Wicklow Mountains - Hydrology

Hydrology

The Wicklow Mountains are the source of several major river systems. Since the thin blanket bog peats cannot hold great quantities of water, many of these rivers exhibit a flashy hydrography, filling rapidly after heavy rain.

The River Liffey rises between the mountains of Kippure and Tonduff at Liffey Head Bog. One of the major tributaries of the Liffey, the River Dodder, rises nearby on slopes on Kippure. The King's River rises on Mullaghcleevaun and joins the Liffey near Blessington.

The River Vartry rises on the slopes of Djouce mountain. Nearby, the River Dargle rises between Tonduff and War Hill, falling as the Powerscourt Waterfall, Ireland's tallest waterfall at 121 metres (397 feet), over a cliff formed by a glacier at the contact point between the granite and mica-schist of the Wicklow Mountains. The waterfalls at the heads of the valleys of Glendalough, Glenmacnass and Glendasan also occur approximately at the schist-granite junctions, as does the Carrawaystick waterfall in Glenmalure.

The River Slaney rises in the North Prison of Lugnaquilla mountain and winds through the Glen of Imaal where it is joined by the Leoh, Knickeen and Little Slaney. Another of its tributaries, the River Derreen, rises on Lugnaquilla’s southern side.

Each of the main branches of the River Avoca – the Avonmore, the Avonbeg and the Aughrim rivers – have their origins in smaller tributaries, many of which rise in the Wicklow Mountains. The Glenealo, Glendasan and Annamoe rivers meet to form the Avonmore near Laragh. The Annamoe rises near Sally Gap and is joined by Cloghoge Brook between Lough Tay and Lough Dan and by the River Inchavore in Lough Dan. The Avonbeg rises on Table Mountain and the Three Lakes. The Avonmore and Avonbeg rivers join to form the River Avoca at the Meeting of the Waters in the Vale of Avoca, celebrated in the song The Meeting of the Waters by Thomas Moore. The Avoca is joined by the River Aughrim at Woodenbridge, sometimes referred to as the “Second Meeting of the Waters”. The Aughrim is formed at the junction of the Derry Water and the River Ow, the latter of which rises on Lugnaquilla.