The ten yearly push by inland vested
interests to divert Clarence River water inland across, or through, the Great
Dividing Range, is on again.
In 2007, a Federal Government proposal to
dam either the Mann or Upper Clarence to divert 100,000 megalitres (ML) a year
to SE Queensland, led to the Bourke and Cobar Councils requesting another
100,000 ML be pumped their way. Not to be left out, SA’s Alexandrina Council proposed
1.3 million ML be diverted to keep the Murray River flowing into their State.
Now it's Griffith that wants the water.
Historically, around 1.3 million ML has
been a common figure. Supposedly 20% of the Clarence River's average flow, this
is based on the myth of a 5 million ML average. However, the Lilydale gauge,
just above the tidal pool, shows average flows over 53 years are 3 million ML,
not 5. So 1.3 million is actually closer
to 40% of the flow.
The Upper Clarence's Tabulam gauge,
showing average annual flows of only 670,000 ML, puts that site out of the
question. The Mann attracts most attention because it carries the most water.
On average the Mann River carries 1.5 million ML annually, but taking 1.3
million ML from there, equates to an unacceptable 80% of its flow.
Dam-filling floods can come decades apart,
so a minimum 5 million ML dam is required, such as that proposed for the Mann
downstream of Jackadgery in 1957. If built it would have inundated over 200 km
of the Mann, Boyd and Nymboida wild rivers, and required another dam at
Nymboida to stop water spilling over the range. Over 150 km of the Armidale,
Gwydir and Old Glen Innes Roads would have required rerouting, and evaporation
would have exceeded inflows during droughts, on average once in every six
years.
Clearly proponents put little thought into
these proposals, something borne out by the Griffith NSW Farmers' submission to
a current NSW Upper House Inquiry, asking Government to “explore the
possibility of diverting the Clarence River inland to mitigate flooding in Lismore”.
Obviously these schemes simply don't hold
water!
- John Edwards
This article was originally published in the VOICES FOR THE EARTH column in The Daily Examiner on August 14, 2017.
This article was originally published in the VOICES FOR THE EARTH column in The Daily Examiner on August 14, 2017.