Vartry Reservoir, reservoir in County Wicklow, Ireland

Vartry Reservoir is a reservoir at Roundwood in County Wicklow, formed by damming the River Vartry. Its lower basin, completed in 1863, is held by an earthen dam across the river valley and holds 11.3 billion litres to a maximum depth of 18.3 metres. A second embankment 3.5 km upstream created the upper reservoir in 1923, with a capacity of 5.6 billion litres and a maximum depth of 13.4 metres. Water is piped from here to a covered reservoir at Stillorgan for Dublin.

The lower basin was built between 1862 and 1863 to improve Dublin's drinking water supply and fight waterborne diseases like cholera and typhus that spread through contaminated water. This project represented a major engineering and public health achievement of the 19th century.

The reservoir takes its name from the River Vartry, dammed to create it. Its lower basin appears in chapter 17 of James Joyce's Ulysses, set in Dublin on 16 June 1904. The scheme was promoted by Dr. John Gray, who chaired the Dublin Water Works Committee.

The lower reservoir lies at Roundwood, with the upper reservoir 3.5 km upstream along the Vartry River; the two are linked by the river valley rather than a single shoreline path. The lower reservoir is 18.3 m deep at its maximum and holds 11.3 billion litres, the upper 13.4 m and 5.6 billion litres. Water is piped from here to a covered reservoir at Stillorgan in south Dublin, and Irish Water operates the site.

The lower reservoir and its capacity appear in chapter 17 of James Joyce's Ulysses, set on 16 June 1904 in Dublin. The scheme was formally opened on 30 June 1863, and its committee was chaired by Dr. John Gray, who promoted what became known as the Vartry scheme.