Tuesday, December 28, 2010

What we need is more "lakes" in the not so wild west

There is quite an eerie duality between the lakes of the "wild" west-flowing rivers (in general they flow to wards Lake Eyre) and the "tamed" west flowing rivers. A series of lakes in the "wild rivers" (eg Lake Yamma Yamma, Diamantina lakes, Coongie lakes, etc.) Considerably slows the flow to the treeless salty pit in the end point (Lake Eyre). On the way, these storages are the lifeblood of both wilderness in these catchments(waterholes, trees, wildlife), and for human resources in those same catchments (mainly sheep/cattle grazing).

If you compare this with the Murray/Darling basin, all the human endeavour that has toiled to tame it has merely expanded on this natural system of floods being trapped. Both for the environment and human uses, it is an amazing extension, as the facts remain that floods and drought are as damaging to the natural environment's inhabitants as they are to human habitation. The remaining floods and droughts in the system are still primarily in the gaps where there is no suitable "lake" to absorb floods and make the water available through some of the following drought. I am estimating that by the end of this La Nina year, as much as all the water capacity of all of the Murray Darling water storages will have flowed out through the barrages of Lake Alexandrina. It is an open question as to whether the floods have nicely "reversed" the whole of the environmental damage done through the 10 or so years of it being a closed system (in drought, as it were). Although climate scientists have deemed the last 10 or 20 years as the new normal - I would suggest that it is a very brave call to BET that there will be similar droughts within our lifetime, as opposed to the usual contrived predictions.

If we could have harnessed even half of that water flowing away to the sea, the floods would have been even more controlled. At least we should have generated some osmotic energy from it at Lake Alexandrina, instead of just talking desalination. In the next few years of relatively plentiful water (even if we have a drought immediately after this La Nina) It makes no economic sense to buy (at a high price) water allocations from farmers who would use it to make a profit, for the environment which doesn't need it at that moment because of the soil storage from this recent series of flood events. Just feel grateful that we have got so much flexibility due to large natural and artificial storages, and perhaps plan some more future bountiful lakes that can be huge long term environmental assets for a relatively small environmental and human adjustment upfront price in drowned valleys.

2 comments:

Chris Fellows said...

I'd be interested to see your estimate of water flows out of the Murray-Darling cf. storage capacity.
Just to be trolly, how do they both compare to the amount of water that flowed into the ocean from Bligh's Cape York 'wild rivers' this year?

Marco said...

Total capacity, from MDBA water management site:

http://www.mdba.gov.au/water/waterinstorage

is 22,581 GL

A graph of the outflow through lock one, which is the closest proxy I can find to what the flow is to the sea at the moment.

http://riverdata.mdba.gov.au/sitereports/a4260903/mdba_a4260903_site_report.html

From that, I would estimate that until the end of December 2010 that no more than 4000 GL has outflowed so far. The latest estimates are that the current outflow of 50 GL a day will continue (due to Lachlan and Murrimbidgee floods in part) and build up to 90 GL a day from the current Darling river flood in about March. Assuming drought conditions through to June next year, I would roughly add that up to be about 10,000 GL. Assuming some more La Nina floods at least in the Darling system - this may double by the end of it by my estimation.

I have no idea about quantitative measures of the cape york wild rivers, but the Cooper Creek wild rivers are well measured at cullyamurra at any rate.

http://e-nrims.dwlbc.sa.gov.au/Telemetry/Plot.aspx?App=FNSW&Period=Hrly&Site=A0030501&SiteName=Cooper Ck at Cullyamurra WH&Params=33,12