Several of these rivers have been dammed to create reservoirs to provide drinking water for the residents of Dublin and its environs. The first of these was the River Vartry, dammed to create the Vartry Reservoir near Roundwood in the 1860s. A second dam was added in 1924 to increase capacity. The River Dodder feeds the two Bohernabreena reservoirs in the northern foothills of the Wicklow Mountains at Glenasmole in County Dublin, which were constructed between 1883 and 1887 to supply water to the townland of Rathmines. The Poulaphouca Reservoir, on the River Liffey near Blessington, was constructed between 1938 and 1940. There are also two hydroelectricity plants at Poulaphouca, constructed during the 1940s. A pumped storage hydroelectricity plant was constructed at Turlough Hill between 1968 and 1974. Water is pumped up from Lough Nanahangan, a natural corrie lake, into an artificial reservoir on Tomaneena mountain and released at times of peak electricity demand.