Lakes

The lakes of the Mersey Valley were formed in the late 1960’s and ‘70’s when the Tasmanian Hydroelectric Corporation began to build a major system of dams across both the Mersey and Forth Valleys. The Rowallan dam and power station and was the first to come on line. The lake was formed in a wide U-shaped glacial valley once known as Howells plains; the remnants of the former landscape can be seen in the distribution of dead trees that are exposed above the lakes surface. At low levels in winter the scene is vivid and disturbing. This dam forever changed the flow of the river downstream; permanently reducing it.

Between Lake Rowallan and Lake Parangana the Mersey Whitewater Reserve stands as a reminder of how this river once flowed, on request by kayak and rafting clubs water is released from the dam to emulate the wild flows of that once existed.
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Lake Parangana is much smaller that Rowallan and was formed in narrow gorge where the Fisher River joins the Mersey. At the dam, water from the Mersey catchment is diverted via a tunnel to the Lemonthyme PowerStation in the Forth Valley. Hydro Tasmanian now takes its environmental responsibilities for the river’s health very seriously, a consistent level of flow below Parangana is maintained. For many years there was around a ten-fold order of magnitude reduction from the naturally occurring flow.