The reservoir is owned by Irish Water and operations are carried out by Dublin City Council.

The original (lower) reservoir was completed in 1863 and has a capacity of 11.3 billion litres and a maximum depth of 18.3 metres. A second embankment, 3.5 km upstream, was completed in 1923 to form the upper reservoir. This has a capacity of 5.6 billion litres and a maximum depth of 13.4 metres.