Regards

Really? the 1956 event had an inflow of approx 25000 GL and the system has 10000 GL or so of storage. The lower lakes will need a couple of thousand too. What we are well over due for is that massive reset.I’m not sure that massive floods are desireable though.

I’m not up to speed on savings targets, is there a site you could direct me to? I don’t think SA should be treated unfairly, nor be forced to carry a disproportionate burden. SA has every right to complain about that.
I wasn’t dismissing Adelaides entitlement to water from the Murray, nor it’s reliance on a river that provides no guarantee of supply- either under current or natural conditions. That it can still draw “fresh” water from a system in extreme drought is testament to those agreements.

We could drain every drop of water from every storage in the basin right now and it would barely fill the lakes back to sea level, let alone benefit the wetland. Extraordinary drought has extraordinary consequences. By all means believe it is over extraction, the fault of the dams, whatever, but also realise the position SA would be in with no man-made infrastructure. Sort of wanting your cake and eating it too. At least acid soils wouldn’t be an issue.

cheers

What gave Adlaide a right to tap into the Murray in the first place? I don’t know. Perhaps the Murray Darling Basin Agreement that was signed by all of the states? A dubious legal agreement I know, but we were sort of counting on it.

You would think that in a period of such extreme drought that all states would be doing their best to meet their obligations and save as much water as possible. Not so. NSW and Victoria have not met their targets for water saving. SA has.

Sucked in us hey.

We are getting a desal plant. Unfortunately it will not be able to produce enough water to save the only Ramsar wetland in the first world that it about to go belly up. And Adelaide will still be reliant on the River Murray.

But thanks for the great suggestion rojo.

I’m really sorry that irrigators relying on the lake system are in such desperate trouble, there just isn’t the water in the system to help them. And that would be no different had there been no irrigation development anywhere in the system but at the lakes. Under natural conditions (without the barrages) the lakes would now have some 10 times the EC as the evaporation losses would have been replaced with sea water.
I can tell you that things are no better in my district (NW NSW) due to allocations that averaged 10% over the last 6 years. Our town population has fallen by 20-30%, with the inevitable loss of business houses, school teachers, nurses and the like. We’ve been through it all before, and know things bounce back eventually, I do understand it’s a bit harder for SA irrigators who have rarely had an allocation of less than 100% until these past couple of years.

I fully agree with your thoughts on reasonable use for environment and industry, I just find the thought that we would specifically store water to allow for several years of evaporation on the lakes an inefficient use of water.

Thanks Anne, sorry for the late reply.

Salt water from the sea has in the past found it’s way up stream, and the rivers still here. My rough estimation is about 70 million tonnes of salt would have been in the lakes (if they hold about 2000GL) yet that has been flushed out in the past.

Interesting that you indicate lack of end flows for 6-7 years(your implication being avoidable) because that is exactly what has occured for the Murray in general, 2002 setting a new low-inflow record at the time, and the mouth on the verge of closing in 2003. Since 2001 the inflows into the Murray have been 40% of “normal”. The inflows for the whole river Murray during this period have been 4800GL/year, the same as the expected longterm flow to SA.

You say water levels that the Ruppia tuberosa depend on are infuenced by barrage outflow, is it possible without the barrages the estuary level would be higher ie if there is no barrage outflow then the mouth is therefore not clear, and tidal prisms are limited. Is it lack of water over the barrages that makes the difference, or the fact that there are barrages full stop.

I absolutely agree the mouth needs to remain open, I just think to store fresh water to do specifically that is not an efficient use, remembering that in longterm averages there is enough water for barrage outflows. This has been an unprecedented dry period, with the rainfall in the catchments setting new record lows for the period since 2001.

It appears we are over-allocated in dry times, no doubt, but if we prepare for a “1 in a thousand year drought”, is that a reasonable use of the resource in the other 999.

litfuse, there is quite a bit of frustration everywhere due to a lack of water, why the Lower Murray should feel it should somehow be immune is perplexing . Little water at the top means little water at the bottom.

there is a lot of frustration amongst scientists and residents of the Lower Murray region. The government has essentially been borrowing water from the future for irrigation now. If they ran their budgets like this, they would be thrown out in a revolt.

The vast majority (>99%)of the water that is released over the Barrages goes out to sea. However when this happens water levels in the South Lagoon are typically 0.5m higher and this is critical in spring and early summer to allow Ruppia tuberosa to complete its reproductive cycle. In years of no flows (this century) water levels drop in the South Lagoon in Sept-Oct leaving Ruppia without a sufficient covering of water and so it dies before reproducing. Ruppia typically flowers and sets seeds in Oct-Dec. A proportion of the seeds germinate each autumn/winter when water levels rise again, but the plant’s have now had seven years with negligible reproduction and have now exhausted their propagule banks.

During winter and into spring water levels at the southern end of the Coorong are about 1m above those at the Mouth so water moves northwards – open the Barrages and the water levels in the northern Coorong near the Mouth become elevated and this slows the rate at which water leaves the South Lagoon. So flows over the Barrages are important for maintaining an appropriate water level in the South Lagoon at critical times.

The EIS for the USE drainage scheme done in the early 1990s showed that even with a 40GL per annum (rolling average) input of water at Salt Creek the water levels would rise no more than 5cm, insufficient to compensate for no flows over the Barrages as far as suitable water levels for Ruppia tuberosa. Inflows of this magnitude had the potential to drop salinities in the South Lagoon and after 10 years the salinities were estuarine in this lagoon (The original EIS only showed the model outputs for 7 years)- but this is not the salinity regime in which Ruppia tuberosa prospers. Ruppia tuberosa in the Coorong does better in hypermarine conditions.

Keeping the Mouth open is critically important for a range of fish and for providing a tidal prism within the estuary that increases the amount of habitat available to migratory waders. Sandpipers typically forage in shallow water <5cm (for some species <2cm). Tidal movements open up access to a much larger amount of mudflat where the birds can feed (the birds shifting as the water levels recede and rise). Without this the birds would be limited to a rather narrow strip of suitable mudflat and have to feed on this narrow strip all the time. So maintaining the Mouth open is important and this is currently done by dredging because there are now flows at present.

The reason that the Coorong has collapsed is not because of the recent drought but due to the water allocation methods adopted that have failed to deliver and maintain both river maintenance flows and environmental flows. In fact the Coorong and Murray Mouth regions have not been provided with a flow for ca 6-7 years now – this has effectively given a seven year drought. Let’s not blame the Murray or the drought for the environmental damage that is happening to the Lakes or Coorong – the blame rests squarely with us because we have over-allocated water for human uses and still fail to appreciate that even in a drought the environment needs some water. Ironically if we had addressed the over allocation 4-5 years ago the Coorong at least would have coped with the current 1-2 year drought. The over allocation of water for human purposes needs to be fixed immediately not in 2,3 or 10 years time if the coorong and lakes are to not change irreversibly.

http://www.dwlbc.sa.gov.au/assets/files/USE_CoorongWQChangeDraftNov05.pdf

suggests that the freshwater aspect of the Murray has had little effect on the Coorong other than, as has been said, keeping the mouth open. Is storing freshwater expressly to keep the mouth open(after allowing for the lakes evaporation) in case of protracted drought an efficient use of the resource?
Perhaps the biggest influence now is a lack of tidal movement keeping the mouth clear, movement hindered by the Barrages when there is no Murray flow. Another real issue is the diversion of freshwater streams in the eastern Coorong staight to the sea, I understand the SA govt was looking at returning those flows.

cheers