Going with the Flows

By The General on July 27, 2017
  • Going with the Flows

    After the flow: another tree down - and grasses killed off

The Boss called in to a forum on environmental flows the other day  and came home looking non-committal. He looks that way whenever I retrieve something quickly for him, but drop it a few steps away rather than give it to him.

It's a kind of half-happy look, you might say. He reckons things are on the improve but he's not entirely convinced.

The show was put on by the Catchment Management Authority, which is providing all the local help for a long-term monitoring project being paid for by the Commonwealth Environmental Water Holder. 

This is the outfit responsible for handling all the water that the government owns, much of it bought back from irrigators over the last decade.

The Boss reckons the Water Holder finally seems to be learning something, after he messed things up in the first few years - keeping the river too high for too long and causing bank collapses and tree falls.

The theory behind environmental flows is that they try and replicate - as much as possible - the natural flows that would have happened before the river was regulated with dams, weirs and irrigation off-takes.

That sounds like a fine idea - but it gets complicated by two factors in particular. The first is that nature would occasionally flood the river, over the banks and clean up the leaf litter and give the floodplain a proper drink now and then.

The Water Holder isn't game to do that because people complain and threaten to sue. So we get a leaf litter build-up, which increases the risk of blackwater events when a real natural flood happens.

The second complication is what The Boss calls "our channel obligations" - the huge amount of water that has to be delivered to irrigators downstream and to South Australia under the Murray Darling Plan. 

What this means is that a lot more water gets forced down the river - in between the banks and at odd times of year - than would happen naturally. The Boss reckons this is a problem now and is likely to get worse.

So he was pleased to see the scientists at the forum being up-front about their findings, some of which are positive. There is strong evidence that the e-flows are stimulating the yellow belly to move and breed and they're seeing a lot more young silver perch in the river.

Against that, the numbers of cod and trout-cod were knocked around by the recent blackwater events - particularly the trout cod.

The shrimp and other bugs seem to be doing well enough, which is good for the fish too. The Boss was interested in the research on stream side vegetation, which confirmed his view that the sedges and grasses that like life by the water's edge get killed off by e-flows lasting more than a week or ten days. 

And the bloke looking at bank erosion told us what we all know - that stuff getting washed away one year gets deposited somewhere else - and then comes back again. 

But he was cagey about the ideal length of environmental flows, which The Boss thinks are too long.

So that's why he was half-happy. The Water Holder is using some smart people to help manage these flows better - but in the end he has to get the increasing amount of water down the river.... which will grow much more if the whining South Australians get their way on the so-called "Up-water.".

And if all that water forced down the river channel damages the river, it can hardly be called an environmental flow now, can it? I can see the Boss is going to keep a close eye on it. Woof.
By The General on July 27, 2017

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