The principal purpose of the dam and its reservoir is to supply potable water for Greater Metropolitan Melbourne.

A walking track leads across the dam, over the spillway, and up to a lookout from which much of the reservoir can be viewed.

The Maroondah Aqueduct was built in 1886–1881 to supply water to the Preston Reservoir from a diversion weir on the Watts River.

The level of the aqueduct was determined by the site of the proposed Maroondah Reservoir, preparatory work for which was undertaken in 1915–1919.

[3] In 1986, the reservoir spillway was widened to increase its flow capacity to that of a 1-in-10,000-year flood and, in 1989, the stability of the concrete dam was enhanced using ground anchors.