Stream Reservoir was assessed in the coming weeks by council staff.

The voluntary water restrictions would most likely remain in place over the summer and more formal restrictions could be considered based on the weather over the coming months.

One of the things we’re not that good at grappling with yet is the confluence of climate change and environmental conditions created by humans. I’ve written in the past about how drought can be driven by climate change but made much worse where humans are using land in unsustainable ways. Likewise flooding.

In this case, I think we need to start looking at land management as a way to mitigate climate change and the on-the-ground effects of climate change. If we’re heading into more frequent drought cycles, then it makes sense to adopt practices that make our landscapes as resilient as possible. A fire the size of Middlemarch once every three or four decades is very different from having such fires regularly.

The questions I have today are this,

  • are local and central government authorities assessing landscapes for increasing fire risk?
  • how are land use changes playing a part in the seemingly more frequent fires? eg land being shifted from farming to conservation estate, where there is a lot more flammable vegetation
  • should we be prioritising high fire risk areas like Central and inland Otago for lower fire risk habitat conservation rather than native conservation?

That last one is going to upset a few people. We’re basically talking about NZ having substantial dry tussock country that used to be under slash and burn farming (burnoffs, aerial spraying, and overgrazing that kee vegetation to a minimum). I don’t know how much this applies to the land burnt at Middlemarch, but there are farmers and volunteer firefighters pointing to the problems of increasing conservation estate that is now highly flammable.

I don’t know what the solution is here, although I would like to see the work being done by regenerative agriculture people in such landscapes/climates. I suspect that it involves planting forests that prioritise non-flammability over forestry or natives except where that forestry or native restoration is low risk.

This ties in with general ecological sensibility and the value in placing ourselves back within nature. The ODT was light on detail about the issue with the water supply but there’s also this to consider. Those catchments require rainfall, and how that rainfall is captured matters. Tussock yields more water into the landscape than short grazed pasture. Trees are probably better yet. Hard to imagine anything worse for that landscape than being burntoff, for its own sake and for ours.

39 comments on “The Middlemarch fire and Dunedin’s water supply ”

  1. Robert Guyton 1

    Have you missed the significance of the detail; "a small amount of run-off containing fire suppressant chemicals."?

    Why use toxic fire-suppressant materials around a city's drinking water reservoir? That's why the warnings are out.

    • weka 1.1

      I did see that (it's in the ODT quote) but no detail on what that means eg how long does it persist in the environment?

      I'm assuming that they used the fire retardant because letting the fire burn was considered a worse outcome, but again, no detail on which to judge that.

      I see the report on the February Nelson fires has come out, might have a read to get a sense of how things get reported later (although that involved arson so may be more in depth than usual).

      My point about the detail was that even if they look at the immediate issues (fire retardant and ash), there are big, long term issues for those catchments that we're just not good at thinking about yet (we being the general public discourse). By 2050, what kind of state are those areas going to be in?

      • Robert Guyton 1.1.1

        Indeed. WTB's paper on fire-retardant trees will be a very useful one as we consider how to replant. Weka; do you know about the hydrological cycle and the role bacteria within trees hold in creating rain/raindrops? As trees respire they release, along with the water vapour that emerges from the stomata in the leaves, the bacteria that when they arrive high in the sky, attract and tiny water "droplets" that eventually fall as rain. Dust can do it too, but tree-bacteria are the most important players; if you want rain (we will all want rain!) we need … trees.

        • Robert Guyton 1.1.1.1

          And it's possible that with rain falling from the sky, the atmosphere will become saturated with water vapour that cannot clump and fall, making the greenhouse effect much more severe. Trees, I tells ya! Trees!

          • weka 1.1.1.1.1

            Lol, I utterly agree. We have this kind of madness about no trees in our bare landscapes, and I'm reasonably supportive of wilding pine forests for that reason, but obviously pine isn't going to be great in a fire either. Nor kānuka and cabbage trees. Would love to read the paper on fire-retardant trees.

            Feeling quite a degree of frustration at the moment about the gap between what the mainstream is thinking about sustainability and climate action, and what the generative folks are thinking and doing. I should probably do most posts on the latter.

        • weka 1.1.1.2

          WTB?

        • weka 1.1.1.3

          I knew about the bacterial role in rain but not how trees are part of that, very, very cool!

        • WeTheBleeple 1.1.1.4

          OK. So the microbes have a structure that catalyses the formation of ice crystals at a temperature lower than is typically required. This induces rain. As the globe warms up there is approx 5% more atmospheric water for each 1 degree C rise. If we lose the trees then the catalyst is gone, and there's conditions for less rain, despite more atmospheric loading. When it does rain, it will pour. We are already seeing this effect.

          Drought and flooding go hand in hand. The surfaces get hard and baked, when it rains it all runs off to flood lowlands rather than replenish the earth. small scale (but multiple) earthworks to retain and slow water starting at the top of catchments are vital to sustainable management of our country as rain/drought cycles (will) get more severe. Fire breaks should be edged with fire-dampening plants. Preferably with a swale to keep them well hydrated.

          • Robert Guyton 1.1.1.4.1

            WTB – how are you progressing? Are you seeing more up-take of your ideas? This business is becoming critical; the east coast of Australia is burning and we're being smoked but is anyone asking the right questions? Do you think we will prepare ourselves or will we be caught out? This is the pointy-end of the stick – are we awake yet? Hope you are faring well.

            • WeTheBleeple 1.1.1.4.1.1

              I got sick of talking to walls. Returned to stand-up. Just finished a show actually. Material including homelessness and climate change, no solutions based stuff for a while. To me, it's all a cacophony. Everybody's got something to say (loudly and assuredly) but rarely are they educated on the subject matter. I just feel I was drowning in a tub of horseshit trying to talk sense to anyone. Those who know know, those who don't don't want to. Wilful ignorance, it's a problem I'm not equipped to address.

              Did you know there are still so many climate denialists on the planet today, if you laid them all head to toe round the globe 2/3 of them would drown.

              And in the future, even more.

      • Cinny 1.1.2

        Re the Tasman fires, we didn't have that problem regarding drinking water contamination, that I know of. It didn't appear at first glance to be covered in the report, so am guessing it wasn't a big issue compared to Dunners. Maybe because many are on bore water?
        https://fireandemergency.nz/assets/Documents/Research-and-reports/Tasman-Fires/Tasman-Fires-Review-2019.pdf

        Was talking with a water filtration specialist ironically, anyways, he is big on people putting in rain water tanks as during a drought water can still be trucked in to fill them.

        Just wondering… could discounted rainwater tanks be just as effective as discounted insulation? No doubt filtration could take care of most nasties and at least people wouldn't be so dependent on the town supply.

        • weka 1.1.2.1

          Might be a catchment and water intake placement issue? Do you know where the various settlements gets their water from?

          Rain water tanks definitely.

          • John Clover 1.1.2.1.1

            My son just sold his house in near Denver where in the valley it is against the local law to have water tanks/storage etc as the authorities want the water to flow off and used elsewhere. Quite mad some societies I think 🙂

          • Cinny 1.1.2.1.2

            The majority of water for Tasman District comes from rivers and bores.

            I guess during the summer fires none of the nasties contaminated the river.

            John Clover… dang….. there most be money involved somewhere for them to ban rainwater tanks in Denver. Surely.

    • Gabby 1.2

      Got to wonder what was going through the firefighters' heads.

      • Graeme 1.2.1

        They may have been defending power pylons. There's a line from Roxburgh to Dunedin that goes through there, loosing that would have been a lot worse than loosing part of the water supply.

    • McFlock 1.3

      I'm also wondering about the ash – does it just turn water black, is it mixed up with burnt pesticides, or would it do a Flint with the water pipes and give us lead poisoning or something?

      • weka 1.3.1

        lots of questions, and I'm not sure the ODT will look at this in depth. Compared to the minutiae coverage of the the Sky City fire.

    • John Clover 1.4

      That was my first thought when hearing the reports of the fire.

      I drink a lot of tap water, perhaps 95% of what I drink. perhaps I should change to drinking 'bottled water' and just use tap water for my other needs.

      The use of toxic fire-suppressants, except in very limited cases, should be banned.

      Better to let the fire burn and risk the harm from ash etc.

      I have yet to read or hear the arguments for using the stuff.

      • Dukeofurl 1.4.1

        It all goes through treatment plants and of course the water supply catchment area is one giant treatment plant, although Dunedin seems to rely on higher stream/creek sources which are fed from peaty bogs. One of the oldest Auckland Waitakere dams has the lake water the colour of strong tea.

    • Philg 1.5

      The article I read used the word contaminant. The authorities are underplaying the magnitude of the potential health and safety implications. Me – "We have to pollute the water to put out the fire"? Really…

  2. Stuart Munro. 2

    Good thing Ross Creek is back online.

  3. weka 3

    This from Greg Mullins, a former Fire and Rescue NSW commissioner and a councillor on the Climate Council, about the current Australian mega fires.

    Together with 22 other retired fire and emergency service chiefs, I spoke out earlier this year. We felt we had a duty to tell people how climate change is super-charging our natural disaster risks. I wish we were wrong, but we’re not.

    https://www.smh.com.au/national/this-is-not-normal-what-s-different-about-the-nsw-mega-fires-20191110-p5395e.html

  4. greywarshark 4

    No water for the town.

  5. Stuart Munro. 5

    Awfully early in the season for a fire really. What's late summer going to be like?

    • weka 5.1

      Fingers crossed for a wet summer.

      • John Clover 5.1.1

        One of society's false concepts…."Rain is bad, Sunny weather is great"

        Something we hear almost every day from folk talking about the forecast.

        • weka 5.1.1.1

          been biting my tongue the few weeks or so with people on twitter loving the extreme high temps and hating on the rain. Where do people think their food comes from?

    • Dukeofurl 5.2

      Fire is a natural part of the Australian east coast environment. The longer the time between the major fires the worse it is when it does happen.

      People homes and farms amoung the forest areas isnt so natural.

      Its hard to accept for them but fire is like rain, a natural order of things. Its just how common it gets thats changing

      • Stuart Munro. 5.2.1

        We humans often moderate our environments. We've been moderating in such a way as to increase fire risk – nothing to stop us doing the opposite for a change.

  6. Philg 6

    So the Dunedin fire fighters contaminate 80% of the water catchment area for Dunedin? This cannot be true ….

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