The Devil's Gully Tunnel- At the Crossroads

 

This gangly structure (above photo), one of about 14 similar 'water bridges', formed part of  the Loddon Company Race which survived for almost 100 years. Stretching from the higher Loddon River near Glenlyon it meandered over 24 km of river flats and forested hills and gullies, emptying what remained of its waters back into Fryers Creek, Chokem Flat. All along its tortuous route it had been used by miners and finally at its destination by sluicers, clay ore being reduced to a mud slurry to allow the extraction of the gold within.

    The story of the Loddon Company Race, built in 1866, is extraordinary, too complex to tell in full here.  An in depth study of it can be found on The Australasian Mining History's website, in a paper by Latrobe University's Peter Davies, Susan Lawrence and Jodi Turbull: 'The River Loddon & Tributaries Water Supply Company' (Journal of Australasian Mining History, Vol. 14, October 2016).

    I'm only going to focus on just one aspect of the Loddon Company Race, the point where the race carrying water from the Loddon River in the south once met water from the Coliban System of Waterworks, passing down the Fryer's Channel from the north, at the Devil's Gully Tunnel. What's remarkable is that both schemes used the same tunnel at the same time even though their waters were flowing in opposite directions.  

    The map below shows the path of the Fryer's Channel (red hatched line) completed in 1895. Arrows indicate its direction of flow south-west to Vaughan. The yellow hatched line is the Loddon race, carrying its load of Loddon River water northwards to an area marked Red Hill on the map. As you can see they cross paths at the Devil's Gully Tunnel, close to the centre of the map (adapted from P. Davies).

    Here is a view of the southern entrance of the Devil's Gully Tunnel.

    So how was it possible for two opposite flows to be incorporated in the one tunnel? Certainly not by some novel law of physics. The Coliban water was piped along the approaches to the tunnel and then through the tunnel. The Loddon River water was allowed to flow through the tunnel around the pipe. 

    Here are photos of the northern and southern approaches showing the direction of flow, red arrows for the  Coliban water and yellow arrows for the Loddon River water. 

    All in all, a remarkable situation only made possible because the tunnel floor, and the northern and southern approaches were level, allowing water to flow in either direction. However the question must be asked. In 1866, when John Amos and Edward Wardle designed and constructed the Loddon Company Race, how could they have known that 30 years later, the extension of the Coliban water system would need this section of the channel to be level, to allow it to be used to run water opposite to the flow of the Loddon race?