Jennifer Marohasy

a forum for the discussion of issues concerning the natural environment

The Disputed Natural History of the Lower Lakes

By

OUR  society places a premium on restoring degraded and polluted places to their natural state. It is clear from the scientific literature that the Lower Lakes have a marine origin and that they could be healthy if filled with water from the Southern Ocean rather than taking fresh water from upstream which has been government policy at least since construction of the barrages. 

That the salt water solution is resisted, and that the Murray Darling Basin Authority insists in its new plan that even more water be taken from irrigators to keep the lakes fresh, suggests that this key institution is more influenced by politics than science.

Filled with seawater, and with regular tidal flushing, the Lower Lakes would possess a different, but not necessarily less natural, or less healthy, assemblage of plants, animals, fish and microorganisms…

Read the complete article just published at Quadrant Online: 

http://www.quadrant.org.au/blogs/doomed-planet/2010/11/jennifer-marohasy

*********

The Murray: salt water solution

by Jennifer Marohasy

November 21, 2010

The disputed natural history of the Lower Murray

MOST of the water the Murray Darling Basin Authority plans to take from irrigators under its new plan will be sent to the Lower Lakes in South Australia ostensibly to keep the River Murray’s mouth open and the Lower Lakes full of fresh water. An alternative would be to let the Southern Ocean flood through the River’s mouth and fill Lakes Albert and Alexandrina with sea water. This salt water solution is being resisted on the basis the lakes were naturally fresh but that is not what the microfossils in the sediment of the lakes indicate.

It is not contested that the lakes formed approximately six thousand years ago when the Southern Ocean broke through the modern coastal sand barriers of Sir Richard Peninsula and Younghusband Peninsula filling the interdunal areas. That point of entry, now known as the Murray River’s mouth, remains dynamic and has moved 6 kilometres over the past 3000 years.

Sea levels have fluctuated throughout geological time. The ice sheets during the last peak in glaciation contained about 55×106 km3 more ice than today and sea levels were on average about 130 metres lower than they are today.

At that time the River Murray extended across the continental shelf and its mouth was about 180 kilometres to the south west of its present location. The climate was much colder, drier and windier, and where the Murray enters the sea today there were distinctive desert dunes running parallel to the distant coastline.

As the ice melted, sea levels rose reaching a peak 6,000 to 7,000 years ago when sea levels were 1-2 metres higher than their present position after which there has been a sea level fall of about two metres. 

The distance seawater will flow naturally onto a landmass is affected not only by the extent of sea level rise but also by the height of the land barrier which may change with tectonic processes that can cause uplift or subsidence.  Studies by Professor Bourman and co-workers from the Universities of Wollongong and Adelaide have shown that the Lower Lakes area has been subsiding over the past 125,000 years at a rate of 0.02mm per year.

The Lower Lakes have also been subject to seismic activity with what is referred to as ‘regional warping’ occurring from the Mount Gambier volcanic region towards the base of the rising Mount Lofty Range which is immediately south west of the Lakes. Residents of the Lower Lakes experienced an earthquake on May 10, 1897, and then again on September 19, 1902. These tectonic movements may have accelerated coastal erosion processes along the entire Encounter Bay shoreline, which shows a general landward encroachment over the last few thousand years.

John Cann and co-workers from the Universities of South Australia and Adelaide have studied fossil foraminifera – tiny protozoa with shells of calcium carbonate – preserved in the sediments of the Lower Lakes to discriminate episodes of seawater incursion from periods of high river flow. Comparing the occurrence of species typical of freshwater with species typically found in the sea, they concluded that the Lower Lakes had a maximum marine influence 5,255 years ago and a maximum freshwater influence 3,605 years ago. The period of maximum freshwater influence is thought to coincide with the period when the Murray Mouth was greatly restricted or closed because climatic conditions in the catchment were much drier. 

Dr Cann and co-workers conclude that the change in the foraminifera complex over the most recent 2,000 years indicate a general trend of increasing marine influence, up until the construction of the five large steel and concrete barrages that now block the natural ebb and flow between the Lower Lakes and Southern Ocean.

This conclusion that the lakes were getting saltier for most of the last 2,000 years is not obvious, however, from studies of another group of microfossils, tiny plants called diatoms that occur in sediment cores.

Diatoms are unicellular algae common in rivers, lakes and the ocean with particular species unique to freshwater and others to saltwater.

Jennie Fluin from the University of Adelaide, and co-workers from that University, and also CSIRO, studied the diatoms in a sediment core from the southern section of Lake Alexandrina. They found that between 7,000 years and 2,300 years ago, a strong marine influence was present. But they conclude that the change in the species abundance over the last 2,000 years shows a general decline in relative abundance of marine species. The data are equivocal, however, and only in the very top section of the core, in a distinctive light grey mud, perhaps deposited after the construction of the barrages, does a species with a low salt tolerance become common.

In summary, studies of the natural history of the Lower Lakes indicate a marine origin, that during long periods the waters of the lakes were salty, and that during other periods they were fresh. It is unclear how salty or fresh and for how long. The area is characterised by environmental variability.

Our society places a premium on restoring degraded and polluted places to their natural state. It is clear from the scientific literature that the Lower Lakes have a marine origin and that they could be healthy if filled with water from the Southern Ocean rather than taking fresh water from upstream which has been government policy at least since construction of the barrages. 

That the salt water solution is resisted, and that the Murray Darling Basin Authority insists in its new plan that even more water be taken from irrigators to keep the lakes fresh, suggests that this key institution is more influenced by politics than science.

Filled with seawater, and with regular tidal flushing, the Lower Lakes would possess a different, but not necessarily less natural, or less healthy, assemblage of plants, animals, fish and microorganisms.

Jennifer Marohasy is a biologist and adjunct research fellow at Central Queensland University

Reader Interactions

Comments

  1. Neville says

    Jennifer,
    I’ve tried to post this to your latest story on the Murray but without luck. I just hope you can explain the difference in the records between the BOM MDB rainfall records and the numbers used in the MDBA “Guide to the Basin Plan”, Neville.

    Some interesting problems with the MDB rainfall record, or BOM versus “The Guide to the Basin Plan.”

    BOM has annual average rainfall across the basin as 489mm but when you add up the raw numbers from 1900 to 2009 you actually get 468mm, a difference of -21mm.

    The MDB Guide ( page 14 ) actually gives the annual average rainfall 1895 to 2006 as 457mm which is minus 32mm as shown by the BOM raw numbers. ( but 1900 to 2009 )

    See BOM raw numbers above graph http://www.bom.gov.au/cgi-bin/climate/change/timeseries.cgi?graph=rain&area=mdb&season=0112&ave_yr=T

    Interestingly the average annual rainfall at BOM from 1900 to 1954 is 452mm and from 1955 to 2009 it is 483mm or an increase of 31mm or approx 1.24 inches more per year in the last 55 years of the record.

    The lowest 10 year period of the record is from 1935 to 1944 ( inclusive)with just 402mm annual average rainfall across the basin.
    By comparison the 10 years from 2000 to 2009 ( inclusive) delivered 421mm or 19mm more than that driest ’35 to ’44 period. ( nearly 3/4 of inch per year)

    The 10 year period 1940 to 1949 ( inclusive) delivered 421mm , the same as our last ten years.

    So once again we can say that the MDB is increasing in rainfall over the last 55 years (483mm BOM record) by approx 1.24 inch or 31mm every year compared to the 55 years 1900 to 1954 ( 452mm bom record)

    So what is the real problem a lack of rainfall ( not )or hopeless catchment management?

  3. val majkus says

    There was an article by Tom Quirk BOM loses rainfall
    http://www.quadrant.org.au/blogs/doomed-planet/2010/10/bom-loses-rainfall
    I don’t know what’s happened to the result of that
    I had an idea there was an update; you might find out by searching Quadrant Online
    here it is
    http://www.quadrant.org.au/blogs/doomed-planet/2010/10/finding-lost-rainfall
    The explanation for the variations in rainfall record is simple. A new method of creating the estimate has been developed and applied. This is not well advertised but the method is described in a published paper. The variations from the records ending in 2007, 2008 and 2009 are of the order of 20 mm per year against an average yearly rainfall of 480 mm for the years after 1948, an uncertainty of 4%. This will be compounded by the sampling process of rain gauges that cannot possibly capture all the local variations of rainfall. The use of satellite detection should better define spatial distribution but the measure of rainfall remains problematic. So the 4% uncertainty may be an under-estimate.

    This new analysis has been carried out by the usual suspects, the CSIRO and the BoM along with the Bureau of Rural Sciences.

    What is really intriguing though is the corrections made to the rainfall record tend to reduce the rainfall in the last half of the twentieth century. This is important since our projected future is for a hotter climate and less rain. An example of this is a quote from a paper Climate change and water use of native vegetation by Cate Macinnis-Ng and Derek Eamus, University of Technology, Sydney (2009), apparently commissioned by Land & Water Australia, that concludes:

    Climate change will cause hotter, drier conditions with less rainfall across the majority of the Australian continent.

    This is the received wisdom based on computer modeling but do the rainfall measurements compiled by the BoM point in this direction with decreasing rainfall as the Australian temperature record shows an increasing temperature?

    Unfortunately they do not. The BoM adjustments to the 110 year record have brought the decadel increase in rainfall down from 5.4 +/- 3.4 mm per decade to 3.3 +/- 3.2 mm per decade. In fact the dominant feature of the record is the random behaviour of the annual rainfall with a scatter of up to 200 mm either way about the annual average of 470 mm.

    This new value of the increasing rainfall is not significantly different from no increase over the century but it does not support any alarmist view of a devastating trend to drier times in the Murray-Darling Basin.

    and I and I think you are talking about rainfall data; runoff is calculated by computer models and we all (sorry most of us) know how accurate computer modelling of climate is

  4. Luke says

    Val says – “BOM loses rainfall” – and as usual more bunkum. The usual unresearched trash we expect from sceptics who are too intellectually lazy to make the most basic inquiry. So here we have promulgation of crap by the usual suspects.

    And more drivel from yourself – runoff calculations for rainfall are not from computer modelling of climate at all – don’t be so utterly ridiculous.

  6. el gordo says

    From the UNSW earlier this year.

    ‘CSIRO’s Murray-Darling Basin Sustainable Yields Project (MDBSY) has been the largest research contract the organisation has taken on in its 80-year history. It has generated a massive data set to drive a computer-based ‘supermodel’ of the Basin’s water resources, created by linking 40 existing and new models of surface and groundwater flows and extractions within the Basin’s 18 individual catchments.’

  8. Another Ian says

    El Gordo

    Re MDBSY

    When you get to the Wallam/Nebine/Mungallala Creeks part just realise that there was only one gauging station – on Wallam Creek!

  9. Luke says

    It’s hardly CLIMATE modelling is it?

    And right after we’ve had a sceptic here reminding us about “Rainfall and Runoff” which (choke) would involve some “modelling”.

  10. el gordo says

    Let’s forget the modeling.

    A paper by Potter and Chiew says ‘the largest signal in rainfall and runoff in the Murray-Darling Basin is a step change occurring around the mid-1940s. Several dry sequences are identifiable using a multiple change-point test, particularly the three ten-year dry sequences of 1895−1904, 1936−1945 and 1997−2006.’

    Perhaps these ten year sequences are attached to the rear end of a warm PDO?

  11. el gordo says

    Except that it was a cool PDO between 1880-1915, which places the Federation drought in a realm of its own.

  13. val majkus says

    Sorry Luke, didn’t realise you are a modelling newbie; check out Warwick Hughes
    #4 Temperature too – not just rain – ongoing BoM utter incompetence – month after month after month; maybe you’ll learn something, as I did
    November 21st, 2010 by Warwick Hughes
    cheers

  15. val majkus says

    Luke, sorry you can’t see the big picture; Dr Marohassy’s initial contribution to Quadrant Online about Save the Murray, remove the barrages
    http://www.quadrant.org.au/blogs/doomed-planet/2010/09/the-murray-a-fresh-perspective
    resulted from and referred to the release of a new Murray Darling Basin plan on October 8, 2010 which she said in the Quadrant article ‘is likely to reignite debate over how best to solve the problems of the Murray River. It will further pit some environmentalists and some South Australians against upstream irrigators as a debate over how to fix the two very large freshwater lakes at the very bottom of the Murray River rages. Lake Alexandrina and Lake Albert are situated behind the narrow expanse of water known as the Coorong, beyond the Coorong is the Southern Ocean and upstream of the lakes is the River proper’

    If you want to see the big picture behind her continued articles on the Murray I suggest you read the plan which was released on Oct 8 2010

    download it from here http://thebasinplan.mdba.gov.au/guide/guide.php?document=the-murray-darling-basin

    check out the word ‘modelling’ in 8.11

    then come back with a question; not a repuditative statement with nothing to back it up

  17. Luke says

    Did I say anything about the barrages? No.

    What I did comment on was your stupid ad hom against the Bureau based on some nonsense in Quadrant.

    And speaking of “big pictures” – do tell us Val – what would be the issues in developing an “MDB” wide estimate of rainfall.

  18. el gordo says

    Precipitation over the basin is historically variable, so gridded meteorological and hydrological datasets are necessary to get a handle on what’s happening.

    To achieve this the government recently invested capital into the BoM water division, but from my understanding the scientists felt obliged to mention CO2 and its impact before they got a dollar.

    Is it possible to have a cyclic trend, or are all trends linear?

  19. Neville says

    This is the best flush of water down the Murray in at least a decade or more. ( probably since early 1990’s )

    If you camped on the river bank at Renmark SA at least 30 GL’s a day would pass by your tent so it’s a good flow by any historic measure.

    Victoria is spending/ wasting billions of dollars on a desal plant that can only deliver 150 GL’s a year or 5 days flow of the Murray at Renmark, so this is a very expensive co2 gobbling method of producing a tiny ammount of fresh water.

    The Bolter has a good article here of the cost to the taxpayer when stupid Govts are duped by urgers and scientists into building these incredibly expensive infrastructures only to be served a good wake up call by nature. What a stupid waste of money when one considers we could have built a dam on the Mitchell river in Victoria for a third of the cost and produce three times the volume of water.

    Of course the dam would not have the annual horrific costs and wouldn’t be gobbling up co2 when producing the vast ammount of power to run the stupid plant every single year.
    So who’s the real protctor of the enviroment?

    http://blogs.news.com.au/heraldsun/andrewbolt/index.php/heraldsun/comments/which_warmist_preacher_fooled_these_premiers_into_blowing_billions_on_desal/#commentsmore

  21. Susan says

    Not only is a salt water solution resisted, ‘the barrages’ are not even mentioned, not even in the historical part of the MDBA plan. How’s that for political…

  22. val majkus says

    an interesting recent study on the accuracy of CGMs
    http://www.informaworld.com/smpp/section?content=a928051726&fulltext=713240928
    quoting from the conclusion
    It is claimed that GCMs provide credible quantitative estimates of future climate change, particularly at continental scales and above. Examining the local performance of the models at 55 points, we found that local projections do not correlate well with observed measurements. Furthermore, we found that the correlation at a large spatial scale, i.e. the contiguous USA, is worse than at the local scale.
    …
    Do we have something better than GCMs when it comes to establishing policies for the future? Our answer is yes: we have stochastic approaches, and what is needed is a paradigm shift. We need to recognize the fact that the uncertainty is intrinsic, and shift our attention from reducing the uncertainty towards quantifying the uncertainty (see also Koutsoyiannis et al., 2009a). Obviously, in such a paradigm shift, stochastic descriptions of hydroclimatic processes should incorporate what is known about the driving physical mechanisms of the processes.

    …
    end of quote

    I suppose when looking at predictions accuracy is important and Warwick Hughes has a bit on his blog about the accuracy of BOM predictions
    http://www.warwickhughes.com/blog/

    and this is what he has to say about the unreliability of modelling:

    Here are some ideas on the issue of runoff/inflows and the unreliability of constructing long term time series of river data modeling so beloved by the “expensive water lobby”.

    These are some essential points I have made re the ACT that mostly apply to the MDB too.
    [1] Trends derived from the time series of historic inflow numbers so beloved by ACTEW and the doomsters and proponents of expensive water, the Wentworth Group etc – are nowhere near as credible as trends from long term rainfall data.
    [2] Stream gaging was not common a century ago. Stream gaging was much more widespread post the 1940’s than pre 1940’s and equipment costs mean the networks are more sparse than rain data networks.
    [3] Stream gaging has been carried out by a multiplicity of methods and techniques and can involve quite expensive equipment to be installed in remote areas – whereas measuring rainfall has always been relatively simple and cheap.
    [4] The Queanbeyan rain history shows with crystal clarity that the last decade has NOT been exceptionally dry compared to the 1930’s-40’s and 1890’s thru to WWI.
    [5] It also must be noted that there are NO reliable long term rain data from high up the vital Cotter catchment – so we are stuck with using Queanbeyan as a guide to ACT historic rain trends.
    [6] So when the ACT Govt promulgates their inflows history which show the last decade to be exceptionally dry – in conflict with the Queanbeyan rain data – I say “..the ACT inflow data – not worth the paper it is printed on in terms of being an accurate comparison of recent inflows with late 19C and early 20C inflows..”
    [7] When you also feed in the facts that the ACT Govt are promulgating this dubious inflow history and they are advocates of CSIRO climate modeling – my conclusion in 6 is reinforced.

    If anybody can show me a 139 year long stream gage record from an ACT/MDB high country stream – using the same equipment throughout – no gaps and missed data – that would indeed be an interesting discovery.
    Other facts worth stating that illustrate the complexities behind trying to make long term time series of inflows;
    Changes in vegetation cover have a marked impact on inflow rates or catchment efficiency – more vegetation = less runoff / inflows.
    So periods in our history when land clearing was dominant – say after settlement and post WWI and WWI soldiers block schemes- would have tended to increase runoff.
    Other opposing factors such as post WWII soil conservation programs – reversion of marginal land to scrub – the huge increase in timber plantations in post WWII decades – the “plant a billion trees” campaign launched by PM Bob Hawke over 20 years ago – would have all acted to reduce runoff and inflows.
    That comment is at http://www.warwickhughes.com/blog/?p=678

    Neville I completely agree with you; El gordo I don’t know the answer to your question

  24. el gordo says

    Ian Holton believes the Sinusoidal solar-lunar model is a better fit for the MDB. It is formulated from lunar and solar cycles and he’s confident the next seven years will see abundant river flows.

    http://www.holtonweather.com/WHAT%20IS%20THE%20MAIN%20FACTOR%20CONTROLLING%20THE%20MURRAY%20DARLING%20BASIN%20SYSTEM%20RAINFALL.pdf

    Holton expects a ‘drier period from 2017 to around 2021 or 2022, in general, normality of rainfall and dam levels will extend through to 2035 at least.’

    Time to turn off the desal plants and prosecute the short-sighted ratbags responsible.

  25. val majkus says

    Thanks cohenite for that link, very educational and I’ve reposted it in other places
    Here’s his website http://landshape.org/about-the-author/
    There’s a comment there by Warwick Hughes referring to this page
    http://landshape.org/enm/inquiry-into-long-term-meteorological-forecasting-in-australia/

    The Committee recommends that CSIRO and the Bureau of Meteorology provide to the Australian Government a report with detailed explanatory information as to why a particular dynamic forecasting model or system was chosen for use in Australia. The report should be completed by the end of 2010.

    As Warwick says something to watch for

    and great link too el gordo thanks!

  26. Ian Mott says

    I am in the middle of my MDBA submission but would like to forewarn folks that I have had to change my view of the value of removing the barrages. The hydrological evidence makes it clear that the barrages have reduced the tidal prism by about 90% and this has actually served to keep the Murray mouth open, albeit with less volume of flushing. The tidal patterns in the area mean that a full amplitude inflow takes place over 8 to 9 hours while the ebb flow takes 15 to 16 hours. This means that the flood tide velocity is greater than the outflow and this brings in more sand than the ebb flow is capable of shifting back out again. When the barrages reduced the area of the tidal prism they also reduced the volume and velocity of the inflows and thereby reduced the rate of sand build-up.

    This is why the South Australians insist on more fresh water to balance these flows. But the use of fresh water is extremely inefficient and poorly targeted. In fact, half of all fresh water discharged through the mouth takes place at a time in the tide cycle when it is incapable of doing the ecological service it is claimed to do. Yes, 50% of the additional 3000GL of expensive environmental flow will be wasted as it will be discharged at a time in each monthly cycle when there is minimal tidal movement, and therefore minimal capacity to push sand away from the Murray mouth.

    There are a stack of other implications that have been missed by all the research to date so I will provide links to the submission when it is completed.

  28. Neville says

    Ian as part of your submission have you come across any rainfall record 1895 to 2006 from the MDBA?
    They claim on page 14 of the basin plan that the average over this period is 457mm but the BOM state that the 1900 to 2009 average is 289mm.

    But when you add up the BOM numbers the average is only 268mm, 452 mm 1900 to 1954 and 483mm from 1955 to 2009.

    If Ian or anyone can provide a link from MDBA showing their raw numbers or a graph over the period 1895 to 2006 it would be appreciated.

  29. John Sayers says

    oh – those pesky farmers who are ruining the environment!

    A decade-long survey has found key species of birds that were in trouble because of land clearing and grazing are on the way back.

    For the past decade, David Lindenmayer and a team of scientists from the Australian National University have been keeping a close watch on woodland birds, studying 300 sites across 150 farms over a 10-year period.

    Over that time, many species that were considered to be in trouble have reappeared, including the speckled warbler, the diamond firetail and the rufous whistler.

    http://www.abc.net.au/news/stories/2010/11/23/3073848.htm

  30. Steve John says

    Ian, re your statement what has changed at the Murray mouth compared to pre settlement and the establishment of dams at one end to store run-off and the barrages at the other to keep the sea out during low river flows?

  32. val majkus says

    El gordo, it’s always best to get in in case in time is not extended
    I’ll be interested to see Ian’s submission – I’ve put in a comment already
    and Luke I missed you up there talking about methane … that’s so yesterday may I say
    I was going to suggest you that you look up the meaning of ‘ad hom’ because you used it incorrectly in a previous comment – you can google it on Wiki
    Once you know what it means come back and try the comment in which you used it again

  33. Susan says

    Steve,

    Muck, mud, reduced tidal prism caused by the barrages. When the barrages were built the resulting debris was piled and left. Now that pile is an ‘island’, in the middle of what should be a channel.

    The terrain is difficult to work in. How do you get trucks into the mud, water, etc to remove the debris? Too shallow for a ship. Local officials were using hovercraft to get out over the mud just to do the inspections during the drought. They nearly lost a few bulldozers in sink holes during the Clayton regulator project. I think it falls into the ‘too hard basket’ to try and clear out decades of this accumulation.

  34. kuhnkat says

    Dear Luke,

    So sorry to hear your mental illness still drives you to no data, ad hom, argument from authority, waste of time posts.

    Yours Truly!!

  35. el gordo says

    This is an old story, but in retrospect the South Eastern Australian Climate Initiative is a gravy train.

    “In the minds of a lot of people the rainfall we had in the 1950s, ’60s and ’70s was a benchmark. A lot of our (water and agriculture) planning was done during that time. But we are just not going to have that sort of good rain again as long as the system is warming up.”

    Bertrand Timbal

    http://www.smh.com.au/environment/climate-change/study-links-drought-with-rising-emissions-20090815-elpf.html

    “In the minds of a lot of people…” and… “as long as the system is warming up.” Who are these people and what happens when the system cools?

  36. Luke says

    Gee El Gordo – let’s ask them to work for nothing. Gravy train indeed – what would you know you old coot? Pfft !

    So this is your intellectual response to a significant mechanistic finding? All lost on KookyKat of course. Another gimp.

    Pity it’s not cooling eh? Weren’t we supposed to be in a bone crushing ice age about now. Blog drongoism. http://www.woodfortrees.org/plot/rss/from:1979/to

  37. Luke says

    And if you thought about it for at least 10 seconds El Gordo – the 1950s and 1970s did create unrealistic expectations for some. Are you that daft?

  38. el gordo says

    We know that flood follows drought on a regular cycle of 20 to 30 years. This is common knowledge for people who have lived on the land for generations, the ‘unrealistic expectations’ must have come from the mouths of politicians.

    What have you got to say about the intensification of the sub-tropical ridge? I expect a significant mechanistic explanation.