2nd try - I sent this a few days ago
> Hi all
> Generally speaking, many wetlands along the River Murray have been altered
> as a result of regulation of the river system. Some have become
permanently
> inundated, while others have been starved of water. Here in SA, and I'm
sure
> further up the river, for those wetlands, that have been permanently
> inundated, rehabilitation projects typically focus on installing a flow
> regulator and re-introducing some sort of wetting and drying regime,
> mimicking what would have happened historically. But there are many, many
> wetlands (over 1,000 along the SA river Murray alone, of which 27 have
been
> fitted with flow regulators) and therefore draining some of the wetlands
> that have not been fitted with such regulators may not necessarily be a
bad
> thing. One thing to keep in mind is that generally we're not talking about
> physically draining these wetlands, rather disconnecting them from the
> mainstream, thereby stopping the continuous flow of water into the wetland
> to make up for evaporation.
> However, care should be taken in that blocking off wetlands should only
> occur if there are no ecological values that have established as a result
of
> the man-made water regime (eg, threatened fish populations) that will be
> placed at risk by a possible drying out of these wetlands. It is
imperative
> to know what lives in these wetlands, and whether there are other
> non-biological processes that could jeopardize their long-term health if
the
> water regime was to be changed (for example, many wetlands have a
freshwater
> lens underneath them that keep saline groundwater inflows at bay; by
drying
> out for too long a period, salinisation may start to affect the wetland
and
> its vegetation. Another example is the risk of development of acid-sulfate
> soils (the rotten-egg smell)).
> Over the last five years, through my work for the SA Murray Darling NRM
> Board I have commissioned and project managed numerous biological surveys
of
> wetlands (covering 90 wetlands thus far) along our stretch of the river.
The
> data collected by these surveys is currently informing further proposals
for
> drying out wetlands to save water.
>
> A little known fact is, that seems to have stayed out of the recent
> publicity on this topic, that between August and December last year we
have
> closed off no less than 27 wetlands along the SA River Murray saving in
> total about 40 GL (40 billion litres). A further nine wetlands will be
> closed progressively over the next few months saving a further 20 GL. I
have
> written up an ecological risk assessment report based on the known data
for
> these 9 wetlands.
>
> Some of the effects we're starting to see in the wetlands that were closed
> last year are as described above. In two wetlands, salinisation is
starting
> to occur. Waterbirds seem to concentrate in those wetlands which still
have
> water in them or have moved away out of the catchment all together. Lots
of
> new mudflat habitat is starting to appear. We are keeping a close eye on
> each individual wetland but it will be near impossible to convince the
> decision makers to allocate water to wetlands that are coming under severe
> stress if there is no water to allocate to consumptive users...
>
>
> Cheers
>
> Peter Waanders
> Waikerie, South Australia
> mob.: 0407 800264
> sat.: 0424 212889
>
> SA Birding: http://www.sabirding.com
> E-mail1:
> E-mail2:
>
>
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