The reservoir was constructed between 1908 and 1911. It now has a capacity of 22,119 megalitres (ML).
After its initial construction, the reservoir operated for several years but as demand increased, it was decided to increase the capacity. To achieve this, the dam was raised by 3.35m in 1930.
In 1945, the inlet to the outlet tower was raised by 4.7 metres to overcome a siltation problem that was inundating the original inlet.
In 1967, the Western Freeway was constructed to improve travel between Ballarat and Melbourne. These works resulted in part of the dam being buried underneath the Western Freeway embankment. As part of these works, the outlet conduit of the dam was extended by about 73 metres to allow it to clear the toe of the highway embankment.
In 1968 the clay core of the embankment was raised by about 1.5 metres up to crest level.
Following a risk assessment study, the left side spillway training wall was raised in 1998 to prevent flows in the spillway chute from overtopping and causing damage to the embankment.
In 2003, major alterations were made to the outlet tower. The old low level inlet was found to be collapsing. This led to the construction of new low level inlet and the old inlet being plugged with concrete. Two new inlet valves were also installed.
The new arrangement allows the tower to be dewatered for inspection and maintenance. In addition, it allows water to be drawn from closer to the surface, reducing the effects of cold water pollution.
In mid 2005, a dam safety upgrade project started, with works being carried out at the embankment / spillway junction to reduce the probability of failure due to piping.
In 2009, $5 million remedial works were completed to improve the reservoir’s flood capacity and its defences against erosion through the embankment.
The works included a filter buttress against the downstream face of the embankment, allowing any seepage to be intercepted and safely drained away. The embankment was raised by 0.8 metres and the spillway widened by 30 metres to improve flood capacity.
RESERVOIR Capacity 22,119 ML Dead storage 1,923 ML Surface area 203 ha Full supply level 396.57 AHD Catchment area 129 km2 EMBANKMENT Maximum height 339.8 m Length 351 m PRIMARY SPILLWAY Crest length 91.7 m Discharge capacity 100,000 ML per day SECONDARY SPILLWAY Crest length 29.8 m Discharge capacity 65,000 ML per day