Fremantlebiz - Paul's Letter from Australia

Yornaning pool

A couple of days ago I wrote about the abandoned Yornaning townsite, which we briefly visited two Saturdays ago.

Slightly west in the bushland behind the townsite is a pool of water now known as Yornaning Dam. Originally in the late nineteenth century a pool was dug in the bed of a stream (Cuballing Brook) to provide a reliable water supply for as many as thirty steam trains a week, which passed by on the Great Southern Railway.

By 1909 the pool became unusable for steam trains because of rising salt levels. These are believed to have been initiated by intensive clearing of agricultural lands upstream.

It seems possible this was a factor which lessened the importance of Yornaning. With the loss of a pure water supply it became a place on the way to somewhere else.

However the pool retained its importance when it became a supply of potable water for the town of Narrogin, some 33km by pipeline to the south. However, the salt problem increased, as did the polluting contribution by fertiliser runoff from upstream farmlands. Eventually in the 1950s Narrogin's main water supply came from the much larger Waroona dam, which is near the west coast.

By the early 1990s the Yornaning dam had become stagnant and devoid of life because of heavy phosphate and nitrogen levels. A major project was undertaken to drain and modify it during 1994-93. Click here for my photo of the pool in 2008.

According to a faded notice board near the site, a low diversion levee which is still evident a few hundred metres upstream was installed to divert the initial winter rush of water loaded with nutrients through a pipe to another nearby waterway, the Hotham River South. Then as the winter rains increased, the cleaner water flowing in the brook would be sufficient to pass over the levee and into the dam. Additionally, a siphon was installed in the bottom of the dam to allow biannual draining of nutrients which had sunk towards the bottom.

I have included two other photos of the levee, one facing southwest and one facing south. Being still autumn, here was no water flow in Cuballing Brook at the time.

Beyond the levee in all three photos can be seen numerous dead trees which became victims of the environmental degradation in the past. The associated bushland in the background is part of the Dryandra State Forest, an area noted for its rare species of native fauna and rich diversity of flora.

A native reed bed has been established between the pool and the levee. This is intended to act as a filter.

Apparently the relatively modern environmental engineering efforts have generated a significant improvement in the pool. There were even a couple of ducks swimming on the surface when we were there. Where were the rest?

At the western end there is a public picnic area, barbecues and toilets. People can swim in the pool, but there was a sign warning them not to immerse their heads. Amoebic meningitis is often present in such places in Western Australia.

© MMVIII Paul R. Weaver.

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Check out each month's subject index on the Calendar Page for my "common-man" monologues about survival in 21st century Australia – plus a little history occasionally. An original essay is added most days as part of an undertaking to write at least couple of million words. Zzzzzzzz!