HUNDREDS of millions of dollars have been spent on fishways, resnagging, riparian revegetation, not to mention the billions for water buyback, all recommendations of the Native Fish Strategy for the Murray Darling Basin 2003-2013 [1]. Those who implemented the program, however, claim no progress, in particular that numbers of Murray cod are still in decline [2].
Interestingly there has been no review of the program of works over the last ten years against the original recommendations in the strategy. Yet such a review could throw light on why, despite all the money spent, Murray cod numbers are still apparently in decline.
Many fish experts met many times to make recommendations that underpinned the strategy. A key recommendation, repeated in the planning documents and then the final strategy, was that the issue of cold- water pollution from the dams needed to be addressed. Indeed the expert panel that oversaw development of the Strategy were confident that the abatement of cold water pollution was the most tangible and achievable of all the proposed interventions to the extent that this “threat could be largely removed from the Basin within 10 years”.
In reality nothing, absolutely nothing, has been done to address it.
The Hume and Burrinjuck dams, like most of the dams through the Murray Darling, have the outlets for irrigation positioned at depth creating a jet of cold water.
Government commissioned reports have considered different techniques for cold-water abatement including retrofitting with multi-level outlets, artificial destratification through mechanical mixing, trunnions (pipes hinged at the outlet drawing water from different levels), surface pumps (large fan-like propellers that pump warm surface water into existing outlets), and submerged rubber curtains to stop the flow of cold water to the outlets.
The strategy, launched in 2003, includes comment: “it [cold water pollution abatement] appears to be a clearly definable, tangible, cost-effective intervention that can be completed for the major storages in the Basin within ten years, through a combination of engineering and operating changes.”
Many workshops, technical papers and government reports have been written since the launch of the strategy and not one of these contradicts the original advice. However, not a single initiative that will practically address the issue of cold-water pollution has so far been implemented.
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References/Links
1. Native Fish Strategy for the Murray-Darling Basin 2003-2013
http://www2.mdbc.gov.au/__data/page/65/Fish-Strat_ful.pdf
2. Edition 34: Bringing back native fish
http://australianriverrestorationcentre.com.au/riprap-is-back-edition-34-bringing-back-native-fish/
So this has been a complete waste of money, the problem seems to me to be ego tripping so called experts yet again getting it wrong at the tax payers expense
HI Jennifer, when I visited Chico in California I noticed dams above the valley floor and asked about them as they were not very deep. The answer was that water from the big storage dams was too cold for irrigation and the water was released to the shallow dams to warm up before being used for irrigation.
They grow lots of rice in central California.
John Sayers,
Water extracted from the surface and delivered to a turbine will have the same head pressure as water extracted from the bottom less any head losses resulting from the additional length of pipe involved. Given the design of most variable off-takes, which are effectively tall cylinders sitting vertically on the reservoir bottom, with moveable gates at different levels, then the head will fall if lower gates are used, unless the gate is large enough to allow a flow into the tower which is significantly greater than the discharge from the base of the tower. But with adequate design, any head difference will be minimal.
Just rough rules of thumb.
A couple of additional points.
SD,
The methane produced at the bottom of dams is not sequestered. Most of it makes its way into the atmosphere. Likewise most of the methane generated in bogs and marshes is dispersed in the atmosphere. Methane is produced by anaerobic bacteria, chomping into organic matter in the absence of oxygen. Otherwise aerobic bacteria produce CO2 doing the same thing. These processes are quite natural and go all the way back to the origins of life. Deep lakes and artificial storages in temperate zones stratify in summer. As the surface water heats its density decreases and depending upon the surface area and wind strength and direction this creates a layer of warm water sitting on top of much colder water, with a rapid transition in temperature between the two over a relatively short distance, called the thermocline.
The effect is to minimise the mixing of the two layers. Aerobic activity in the cold layer continues until the dissolved oxygen is depleted and anaerobic activity takes over, generating methane and H2S, among other things. Depending upon the buffer capacity of the water a significant drop in pH, as much as one unit, can also occur. This is usually accompanied by an increase in dissolved iron and manganese, promoted by the zero oxygen environment and also the low pH. These conditions induce a chemical reaction, called reduction, whereby insoluble ferric and manganic oxides and hydroxides are converted into water soloble ferrous and manganous forms.
In the case of potable water storages, where the water is usually transported long distances via pipelines, engineers construct multiple level off takes so that when the storage is stratified they can avoid the anaerobic layer. Drawing water from this area can promote the development of iron and manganese slimes on the inside of the pipes, which over time significantly reduces their carrying capacity. Also water from the anaerobic can cause "dirty water" and taste and odour problems for consumers.
In nutrient rich storages multiple level off takes also allow engineers to avoid algal blooms, which are generally confined to the surface few metres, where light intensity is greatest.
These considerations are of much less importance in irrigation and hydro-electric storages. Also the required discharge capacity of these storages is generally much higher than for potable water storages. Therefore a variable off-take system is necessarily much more substantial and therefore more costly. Retrofitting such dams with variable level off-takes is not impossible. But it would certainly be very expensive.
Yes SD,
shifting goal posts?
I hope Graeme reports back?
Good grief Luke!
Re dams and benefits. . . .
On balance for goodness sake. . . ON BALANCE!
& the areas where we could make a positive difference in this part of the MBD is mitigating carp, redfin and cold water releases.
& good old mother nature has done far more re the Murray Cod than 10 years of Native Fish Strategy and $millions of tax payer funds. 🙂
Thanks Ian Thomson
Thanks Ian. Hey can you believe ol' Flannelmouth! He's now supporting that new paper on flooding in the MDB due to AGW after conning us into building desal plants because it was never gonna rain again:
http://www.abc.net.au/worldtoday/content/2013/s3778263.htm
Hi sd,
I may have spoken of it on here before, but I'm not sure.
At the end of the January before all the water hit Qld, there were heavy rains in NW NSW.
Prior to this downpour a yabby net in the huge billabong at Toorale Station, (on the Warrego, close to the Darling conjunction), came out packed with baby catfish . Also lots of other juveniles and little Warrego Crabs. And of course lots of fat blue yabbies.
When the rains came we had to get out quickly , with some of the slow movers needing to wade through an overflow form the billabong. There was a sea of water pouring toward the Darling across the flood plains.
The native fish know exactly what they are doing and when it should be done. When the big dry started , the carp were caught out all over the place in thousands.
I have not been back since Toorale was purchased as a National Park , but I believe that the wise people who grabbed it have found no way to dismantle the billabong infrastructure.
Gates on the river harvested small floods , while large ones spilled out onto a huge natural floodplain. It was all built around the 1890s by Samuel McCaughey, the "father" of Debbie's MIA
Here's a 2004 study on cold water pollution. They say there are nine dams causing major cold water pollution.
http://www.water.nsw.gov.au/.../desktop_assessmnet_cold_water_pollution.pdf.