Tuesday, July 15, 2014

Branching out - a diverting lesson

I recently had the opportunity to visit a part of the Moorabool River which I had not seen before with the Meredith History Interest Group who visited the Caroline Chisholm School Camp. The facility owned by the school, provides an outdoor education program for children in years 7 to 10 offering camping, archery, kayaking, rope courses and a variety of other nature-based learning experiences.
The Moorabool River looking south east from the school camp

Looking north west along the river at the camp
The camp is situated at the end of Pioneer Ridge Road between Steiglitz and Meredith on land which stretches down to a section of the Moorabool River where the students practise their raft-building and kayaking skills. The scenery is quite dramatic, with impressive granite outcrops towering over the river, giving students a chance to consider the geology of their surroundings.

Granite outcrop on the banks of the Moorabool River at the camp
Also located on this stretch of the river is the She Oaks Diversion Weir which lies about 25km downstream as the crow flies, from the larger Bungal Dam - or Lal Lal Reservoir as it is also known. The winding course of the river actually covers around twice this distance and it is through this section of the Moorabool that the portion of water from Bungal Dam which is allocated to Barwon Water flows to the She Oaks weir. From there it is pumped to the nearby Moorabool Water Treatment Plant where it is treated and combined with flow piped from the Stony Creek reservoirs at Durdidwarrah*.
Dam wall and pumping station of the She Oaks weir

The Moorabool River immediately downstream of the She Oaks weir
From the Moorabool treatment plant, the purified water is diverted via the She Oak-Montpellier pipeline to the Montpellier holding basins in Highton, Geelong. Water from the Montpellier basins is then combined with water from the West Barwon Dam and distributed for urban use - mostly across the western suburbs. A branch of this pipeline also supplies the townships of Bannockburn, Inverleigh and Teesdale, however in times of drought, water can also be back-fed from the Montpellier basins to these towns.
Previously, Meredith township was supplied by its own pumping station and treatment plant located upstream of She Oaks Weir, just over 3km north west of the town, however water quality issues during drought years has seen this plant decommissioned. According to Barwon Water, supply for Meredith is now also provided by the Moorabool treatment plant via a pumping station and rising main to a balancing tank at the old treatment site. Lethbridge likewise was reliant upon the decommissioned Meredith plant, so water for that town is now fed from the Meredith pipeline to a balancing tank between the two towns, enabling a gravity feed.
Work on the weir and connecting pipeline began in 1972 and required tonnes of concrete and other supplies which were carried in on trucks down the steep southern bank, crossing the river at a narrow ford about 300m downstream of the weir.
Ford across the Moorabool River
 To allow passage for the construction vehicles, the flow of the river was diverted under the ford through a pair of large concrete pipes. The ford and pipes remain in place today.

One of the concrete pipes carrying the flow of water under the ford
Nearby are the remains of a gravel pit, the contents of which were used during construction of the dam.

As works progressed on the weir, the pipeline to carry the water to the Montpellier basins was also built, with both completed late in 1973. The system came online in January, 1974 when water from the She Oaks-Montpellier pipeline began to flow into the Montpellier basins, thus completing - as the plaque below states - a scheme to bring water to Geelong which began a century earlier in 1874.

Plaque commemorating the formal opening and release of water from the She
Oaks-Montpellier pipeline

A more detailed description of the evolution of Geelong's water supply can be found in Leigh Edmond's Living By Water: a history of Barwon Water and its predecessors (available in print or online) including details of the construction of the She Oaks weir and pipeline.
*The water held at Stony Creek is taken from the Bostock Reservoir on the upper reaches of the East Moorabool River (flowing via the Bostock and Ballan Channels). It is then transferred from the Stony Creek Reservoirs to the Moorabool Water Treatment Plant by a pipe running under the Brisbane Ranges. This replaces an earlier open channel and pipe which carried the water through Anakie Gorge to holding basins at Lovely Banks which I discussed in my Turning on the waterworks post.