Shall we see what this is about? I found the answer on a blog called Think-Tasmania, one I already take a quick look at anyway. I'll begin with a location. The dam wall is in north eastern Tasmania about equi-distance between the towns of Scottsdale and St Helens. It was constructed on the Cascade River in 1936 by the Mount Paris Tin Mining company for operation of its hydraulic equipment. A water race took water several kilometres to the tin mine. The dam wall was hand built, a rather impressive feat.
The mine closed in 1961 by when the state government had already taken ownership of the dam. By 1985 it was under the control of the Water and River Supplies Commission. While it had held little water since the 1970s, the Commission blasted a hole in the dam wall to ensure proper river flows.
Vegetation is reclaiming the floor of the dam. The dam wall is popular with visitors and loved by locals.