Imposing Our Prejudices on the Value of Flood Waters: A Note from Cathy Green

WHEN nutrient rich water flows into Lake Eyre it is considered good for the environment, but when nutrient rich water flows into the Great Barrier Reef lagoon it is considered bad for the environment. 

Indeed every time that Lake Eyre in central Australia floods, our oh-so-sensitive-to-nature journalists provide us with the sort of happy purple prose that we see on the front page of today’s The Australian, where Jamie Walker says:

“The torrents that swept down the swollen Georgina and Diamantina rivers, mixing in Goyder Lagoon before surging through Warburton Creek and into the lake proper, carry a bounty of new life: nutrient-rich sediments to feed the thirsty native vegetation that has erupted all around it, and in turn herbaceous native rodents; fish for the mass of birds tracking the flood; all the water the wild camels from the Simpson Desert can drink.”

Meanwhile, every time it rains hard enough in north Queensland for rivers to flood into the Great Barrier Reef lagoon, which represents precisely the same phenomenon as the Diamantina feeding Lake Eyre, journalists at The Australian provide us with much lamenting and concern like the following:

“A MASSIVE surge of polluted water has spewed onto the Great Barrier Reef following heavy rains that hit north Queensland last week, environmentalists say.

The WWF estimated up to one million megalitres – enough polluted water to twice fill Sydney Harbour – entered the reef after a monsoon brought drenching rain to north Queensland.

Mr Heath said satellite imagery confirmed water flows travelled to mid-shelf…”

Nature herself simply doesn’t care about the big environmental impacts and changes, no matter how much birthing, killing or (from our perspective) environmental degradation they may cause – it’s all just part and parcel of being a dynamic planet.


Cathy has a PhD and lives in Far North Queensland.

The photograph of the pelicans was taken by Jennifer Marohasy below the Torrumbarry Weir, Central Murray Valley, in October 2007.  Pelicans (Pelecanus conspicillatus) can be found in coastal and inland Australia – where ever there are fish.  Some fishermen say that when there are floods on the land there is bounty in the sea.


71 Responses to Imposing Our Prejudices on the Value of Flood Waters: A Note from Cathy Green

  1. Luke February 28, 2009 at 9:33 pm #

    It’s more a question of what the trends are – the issue being debated with Motty on the thread below. Burdekin exporting 5x-10x sediment now than pre-European. Heavy export of N from sugar catchments. Photosystem II herbicides turning up in sediments and corals.

    Very hard to deny that land use isn’t having an effect? But does it matter long term?

    There’s lots of vested interests on both sides of the debate eh?

    But more environmentally friendly land management practices probably are a win-win for agricultural efficiency so why not do them?

    And for the Gulf and maybe inland systems lots of recent news of heavy metal spills from mines in the north? With who knows what consequences. Copper with your Barra anyone?

  2. Ian Mott February 28, 2009 at 10:16 pm #

    Still flogging the mantra, Luke. The post is about double standards but, of course, in the brave new green utopia that is par for the course.

    And how can you talk about environmentally friendly land management practices when you don’t even accept the need for data integrity, true and fair reporting of fact, and the seperation of opinion from fact.

    The controlling of native regrowth in a 15 year pasture maintenance rotation was once a win-win for both the farmer and the environment until some departmental pond scum discovered that it could be detected by satellite and falsely presented as remnant forest clearing. The rest is history and we now have a premier in Qld who is now preparing regrowth “protection” measures that will deny the farmers very right to exist.

    Win f@#$%g win, indeed.

  3. Luke March 1, 2009 at 12:43 am #

    Stilling flogging the same aggro mantra Motty – why would you think science comes up with such things – regrowth clearing issue is more like WWF et al lobbying.

    But somehow I don’t think sugar cane farmers or broadacre croppers experience much regrowth.

    But canegrowers have developed a whole precision agriculture framework, legume farming, soil mapping, and total farm nitrogen management system to optimise nitrogen input. Not that a single issue guy like you would be interested in such things. So clearly you don’t accept the need for facts either.

    There are considerable improvements like this to be made. Minimum tillage broadacre cropping another.

  4. Ron Pike March 1, 2009 at 8:37 am #

    Hi Cathy,
    What a wonderful breath of fresh air to hear someone with the courage to show the media for the sensationalist seeking, balance averse and truth shy, group they have become.
    Our democratic decision making process can only ever be as good as the quality of the facts in the debate.
    Sadly in Australia it has been some years since there has been any pretence even of presenting researched, balanced comentry on environmental issues.
    Truth has been replaced with personal predjudice, dressed up as sensationalist man-made problems.
    Hey Luke, you really are a modern day “Hanrahan,” without the humour.

  5. Dennis Webb March 1, 2009 at 9:15 am #

    Hi Luke,
    Would the water flowing into Lake Eyre be more polluted than anything likely to flow into the sea?

  6. Luke March 1, 2009 at 10:12 am #

    Dennis – I guess it’s the definition of polluted. In that environment we shouldn’t find any fertilisers, herbicides or heavy metals (well depends after some recent news of mines in the North). Are the headwaters in good condition ? Depends on grazing practices. So I’d suggest yes the waters are well within the bounds of what the environment has evolved to cope with. But yes you’d expect to find heaps of sediment. If you read this article clearly graziers think they have a clean green product to protect and are angry at any hint of additional water pollution.,23739,25111319-952,00.html “The grazing industry’s been here for 200 years and then these bastards come along and rip the guts out of the country,” Cr Britton said.

  7. SJT March 1, 2009 at 12:48 pm #

    “WHEN nutrient rich water flows into Lake Eyre it is considered good for the environment, but when nutrient rich water flows into the Great Barrier Reef lagoon it is considered bad for the environment. ”

    HINT! Look at the different ecologies of the reef and Lake Eyre. Nutrients in the wrong place can be devestating for an ecological system.

    It’s a puzzling paradox as to why coral reefs need nutrient poor water that is crystal clear to survive, but they do. Change that, and you won’t have the same reefs there any more.

  8. Walter Starck March 1, 2009 at 1:07 pm #

    A couple of the recent satellite images said to depict “a toxic cocktail of sediments and chemicals from agriculture pouring onto the reef” were of rivers on Cape York which have only undisturbed wilderness in the catchment.

    It is also interesting to note that when it was recently discovered that internal waves often bring surges of nutrient laden deep water onto many reefs (including the GBR) this natural phemenon was immediately proclaimed to be of benefit to reefs.

    A few years ago, GBRMPA funded an extensive study aimed at better understanding the coral/nutrient “problem”. This involved pumping solutions of various combinations and concentrations of nutrients directly onto reefs. Contrary to expectations, the algal bloom did not occur, even when nutrient levels were raised to many times natural levels.

    At the start, the experiments were presented as aimed at determining more precisely the detrimental effects of nutrients on reefs and initiation of the work received national news coverage. But, contrary to all expectations, no increased growth of algae resulted at all. Even growth plates of algae subjected to water with 20 times normal nutrient levels resulted in no enhanced growth. The project leader, Professor Tony Larkum of Sydney University said, “We have conclusively established that persistent, small increases in nutrients have no effect on the algae.”

    However, this really good news that nutrients were found not to be the problem so feared received no publicity and the study was quietly terminated. Good news is simply not welcome in the reef salvationist industry.

  9. John Chrysostom March 2, 2009 at 9:39 am #

    Dear Walter,

    “A couple of the recent satellite images said to depict “a toxic cocktail of sediments and chemicals from agriculture pouring onto the reef” were of rivers on Cape York which have only undisturbed wilderness in the catchment.”

    Do you have a link for that?

    “It is also interesting to note that when it was recently discovered that internal waves often bring surges of nutrient laden deep water onto many reefs (including the GBR) this natural phemenon was immediately proclaimed to be of benefit to reefs.”

    Because it is a natural phenomena – as opposed to anthropogenic nutrient laden influxes from rivers.

    “A few years ago, GBRMPA funded an extensive study aimed at better understanding the coral/nutrient “problem”. This involved pumping solutions of various combinations and concentrations of nutrients directly onto reefs. Contrary to expectations, the algal bloom did not occur, even when nutrient levels were raised to many times natural levels.”

    Because they forgot to measure the grazers consuming the algae.

  10. Jon Brodie March 2, 2009 at 11:16 am #

    The Cape York river from which sediment plumes observed from satellite images were seen to reach mid shelf reefs was the Normanby and Hann complex. This catchment certainly does not consist of ‘undisturbed wilderness’ having had a widespread beef grazing industry for over the last 100 years and small amounts of cropping around Lakeland. The steeper areas of the catchment are heavily gullied, pasture condition is less than optimal and as a result we estimate sediment delivery to the coast to be about twice natural. The quality of the water leaving the Normanby is of course far better than rivers further south such as the Tully, Burdekin and Fitzroy not having the ‘cocktail’ of pesticide residues and nitrate from fertiliser use and not as much extra sediment over natural.

  11. Ian Mott March 2, 2009 at 9:33 pm #

    We keep hearing about how much sediment flow there is in our rivers but to date, none of our major Dams, even the very old ones, have suffered major loss in storage capacity due to build up of sediment.

    And lets not delude ourselves here. Once water comes to a large, long, artificial base level it slows right down and the non-colloidal suspension sediments drop to the bottom. The fact that it might speed up again as it goes over the spillway does not alter the fact that the majority of sediment load will have been deposited.

    So where, exactly, is all this sediment, if it is so abundant, yet refuses to show up in the places it would most likely be found?

  12. Luke March 2, 2009 at 11:15 pm #

    Let’s not delude ourselves.. Depends on the particle size doesn’t it.
    Gee that water going over Fairbairn Dam and Burdekin Falls Dam lately looked almost transparent. Not !

    And why is it that Thomson Fold Belt (western Nogoa) and Tertiary Basalts (CQ cropping belt) are disproportionately represented in Keppel Bay?

    Fitzroy River Basin, Queensland, Australia. III. Identification of sediment sources in the coastal zone
    Environmental Chemistry, Vol. 5 No. 3 Pages 231 – 242, Published 19 June 2008

    Come on Motty – facts not opinion pls.

  13. FDB March 3, 2009 at 9:50 am #

    Lake Eyre ≉ The Great Barrier Reef.

    Hope this helps.

    “Nature herself simply doesn’t care about the big environmental impacts and changes”

    Anthropomorphising nature now are we? I thought only deep green nutballs did that. In any case, I’d bet tourism operators on the GBR care. Plenty.

  14. Jon Brodie March 3, 2009 at 3:00 pm #

    There are no dams on the rivers on the Queensland east coast near the end of the catchment of any great age. The Burdekin Falls dam dates from 1987, Peter Faust Dam om Proserpine from about 1991 and Paradise Dam on Burnett from 2007. These dams are no doubt trapping quite a bit of sediment but the only one we have any good data on is the Burdekin Falls Dam. From our data from the last four years we estimate this dam traps about 60% of the suspended sediment which enters it. The dam will take several hundred years to fill with sediment at this rate. Of equal interest is our estimates that even with the dam trapping 60% of the suspended sediment which enters it the Burdekin River is still discharging between 5 – 10 times as much suspended sediment as it did in pre-European times. Our estimates are a bit uncertain (5-10 range) as the pre-European estimate, derived from modelling, monitoring undeveloped streams and coral core records has a high uncertainty. The Fitzroy River does not have a big dam near the coast, only the Fairbairn Dam well up the catchment, hence as noted much of the sediment reaching the coast comes from the basaltic soils of the western part of the catchment. The Paradise Dam on the Burnett is a large dam near the coast and is yet to fill due to low rainfall in SE Queensland. However it is predicted to be a very good sediment trap and will reduce sediment loading from the Burnett River greatly.

  15. Luke March 3, 2009 at 6:57 pm #

    Jon Brodie – thanks for the excellent contributions. Certainly the sedimentation rates into Fairbairn Dam seem to have been revised downwards from earlier more pessimistic predictions of heavy sedimentation.

    What is your assessment of the evidence that the increased loads of sediment, soluble nutrients and herbicides are affecting different areas of the reef. How well is the reef able to cope with these fluxes – given historical flow variations have been considerable. Is the reef able to cope with short term damage ?

  16. Ian Mott March 3, 2009 at 10:06 pm #

    Interesting numbers John Brodie. So if an undamed river has 5 times the pre-settlement sediment load, and a large dam will capture 60% of that load then the remaining load would only be double the original level. Makes new dams look like a pretty good deal to me.

    But wait, there are other variables, like water volume and dispersal in time. If the total volume of water flowing over the dam is reduced, and is also delayed to non-flood periods then it follows that the actual volume of sediment will also drop. And as the volume is lower then the area of sediment dispersion must also be reduced.

    In fact, if half of each flood flow is captured by the dam then it would seem unavoidable that the resulting sediment load would return to pre-settlement levels. And this would be associated with less coral killing fresh water discharge to boot.

    But in reality, your quoting of the 60% sediment capture figure by Dams is not entirely true, is it? That is because the sediment retention rate is entirely contingent on the rate and timing of discharge.

    Clearly, if a big empty dam is capable of capturing an entire flood surge, and holding it with zero release for a month or two then the sediment retention rate would be very close to 100%, would it not? It could then release some very large volumes, even to minor flood levels, with close to background sediment loads.

    But if some sad EPA types got control of the release schedule and decided to let half of the flood surge go at the same time as it was flowing in at the top then the sediment loads would be very much higher, and the recorded Dam retention rates would be much lower, wouldn’t they?

    It would seem that the logical thing to do with waterborne sediments and nutrients from upstream agriculture would be to capture them on downstream flood plains. It has worked very well in the Nile Valley for more than 6000 years but that would be totally beyond the wit of urban green governance.

    Just a low bund, an upstream diversion, and the temporary parking of a couple of megalitres per hectare, would be all it would take to deposit the silt before sending the clean water off down stream.

    But that would involve a mutually beneficial partnership in a context of trust, integrity and good governance. And that, in Queensland, will be after the pigs fly past.

  17. Luke March 4, 2009 at 9:36 am #

    Yes Motty but there are even more variables like ongoing overgrazing with areas of bare ground – and perhaps even more important areas of decreasing infiltration rate with increased runoff volumes resulting. Have a look at the Wambiana trial treatment effects.

    And then there would be Lough 2007 showing how variability (wet and dry) of rainfall and runoff volumes for the reef have increased over the last century compared to the 300 odd years previous.

    And much of the damage occurs in big events e.g. both Fairbairn and Burdekin Falls have been over the spillway of late. We’re not talking about a nice Wivenhoe flood compartment.

    Denial of the full account won’t help your case.

    But hey – all I’m saying we know about overgrazing – why don’t we have acceptance and implementation of the sustainability research. Why are we still talking ?

    Similarly a lot is known about optimum nitrogen use in cane. Why are we still talking?

    It’s not about anti-farming. It’s about responsible adoption of good practices.

  18. Ian Mott March 4, 2009 at 9:57 am #

    Just another interesting question, John Brodie. You claim that sediment loads after a dam is in place are still in the range of 5 to 10 times pre-settlement levels. But if the dam is capturing 60% of sediment then the 10 times level you claim to be going out to sea at present represents 40% of total sediment volume. And that would mean that the total sediment volume is 25 times pre-settlement levels with 15 times being captured by the Dam.

    So which undamed river is your control? Which river with extensive agricultural development in its catchment, is currently producing 25 times its pre-settlement sediment volumes?

    And don’t give us any of those moronic coral core samples from specific sites. Give us a proper calculation of deposition layer depth times the area over which deposition has taken place. Either the area has remained the same and the depth has increased or the depth has remained the same and the area of deposition has increased 25 fold, in every stage of the deposition cycle.

    And could you please explain how the yet to be filled dam on the Burnett could actually reduce sediment flows if the catchment has been in drought for more than a decade? Forgive me, but I thought dry times meant low river flows, and low flows meant minimal sediment loads, and zero flows meant zero sediment loads.

    Could it be that the whole sediment/reef debate has been conducted on an entirely hypothetical framework? So when you guys talk about high sediment loads, and supposedly drastic rises in sediment deposition, you are actually talking about modelled sediment deposition in hypothetical flood events when the actual river flows, and their actual sediment volumes, have been very low because of widespread drought and increase flood capture?

  19. Jon Brodie March 4, 2009 at 2:05 pm #

    I can only answer some of the major points of Luke and Ian Mott in this response. With respect to using downstream floodplains as sediment trapping areas from upstream agriculture the problem is simple – these areas are almost universally used for cropping, primarily sugarcane, and you will have a fairly interesting war with canegrowers if you suggest we retain water on the floodplain which kills the cane. In fact of course the drainage of the floodplains used for cane production have been deliberately drained at great commonwealth government expense to get water off the floodplain as quickly as possible to improve cane production.

    Why aren’t dams being run completely as sediment traps such that 100% of sediment is trapped – obviously that is not their purpose – they were built for agricultural water supply and are managed for that purpose.

    Of course the Paradise Dam is not acting as a sediment trap at present – there’s no flow in the Burnett River. Once there is some rain we can expect it to act as an effective trap.

    The river we have the most data for sediment budgets is the Burdekin although quite a bit of data is also now available for the Fitzroy. In the Burdekin we have been measuring suspended sediment (SS) delivery from the 4 main catchments above the dam (Cape, upper Burdekin, Suttor Belyando), SS discharge from the dam in over-spillway flow, SS delivery from the major catchment below the dam (Bowen Bogie) for about 5 years and SS delivery at the end of the river (Home Hill) for the last 20 years. The overall picture from this is that indeed there is up to 20 times as much sediment delivery to the rivers than ‘natural’ but that because of dam trapping and other trapping delivery of SS to the coast is only about 5 – 10 times ‘natural’. With respect to marine sedimentation from sediment cores off the Burdekin there is limited published data although Gregg Brunskill from AIMS collected many cores the results are yet to be published. However I personally trust the coral core results published in the journal Science by McCulloch et al from which one can make an estimate of sediment delivery history from the Burdekin.

    With respect to Luke’s request for my assessment of the effects of land based pollution on the Great Barrier Reef this was published recently as “The Scientific Consensus Statement on Water Quality in the Great Barrier Reef’ and can be found at:

    The is the Consensus Statement itself and a more detailed background report is also available at the site. The statement was prepared by a group of reef and catchment scientists involved in GBR research.

  20. Luke March 4, 2009 at 2:38 pm #

    Jon thanks for your endorsement of the science and frank discussion of uncertainties.

    The recurring themes here on this blog with respect to the reef are:

    (1) reef is in fabulous condition
    (2) terrestrial runoff and land pollution has not increased or is non-significant compared to climate variability
    (3) disputes over catchment condition – there is no land degradation 🙂
    (4) the reef is well able to cope with some extra runoff
    (5) government agencies and researchers are self- seeking on doom and gloom to funding providers
    (6) runoff only impacts a very small proportion of the inner reef
    (7) there is no current hint of climate change impacts

    I’m not advocating these positions – but I do suggest they are the obvious contrarian undercurrent positions to reef research.

  21. Ian Mott March 4, 2009 at 3:32 pm #

    “Why aren’t dams being run completely as sediment traps such that 100% of sediment is trapped – obviously that is not their purpose – they were built for agricultural water supply and are managed for that purpose.”

    Sorry, not good enough. It would seem that a primary purpose of supplying agricultural water would be particularly suited to management of dams to maximise sediment capture. This involves maximum use in the dry season to allow maximum capacity to capture the following wet season flows and hold them until needed in the next dry.

    It is more and more clear that it is actually the early, and even immediate, release of sediment laden so-called “environmental flows” that is needlessly maintaining high downstream sediment levels and blaming the results on farmers. These releases could easily be delayed so a greater portion of sediment settles out. And if the sediment really is such a problem then why are the proponents of sediment reduction measures ignoring such a clearly effective tool?

    And the issue with cane is not that any flood will automatically kill the cane, it is the mode of delivery, the duration of innundation and the speed of its release down stream that determines whether a flood is of benefit or harm. The really big cane killer is slow release of shallow flood waters which are warmed by the sun to effectively boil the base of the plants. Deeper water does not do this, provided it is released quickly, and on time.

    But you have ably illustrated how the non-entrepreneurial mind will proceed along a thought process until the first pretext to take no action presents itself, and stop. Farmers, and other people who live by their wits and bear the consequences of their decisions, tend to look a lot further than the first hurdle. It was never a case of whether downstream floodplain sediment capture could be done. Rather, it is a case of; how can it be done? and how much of it can be done in concert with other farming activities?

    And Luke’s boorish attempt to narrow this debate to fit his own take on it is not worth the paper it is written on. ie zilch.

  22. Jon Brodie March 4, 2009 at 3:58 pm #

    Ian I’ll let you be the person who suggests to canefarmers in the lower Herbert, Tully, Burdekin, Pioneer, and Burnett that they deliberately leave deep water on their fields in the Jan to April period for a significant period of time. Good luck.

  23. Ian Mott March 5, 2009 at 12:46 am #

    No Jon, I wouldn’t suggest anything. I would ask what the time and cost threshholds were, what the cost, volume, profit relationships were, and the risks, and if there was the scent of a benefit or opportunity there I would then go into the detail of what we know, what we don’t know and what we need to know, for ultimate comparison with alternatives for cost effectiveness.

    And if it eventually leads no where then we will understand exactly why. But before you go dusting off your sneer you might reflect on the fact that this is exactly the function provided by River Red Gum forests on the Murray and is the very same process for which some people want to take water from irrigators and deliver it to wetlands.

    The only difference is that you guys refuse to ever contemplate something that might be of benefit to farmers and deliver ecological benefits as well. If not with cane then would it work with rice?

    But lets get back to the discharges. Do you accept or reject the suggestion that early flood releases for environmental flows could actually be reducing the effectiveness of dams as sediment traps and delivering more sediment to the reef than need be? And why?

  24. Luke March 5, 2009 at 8:47 am #

    Motty’s an expert in everything from sugar cane agronomy to “husbandry of whales like cows”. Face it mate – you have shown total disdain for any reef related research. Has there been one single bit of research that you wouldn’t have a shot at just on instinct. What was it about reef workshops as hooch parties? All the grazing research being sus …. (still awaiting your review too)

    You’d do well in the butchers shop with one finger on the scales. Do you accept the degradation of the Burdekin rangelands or are you still obfuscating? And how do you manage “an early flood release” when the dam flows over the spillway i.e. is more than full ! What occurs into the inner reef lagoon is an accumulation of many factors not your attempt to cherry pick one issue.

  25. Ian Mott March 5, 2009 at 10:18 am #

    Hmmn, massive side step, with diversion, dummy spit and abuse from Luke. Must be pretty close to checkmate then, are we?. Sure, a big flood into a full dam is hard to manage but you know perfectly well that these are the exception. And it is an entirely moot point when so many of our rivers, like the Herbert and the Tully, don’t have a dam at all. So they lack the capacity to achieve even a modest 60% sediment capture.

    It is clear that better management of environmental flows could produce significant improvements on this figure while reducing the destructive impact of fresh water on coral.

    And if you had a rudimentary grasp of the issue then you would know that the Wivenhoe/Somerset Dam system has been using private land as a temporary store of flood surplus for decades. Both dams have provision for capturing additional water in excess of their normal capacity as flood insurance for Brisbane. Wivenhoe can capture an additional 1.6 million megalitres of flood surge if needed and a large portion of this volume is stored on the lower paddocks of farmers on the lake shore. I have walked on such a paddock, that is occasionally inundated for public good without compensation, and without the approval of the owner, at the back of Somerset Dam.

    But despite the fact that Wivenhoe has not overflowed for the best part of a decade, we still have shonkademics and departmental spivs telling the public that sediment flows are still a serious problem.

    Meanwhile you two “experts” display the strategic vision of a costing clerk, denying that an option is even possible when it has been operating under your own noses for decades. You portray yourselves as custodians of the environment whilst sneering at an option that does nothing more radical than mimicing what nature does in a Red Gum forest. And in a Queensland Blue Gum forest for that matter.

    And you persist with your entrenched ideology of maximising penalties on farmers when you don’t even maximise the capacity of existing infrastructure to capture both the sediments and the fresh water that kills coral. And when Rudd’s so-called economic stimulus merely boosted alcohol sales by 14%, real investment in new productive infrastructure that would pay for itself is dismissed on the most spurious, even fraudulent grounds.

    So what have YOU done today to make you feel proud. Beheaded a few more daisies with a stick, have we?

  26. Luke March 5, 2009 at 1:15 pm #

    Dummy spit? Abuse?

    Confronted with the evidence – abuse and denial. It’s lonely at the top …

  27. Luke March 5, 2009 at 1:28 pm #

    This would have to be remarkable Mottsian logic – where’s the dam going in the Tully catchment – you’re going to flood the forest are you? Or permanently inundate the cane fields? For 110,000 tonnes of sediment. c.f. 5.4 Mtonnes from the Burdekin? LOL !

  28. Ian Mott March 5, 2009 at 2:30 pm #

    No problem with flooding part of the forest in the Tully catchment as it is still 82% forested. I hear there is a good site called Tully/Millstream. And provided the trees are harvested and converted to long storage carbon products then the hydro-electric power will have only minimal indirect emissions and zero direct emissions.

    And thanks for reminding me that hydro-electric power from dams is also highly compatible with managing for sediment capture too.

    But really, is that the best you can come up with? Pathetic. Still desperately seeking any pretext to do nothing, you’re in complete denial.

  29. Ian Mott March 5, 2009 at 3:06 pm #

    By the way, where did you get your sediment figures for the Burdekin (5.4m tonnes) and Tully (0.11m tonnes)?

    The Tully catchment is 168,000ha while the Uper Burdekin is 3,625,000ha and the Suttor is 3,811,000ha for a Burdekin Basin total of 7,436,000ha. Divide each total by area and we get Tully sediment at 655kg/hectare and Burdekin sediment at 726kg/hectare of catchment.

    Interestingly, The Tully is 82.1% woody vegetation while the Upper Burdekin is 76.3% and the more inland Suttor catchment is 62.1% woody vegetation. The combined Burdekin Basin vegetation cover is 69%. This is a 16% drop in woody vegetation cover and a 10.8% increase in mean sediment load per hectare.

    That doesn’t leave very much room left in the equation for all this supposedly outrageous grazing degradation in the Burdekin, does it? Sure, Tully rainfall is much higher and intense but the vegetation in each catchment has evolved to cope with those conditions. And the Burdekin rainfall events can be just as intense but they are less frequent.

    And for Jon brodie’s claimed 20 fold increase in Burdekin sediment since european settlement to have any sort of veracity then the Queensland NRM research community would need to show us an untouched sub catchment that is representative of the Burdekin Basin where annual sediment amounts to only 726kg/20 or only 31.3kg/hectare of catchment.

    Fat chance, Bozo, fat chance.

    This is more evidence that the Pandora coral cores do not present a true and fair approximation of past Burdekin sediment loads. As I have stated earlier, these sites are in locations where modest changes in sediment and discharge volumes will present with disproportionate significance.

  30. Ian Mott March 5, 2009 at 3:32 pm #

    One little correction to my numbers above. The area for the Burdekin Basin did not include the Lower Burdekin and the Bowen, with 1,047,000ha and 945,000ha respectively. When this is included we get a Basin area, without small coastal catchments, of 9,428,000ha which leaves us with a sediment load per hectare of 5.4mt/9.4mha or only 572kg/hectare. This is 83kg/ha (12%) less than for the Tully catchment, even with less woody vegetation in the Burdekin.

    This tells us two things;

    There appears to be even less room in the equation for the much claimed apocalyptic sediment loads from over grazing in the Burdekin, and

    If the current 572kg/ha of Burdekin sediment is 20 times higher than pre-settlement times then those pre-settlement volumes were only in the order of 29kg/hectare.

    And the Qld NRM community would need to find an untouched Burdekin sub-catchment that only delivers that volume of sediment flow to substantiate their claim.

    I say again, fat chance, Bozo, fat chance.

  31. Luke March 5, 2009 at 5:47 pm #

    Why do we keep Motty on the line. Coz we like to do him slowly.

    (Dear readers – well we actually have a fair degree of affection for Motty, he’s not a bad bloke really, but it’s one’s duty as a thinking citizen to keep him on track – this blog is where he learns most of his science).

    Anyway as we were –

    So you’re going to build a bloody big dam in the forest which has been measured to produce bugger all sediment vis a vis the cane and the nanas. EMCs 1/8 the cane. And after you clear all the trees it will be producing shitloads of sediment while it fills. Meanwhile the real sediment production area is untouched. (net result – probably even more sediment)


    And even though he thinks he’s remove the existing trees for the methane – he forgets the major contribution of organic matter from the remaining forest which will sink into the pits of this very very dark deep storage in what once was a gorgeous gorge, where it will anaerobically decay to produce methane over 500 years.

    ROTFL !

    hmmmm – uh huh – thanks for that. We’ll call you. But don’t wait by the phone.

  32. Jon Brodie March 5, 2009 at 6:18 pm #

    The Burdekin is actually 13,700,000 ha. There are a number of Burdekin sub-catchments which have low erosion down towards the 29 number you suggest because they have low slopes, good grass cover and extensive in-catchment flood plains for overbank flow trapping of sediment. Remember the 5.4 m tonnes is for the Burdekin Basin, the best number to use for the Burdekin Catchment (the 13,700,000 ha area) is probably 4.5 m tonnes (from long term monitoring data) but this already includes the loss due to trapping in the Burdekin Falls Dam. Its difficult to estimate what the average load in the Burdekin River would be now if the Dam wasn’t there but roughly we estimate 1.5 m tonnes from below dam and hence 3 m tonnes from above dam. The delivery from above the dam would then be something like 7 m tonnes (assuming 60% trapping) if the dam wasn’t there. That would give a total load to coast of 8.5 m tonnes without dam. This still isn’t the correct number to estimate erosion rates in the catchment (i.e. kg/ha) as of course only a proportion of eroded sediment gets to coast the bulk (50 – 60 %) is trapped along the way on floodplains and in the river channel. So an estimate of the sediment delivered to streams and rivers would be about 22 m tonnes. So this looks like about 1500 kg/ha consistent with other studies on the Burdekin but of course very variable across different landscapes.

    Your Tully numbers look OK but we don’t know as much for the Tully as to the source of the sediment. Recent work using isotope analysis suggests most of the sediment is coming from the cultivated lands (sugar, bananas, forestry) and not the closed forest of the upper catchment. Recent monitoring has supported this picture which overturns an earlier picture of high sediment delivery from the closed forest upper catchment. This is also surprising as we have been assuming that good management by landholders for erosion control in cane, wet tropics grazing, bananas had minimized soil loss. However some of the sediment is also coming from bank erosion and we need further work to see what the detailed sources of sediment in the lower Tully really are.

    In general comparing the Tully to the Burdekin doesn’t work well due to their completely different type. They probably fall at the opposite ends of our ‘river type’ range for GBR catchments. The Burdekin is hugh, mostly woodland/savanna, little closed forest, relatively dry (average rainfall about 700 mm I think), landuse dominated by dry tropics grazing, while the Tully is almost the opposite in all ways – smaller, mostly closed forest and cropping, very wet (average rainfall a few metres), agricultural landuse dominated by sugarcane and horticulture.

    Note that there is a dam on the Tully River called Koombaloomba primarily used for hydroelectricity generation but also nowdays to help rafting on the river by controlled release of water. Its well up the catchment and would not contribute greatly to sediment trapping. Note also that the site you mention called Tully/Millstream is actually a plan for a number of dams to generate hydroelectricity which was around in the late 1980s. The main planned dam sites were on the upper Herbert River (the Millstream and Blunder Creek) and water would have been transferred across catchment boundaries to the generating plant. Interestingly these are the same dam sites and others) that Bob Katter sometimes promotes as suitable to transfer water across the divide to the Flinders River and use for irrigation on the blacksoil plains of NW Queensland.

    I might finish by saying that all the information I present in the posts comes from a long history of studies in the GBR catchment , long-term monitoring data sets on rivers from NRW, AIMS and others, paddock scale studies on management practices in sugarcane, bananas, grazing, .. from DPI, BSES, CSIRO and others, studies into the sources of pollutants in catchments by DPI, NRW, CSIRO, MLA, SRDC and so on. This work has been published and is freely available for all to use.

  33. Luke March 5, 2009 at 7:11 pm #

    And alas Motty there have been grazed and ungrazed catchment comparisons in recent years 2001-2004 in the Burdekin. 2.7 times the suspended sediment, 3 times the total N, 2 times the total P.

    Not the wettest of years.

    And there would be hundreds of photos of fenceline contrasts showing management impact, gullies and erosion patches.

    And Motty is still in denial. Denying all research results from all sources !

  34. Luke March 5, 2009 at 7:26 pm #

    Face it Motty – forensic work way out of your league simply gives you nowhere to hide.

  35. Ian Mott March 6, 2009 at 11:03 am #

    Not so fast, Jon. The discussion we were having was in relation to discharge onto the reef and that has always been a net figure after flood plain deposition etc has taken place. I expressed Luke’s discharge totals on a river mouth discharge per hectare of catchment basis.

    Your eagerness to inflate the per hectare rate of discharge with elements like internal deposition exposes your underlying intention to confuse and exagerate rather than clarify.

    And your little attempt at back of envelope calculations makes it clear that you either do not have actual data for sediment flows into the Dam, or were too lazy to provide them.

    Your listing of cropping activity as a major source of sediment is based on false assumption rather than fact. We know this because almost all of the cropping takes place on flood plains which, by your own admission above, are the primary in-catchment areas of sediment deposition.

    The abundant evidence of buried 100 year old fence posts on cane land in the Burdekin delta makes it absolutely clear that the major cropping activity in that catchment is an unambiguous sediment sink, not a sediment source.

    The entire NRM research community is guilty of serious and serial substitution of assumption and value judgement for hard evidence.

    And thank you, Luke, for confirming that the difference between grazed and ungrazed catchments is only 2.7 times sediment loads. That is a very big difference to the 25 times that is implicit in a claim that below dam loads are 10 times pre-settlement levels. The only surprise is that you were stupid enough to post such self contradictory material and boorishly gloat about your imaginary victory.

    Now lets see, 2.7 times ungrazed levels, less a modest 60% capture in a dam, leaves a discharge of only 1.08 times the ungrazed sediment load. Indeed, on your figures, dam sediment capture would only have to increase to 63% and ALL of the increased sediment from grazing would be recaptured in the dam.

    Good one, Lukey, you just blew Jon out of the water as well.

    And as the existing 60% capture level is the level achieved without any formal sediment capture measures in place, we can safely conclude that a well, and properly managed dam could actually reduce sediment loads below pre-settlement levels for the portion of the catchment above that dam.

    Now if you turkeys would kindly point me to some hard data from above and below the Burdekin Dam, and preferably for all the Burdekin catchments, and for the river mouth, we might get close to actually informing the public on this important issue, as is their right.

  36. Ian Mott March 6, 2009 at 11:16 am #

    It should also be noted that Jon’s claim that the Tully and Burdekin are too different to enable comparison is spurious. The vegetation in both catchments have evolved to match their conditions. And the persistence of both geographical types over very long time frames demonstrates that neither is subject to major variances in so-called natural, or pre-settlement sediment loss. Both catchments are a source of sediment in their upper regions, are a sink of sediment on their flood plains, and have a comparatively minor loss of sediment by way of discharge at their river mouth.

    And consistent with higher rainfall in the Tully, total movement of sediment from source and sink, on a per hectare of catchment basis, is proportionately higher. It is what rivers do. Get used to it.

  37. Luke March 6, 2009 at 1:13 pm #

    As I said Mottsa – we only keep you on the line to do you slowly. The period those trials were over was below rainfall years. Are you really that inept as an inactivist. Big erosion events are episodic. You question was whether there were any comparisons of grazed vs ungrazed catchments.

    At this rate you’ll have to stand down the back at cross burnings.

    If you think Tully forest and Burdekin woodlands produce similar rates of sediment per hectare you might want to look at some actual numbers. At this rate we may have to conclude that the inactivist denialist community is guilty of serious and serial substitution of assumption and value judgement for hard evidence.

    LOL ! (thanks for playing)

  38. Ian Mott March 6, 2009 at 4:17 pm #

    I have just been looking at some of the published papers on the Burdekin and must place on record my contempt for the variance between what you two have been saying on this forum and what Jon has published under his own name.

    Clearly, neither of you comprehend the difference between a record of fact and a hypothetical outcome. The only event to come anywhere near Luke’s claim of 5.4 million tonnes of sediment discharge from the Burdekin was 2006/7. The wet season involved 8.3 million megalitres of discharge with only 6.14mt of sediment. But that year was 38% higher than the mean annual event. It also amounted to only 472kg/ hectare of catchment, only 60% of the Tully mean as calculated by Luke’s rectal thermometer.

    See P. 31 at

    And as luke deceptively points out, all the other years were very much below average. Indeed, as we have been continually told, we have had a long stretch of below average years. Many of these years have involved nil discharge and nil sediment outflow.

    Yet, the GBR mafia continues to claim that sediment loads are too high. They make this claim, not on the basis of actual sediment flows but, rather, on projections from this data in an imaginary world where rainfall and river flows conform to the long term mean.

    In one of Jon’s earlier publications they even left out 2003/4 data from a calculated mean because it was too low. So they effectively divided the total discharge for a four year period by a factor of only 3 to produce what they seriously believed to be a 3 year mean. And even then the data for the river mouth only had 2 years data in it so they divided it by a factor of 2.


    In 2005/6 total sediment discharge was only 437,000 tonnes which, when divided by 13 million hectares, would explain why Jon was able to report that some studies have shown sediment loads as low as 33kg/ hectare. Thats what it was for the entire basin.

    More interesting for this discussion is that, along with Fentie et al, a guy refered to as Brodie J reported that Burdekin Falls Dam was capturing 77% of suspended sediments. But this being a touch inconvenient, has subsequently been revised down to 60% for our readers.

    It is interesting to note that in Table 4 p31 of the first link above we can see that in the above average event year 2006/7 the BFD captured 62.5% of sediment. Furthermore, in that year almost the entire wet season inflow to the dam was released during the same event so there was no extensive delay between inflow and outflow which would have maximised sediment capture.

    Clearly, the scope for wise sediment capture by Dams is very substantial.

    And while we are at it, it should also be noted that the recent coral core data, supposedly showing major changes in sediment on the coral sites, are seriously distorted by the 1974 and 1991 wet seasons. In 1974 total discharge, at 52 million megalitres, was more than twice that of the average outflow for the entire Murray Darling Basin, at 24 million ml. In 1991 outflow was over 40 million ml against a long term mean outflow of 8.3 million ml.

    There were no such similar events prior to the 1940’s.

    You guys are a disgrace.

  39. Luke March 7, 2009 at 8:43 am #

    Ah yes – Mottsa is now desperate and starting to flail about madly trying to excavate himself from the intellectual cesspit.

    The story so far –

    (1) he takes some recent sediment load figures provided simply as a broad comparative between Burdekin and Tully systems as a long term average
    (2) continues to rant on about the above even though Jon has already informed him they’re recent figures and not means
    (3) denies any change in sediment generation from grazing of domestic stock in the Burdekin
    (4) when confronted with some actual results (which he said fat chance would exist) changes tack – then bogusly extrapolates drought years to whole record –
    (5) denies Nature paper on Coral record of increased sediment flux to the inner Great Barrier Reef
    since European settlement – doesn’t even read the other paper
    (6) thinks Tully forest is high source of sediment when recent monitoring shows it’s very low
    (7) thinks waterlogging canefields will help
    (8) misreads the Fenti 77% figure – fails to notice concern that the dam has low trapping efficiency

    “Current SedNet modelling of the
    Burdekin catchment suggests that the BFD is a
    very efficient trap for sediment and particulate
    matter, trapping 77% of suspended sediment
    entering the dam (Fentie et al., 2006). However,
    field studies using sediment traps, bottom
    profiling and water sampling within the dam
    reservoir during flow events do not support this
    high trapping efficiency (Faithful and Griffiths,
    2000; Bainbridge et al., 2006). The trapping
    algorithm within SedNet is based on a
    relationship between trapping efficiency and
    hydraulic residence time which may not be
    relevant for rivers characterised by dry tropical
    hydrology (i.e. highly episodic flows with shorter
    residence times than that assumed by SedNet)
    (Sherman et al., 2007).”

    “The reservoir was expected to act as a sediment trap and to clarify each year
    during the dry season, however it fills and overflows during wet season
    flow events, which carry large amounts of fine suspended
    particulate matter, and suffers from persistent turbidity
    (>45NTU in the dry season).”

    Face it Motty – you’ve made a hash of this one !

    Telling someone of Jon Brodie’s ability and committment that they’re a disgrace is simply indicative of the depths that the inactivist movement will sink to win a point. Why not ask some questions and learn something about a topic you clearly know nothing about. Didn’t your Mummy tell you not to do the nana when losing?

  40. Ian Mott March 7, 2009 at 10:44 am #

    So you also have a serious comprehension deficit, Luke. In the post directly above yours I directed you to an actual record of an above average year 2006/7, not a modelled projection, and said,

    “in Table 4 p31 of the first link above we can see that in the above average event year 2006/7 the BFD captured 62.5% of sediment. Furthermore, in that year almost the entire wet season inflow to the dam was released during the same event so there was no extensive delay between inflow and outflow which would have maximised sediment capture.”

    Yet, you provide a quote which seeks to imply that the simultaneous inflow and discharge is something entirely beyond the capacity of the resource managers to remedy. This would only be the case if the Dam was full at the beginning of the rainfall event.

    The fact that the dam is not being properly managed, and the fact that the research community is using this ineffective management as a given, would lead many observers to conclude that sediment loads are being deliberately kept high for other political objectives.
    What? you say. Qld NRM producing selective information for their political masters? Who would have thought that possible?

    It is obvious that the most extreme flood events will completely overcome all storage infrastructure’s capacity to capture sediment. But effective storage and release management can play an important role in speeding up recovery from these major events by improving capture in normal (mean) and below normal (median) years.

    Research that makes vague references to tubidity without reference to actual suspended sediment volumes is not research at all. It is opinion and speculation masquerading as research.

    And by then extending the analysis to include all the undamned rivers in the system the research merely highlights the lack of adequate storage infrastructure on those other parts of the system, particularly the Bowen.

    I note that neither of you have responded to my point that Pandora and other reference points, that are claimed to show a major increase in sediment from the Burdekin, are purely fringe reference points. And due to their location any relatively modest increase in discharge volume that extends these margins of deposition will produce disproportionate readings in the sample sites.

    It is clear that the Qld NRM research community is quite capable of going no further in their inquiries than the point at which their prejudices are reinforced. Hence their reliance on an inappropriate surrogate like fringe coral cores when the real story is waiting for a thorough and representative set of mud core transects to be done, all the way from the mouth to the edge of the deposition zones.

    And for the record, bozo, at no stage did I deny that grazing might increase sediment loads. What I have been very obviously questioning is the claim that current flows, after 60% capture by BDF, are 10 times pre-settlement flows. That would imply that sediment volumes above the BDF are an astronomical 25 times pre-settlement flows.

    And what was the best you could come up with in response? Research that only showed a 2.7 times increase for grazed land vs ungrazed, which, at the 62.5% capture rate recorded for the above average 2006/7 year, would restore below dam sediment loads back to the ungrazed level.

    The simple facts of the matter are that none of the various claims about Burdekin sediment changes can be supported by reliable, conclusive, science. They are gross exaggerations based on highly suspect surrogates and gonzo maths. And as your little lists of imaginary victories above make clear, you are most certainly in the bull$hit business.

  41. Luke March 7, 2009 at 6:17 pm #

    The simple fact of the matter is that you’re uninformed and simply political.

    The science is well available and open. But you wander in, guns blazing, without having even familiarised yourself with some of the issues or contemporary work – equipped on with a tattered back-o-the-envelope. But hey after PIG glaciier, husbanding whales and kangaroos what would you expect.

    In your little ungoing rant you’ve forgotten to add in the considerable amounts os sediment below the dam. And what 60% in “A YEAR” – hardly a long term view. Which branch of the system produced most of the sediment – have you checked if that’s typical? But hey you know all about plucking cherries.

    There is absolutely nothing wrong with the location of Pandora for a long term view. Indeed any variations in flow are well part of the land degradation factor. Indeed variable versus low stocking rate treatments can show a doubling of infiltration. More runoff is part of the land degradation picture now being well established by infiltration rate comparisons in grazing trials.

    Additionally the coral core work shows a change in the magnitude of wets and drys in the last 100 years compared to the 300 previous. (more extreme) All part of the picture that land managers have to consider.

    Additionally the Lewis et al reference provided above gives additional solid evidence of the significant catchment changes resulting from the introduction of domestic stock – sheep and beef cattle.

    You have provided no basis for a long term view. You have dismissed Jon’s expert opinion. (Courageous position or maybe just silly?)

    If you fancy yourself as a player why don’t you bone up and write the blog a guest post on your interesting reef catchment theories. You’ve previously dismissed all the grazing research as baloney so you can put the sword through that at the same time.

    LOL !

  42. Ian Mott March 8, 2009 at 1:14 pm #

    More froth, Luke. The best you could deliver was research that showed there was up to (note, up to) a 2.7 times increase in sediment load from grazed catchments while Jon Brodie claimed there was a 10 times increase from pre-settlement levels, below the BF Dam.

    This range of recorded grazing induced increases is entirely consistent with QLD DNRM’s own published technical notes on catchment water yields. But even you should be capable of comprehending that not all the Burdekin Catchments are 100% grazed. And clearly, not all the grazed portions are in a maximum grazed condition during any given runoff event. This is for the very good reason that even in the absence of rotational grazing of various paddocks, many large runoff events are preceded by smaller rainfall events that produce partial restoration of pasture cover. And this partial cover reduces sediment loads from the level that would have taken place if minimal ground cover was the case.

    It is an indictment of the entire Qld NRM community that they consistently fail to comprehend the simple, incontestable, fact that the grazing based runoff and sediment levels that may be present during the first major runoff event of each wet season will be nowhere near the same extent in subsequent runoff events due to the re-establishment of ground cover after the earlier rainfall event.

    So where does that leave us in a scientific sense?

    A. On one hand we have a set of questionably located coral cores which appear to indicate that there has been a major increase in sediment discharge from the Burdekin basin onto the Great Barrier Reef.

    B. One of the principal research scientists in the field, J Brodie, has stated that sediment flows below the BF Dam is from 5 to 10 times greater than pre-settlement levels and that the dam (normally?) captures 60% of sediment flows into that dam.

    C. It follows that if 5 to 10 times pre-settlement sediment flows below the dam amount to 40% of flows into the dam from the catchment above, then the sediment flows into the dam range from 12.5 to 25 times pre-settlement levels.

    D. Unofficial departmental spokesman, Luke, then refered to research that indicated a maximum sediment load for grazed catchments of 2.7 times that of a similar ungrazed catchment. And this is consistent with other Qld DNRM published material.

    E. As the upper Burdekin catchment remains at 76% woody vegetation we can reasonably conclude that the sediment loads from an ungrazed sub-catchment are essentially the same as for a pre-settlement catchment under identical circumstances.

    F. Data from the recent 2006/7 wet season, (38% above mean) revealed that the BF Dam captured 62.5% of sediment flows into the dam. And this strongly indicates that all lesser flows would result in higher sediment capture rates.

    G. It follows that an inflow to the dam that represented 2.7 times pre-settlement flow would, in all flow cases less than 138% of mean annual flow, reduce sediment outflows from the dam back to pre-settlement flow levels (ie, 2.7 x 0.375 = 1.01).

    H. One is left with no alternative but to conclude that the level of change in sediment deposition from pre-settlement times, that has been indicated by J. Brodie on this thread, cannot, and has not been, replicated by research at the sub-catchment scale.

    I. One is left with no alternative but to conclude that the level of change in sediment deposition from pre-settlement times in the Burdekin catchment, that has been inferred from selected coral cores on the Barrier Reef, cannot, and have not been, replicated by actual sub-catchment research or recent catchment wide data.

    J. The closest level of substantiation achieved by current research is only from 10% to 20% of the implied change in sediment loads from pre-settlement levels.

    K. One is left with no alternative but to conclude that levels of sediment flows have increased as a result of grazing in this and similar catchments. But the evidence is more than capable of establishing that adequately sized, suitably located and properly managed dams on any of the Queensland catchments flowing into the Great Barrier Reef are fully capable of returning sediment discharge to pre-settlement levels or below, for the portion of catchment above those dams.

    And I note that Mr Brodie has conspicuously absented himself from this thread from the moment the inconsistency between his stated belief as to post settlement discharges of up to 25 times pre-settlement levels and the actual sub-catchment scale research was pointed out.

    So lets forget what Luke, the anonymous departmental spinmeister has to say. What has the named “expert”, Mr Jon Brodie, (a recipient of public research funding with serious obligations under the Public Sector Ethics Act 1994) have to say about the above points?

  43. Ian Mott March 8, 2009 at 1:54 pm #

    The conclusion at point K above should have one final clause for greater accuracy.

    “K. One is left with no alternative but to conclude that levels of sediment flows have increased as a result of grazing in this and similar catchments. But the evidence is more than capable of establishing that adequately sized, suitably located and properly managed dams on any of the Queensland catchments flowing into the Great Barrier Reef are fully capable of returning sediment discharge to pre-settlement levels or below, for the portion of catchment above those dams”, for all but the more extreme flow events.

    Clearly, major events like 1974 with 54 million megalitres discharge, and 1991 with 40 million megalitres, could only undergo significant sediment capture with Dams of commensurate capacity.

    Burdekin Falls Dam has capacity of 1.86 million megalitres with no apparent capacity for above capacity flood storage. The Burdekin catchment is 13,000,000 ha and a rainfall range from 1200mm to 500mm. In contrast, Brisbane’s Wivenhoe Dam is 1.16 million ml with another 1.45 million ml in flood capture capacity. The linked Somerset Dam has 0.38 million ml of storage and another 0.52 million ml of flood capture for a combined capture of 3.51 million megalitres.

    The Wivenhoe catchment is only 555,400 hectares with 940mm rainfall while Somerset has 150,300 ha with 1230mm rainfall.

    It follows that if the Brisbane catchment is being managed sustainably with it’s level of capture then the Burdekin has major scope for additional sediment capture, with obvious benefits for the Great Barrier Reef, whilst remaining within the sustainability bounds that already apply to the Brisbane River.

  44. Ian Mott March 8, 2009 at 4:05 pm #

    Interestingly, Brisbane has 3.5 million megalitres of storage capacity for catchment with 7 million megalitres of mean annual rainfall. Apply that ratio to the entire Burdekin catchment and we would have at least (13m ha x 6ml/ha) 78 million ha of annual rainfall and 39 million megalitres of storage capacity. But as only half of the Brisbane catchment feeds into any dams then the same ratio for the Burdekin would be 20 million megalitres of total flood capture capacity.

    That would involve 4 more dams the size of BFD and an equivalent volume of flood surge capture capacity. But of course, we all know that there is one rule for Brisbane and another, altogether for the rest of Qld.

  45. Luke March 8, 2009 at 8:01 pm #

    Well a serious person like Jon – a gentleman and a scholar is unlikely to hang around and debate with some extremist like yourself is he? You’ll just abuse him for each attempt. He will try to impart what he knows and you’ll just put the boot in as you have no shame.

    As for your bleating about 2.7 – that’s like HEAPS in the drier years represented. All experiments are inevitably prisoners of sites and seasons. Some extrapolation takes a systems mind which you clearly don’t have. You’re trying to jam a single season number into what needs to be a 100 to 400 year analysis.

    Then there’s the little porkies that you slip in hoping the lurkers don’t notice … on the 2.7 times angle …. “And this is consistent with other Qld DNRM published material.” – OH YEA – it is?? Like what?

    You have no idea of feedbacks – erosion processes that once started themselves increase runoff. More becomes more. No idea of gully erosion sequences now set in train.

    All you’ve done is cherry pluck a few numbers to help your shonky fat pinky on the butcher’s scales.

    So by now the thread speaks for itself. The lurkers can decide.

    The best one here is flooding the Tully catchment forest to capture non-existent sediment. LOL …..

    As for representing some department – you’d have to be joking?

    But you have by your generalisations disparaged all the serious attempts to understand natural resource processes and all the hard work that involves. From many institutions and regional bodies. And by association all the volunteers who make the effort to take the samples when the creeks are in flood. And all the producers that have allowed scientists to undertake comparative land management treatments on their properties.

    You’ve imparted motives to those researchers without ever really knowing their views.

    Shame on you. But that’s what inactivist bullies are usually like.

  46. Luke March 8, 2009 at 8:06 pm #

    BTW – as for Brisbane River – well most of the sediment isn’t coming from the upper Brisbane is it. But that’s another debate for another episode.

  47. bazza March 8, 2009 at 9:19 pm #

    Motty says :
    “Interestingly, Brisbane has 3.5 million megalitres of storage capacity for catchment with 7 million megalitres of mean annual rainfall. Apply that ratio to the entire Burdekin catchment and we would have at least (13m ha x 6ml/ha) 78 million ha of annual rainfall and 39 million megalitres of storage capacity.”
    Yet another example of what Motty sems to think is science bercause it has numbers like A and B and then, what else would you do but a ratio, bleeding obvious. Now applying a ratio out of context is simply a crook and desperate analogy, learned as it may make Motty feel. Even a cursory or intuitive knowledge of stats would caution one with the observation that the error term for a ratio is the sum of its constituients error terms.

  48. Ian Mott March 8, 2009 at 10:45 pm #

    How predictable. We note that neither Luke nor Brodie, and least of all Bazza, have provided any material that could contest any of the points A to K in my post above. Just the usual mixture of vague winge, grumble and off topic mutter. And of course there is always the indeterminant and unsubstantiated portent of doom by extrapolation which now passes for some sort of religious validation for the desperados.

    So lets just return to the key point again. The claimed increase in sediment loads inferred from selectively located coral core samples CANNOT BE REPLICATED BY ACTUAL SURVEYS OF GRAZED AND UNGRAZED RUNOFF AT THE SUB-CATCHMENT LEVEL.

    You do accept that one of the essential elements of sound science is the requirement for validation through replication, don’t you?

    Jon? Are you there Jon?

  49. Luke March 9, 2009 at 10:10 pm #

    Like Bazza tried to tell you – you’re swift and loose with selected data.

    To replicate a few hundred years of coral core you need a few 100 years of grazing trials.
    “Trials” are prisoners of sites and seasons.

    How are you going with the sediment input below the dam BTW.

  50. Ian Mott March 10, 2009 at 10:05 am #

    Luke said, “To replicate a few hundred years of coral core you need a few 100 years of grazing trials. “Trials” are prisoners of sites and seasons.” This is complete bollocks.

    All that is required is a standard control site (sub-catchment) that is as close to so-called pre-settlement condition as possible and a few grazed sites of similar landform etc. One of the grazed sites should be very heavily grazed at the start of a wet season while the other should have a mix of partial grazing that approximates mean conditions for the entire Burdekin basin.

    The heavily grazed site would identify the upper limits of sediment flow at any given season while the partial one would approximate the basin wide mean flows while the untouched site would obviously provide the comparison with pre-settlement levels. All of these could then be compared with what is assumed to be a similar event from the coral cores.

    Straight forward ground truthing stuff so why has it not been done? Because the truth would not be politically convenient.

    Inputs below the BFD currently supply less than 25% of total discharge. Most of it from the undamed Bowen catchment. The heavily cleared flood plain supplies minimal sediment discharge because it continues to function as a zone of sediment capture.

    Readers might also be interested to note that Burdekin Falls Dam has been designed with provision to increase capacity from 1.86 million megalitres to 8.5 million megalitres. This capacity is more than the entire wet season ocean outflow in 2006/7 (8.3 million ml). which, as stated previously, was 138% of the mean annual event.

    A proportionately sized dam on the Bowen would enable a much higher level of sediment capture as even this sized event could be held to settle for months, rather than days. The benefits for the Great Barrier Reef would be obvious as sediment discharge would fall below pre-settlement levels.

    But that would be a win/win/win situation with unduring benefit for farmers and neither the NRM goons nor the ALP would have a bar of that, would they?

  51. Jon Brodie March 10, 2009 at 11:40 am #

    A few comments on the points I have time to respond to in this discussion. Theres a hugh amount of published literature from studies in the Burdekin (and Fitzroy) on erosion under different pasture and tree cover states. All this shows that hillslope erosion rates can vary by a factor of 100 depending on the status of grass cover and tree cover. One paper to look at that also summarises much of the earlier work is the Bartley et al paper in the journal Hydrological Processes in 2006. This does not include gully erosion which can add another large increase in catchment erosion in poor landscape conditions.

    With respect to building 4 more dams on the Burdekin the size of BFD – there are not the dam sites for these. As noted the BDF could be raised substantially but this would only increase trapping from current 60% to perhaps 80%, a fairly small gain. A dam would be needed on the lower Bowen to have a big effect but there is no suitable dam site there. All the other good dam sites are on the upper parts of rivers (e.g. Hells Gate on upper Burdekin and Uranna on upper Bowen) and while useful for water supply will not be good sediment traps. Overall this would be very expensive for minor gains. Far better and economical to manage erosion at source by working with graziers to maintain pasture cover and quality as is happening the current projects in the Burdekin and Fitzroy.

  52. Jon Brodie March 10, 2009 at 12:10 pm #

    Just a point about the Tully. As I noted recent studies suggest most erosion is still happening in the cropping areas of the lower catchment via drain erosion and streambank erosion. This is not possible to manage by building dams in the upper catchment. However erosion is not the main issue for the Tully anyhow – fertiliser and pesticide loss and discharge are. This needs to be managed in the lower cropping areas (sugarcane and bananas) and is now starting to be managed there using Reef Rescue funding.

  53. Luke March 10, 2009 at 1:05 pm #

    OK Mottsa – with Jon additional comments – he has just told you trials are prisoners of site sand seasons. For you not to understand this shows the total landscape ignoramus that you are.

    Try graphing the rainfall for a few Burdekin rainfall stations over the last century. Check a Burdekin soils map.

    The tally so far for our resident property rights inactivist and research basher.

    (1) upper Tully dam a very silly idea for sediment control. Other issues of nutrients and pesticides also not addressed.
    (2) little expansion dam capacity for sediment control available in the Burdekin
    (3) no understanding of the spatial variation of management, soils, slopes and rainfall – or existing land degradation status
    (4) no substantiation of allegation of bias for the various coral core sediment studies
    (5) no appreciation of existing grazing systems and landscape research


    ho hum ….

  54. Ian Mott March 10, 2009 at 3:21 pm #

    Yeah, right Luke. So a design feature that has already made provision for an increase from 1.86m megalitres to 8.5m megalitres capacity in BFD is your idea of “little expansion capacity”? Give us a break. It is a 4.57 fold increase.

    And Jon has clearly plucked his 80% maximum capture number out of his bum. The expanded BFD would have the capacity to capture 100% of sediment if it captured 100% of an annual event and let the remainder of the system flow to the sea. Similar rates would apply if it merely delayed release for a number of months.

    The Lower Bowen catchment may not have a dam site but it would appear that a standard barrier and anicut (canal along the contour) to the BFD may well be possible as distance may be as short as 100km. Hardly new thinking as such tools have been around for more than 2000 years. But this is further evidence of the departmental mindset to find the first excuse to do nothing. Combine that with the upper bowen site and major gains are possible.

    And it is one thing to find microscale variations in sediment flows of 100 times but another altogether to find anywhere near this variation on a major catchment or sub-catchment scale. This is because those extreme examples are rarely replicated over an entire catchment and the extreme examples of minimal ground cover never persist right through a wet season. Grass grows when it rains and, having grown, gives ever increasing protection for the soil it grows on. Get used to that one fellas.

    And before I would accept such a claim of 100 fold variation I would also need to see the full range of variation for pre-settlement sites at similar micro scale. There is obviously a significant variation in pre-settlement sediment flows due to soil types, slopes and vegetation classes and the duration and intensity of the previous dry season. And these are obviously not uniform all over the catchment.

    So your little ploy of allowing less well informed readers (like ministerial advisors) to assume that all the outcomes between factor 1 and factor 100 are the product of farming practices is as false as it is dishonest.

    It is for that very reason that I indicated that more than one non-control sites would be needed to validate any inference from coral cores.

    And Jons claims re the Tully are not very credible. Even if most erosion takes place on the lower flood plains from drain erosion and stream bank erosion, a large portion of the water volume that produces this is upstream water flowing past. So an increase in the volume being captured would reduce the volume flowing past at peak flow times. And of course, both of you have carefully avoided the fact that the capture of even fresh clean water during a flood event will mean a direct reduction in the amount of coral being killed off by that fresh water.

    And both of you are running spin on gully and bank erosion. Most farmers know that major gully and bank erosion takes place in the extreme events. And once the stream or gully cross section has been modified there will be only minimal follow up soil loss until vegetation build up, along with deposition in lower flow years and snags etc produce conditions that demand a change in cross section at the next extreme event.

    Most farmers also know that stream bank erosion is actually exacerbated when trees are added to a pastured riparian zone. You could discover this as well if you would just walk along any creek from pasture to trees without your heads in an ideological paper bag.

    So here we are, still far from seeing any evidence that would conclusively validate the claims from coral cores that current sediment flows are 10 to 25 times higher than pre-settlement levels.

    But the really breathtaking claim was the one that suggested that a rise from 60% capture to 80% capture would be small beer. There is no doubting that cell grazing and avoidance of overgrazing produce reduced sediment flows and faster recovery of fodder reserves. But in a context of major vegetation thickening events, extremely ill-conceived clearing controls, and minimal management of a greatly expanded Kangaroo herd, demanding that graziers further reduce their stocking rates to deliver a public benefit at their sole expense, is worse than ignorant, it is downright predatory.

    You just can’t get it through your twisted departmental brains that farmers might be quite willing to reduce grazing pressure on their rangelands if they had reliable water supplies to grow their own fodder reserves to supplement the seasonal gaps. But all you can think of is “gimme, gimme, gimme”.

  55. Luke March 10, 2009 at 11:00 pm #

    Grass doesn’t grow without soil. Get used to that one fella.

    Low stocking rate vs variable stocking rate may double infiltration on some soils. Get used to that one fella. Little infiltration – more runoff – more erosion.

    Gullies and channels are a major source of sediment – maybe half the story. And they are still incising. Get updated mate.

    Anyway who says you’re speaking for the grazing industry. They’re supporting and participating in the research. Would you like to abuse them too?

    Indeed in an increasingly fussy market – production from a well researched sustainable production system is a selling point.

    I see you’ve dropped the Tully dam as a bad idea. At least you’ve learnt something.

  56. Ian Mott March 11, 2009 at 10:54 am #

    So now we have Luke resorting to simplistic drivel. Grass clearly grows on creek banks and riparian zones and demonstrably provides a very effective ground cover. And when such zones are subject to flood flows it is the close cover of grasses and forbs that prevents erosion much better than overhead tree canopy and very sparse understory vegetation.

    Exposed roots and bare soil (after all the leaf litter has washed away) in tree covered riparian zones demonstrate why the pre-settlement flows were nowhere near as sediment free as the NRM mafia would have us believe.

    This deliberate policy fraud by the NRM mafia has three elements. 1. under statement of the range of sediment loads that took place prior to settlement, 2. overstatement of the current sediment loads in relation to pre-setlement levels, and 3. exclusion of cost effective methods for reducing sediment loads whilst promoting methods that are entirely borne by the landowner.

    Most of the industry are on leasehold land and must kow tow to the resident thugs, as serfs have had to do for a thousand years. And surely you are not suggesting that there has not been a substantial element of coercion in Qld leasehold land policy? Besides, there is nothing wrong with researching additional options. The problems start when the research is tainted by the ideology and acquires the status of exclusive gospel.

    And which “increasingly fussy market” would that be? Twelve months into the global financial crisis and you still don’t get it do you? You and your mates still think you are in a long, artificial bull market where no-one loses their job and no-one goes hungry.

    Economies and governments are like farm ponds. An excess of nutrients will allow the build up of an entire layer of unproductive scum on the top of it that impairs the health of the whole thing. And the only way to fix it is to either dry it out completely or flush it out with a good purge.

    And I have not “dropped” the notion of a Dam on the Tully. It still discharges more sediment and more wasted fresh water per hectare than the Burdekin. And if it can make a contribution then it should do so.

  57. Luke March 11, 2009 at 7:16 pm #

    What a ripper. So here’s bloke who’s used to the soft life in the idyllic but atypical Byron hinterland with a European notion of hedgerows and quiet streams. Mate are you for real !

    Most of the rangeland droughts break in a big deluge – this is when the erosion damage is done. The grass on your banks will be dead – it will be all swept away. Do you think you’re managing a nice little grassed waterway on some quiet English stream. The reality under Mottsian management is that your yaks would have also trashed the stream bank.

    Tree roots will be heaps more effective. You have ZERO evidence of anything else in this environment. Of course trees provide other ecological functions unknown to someone such as yourself – i.e. reducing waterhole temperatures, habitat. Waterholes that are being documented as filling in under Mottsian management regimes from your vastly increased soil loss (many many X pre-European).

    Still no rebuttal of the coral work. And you haven’t even stepped up to Lewis et al. A multi-trace element coral record of land-use changes in the Burdekin River catchment, NE Australia (link above)

    As for “Most of the industry are on leasehold land ” – not the majority of production though eh? More pinkies on the butcher’s scales. Anyway Delbessie would have to be a pretty wussy bit of compliance. Mate even you could make it through the requirements – they’re that weak. Unless of course you’re some landscape raping heathen.

    Fussy market – like this one.,27574,25111319-3102,00.html

    So given the Tully forest produces little sediment – you must be going to dam over the sugar and bananas – mate you’ll be popular up north ! You might even win a Darwin award for numb nuttiness.

  58. Ian Mott March 11, 2009 at 11:38 pm #

    So now all he can quote is that beacon of truth and accurate reporting, The Courier Mail. Good one boy wonder.

    And what an ignorant load of cobblers on the drought breaking on rangelands. Yes it takes a good sized fall before a drought is considered to be broken but such falls are almost always preceded by what are called “promising rain” events which are enough to get pastures growing but not enough to deliver a full moisture profile.

    Go to page 54 of the 2006/7 report at
    And observe how the main event was preceded by a number of small events which would have obviously induced growth in all grass cover. Your little delusional fairy tale about dead grass giving no protection against erosion is exposed as pure bollocks. It is all in your head you sad plodder.

    And the table on page 36 of the report makes it very clear that Jon Brodie was also talking through his backside on what he claimed were the average sediment flows. Remember, 2006/7 was 38% above the mean and sediment flows into the dam were only 3200 ml on a water volume of 5.5 million ml, but on 5th March above he said,

    “Its difficult to estimate what the average load in the Burdekin River would be now if the Dam wasn’t there but roughly we estimate 1.5 m tonnes from below dam and hence 3 m tonnes from above dam. The delivery from above the dam would then be something like 7 m tonnes (assuming 60% trapping) if the dam wasn’t there. That would give a total load to coast of 8.5 m tonnes without dam.”

    Complete bull$hit. The guy has done the multiplication factor twice.

    If 3.2 million tonnes went into the dam and only 1.2 million tonnes came out then only a departmental moron could possibly conclude that the outflow from that location, if the dam was not there, could be ANYTHING BUT 3.2 MILLION ML. That is, the same volume that went in at the top.

    So note that even in a 38% above mean year the total outflow was 6.14 million tonnes with another 2 million tonnes captured in BFD. So even if this was adjusted on a directly proportionate rate it would only amount to a mean annual discharge to the sea of 4.4 million tonnes.

    But it is clear that the rate of sediment flow would be less than proportionate to the 2006/7 year and the rate of capture by the BFD would be higher because of the smaller volume involved. That is unless some sort of departmental bogan was letting the smaller flow volumes go straight through with no delay to allow sediments to settle.

    Interestingly, if the 2006/7 dam sediment inflows of 3.2mt are divided by 1.38 we get only 2.3mt and when this is subject to 60% capture we are left with only 0.92mt of dam sediment outflow. A similar adjustment to the un-damed parts of the catchment would produce only 3.58mt. But if we adjust all these flows down by a conservative 10% and increase the capture rate by 10% for the lower volumes then the dam inflow drops to 2.07mt and the post capture outflows drop to 0.7mt while the rest of the catchment flows drop to 3.2mt.

    So assuming there is no increase in stream bed deposition in less than average years then mean sediment discharge from the Burdekin mouth is unlikely to be more than 3.9 million tonnes.

    It is also worthy of note that the NRM mafia has opted to describe sediment loads in terms of millions of tonnes rather than in the same megalitres as used for the water flows. A volume of 3,900 megalitres of sediment just doesn’t have the same shock value as 3.9 million tonnes.

    If Jon Brodie had used the same units of measure he would have realised that with an annual sediment capture of about 1500 megalitres the 1.86 million megalitre dam would take a great deal longer than a century or so before the dam was filled with sediment. In fact, 1,860,000/1500 gives us 1,240 years of sediment capture. Enlarge the dam to 8.5 million megalitres capacity and it will do the job for 57 centuries, give or take a climate change or two.

    And on you go about the Tully. The Tully Millstream project was viable on hydro generation alone. As it still would if the greens and the left actually believed in reducing carbon emissions. They clearly do not. Silt capture would be a bonus but the reduction in sediment loss from the lower plains due to less scouring by lower water volumes would be a very useful contribution.

    By the way, Luke, sediment loss from bananas on steep slopes is almost as low as from a thick Kikuyu cover. So sediment from bananas on the Tully flood plain would be even less. So your little theory is more imaginary bollocks from the departmentally ignorant.

  59. Luke March 12, 2009 at 1:03 pm #

    The Mottsian view of Australia:

    The love of field and coppice
    Of green and shaded lanes,
    Of ordered woods and gardens
    Is running in your veins

    Knowledge of episodic rangeland degradation events = zippo !

    Sediment loss from bananas on steep slopes is low – hahahahahahaha !

    Anyway I look forward to your bizarre interpretation.

    Face it Mottsa – where would you be without us to educate you? And for free too.

    I see Lewis et al was too hard for you.

  60. Ian Mott March 12, 2009 at 8:42 pm #

    So when presented with hard data that makes it very clear that major events are often preceded by smaller events which restore pasture cover and thereby reduce sediment loss during the major events, the bogan responds with completely off-topic poetry.

    And then provides a link to a very sloppy report on sediment modelling as if it were a record of fact.

    Cornered rat sqwarks loudly but convinces no-one.

  61. Luke March 13, 2009 at 12:34 am #

    Major events preceded by smaller events that restore cover- bunkum – where’s your evidence?

    Modelling ? – huh? – who didn’t understand what they just read ? I know it’s a bit scientific for your level.

    LOL !

  62. Jon Brodie March 13, 2009 at 10:35 am #

    Ian your calculations as to sediment budgets for the Burdekin were from the 2006/07 data whereas my ‘back of the envelope’ calculations were from an average position based on our long term data. While the 06/07 event was near average in flow (i.e. near 8 m ML) the distribution of flow and sediment flux was not near the average so there is no reason for the details of the sediment budget to match.

    We use tonnes of sediment for a number of reasons including that the measurements are done by weighing and expressed in mg/L, many of the water quality guidelines are in mg/L and we have relationships between factors like turbidity and clarity and mg/l (for particular sites). Conversion to sediment volume is difficult as you have to pick a density value to use. Your calculations do not seem to have taken this into account. If we pick a density of 5 kg/L (numbers like 3 and 4 kg/L also possible – need actual studies to find the right conversion) then 3,900,000 tonnes of sediment converts to 750,000,000 L (not 3,900,000,000 L). This supports your position that the BFD will not fill with sediment any time soon. However I thought we agreed about this long ago in this discussion and its irrelevant to our current posts. We (in collaboration with CSIRO) are currently putting together are number of papers which will use the long term data from a number of scales in the Burdekin (some of which is in the technical reports you have been looking at) to clarify the sediment budgets and patterns of sediment delivery.

    WRT diverting water and sediment from a weir on lower Bowen River, unfortunately all sites on lower Bowen are about 100m lower than the BFD and you would have to pump water up to the BFD at considerable cost.

    As Luke notes there are no significant wins for reducing sediment delivery from the Tully by building more dams on the upper Tully. The Tully Millstream sites you mention are, as I noted, actually on the upper Herbert River – if you built them for hydro as was envisaged they would actually increase water delivery down the Tully (diverted from Herbert) and perhaps only increase stream bank erosion in the lower Tully (perhaps they would then reduce erosion in the lower Herbert? – I think the whole argument is flakey). Any dams actually on the upper Tully in the forest would not trap any significant amount of sediment as the forest does not deliver any large amount of sediment. If reducing sediment delivery from the Tully River was a high priority we would of course target the actual sources (as definitively known from studies in the Tully area) – cane drain erosion, stream bank erosion, plant cane (bare soil) periods of the cane crop cycle, bananas on sloped land, urban development, road construction. In fact fertiliser and pesticide residues are a higher priority than sediment in the Tully region and while some of the sediment issues mentioned above are being addressed they are not a top priority.

  63. Ian Mott March 13, 2009 at 11:01 am #

    So now you are in complete denial on the nature of rain events and their implications for ground cover and sediment loads. As you would, of course, as so much of Qld NRM corporate culture is pure ideology, and twisted ideology at that.

    So I say again, as I said above, “Go to page 54 of the 2006/7 report at
    And observe how the main event was preceded by a number of small events which would have obviously induced growth in all grass cover. Your little delusional fairy tale about dead grass giving no protection against erosion is exposed as pure bollocks. It is all in your head you sad plodder.”

    But this time go to the hydrographs, p39 for the Cape, P43 for the Belyando, P47 for the Suttor, P51/52 for the Bowen at Myuna and p33 for the Upper Burdekin. Note that river flows are not a surrogate for rainfall and remember that modest flows usually only start when the soil moisture profile is restored.

    From these hydrographs we get very clear evidence of peak flows being preceded by smaller events between 1 month and 2 weeks earlier. The high sediment loads in the Bowen at Myuna reflect the larger size of the initial events where pasture had not been restored in time. But for the majority of the Basin, previous rainfall events have taken place well before the major flow event.

    Will have more to say on Tully later.

  64. Luke March 13, 2009 at 1:24 pm #

    More Mottsian bunk on “break of drought” effects – defying reality:

    “We find that, in the early part of the record, suspended sediment from river floods reached the inner reef area only occasionally, whereas after about 1870–following the beginning of European settlement–a five- to tenfold increase in the delivery of sediments is recorded with the highest fluxes occurring during the drought-breaking floods. We conclude that, since European settlement, land-use practices such as clearing and overstocking have led to major degradation of the semi-arid river catchments, resulting in substantially increased sediment loads entering the inner Great Barrier Reef.” –

    DLWC NSW – “drought-breaking rain can make up 90% of the total soil loss in a 20–30 year cycle ”

    Check that Yttrium trend in Lewis et al – erosion ongoing. Has it peaked ? time will tell? lessons learnt – well not for Mottsians. LOL !

    Why do we bother !

  65. Ian Mott March 13, 2009 at 2:37 pm #

    Thanks, Jon. It seems clear that the 2006/7 event is well above (+38%) average. But I have no problem conceding on the height difference between Bowen and BFD. That does not rule out a sequence of smaller impoundments on the lower river levels.

    As I had indicated above, sediment capture in the Tully would only be a small contribution but Luke has manufactured this strawman as an issue as it was his only real chance of ever appearing to win a point.

    I am aware of the relevance of density issues in sediment but was uncertain of actual conversion rates and hence did not mention this aspect.

    I regard the modelling work on the Tully, as linked in Luke’s post above, as seriously underwhelming. It is clear that a major relevant overlay in this catchment would be the length and slope of unsealed roads. If the relationship between unsealed road sediment and general clearfall timber harvest area sediment flows is in the order of 100 fold in mild Victorian rainfall, as demonstrated by Vertessy et al, then the variance would be even higher in Tully.

    But even when using the low Victorian multiples, a 100 metre length of unsealed road that is 5 metres wide would deliver as much sediment as a clearfall harvest of the adjoining 5 hectares. And the practice of allocating council road sediment loads to the adjoining land use, as was done in this case, is more than a bit suss.

    The former Cardwell Shire had 550 km of council roads with 140km of state roads (presumably sealed). So an assumed unsealed road length (not including private ones) of 350km would deliver the sediment equivalent of 3,500 hectares of clearfall harvest. I note that the total area of Bananas is only about 5,000 ha.

    The research has not got anywhere near close enough to the problem to properly identify priorities. The use of such indeterminant terminology as describing a catchment as “predominantly” cane or some other land use is well short of ideal. And the variance between the monitored results and the modelled outcomes highlights this point.

    Having said that, it must be said that Banana growing in Tully is very much removed from the way it was done by my family and neighbours in the 60’s and 70’s. In Tully the plantations are on gentle slopes and tractors are used between rows which does have major implications for compaction, infiltration and runoff.

    NSW Bananas, on the other hand, were, and still are, grown on steeper slopes but with blanket trash retention, zero compaction beyond foot pressure and longer rotations between replanting. It was and remains less efficient than NQ style Banana growing but impacts were also much lower, at least in plantations under our control. Those with a penchant for sustainable farming practices should remember that next time they have a choice between NQ and southern Bananas.

    Meanwhile, back in the Burdekin, if ever there was a catchment where the widespread on-farm use of “water spreading” should be encouraged, it is the Bowen. Yet, thanks to more of that famed enlightened governance in Qld, this practice, along with many other forms of on-farm water management, is subject to blanket moratorium.

    By “water spreading”, I refer to the practice of installing a sequence of low bunds along the contour with breaks at every second end so that the overland flow of water must flow back and forth in much the same way as a fish ladder. This substantially reduces the speed of runoff while extending the distance it must travel. And it allows increased infiltration. It reproduces the classic dry paddock and adjoining wet paddock on a linear and micro scale. And it can be selectively applied to a slope by the use of side gates, at intervals, that divert flows back into the nearest drainage line.

    This technology is particularly useful in catchments with large storage capacities which can maintain normal seasonal stream flows while compensating for reduced flows from the portion of the catchment subject to spreading.

    In the Bowen catchment in 2006/7 a mere 940,000 megalitres of flow carried 2,240,000 tonnes of sediment, or 36% of total basin discharge. Water spreading, involving 2 megalitres per hectare (1 of flow and 1 of infiltration), over an area of only 2350km2, would have halved the initial flood peak by delaying 25% of it and absorbing another 25%. It would also have halved total sediment flow, either preventing 1,120,000 tonnes of sediment loss or re-spreading it back over the subject land. The lower flood peak would also have reduced chanel and bank erosion downstream.

    And the works would pay for themselves with increased and extended fodder supplies and better utilisation due to improved dispersal of watering points. The only impediments are the lumps of wood between the Premier and Minister’s ears.

  66. Luke March 13, 2009 at 6:32 pm #

    You’re loopy on the Tully sediment story mate. The numbers are MEASURED not modelled dofus.
    Your whole raison d’etre for dam construction is bullshit. Note well dear lurkers !

    “The use of such indeterminant terminology as describing a catchment as “predominantly” cane or some other land use is well short of ideal.” – more crap – the land use mapping is quite precise.

    If you had noticed the Hateley et al research through clever chemistry and statistical techniques projects back the source of sediments as one outcome. All that passed over your Intel 8086 processor.

    And now the refuge of snake oil merchants – Motty is flogging the old keyline scheme. My oh my.
    Will start a few more erosion gullies. We’ll be up to 30x sediment soon enough.

    The important thing is that while our resident inactivist bays at the moon and see conspiracies behind each bush, real research by scientists of good faith on real producers’s properties is showing the way forward.

    That path is going with the environment and the resource base – not terraforming it and damming it into a Mottsian theme park.

    At the end of ten years the results showed that good pasture management through moderate stocking rates delivers a raft of triple bottom line benefits. Relative to the commonly used higher stocking rates throughout the industry, the moderate stocking rate increased accumulated cash surplus by $9,000 per 100 hectares after ten years. Animals were on average 50-70 kg heavier, with less year-to-year liveweight variability, and produced higher quality carcases that received approximately 20c/kg more at sale. While liveweight grain per hectare was lower there was no need for drought feeding.

    Under heavy stocking rates there was a 30 per cent decline in carrying capacity, a three-to four fold decline in cover of palatable, perennial pasture species and an increased frequency and intensity of runoff with increased nutrient loss.

  67. Ian Mott March 14, 2009 at 10:07 am #

    So the dopey departmental gollum is unable to distinguish between Keyline and water spreading and cannot comprehend that actions are possible that will produce a structural improvement in long term carrying capacity.

    Worse still is his mindset that insists that there can only be one option in grazing management. No-one will contest that the rate of fodder utilisation must be matched to long term fodder production. It is, after all, what Kidman was doing a century ago. But to then argue that any option that seeks to go beyond the existing climate parameters and improve underlying capacity is tantamount to rejection of the fundamentals is the mindset of the ideologue.

    And the whole issue of long term carrying capacity is rendered void if the public’s grossly expanded Kangaroo herd remains on site, to continue grazing, long after the farmers herd has been sold or is being hand fed.

    The NRM mafia has gone to considerable lengths to understate the impact of Kangaroo grazing but they cannot escape three essential facts;

    1 The Kangaroo herd is much more than ten times greater than it was pre-settlement, and

    2 It is not subject to anywhere near the stock reduction measures that graziers apply to their own herds as drought hits, and

    3 They are free to move from property to property so any grazier who might have carried less cattle to preserve ground cover, or who destocked early for the same reason, will have an enlarged ‘Roo population that inflicts critical damage to his pasture anyway.

    The research that has attempted to downplay the impact of Kangaroo grazing on the landscape has conspicuously remained within the bounds of generalisation. It has not dealt with any specifics in respect of what all these animals are doing to the landscape AFTER the sheep and cattle have been de-stocked.

    After destocking, the public’s Kangaroo herd accounts for almost 100% of grazing pressure at the time when the landscape is least able to deal with it.

    Everyone but a departmental goon can understand the need to adopt as many useful options as are available. Water spreading was trialed at Barcoorah, and with the assistance of federal funding. It demonstrated a substantial, cost effective, increase in long term carrying capacity.

    It is not an option that should be promoted in a catchment that has already been over allocated as it would have a significant impact on flow regimes. But the Bowen, among many other Queensland catchments, is seriously under utilised. Water spreading, of itself, in the Bowen catchment will substantially reduce sediment loads. And it will also increase long term carrying capacity in a way that will reduce sediment loads further. That is, provided it is implemented by people who are not connected to the current malevolent and predatory regime.

    If we were not governed, and administered, by such lilliputan morons, they might realise that compliance with a properly determined and substantiated new long term carrying capacity equation would be readily accepted if it were incorporated as a condition under the development approval for a water spreading project. It would represent the sharing of the benefits of capital expansion rather than the taxing of a reduced capital.

    But these thugs, to their shame, merely perceive a carrot as a stick that is too short and soft to hit anyone with.

  68. Luke March 14, 2009 at 10:22 am #

    Thought you would have stayed off roos after being cleaned up on that last time.

    What roo herd in the Burdekin? More fanciful out of touch distractions.

    “No-one will contest that the rate of fodder utilisation must be matched to long term fodder production.”

    ho ho ho !! Yea like fun. There wouldn’t be any issues if this was the case.

    But as always we’ve given up our time to educate you on modern research. At no cost.

    We can’t have our property rights dudes wandering around the country spruiking utter rot. Thanks to our efforts you now won’t be caught out not knowing that the Tully forest produces little sediment.

  69. Ian Mott March 17, 2009 at 10:58 am #

    Nice try, but the Tully paper is nothing more than a comparison between some selected sample points and a model. The sampling was no-where near detailed enough to produce valid data. And the variances between reality and the model remain very significant, ie, up to five fold, in both directions. I note that you declined to comment on the sediment load from roads but was content to allocate the sediment from an unpaved council road to the land use it goes past, not the land use the road actually services, or the urban and non-urban people who use that road.

    And not a word on water spreading even though the research had full NHT funding. Oh, of course, you claim that “no farmer would want to see his farm under water”. So why was it subjected to the moratorium then if no-one wanted to do it?

    And now you are suggesting that the range of the Eastern Grey Kangaroo and the Common Wallaroo does not extend to the Burdekin? As I said above, the research on the impact of ‘Roos remained at purely generalised level, with loaded assumptions as to animal size and fodder consumption. More importantly, it failed to consider ‘Roos impact on fodder when they are the only animals left in the paddock, ie after the stock have been sold or are being hand fed.

    The Minister’s animals are still ripping away at the remnants of pasture long after the farmer has concluded there was nothing left to eat. And you then blame the farmer for over-grazing.

    Lets face it, Luke, you are nothing more than a fully paid departmental spin meister.

  70. Luke March 17, 2009 at 1:25 pm #

    Bunk – sampling from the MAIN waterway is perfectly adequate. Any forest roads are in the forest figure. It’s still a very low number. The modelling is simply irrelevant in this context.

    Go on put up the roo grazing pressure for the Burdekin. Don’t bluff.

    The grazing trial data are all there. Pages upon pages of detailed research. Hey weren’t you going to tell us where all that research was wrong? ROTFL ! The sequence of overgrazing in the Burdekin is WELL documented and you have made the most pitiful attempt I have ever seen trying to bulldust your way out of it.

    Face it – real industry has ignored you, innovated, and moved on.

  71. Ian Mott March 20, 2009 at 10:35 am #

    And still he flogs the departmental spin while ignoring the fact that the research “failed to consider ‘Roos impact on fodder when they are the only animals left in the paddock, ie after the stock have been sold or are being hand fed”. That is, when pasture is least able to deal with any grazing.

    Sampling from the main waterway is totally inadequate for the very good reason that almost every sub-catchment has a transect from agriculture on the river flats to forest on the slopes. And the slopes, of course, have differing slopes, and consequently will have differing sediment flows. But at least you have demonstrated how NRM “science” is content to only inquire as far as is needed to confirm the official position.

    And once again, you have completely sidestepped the fact that in un-damed catchments like the Bowen, major reductions in sediment flows, and major increases in stocking capacity, can be achieved by on-farm water spreading. But it is official NRM corporate culture to reject any option that might produce an environmental benefit while also benefiting farmers.

    Readers can see for themselves as they read back over the thread above how you have provided minimal substance while exercising a rather ordinary under-graduate sneer on behalf of your political masters.

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