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Goodbye old Cotter … may we never see you again

ACTEW water Project engineer Ben Smith standing between the new 80m high dam wall which is near completion and  the old wall, which is only 30m high and will soon be under water.

ACTEW water Project engineer Ben Smith standing between the new 80m high dam wall which is near completion and the old wall, which is only 30m high and will soon be under water. Photo: Melissa Adams

Canberra's 101-year-old Cotter Dam wall is expected to disappear forever this week after having saved the capital from draconian water restrictions ''one last time'' during the 2004 drought.

It will be the second time the 30-metre wall has been submerged in just on a year following a freak weather event on March 1.

This time the inundation is deliberate and permanent. ACTEW Water said on Monday it had closed the 3.4 metre-high river diversion construction gate that was directing the Cotter flow around the site of the new 80-metre dam wall.

The enlarged cotter dam project. ACTEW water Project engineer Ben Smith standing between the new 80m high dam wall which is near completion and  the old wall which is only 30m high and will soon be under water has begun to fill up between the old and new wall. Click for more photos

Enlarged Cotter Dam project

The enlarged cotter dam project. The new 80m high dam wall is near completion, the old wall which is only 30m high and will soon be under water has begun to fill up between the old and new wall. Photo: Melissa Adams

The original structure, one of the first infrastructure projects to be commissioned for Canberra, along with the Cotter pumping station and the powerhouse at Kingston, dates to 1912. It was increased in height in 1951.

For the past few years it has been holding water back from the construction site of the replacement dam, which is now holding water in its own right and has 20 times its capacity.

Once the 100-metre basin between the old and the new walls fills up, something ACTEW Water managing director Mark Sullivan says should happen in the next few days, the old concrete structure should be submerged permanently.

Mr Sullivan said given the old dam is only 30 metres high it was unlikely it would ever be exposed again.

If it does reappear, it will be a dark day for the ACT.

The enlarged dam is part of a $363 million investment in water security that includes a pipeline from the Murrumbidgee River to Googong and a major buy-up of water entitlements from users downstream.

It is a water storage of last resort, not a day-to-day source, and will be called upon only when there is a danger of severe water restrictions.

The need for such a back-up was highlighted during the 2004 drought when the old Cotter Dam was brought back online after more than 30 years as an emergency reserve to avert severe water restrictions in the ACT.

Big rains in 2010-11 and last year and unexpected issues with the geology of the site in 2011 pushed out the original completion date by about 18 months.

Mr Sullivan was confident all the infrastructure needed for water to be pumped from the new dam into the Canberra water supply would be in place by April.

While that capacity will be tested regularly it will not be called upon unless the Bendora Dam and the Corin Dam run low. Both are upstream from Cotter Dam and can send water to the Mount Stromlo Water Treatment Plant by gravity. Water from Cotter Dam must be pumped to Canberra.

7 comments

  • Great photos! Can't get over how much bigger the new dam is. Hopefully this should do us for water for the next 100 years.

    Commenter
    Badger
    Location
    Canberra
    Date and time
    February 26, 2013, 8:57AM
    • Whatever happened to encouraging water self sufficiency at home with personal water tanks along the lines of Photovoltaic panels for electricity? Relying on Water authorities and Electricity companies for these is so last century.......Building bigger dams just encourages unchecked growth and an attitude of wasting resources rather than making people personally responsible for their consumption. If you require more water at home, water tanks are not that expensive these days to install. Humans, as usual, think the answer to problems are to build more infrastructure, which uses much more carbon intensive materials ( think how much Concrete a dam takes to build and the embedded energy required ). Instead of seeing these giant projects as a amazing examples of human progress, instead see them as an example of doggedly holding on to old ways of thinking about solutions to a problem

      Commenter
      benjamin.garden1
      Location
      Campbell
      Date and time
      February 26, 2013, 9:40AM
      • I think you have missed the point Ben. The whole idea is that this now allows the city to grow. We are not going to remain at 350,000 people forever and the previous dam was putting a lot of constraints on our standard of living. There are still plenty of water saving things in place. Just ask any new home buyer about the regulations in place when you build. The campaigns will still be there. You need to step into reality and get down from your high horse.

        Commenter
        Jezza
        Location
        Canberra
        Date and time
        February 26, 2013, 12:11PM
      • ben ben ben ... so when your water tank runs out what are going to do, steel the next door neighbours, build a neighbourhood dam maybe ??

        Commenter
        Robzz
        Date and time
        February 26, 2013, 1:17PM
      • You also assume that the cost of building a dam is greater than the cost of each individual taking the steps you suggest. What is the cost (in embedded energy) of every household having a plastic water tank? Along with the concrete base and pump and so forth? (let alone the monetary cost)

        Commenter
        asdf
        Date and time
        February 26, 2013, 1:20PM
      • @ Jezza No, I think those that think we can continue to grow as a species on this planet forever have missed the point. Infinite growth is impossible, whether for bacteria in a petrie dish or for the human race. The cost of this dam could have been spent in subsidies for home water tanks and in encouraging new ways of thinking about water consumption. Building a dam is just like kicking the can further down the road of endless consumption and not having to think about whether our lifestyles we enjoy at present are sustainable in the long term for the health of the biosphere we must all live in. Of course the disconnect from nature that our current civilisation encourages does nothing to stop this. The question really has to be asked as to what the true carrying capacity of our local environment in Canberra is for the city to keep growing and growing. Of course, both major political parties are addicted to the mantra of growth being good forever, and I see this dam as just another manifestation of this outdated and quite honestly dangerous way of thinking...

        Commenter
        benjamin.garden1
        Location
        Campbell
        Date and time
        February 26, 2013, 1:32PM
      • @robzz robzz robzz..No need to steal water from your neighbours or build your own community dam, good neighbours might transfer a coupla thousand litres of surplus stored rain for free or you could buy it from a water carter by the truck load at + or - 10c per litre delivered.
        I've never run out or come close even in a drought,,,it ALWAYS rains sooner or later.

        Commenter
        dusty
        Date and time
        February 26, 2013, 6:26PM
    Comments are now closed

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