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Tumut River Degradation
6 Nov 2009
Description

Regulation of the rivers :- Nowadays the Tumut River is highly regulated. it tries to cope with twice its historic volume of flow, acting as a conduit for half the output of the Snowy Scheme. Blowering Dam, the irrigator’s dam was finished in 1968 and signalled the completion of the entire scheme. Nowadays it flows at up to 10,000 megs or10 gigalitres/day (Sydney consumes about 10 gigs in a week) for up to eight months of the year and over winter months is screwed down to virtually a trickle. It virtually never floods any more. The water coming out of the bottom of Blowering dam is too cold to support the breeding of native fish and severely depleted in Oxygen. Consequently since the 1970’s there have been no native fish in the river. It now only supports the ubiquitous European Carp and sporadically newly released trout. The river has literally been devastated. Its grassy treelined terraces have been replaced by stark rapidly eroding banks. Erosion has converted the 28 metre wide, high velocity mountain stream into a virtual irrigation canal up to 125 metres wide. During the 1950’s State Water Authorities “desnagged” the river, winching massive old dead trees out of the river bed and tearing live trees off its banks. The destabilised banks were devastated by the newly implemented high flows, plus Snowy Hydro electricity generation Consequently native vegetation and associated fauna and flora largely vanished from many sections of the river. By the early 1980’s local landholders were forcingGovernment to attempt bank stabilisation. The only successful method proved to be rockfacing the river’s banks at a cumulative cost of $27million to date but It is mere window dressing. Nothing can reverse the effects of waterlogging all across the riverflats as high flows choke the river’s aquifers every summer. Deep rooted species like lucerne no longer survive and with the exception of some horticulture on the higher flats above Tumut town agricultural and grazing enterprises have been severely curtailed since the inception of the Snowy Scheme. Giant gravelbeds have formed throughout the length of the river,accellerating the erosion. The dairies are gone, crops struggle, and cattle no longer fatten readily on degraded pastures in the summertime. The idyllic picture of the valley in the 1950’s, described above, has vanished forever.

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