Hi all,
In response to Peter's concerns about wetlands, it may be of interest to
note that, under the Living Murray Initiative, different types of wetlands
have been identified and are to be managed differently.
The following contains an extract from a page on my web site
(http://users.mcmedia.com.au/~stocky/gunbower-perricoota.html) about the
Gunbower-Koondrook-Perricoota forest, one of the Living Murray Initiative's
icon (significant environmental area) sites and a Ramsar site. The notes
were based what I was told during a community information session about the
forest.
Gunbower Creek is an anabranch of the Murray River.
Gunbower-Koondrook-Perricoota forest is downstream of Echuca-Moama,
straddling the Victorian NSW border, and is Australia's second-largest red
gum wetland.
Extract begins:
"In attempt to restore a natural flooding and drying regime to the
(Gunbower-Koondrook-Perricooota) Forest, a number of environmental works
and measures have been completed or are planned. A number of regulators
have been constructed along Gunbower Creek, the Murray River and other
streams in order to keep water out of the wetlands for much of the year.
"Under The Living Murray Initiative...environmental water is to be released
from time to time to help conserve the wetlands and promote breeding by
water birds.
(The aim is) "that 'permanent' (sic) wetlands will contain water for
between nine and twelve months each year. Such wetlands occupy a relatively
small area of the (G-K-P) forest, e.g. Reedy Lagoon, Green Swamp. Reedy
Lagoon is regarded as one of the healthiest and best wetlands along the
Murray; it contains relatively few weeds.
"'Semi-permanent' wetlands should contain water for between five and ten
months at least six years in every 10.
"It is hoped that areas of Red Gum with a flood-dependant under-storey can
receive water for around four months at least seven years in every 10.
"Temporary wetlands should occasionally receive water for between one and
nine months."
(End of extract)
As I commented in an earlier posting, most, if not all, riverside wetlands
benefit from a period of drying.
Once mankind interferes with natural regimes, there are consequences and,
possibly, problems.
If the duration and typical depth of natural flooding events is varied as a
result of river regulation, climate change, etc, then vegetation changes
may occur, e.g. Moira Grass plains may be overtaken by River Red Gums
(small Red Gum saplings are drowned by floodwaters; dry periods may enable
the saplings to grow above flood levels and survive), rushes may take over
some areas.
Regulators and obstructions may inhibit the movement of native fish,
reducing their numbers and therefore impacting on water bird numbers.
According to recent newspaper reports, once a riverside wetland starts to
dry, native fish can quickly sense this and swim back into the river. On
the other hand, European Carp retreat to the deeper water and perish as the
wetland dries.
Near-surface fish traps are being installed at some weirs and regulators: a
trial at Torrumbarry Weir suggests that native fish swim under the trap and
that the overwhelming majority of fish caught in the trap are Carp. The
trapped Carp are extracted to produce garden fertiliser.
Some lakes and wetlands become increasingly saline as water levels fall,
rendering them less useful to most waders and waterbirds. Lake Tutchewop,
one of the Kerang lakes, is an example: at times it supports a profusion of
birds but when very low and salty next to zilch. When this lake floods, the
salinity level falls.
It is important that some wetlands along the rivers of the Murray-Darling
Basin contain water so that there are drought refuges for birds, fish and
other animals.
It may be of interest to note that well over 90 percent of the
environmental water released into Barmah-Millewa Forest over the summer of
2006-06 eventually found its way back into the Murray (according to a DSE
report). This water was used again downstream (e.g. to flood other icon
sites and by irrigators). So, releasing environmental water into wetlands
does not mean that all that water is 'used up'). This fact significantly
strengthens the case for allocating some environmental water, even during
such dry times.
Fortunately, there have been very good rains here over recent days (which I
am pleased about despite leading a two-day walk mainly on native pine
sandhill country in the Gulpa Island section that Barmah-Millewa Forest
over the weekend ~ lots of birds, including lots of Emus and Diamond
Firetails).
Peter, a terrific report ~ thank you for informing us of your concerns.
Let's hope that politicians and water regulators make wise decisions and
act to avoid any long-run adverse consequences.
Keith Stockwell
Moama.
>
>
>> 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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>>
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