Praying for rain

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Tasmania may be experiencing a long term shift in precipitation of the ilk seen in south-western Western Australia over the last 50 years.

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The Conversation

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On the back of four years of dry and the shadow of El Niño looming large, recent rains across parts of inland Queensland must come as great relief. While plenty of follow up will be needed to restore surface water stores and recharge aquifers, we should be thankful for such mercies.

As I sat down on Thursday morning (November 5) to start this piece, it began raining proverbial “cats and dogs” in Melbourne, bringing relief to parts of Victoria, including my garden (the 2-3 cm of rain that fell across Melbourne was twice as much as fell in all of October).

However, the news is not so positive in Tasmania, which seems to have largely
missed out on rain again, after several near record dry months.

Bureau of Meteorology south-east Australian rainfall deciles for the last 3 months Bureau of Meterology – original imaged sourced from http://www.bom.gov.au/jsp/awap/rain/index.jsp?colour=colour&time=latest&step=0&map=decile&period=month&area=seaus

And that is compromising the health of Tasmanian hydro storages. By the end of October, Tasmanian hydro capacity was already below 30% capacity, and falling calamitously, despite a dramatic reduction in Tasmanian hydro power output.

Tasmanian hydro capacity as a percentage of total capacity. Diamonds show capacity at November 2nd for respective years. Data from Hydro Tasmania (http://www.hydro.com.au/system/files/water-storage/). Image by Mike Sandiford.

 

Tasmanian hydro storage as weekly percentage change (light grey line), aggregated by month (vertical bars), with annual seasonal variation (black line). Diamond shows the -2.5% capacity change in the week ending November 2, 2015, on the back of record October falls. Note that all previous Octobers in the time window shown here have seen net increases in capacity, albeit only marginally in the years 2010-2012. Horizontal coloured line show that the averages for the summer (blue) and winter months (red), respectively. Data from Hydro Tasmania (http://www.hydro.com.au/system/files/water-storage/). Image by Mike Sandiford.

I presume that in an attempt to shore up storage capacity, Tasmanian hydro output has been substantially reduced in recent weeks. And that has implications for energy flows and generation across the National Electricity Market. Because reduced hydro output is compensated by Latrobe Valley brown coal generators, and further along the chain by black coal generators in NSW, CO2 emissions from our electricity sector have rocketed.

In my last post, just a few days back (“Winds of – not so much – change”), I commented on the way wind was impacting the Victorian energy market at the margins. While wind generation was lowering the emission intensity of Victorian power supply, it was overwhelmed by countervailing forces unleashed by the uncertainty of carbon policy.

And that has everything to do with the way the hydro resources have been used, quite legitimately, over the years of carbon pricing when capacity of hydro dams was drawn down.

The problem now stems from the fact that our largest hydro reserves in Tasmania have yet to recover following repeal of the carbon tax in mid 2014. With developing El Niño conditions, no one can be certain when that recovery will occur.

More concerning is the prospect that Tasmania may be experiencing a long term shift in precipitation of the ilk seen in south-western Western Australia over the last 50 years.

Energy flows

The figure below compares the dispatch from all Tasmanian generators (hydro, wind and gas) over the last fortnight in October in the years 2013 and 2015. The key point is that Tasmanian dispatch is now running at about half the level it was in the carbon tax years, only serving about 2/3 of Tasmanian demand in the period shown.

Electrical power dispatched onto the NEM in the Tasmanian region for the fortnight Oct-18 through Nov-1 in the years 2013 and 2015, colour coded by fuel source (blue for hydro, green for wind, red for gas). The white/blue line shows Tasmanian demand. When total dispatch exceeds demand Tasmania exports to Victoria, when demand exceeds dispatch Tasmania imports. Units are megawatts. Data from AEOMO five minute dispatch reports, image by Mike Sandiford.

In order to balance demand, energy flows across the Basslink interconnect have reversed, from northwards at near full capacity in the carbon tax years, to southwards at near full capacity in the last fortnight.

Tasmanian net interchange for the fortnight Oct-18 through Nov-2 in the years 2013 and 2015. +ve values mean export across the Basslink interconnect into Victoria, -ve values imply import from Victoria. Units are megawatts Data from AEOMO half hourly Trading reports, image by Mike Sandiford.

The change in Tasmania’s electrical power balance is quite phenomenal. The halving in hydro output for the periods shown here was balanced by an aggregate 890 megawatt reversal in flow across Basslink. To put that in context, Tasmanian electrical power demand averaged only 1100 megawatts for the periods shown. At 465 megawatts, the average southerly power flow across Basslink in the last fortnight represents over 1/3 of Tasmanian consumption.

And that has implications for power generation elsewhere on the grid. With the deficit in Tasmanian power production picked up by mainland coal generators, the emissions intensity across the NEM has risen from 0.89 to 0.96 tonnes CO2 for each megawatt hour of power production, for the periods shown here. That equates to about 11 million tonnes extra CO2 over a year.

Emissions intensity in tonnes CO2 per megawatt hour of electrical power dispatched across the NEM, for the fortnight Oct-18 through Nov-2 in the years 2013 and 2015 Data from AEOMO five minute dispatch reports, image by Mike Sandiford.

Changing Climates

Much of southern Australia appears to be experiencing progressive long-term drying.

The drying trend is most pronounced in south-west Western Australia where it has dramatically affected stream flows in to reservoirs. There the decline is astonishing – since 2000, the stream flows have been at around 30% of their average for the period 1911-1971.

In Tasmania, the drying trend is less severe, but it has impacted the flows in hydro catchments and the drying is predicted to continue across the remainder of this century.

In the south-west of Western Australia, the drying trend can be tied to the reduction in the number of winter storm tracks affecting the region, as the tracks shift south into the Southern Ocean. That shift has been variously linked to the rise in greenhouse gas concentrations, to Antarctic ozone depletion and to natural variability.

In a recent study in Nature Geoscience, Delworth and Zeng argue that the greenhouse gas forcing captures the trends and patterns of variability of rainfall in Western Australia in ways that natural variability and other forcing does not (see also David Karoly’s commentary). If their analysis is on the money, it suggests we can expect the continued southward push of winter storm tracks will increasingly spread its drying influence across southern Australia, progressively impacting states to the east.

The question that should be worrying those concerned with our energy system, is what will be the likely scale of this shift. If the experience of western Australia is to be replicated in Tasmania, even in small part, then it will make the challenge of balancing energy security with the needs to reduce emissions just that little bit harder.

While the current state of Tasmanian hydro dams is likely impacted mainly by natural variability, as well as Hydro Tasmaina’s dispatch strategies during the carbon pricing years, the worry is that we are glimpsing a future of less productive hydro generation.

Source: The Conversation. Reproduced with permission.

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5 Comments
  1. Sam0077 4 years ago

    2003 driest so far for our area for November. July had very high rainfall. Problem with water is not enough dams and that sheets home to the Greens across the whole nation – starting with not damming The Franklin. We have had record rainfall across the nation but no enough damns to catch it for drought proofing. Til we put Greens and left Labor these days, back in their box along with UN and its AGW aka Global Warming – we’ll be chasing water.
    Water needed for growing food for an overpopulated world. Where foreign nations buying our arable land to preserve their food supplies in coming as they say food wars. Yet very little being done AFAIK to make sure our own food supplies are stable if this also comes about. UN is very good at predicting chaos and instability. But then aim of NWO & OWG them. God Help our Earth is this comes to pass.Greed and own back pockets dominate Parliaments. Rather stick it to poor with GST than pay up or even govern for the public good. Pander to these incredible tales that turn out to be myths. Every time forecast shocking weather event – turns out to Left’s chagrin that it happened so many years before. Like last storms yesterday supposedly worst ever recorded.
    When will majority wake up and say enough. Report true and do something re water that’s the most important essential for life ever and it should never ever been used for profit. Today’s fruit (oranges mandarins and even last lot tangelo’s are dry and can be sheeted home to cost of water rising dramatically . We pay domestically just on $1 a KL due to profiteering by State in Tassie Labor took it from Councils and made a 3 HQ company structure as usual – Libs took it down to 1 HQ common sense but did costs come down with only 1 lot of Expensive HQ payments – NO>. Same with Hydro also used as cash cow.
    Yes Australia and Tassie have nasty droughts and the weather pattern with La Nina and El Nino is cause. But have to live with it. Time we demanded water be proofed against drought with dams and anything else needed.

    • JeffJL 4 years ago

      Sam. I hope that you get some decent rain soon. Your observations about the lack of reduction in bills when restructurings have taken place are spot on in my experience too.

      Lack of water can be dealt with two ways. Cut use or develop more sources. In the West we have had to put in two desalination plants to deal with the hand we have been dealt with due to reduced rainfall (and increased use due to population increases). More dams would not have solved our issues.

      Were dams overflowing Sam I might believe your statement that we have had “rainfall records across the nation”. As can be seen from the hydro dam capacity the “rainfall records” do not seem to be resulting in flows to the dams.

      I really do hope that Tasmania does not experience the loss of rainfall the SW Western Australia has but blaming the lack of new dams is like yelling at a cyclone. It may feel good but it achieves nothing.

      • Sam0077 4 years ago

        Jeff I meant the floods across eastern states last year or so no dams to catch much of water due to greens. Tassie lacks dams too which is why Hydro lacking water. Small Island much differentiation in spread of weather. Where I live on the coast we haven’t been able to grow tomatoes outside for 3 years due to colder nights, last lot we planted ripened and rotting same time on vine first ripe April prior had been getting later and later less harvests. Not alone need hot house now. And still cooler each winter since 1997.Same in Northern Hemisphere. Follow the money trail when experts say its warming all too lose their jobs if dont agree with AGW. Greed is king today. Everything s geared to make the poor poorer and rich richer. Hence tax = GST.Other way hits those making the rules as well as those who pay donations for these favours. Solar gov handouts went mainly to better off – low income/pensioners etc couldn’t afford it. But copped the high prices re RET when wont meet base load ever. Nuclear take 15 yrs to build huge expense – and fallout huge too. We have cleanest coal and cheap – better for all of us particularly if warming were true as need more power for cooling. Again hits less well off every time. 100 years ago coal filthy smog etc today cleaned up and as I said ours reputed to be one of the cleanest burn on the planet. But doesn’t suit UN and its redistribution of wealth from us to them. Gillard promised 7 billion from increased power price. Did it go? Who knows. I do know wealthy got wealthier on selling certs of you can have my clean emissions etc. We have ppl in bed most of the winter due to no money for power. Honestly is this fair and equitable. Robbing our poor for supposed poor who will be lucky to see much of the collection once its passes over hands that tend to cling to much as it passes.
        Trickle arriving maybe which is why Howard wanted to give goods paid for here in place of cash. Even then got sold off. Greed. We’re surrounded by solar panels on roof and wonder how the Aurora will go on when only those on benefits take power off grid. I got told our place no good for solar. Mind you next door has it now and faces same way. So may have changed and with storage. Well way to go then who will be hit once again when not many left on grid. Our poor.
        Magnetic poles shifting has effected weather patterns I’m told but has the crowd of true believers taken it on board? Not until worked out a way to make even more money out of trading off on paper and getting even wealthier. Nothing gets done unless it benefits those who make things happen. Follow the money.

        • Geoff Burton 4 years ago

          Tasmanian Hydro would be well placed to increase it investment into supplementing its hydro with wind farms. Tasmania has excellent strong, reliable winds. Every megawatt produced is one that does not have to be imported from Victoria and frees up water for use domestically or for later export. Just like hydro, wind has low operating costs. The two are a great fit.
          The cost of capital is at record lows so this is a good time to get moving.

          Worth thinking about and doing.

  2. Malcolm M 4 years ago

    At the end of the carbon tax, Hydro Tasmania had the option of using its Tamar Valley combined cycle gas plant to off-set some of the power demand that would otherwise be met by hydro, and allow its storages to return to a more normal level after being depleted during the time of the carbon tax. Early this year spot gas prices were low because the Queensland LNG plants were still in a ramp-up phase. Instead, Hydro Tasmania passed up the opportunity, no doubt pressured by the Tasmanian government as its owners to produce dividends rather than pay for gas that would lead to higher dams levels.

    For most of this year Tasmania has been importing only small quantities of power from Victoria, and this generally night when Victorian power prices were low. While it saved on the financial cost of paying for mainland power, the cost has been low dam levels, and a lack of resilience should a forecast drought eventuate. However over about the last 2 months the system has been run much more conservatively with maximal importation from Victoria. It is as if the penny finally dropped in Hydro Tasmania management that there was some resilience in having water in storage.

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