Let’s be honest: a dry river is not necessarily an environmental catastrophe.
Two weeks ago Australians were warned that a leaked government report claims there is only six months to save the Murray-Darling Basin.
In response, the Federal Opposition leader, Brendan Nelson, called on the Prime Minister, Kelvin Rudd, to make a joint tour of the River Murray’s lower lakes region.
Mr Nelson said he thought it was “very important that the leaders of this nation have a first-hand look at the environmental, economic and human catastrophe which is unfolding in the Lower Murray lakes.”
The leaked report focused on the lower lakes, and as I have previously written (Acid Sulfate Blame Floating Upstream, The Land, May 15, pg 30), a solution to many of the environmental problems at the Murray’s mouth is to simply open the barrages and let the area flood with saltwater.
The barrages were built from the 1920s to keep the Southern Ocean out and to raise the lake level, including for boating.
These same barrages also facilitated the development of irrigated farming in this area, but they are unnatural.
If the barrages were now opened, irrigators dependent on freshwater from the lower lakes would need to be compensated.
But the alternative, continuing to send large quantities of water from the drought-drained reserves in the Hume and Dartmouth dams during this protracted big dry, is less viable.
Some argue that if a permanent weir was constructed just upstream of the lakes at Wellington and the barrages used under “an adaptive management regime”, there could be water savings in the order of 750,000 megalitres a year.
Opening the barrages would take some pressure off the system, because less water would need to be allocated to South Australia, but the river could still run dry.
Indeed, it doesn’t matter how many leaked government reports call for more water for environmental flows, if there’s ongoing drought and the upstream dams runs dry, there will be simply no water for the river.
It would be an economic and human catastrophe for the many towns now dependent on the river for their water supply, but it would not necessarily be a catastrophe for the environment.
The River Murray in its natural state could be reduced to a chain of saline ponds.
Indeed, the idea that a river should be always brimming with freshwater is a very European concept – in reality, alien to a land of drought and flooding rains.
So, let’s be honest, many South Australians want to keep the barrages shut to the Southern Ocean and many Victorians and New South Welshmen want to keep the river full of water – not to save the environment, but to avoid what Mr Nelson has described as a potential economic and social catastrophe.
————-
This is an edited version of my column published in The Land on Thursday June 26 entitled ‘Barrages Block Sense’.
You can read many of my The Land columns here: http://www.jennifermarohasy.com/articles.php
Jennifer Marohasy BSc PhD is a critical thinker with expertise in the scientific method.
Jen – a weir at Wellington is an improvement in your argument.
What’s an “an adaptive management regime” mean?
And what land use around the existing lakes would be affected if they were salt?
Luke, a weir at wellington was part of SA’s emergency plan over 18 months ago.
http://www.abc.net.au/water/stories/s1826133.htm
Of course it obviously wasn’t a core promise: http://www.abc.net.au/news/stories/2008/03/05/2180588.htm
So govt can now buy non-existant water to “fix” the lower lakes.
No doubt irrigators/communities depending on the lakes need looking after, but they are in a positon now where the the salt EC is approaching 5000 in the lakes – assuming it’s deep enough to access. Basically we could say they have no useable water now at present, with record low inflows for june into the murray system.
If it really is crunch time for the lakes, open the barrages and let nature take the reigns. It always did in the oast.
We often hear reports of how inefficient unlined irrigation ditches are, especially when used for flood irrigation. But the entire 86,000 ha of the Lake Alexandrina system is being used as one big wide and hideously bloated irrigation ditch. And all to supply how many farms in the area? At the expense of how many farms upstream?
Given how long this dry period has gone on for, that the Murray is still full along many sections is unnatural.
Without all the weirs and other engineering works, in a dry period like this huge sections of the Murray would be just small pools and Lake Alexandria would be part of a inlet from Southern Ocean.
The issue is, would a system of barrages pass an EIS today? Clearly not. So why would anyone regard it as a set of attributes that should be protected?
But we need to distinguish between the specific application which is bad and the principle of capturing fresh water at river mouths, which can be good. In fact, a river mouth is the one point in a catchment where the water has already served most of its environmental function as it has already flowed the length of the river itself. Up stream extractions obviously reduce the delivery of environmental services by that water to the downstream portion.
The interception of fresh water just before it mixes with sea water would seem to be the logical place for a desalination plant. There is less salt to remove and the resulting fresh(er) water will be cheaper than from plants taking all sea water.
The interception of fresh water at river mouths would seem to be beneficial in situations where the long term water storage does not substantially interfere with the functioning of the estuary system. This is not the case with Lake A.
River mouth interception would also need to be able to function at both extremes of the flow cycle. That is, taking a large extraction from flood surges while being able to adjust extractions to lower flows without the pressure of fixed water commitments.
That storage must also be evaporatively efficient. That is, the storage must be deep enough to ensure that only a small portion of total storage is lost to evaporation. This means an average depth in excess of 10 metres, unlike the 3 metres of Lake Alexandrina or the <2 metres of the Menindee Lakes.
This means off-stream storage with pumping, provided there is an adequately shaped landscape feature that could be used, ie, a deep valley or adjacent deep ocean inlet with minimal catchment.
Or it means in-stream storage in a portion of the estuary that can be economically isolated from the functioning of the main estuary, and is either appropriately shaped already, or can be made that way at a cost consistent with the value of water.
And this raises the question, are there parts of the Lake Alexandrina complex that could be divided off, (esp close to the existing farmland)and made deeper so they can capture sufficient volume to serve their needs whilst allowing the natural functioning of the main part of the estuary?
Given that the raw cost of evaporated fresh water is $460 million a year then the break even capital cost of such works would be well over $4 billion.
At the moment there is a huge volume of fresh water in the middle of the Lake that is wasted to provide a small volume of fresh water to the edge of the Lake. And as the depth is only 3 metres or less, the cost of dividing the two functions so the volume in the middle can be served by fresh water would not be prohibitive.
It is certainly an option worth investigating.
Jennifer,
it’s always amused me when people talk about the pristine Murray river before the white man ruined everything.
When Sturt reached the end of his long journey down the Murray in 1829 (?) he found it completely blocked and couldn’t get his boat through to the sea.
Probably due to many dry years previously and probably similar to our present situation.
Two years before when he and Hume discovered the Darling their party was desperately short of water both for themselves and their stock.
They and their stock tried in desperation to drink the water but it was far too salty and the cattle just stood in the water but wouldn’t drink.
The native born bushman Hume went off and within a day or so found a fresh supply ( billabong )of water and saved the party.
My ancestors have lived on the Murray for 130 years and in that time the river has dried to a series of pools a number of times.
The huge storages have saved the day up until now but we cannot allow water to be wasted from them to supply water to the unnatural bottom end of the river.
Compensate these farmers by all means but I think the barrages should be removed.
BTW the Darling was called the salt river for many years by the early settlers.
Interesting post, Neville. And you touch on another interesting issue. How much water is evaporated from the Hume and other storages while it waits to deliver out of season flows to Lake Alexandrina where even more will evaporate?
Forgive me, I feel like reaching for my gun already.
Note from the map at http://www.bom.gov.au/cgi-bin/climate/cgi_bin_scripts/evaporation.cgi
that both Hume and Dartmouth are near the 1600mm evaporation level.
Hume has an area, when full, of 20,019ha which, when multiplied by the 16ml of evaporation means an annual loss of 320,300 megalitres or 10.55% of its 3,036,000ml capacity. Its average depth is 15 metres.
Dartmouth fares a lot better with an area, when full, of 6,380ha which, when multiplied by 16ml of evaporation means an annual loss of 102,080 megalitres. This is only 2.6% of its 3,907,600ml capacity. Its average depth is 61 metres.
But note, these evaporation losses are only when these dams are full. If we assume a constant slope to the sides of these dams then annual evaporation will be in proportion to their percentage of full capacity. They are both in the order of 10 to 15% of capacity at present so their current combined annual evaporation loss is likely to be only in the order of 60,000ml.
Lake Alexandrina, in contrast, has a depth of only 3 metres and evaporates 1.6 metres or 53.3% of capacity EVERY YEAR. The system needs at least 1,090,000ml EVERY Year to replace evaporation. And this volume represents 59% of South Australia’s minimum annual entitlement of 1,850,000ml.
The MDBC plays a little accounting game of pretending that all of SA’s water comes from the more efficient Dartmouth Dam but when total evaporation is averaged between the two main storages it comes to about 6% of capacity.
And this means that in any year where the SA allocation has been stored from a previous year, another 111,000ml of evaporation should be added to the SA total. In these years total SA evaporation rises to 1,200,000ml or 61.2% of the real total of 1,961,000ml.
That is one hell of an indulgence, don’t you think?
Just to see if anyone is reading, there is a flaw in my analysis above. Can you see it?
Yet, the bull$hit goes on and on.
COAG fails ‘to deliver for lower Murray’09:59 AEST Fri Jul 4
The federal and state governments have formalised long-promised, long-term plans to save the Murray River but have done nothing to take immediate action, a key council along the river says.
The Alexandrina Council, near the Murray mouth in South Australia, says long-term action endorsed by Thursday’s Council of Australian Governments (COAG) meeting means nothing if urgent steps are not taken now to save the lower lakes.
“This was a chance for premiers and the prime minister to immediately purchase and release 250 gigalitres to save the lower Murray,” said Alexandrina Mayor Kym McHugh.
“Instead, they stuck to dry arguments and consigned the parched mouth and lower lakes region to environmental, economic and social disaster.
“The water is available in the Menindee Lakes and in huge private storages upstream. All the politicians need to do is find the will and spend the money to save the Murray.”
Alexandrina Council said 250 gigalitres could be sourced immediately from the NSW storage of the Menindee Lakes.
Other potential sources include private storages in the Darling catchment.
Mr McHugh said the council wanted to know why the state and federal governments were not looking at these options.
“The lower lakes, lower Murray and Murray mouth are in their death throes and this option is just being ignored,” he said.
“We welcome (SA) Premier Mike Rann’s promise of improved irrigation infrastructure for the lakes regions, but this should not mean we sacrifice the lakes environment.
“And these projects will do nothing for the current emergency.
“It is quite simple – South Australia needs the water now.”
Meanwhile, Queensland farmers have backed the agreement to support more efficient water use in the Murray-Darling catchment.
Queensland Farmers Federation CEO John Cherry has said the state’s farmers draw only five per cent of the water taken from the Murray-Darling system, but were willing to play their part in the 10-year water reform process.
However, irrigation farming and the towns servicing the industry need to have their existing water entitlements protected, Mr Cherry said.
“We want to make sure that the governments’ investment is cost effective, and that any buyback of water entitlements meets clearly identified priorities to protect defined environmental assets,” he said.
“They must also be careful to ensure that irrigation farming and their towns and communities remain viable after the buy-back program is completed.”
Mr Cherry said the COAG agreement confirmed the commonwealth would accept responsibility for the risks of a reduction in, or less reliable, water allocations on the expiry of Queensland’s existing Water Resource Plans in 2014.
“This is an important protection of irrigators’ rights in the implementation of the reform process,” he said.
These bogans obviously still believe there is still a mountain of water at Cubby Station (it is in financial difficulty due to minimal crops for past few years).
I’m reading Ian, but the only thing I wonder is it gross evaporation or net after rainfall is taken into account.
Flaw that the lakes are in a region of higher evaporation?
The former, Rojo, and thanks. There is 16ml/ha of evaporation from all of the storages (except Menindee Lakes 22ml and Lake Victoria 20ml) but I did not adjust for the 4ml of annual rainfall at Lake A. That is, in a normal year, which this year and last year are/were not.
Generally, in the dry years the RF is only in the order of 2ml so we need to revise the numbers down by about 12% in dry years and 25% in normal ones.
In any event it is still a hideous amount of water going to waste in a far from best practice storage facility for a far from best practice purpose.
Very interesting arguments there for a city dweller. I have some film from c1939 showing people boating and fishing (and beering) on the water from Goolwa. I was looking up just when the barrage (seen building) was put in. Thanks everybody for lucid and polite discussion.