WHY is it a good thing that the Needles Dam will not be built?
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State Water had identified 13 sites on the Belubula/Lachlan river system where a new dam might be built or an existing dam enlarged. Politicians, however, had latched onto the Needles site as the preferred site - despite it, superficially suitable, twice being rejected by their own geologists.
A 1941 report by government geologist, E. J. Kenny, concludes:
“I am of the opinion that the site is not suitable for the construction of a major masonry dam for the principal reason that to attain a reasonable wall height and make use of the sandstone for abutments it would be necessary to found the structure upon a mass of shales, which although essentially sandy, embrace clayey layers liable to induce slippage when lubricated by percolating waters. Moreover, the thickness of shales beneath the cliffs does not impress from the viewpoint of strength to resist abnormal pressures.”
Fortunately the state water minister announced on February1, 2015 that the government’s preferred site for a new dam on the Belubula River was Cranky Rock.
Had the Needles Dam gone ahead what would we have lost ?
Obviously, the caves. You may have seen their beauty on 7.30 NSW several weeks ago. Many will be inundated.
There are 118 known caves and features at Cliefden and it would take only one flood event to silt them, as many drop to current river level. Their beauties compare favourably with Jenolan.
An extract from The Australian Karst Index (the textbook on Australian limestone) will give readers an idea of the treasures that could have been lost: “The helictites (mysteries) in the jewel chamber could be the best in the southern hemisphere.”
As well, there are rare blue speleothems, their colours formed by water leaching through copper as it drains underground.
The fossil beds (Ordovician), Fossil Hill and Trilobite Hill, too, would have been lost.
There have been over 45 studies (Australian and international) of these sites and the National Parks and Wildlife Service ranks Cliefden’s treasures the highest on any limestone area outside their parks. Cliefden ranks 5/5 as a scientific area; the next ranking on their scale is 2/5.
Cliefden may well rank as the area of highest scientific importance of any limestone area. The Geological Society of NSW Newsletter #168, 2013, describes Cliefden in this way: “The Fossil Hill site is one of the best exposed sequences of Ordovician fossiliferous limestone in eastern Australia … Fossil Hill is truly a site of geoheritage significance.”
Overseas speleologists are coming to Cliefden in 2017 to see this site.
Thirty-two species of fossil corals, stromatoporoids, trilobites, brachiopods, bryozoa,echinoderms and graptolites are found there.
As can be imagined Cliefden is a major research site. As I write, two studies are in progress: a bat study that has exciting initial findings of unsuspected numbers and species of microbats, and a geomorphology study looking at the process that has formed the caves.
There is a rare warm spring there (one of only three on limestone in NSW), so obviously there are at least two sources of water - the river and a deeper subterranean source.
The area’s magnificent tufa dams have recently been studied, and a climate study - looking at speleothems and past climate change - has been undertaken.
Early colonial ruins rest amid fertile flats on the river banks and indigenous remains have been found and recorded.
All this, as well as productive agricultural land, would have been lost. The geological and biological chain linking the Canowindra Age of Fishes Museum and Wellington Caves would have been broken.
Local community connection with the caves would have been severed too.
The Orange Speleological Society, formed in 1955, has had over 300 local members.
These members have, through the years, shown many groups from the nearby towns through the caves. Recognised nationally as efficient cave managers, OSS has assisted local landowners in preserving these sites.
It is a wise political decision that has saved this site.