Predictions of when the Murray will next flood and why

Hi Scoof
Any reason or is it a guess?
GN

I went to seminar about a year ago and it was discussed.
It is just a cycle of dry and wet and over the last 150years give or take 20 or 30yrs because I can't remember exactly but the guru said that the dry spells have been getting longer each time. He said by 2010 - 2011 we should see some improvement in river flow, let hope he is right.

hmmmm
interesting
I looked at the longest gap between floods i could see (although the info was a bit hard to find) and seems the longest between floods has been in last 100 years was 1917 to 1931 = 14 years.
Last flod was 1996 so + 14 = 2010 ??????


GN

G N (VIC) - was the 1996 flooding of the Murray the result of heavy rain or was it when they decided to release huge volumes of water from Hume Lake as the wall had moved. I think it ran a banker for some six months whilst they let water out as they thought it was going to break.



A J

Hi AJ

I am not sure to be honest?
You may be correct, if so previous flood was 1993, so we were due in 2007, UH OH.

Not sure if this make it sound better or worse?

regards
GN

There's bugger all there to let out now.Image Could Not Be Found

Another southerner going off half cocked again. Queensland represents 25% the area of the Murray Darling catchment and only extracts 4% of the irrigation water in the system.
You don't hear anyone bagging the southern irrigators or talking about the huge evaporation losses in menindee lakes.
It is a common misconception that there is massive amounts of irrigation captured in queensland, but we too are in drought.
Maybe people should have a look in their own back yard before going off.

MAF, I take your point , however, (slightly off topc) nothing Victorians do can help put water into the Darling river.

Peter

Queensland may only draw 4% of river irrigation but properties like Cubbie Station harvest runoff water before it even reaches the river in their large dams. This gives them more water that is unregulated so they do not have to draw on the river that is regulated. In an average year Cubbie Station uses 200,000 mega liters of water most of which would not be regulated. They are not the only property that harvest water before it reaches the river but they are the largest.

The whole river is over allocated not just up river but down as well.
I think allocations should be kept below 25% until the river floods again the whole way down....whenever that will be.

maf, Menindee Lake has been dry for about six years, so there hasn't been much evaporation from there.

Dave

The Darling has only ever contributed 10% of the Murrays flow, most comes from the snow fed mountains. Biggest problem ground is so dry when it does rain their is little run off. Their was recent minor flooding of the Kiewa river in Vic, but it is most likly trapped by a dam somewhere.
Cheers Pete

I don't know about when the next flood is going to happen, but there is a great documentary released by the ABC called "Two Men in a Tinnie" that shows the water flows along the Murray Darling.

At the risk of upsetting maf further, I would have to disagree with his comments about QLD on taking a little.

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Madfisher, my point exactly. The impact that Qld has on the lower Murray river is quite small- but Queensland gets all the bad press.
Dave, I appreciate that the lakes have been at a low level in recent years, but when they receive a inflow, the amount of evaporation losses makes the QLD Murray Darling irrigation industry look small.
I wasn't going to mention cubbie, but seen as Malleerv brought it up, Cubbie holds 564 000 megs and I'm not sure it has ever been filled to capacity. I know the figures you quote are far from the average annual useage figures, especially for the last 5 or 6 years. I think that all irrigators would be thrilled to get the 25% allocation you mentioned.
Cubbie water is measured as it is mostly diverted out of the Culgoa river and not 'stolen' from the vast inland sea of freshwater that southerners think exists in sw QLD.

LOL In the not too distant past, on a river elsewhere on this planet, a war would have been fought over exactly this issue.

Hi Maf

think you may be wrong about how cubie gets most of its water, its not via diversions thats how they got around the law!
GN

Gramps, I think you could also say...

LOL In the not too distant future, on a river elsewhere on this planet, a war will be fought over exactly this issue.

Perhaps the word 'elsewhere' could even be removed.

Hi GN, not sure how well you know the area but most of their diversions only occur when the rivers run. As for 'getting around the law', Cubbie doesn't do anything else any other irrigator (or landowner) is entitled to do along the river.
Cubbie only developed what the QLD Dept of Resources gave them licences to do so, 20 years ago. Whether that was the correct policy is debatable??
All the licence conditions are public information and the farm now advertised for sale, and cubbie comes under more scrutiny than anyone else, so I doubt there is anything illegal going on.
I think that if it was developed as 5 separate farms with 5 different owners, it wouldn't get a mention in the media. cheers mick.

Mick,

Will we see you in St George for the Gathering or will you be planting??
As I reckon a few people attending would enjoy learning more about this topic around the campfire.


Cheers Kev

Hi Kev, Unfortunately I will be busy planting the last week of september. Hope you guys have a good time at the gathering, cheers mick.

I thought you may be planting around then as I have had a few issues getting some of the Farmers interested in doing a farm tour due to them planning to be planting around the time of the gathering.

If the bloke who I have lined up falls through I have another lined up who knows the area very well but is no longer hands on with the everyday running of the properties to take the group through a farm.

Cheers Kev

Hi Maf

you are right they havnt broken the law, but the law has not managed to keep up with their well organised way to take such vast amounts of water.
also they stop most of their water BEFORE it gets to the river system so therefore do NOT have to comply with DIVERSION laws!

Regards
GN

I know we all have different opionons but it is alarming how many have the whole sitution summed up incorrectly.

this was meant to be a fun post to see who had any reasons to sugest when the river may next flood and now its become a negative winge.

when this river floods there is no dam, weir, or irrigation diverion that will stop it!

depending on the areas - there is far more groundwater now than ever due to clear felling for farming. This has resulted in rising water tables and land salinisation. and has increased salinization of SW rivers which have their source in the weatbelt

This is obviosly not the case everywhere and in the Perth Area the water is quite usable so has been drained to an extent it effects wetlands and cave systems


Yet further east diposal of groundwater from mining activities can be a big problem as there is so much of it. Most of it is competely unusable for all but comercial use . even then its use must be properly contained as it will kill all vegetation far quicker than ariel roundup spraying

Warning - This answer is coming from a Hydrologist :-)

There are two sides to the salinity story- dryland and irrigation. While dryland salinity (caused by removal of deep rooted native vegetation and subsequent rise of the water table) is responsible for some of the salinity problem in this country, a large amount is also caused by irrigation salinity- that is, rise of the water table caused by increased recharge from irrigation sources. Clearly, these two factors are more often than not coupled; land is cleared of native vegetation, shallow-rooted crops are planted and then irrigated by surface water which in time can lead to dramatic salinity problems. Additionally, the lack of natural flooding processes due to weirs and river regulation lead to the build up of salts in soil zones. As well as salinity, sodic soils are a huge problem in Australia (around 1/3 of soils are sodic). Sodicity in soils (chemically characterised by an excess of sodium ions with an imbalance of calcium and magnesium or other 2+ ions) leads to problems such as hardsetting, poor plant growth and impermeable layers forming as clay particles swell with the addition of fresh water, and is too exascerbated by the lack of flooding of the land surface. Groundwater use has traditionally been unregulated and thus the true figures regarding consumption are largely unknown. Regardless, excessive groundwater consumption can lead to severe problems including land subsidence, drying of springs and soaks, reduced river flow especially in summer periods when rivers were traditionally sustained by baseflow (yes, that equals less surface water too), loss of vegetation, loss of town water supply, the list goes on.

There has been huge extraction from the Great Artesian Basin (GAB) over the last century, resulting in a considerable loss of pressure from the system. Unfortunately what the mining companies don't tell you is that is takes 2 million (yes, 2 million!) years between when water enters the system via the Great Dividing Range to when it discharges at Lake Eyre. I do know that in the WA goldfields there has been some research done into using Aquifer Storage and Recovery techniques to replenish the groundwater that is extracted for mining operations, though the research is still in its infancy (as is ASR in general actually). Tailings and mining waste disposal is another issue altogether.

Phil G is right- much of the land use in this country is rather stupid (though the processes governing whether water runs to rivers or to groundwater recharge are more complicated). Flooded crops should never have been planted in NSW- just ridiculous! My own view is that the Murray isn't going to flood again unless there is some total freak of an enormous ongoing storm- just too many dams and weirs to fill upstream. As for Queensland, they have made good progress with their reduction of domestic water use via water restrictions, but as with the rest of this country, irrigation practice (and not just on individual farms, but the whole setup of what is planted where in general) leaves a bit to be desired. Leaving you with yet another can of worms!

Thank you for what is often a rareity on forums - an informed coment

couple of questions/comments


Where ive seen salinization at its worst which is weatbelt areas little to no irragation takes place (you dont water weat and brley) but I can see this being an issue in more fertile vege areas


also In the Eastern Goldfields a heck of a lot of water is pumped for the mines both for de watering and mill/other use.
i am no Hydrolagist but i can see no usefull natural purpose for this groundwater. If it gets near the surface it kills everything being hypersaline.
as a layman i see no detrimental effect in returning this groundwater to the water cycle as it supports no springs - is poison to creeks etc

as for aquifer replenishment I worked at a mine that tried it - dewatering and re injection and it was an abysmal failure with the re injection of such massive amounts of water being far too problamatical

G'Day,

Thanks for your response and questions. In non irrigated areas it is likely that the biggest cause of salinity that's going to stop cropping is the dryland type - the removal of deep-rooted native vegetation as you mentioned. However, Australia is an old, salty place in general and it has only been in somewhat recent times that people have really understood the processes that govern salinity. Some researchers believe that natural cyclic rise of groundwater is the largest contributor to salinity in Australian soils (other sources of salt include weathering of minerals eg feldspars and marine salt that evaporates and is blown inland and deposited several hundred km from the coast) and well, I probably wouldn't argue with them myself- Australia was always salty, just had natural flushing processes to clear the salt out of the top soil horizons. The biggest issue now is management and really, it is exceedingly complicated as you are aware.

I agree with you that it is preferable to use saline groundwater for mining operations as they do in the WA Goldfields. The water is extracted from considerable depth and it is unlikely that it would have ever reached the surface under natural conditions. Some trials have been conducted (particularly in the Murray in South Australia, where there is a salt interception scheme) with disposal of saline water into disposal basins for evaporation. I am not sure how they dispose of mine waste water other than in the tailings dam to be honest, but if excessive quantities of saline water are a problem as you describe then an evaporation pan might be an option.

Yep, ASR is definitely a tricky kettle of fish! Unfortunately there are problems with 1. loss of the injected water due to natural movement of water through the aquifer, 2. mixing of the injected fresh water and the more saline aquifer water via convection, and 3. biological processes causing clogging of the pore spaces in the aquifer material, preventing injection. There is considerable research being conducted at present into all of these processes for more efficient and reliable ASR schemes- hopefully it will become a more viable idea as it's really quite a sensible one. I can imagine that attempting to rectify a dewatering scheme would be a nightmare- not surprised it failed. Hopefully one day it will be a viable option.

Cheers

the most common ways of getting rid of minewater is into ld disused open pits and more difficult for approval is into saltlakes

besides using it in treatment plants and ultimtly tailings dams

But the lock were there in 56

While the 10 locks were there by 1956, further development was undertaken including the 4000GL storage of Dartmouth Dam during the 1970s. Additionally, there has since been increasing demand for water due to increased population size and greater irrigation demand. I personally don't think another flood is very likely at all.

I should also mention there is considered 1 in 100 year flood theory. Its worth a read.

http://en.wikipedia.org/wiki/100-year_flood

Unfortuantely most of the high rainfall amounts were along the Queensland coast and in North Queensland. The areas of the Murray Darling catchment had well below average rainfall amounts.