DIVERTING THE CLARENCE RIVER IS AGAIN ON THE AGENDA

Calls to divert the waters of the Clarence River occur regularly.  The latest calls have come from Griffith (once again) in the south-west and Toowoomba to our north.

 

One of the claims of those promoting dams and diversions is that the water flowing out to sea from the Clarence is wasted. 

That is missing the point of the function of natural waterways.  They are not concrete-lined drains constructed by engineers to serve humankind. Rivers have developed over millennia to perform geomorphic and ecological functions which involve interactions with the landscape and the myriad of life forms which depend on their water.

All major diversion schemes obviously involve the construction of large dams.  Those dreaming of a western diversion envisaged something like a Snowy Scheme of the north with massive tunnels and pumps. Such a scheme would lead to the Clarence below the dam being as degraded as the Snowy River became as a result of the Snowy Scheme. 

 

And if the water was diverted to the Murray-Darling Basin, as those in Griffith and elsewhere over the range would like, would it be used to improve the health of the river systems there or to allow expansion of the cotton industry in the north and horticulture in the south?

 

Another suggestion is that humankind downstream would benefit if there was a massive dam built on the Clarence for flood protection.  In floodtime, particularly when there are very heavy falls across the entire catchment, the volume of water flowing down the Clarence is huge. How big would a flood protection dam have to be?  Just how realistic is this idea? 

While floods cause problems for humans on floodplains, they are vital to the rejuvenation of the river system. The health of the Clarence and the industries which rely on it – like our important fishing industry - would be severely impacted if such a dam were built just as it would be if the river was dammed for a diversion.

One way of keeping the Clarence River healthy is to ensure that there are no further diversions or dams.

            - Leonie Blain

 This article was originally published in the VOICES FOR THE EARTH column in The Daily Examiner on May 28, 2018. 

DIVERTING THE CLARENCE RIVER TO THE WEST

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.