Overview
Bohernabreena’s two reservoirs have supplied Dublin with drinking water since the 1880s, and the glacial valley that holds them, Glenasmole, gives you one of the closest proper hill walks to the city, about 15 km southwest of Dublin city centre. The old stone channels and bridges show how the valley was adapted for waterworks in the nineteenth century, and the reservoirs still supply drinking water. They sit between the Dublin Mountains and the edge of Wicklow’s uplands, with views to Seefingan, Corrig and Kippure. It is a quiet walk, close in, without a long drive.
History and the waterworks
The lakes were built between 1883 and 1887 to do three jobs at once: supply drinking water to a growing city, feed the many mills along the Dodder valley, and control the flooding the river was prone to. The design is neat. Clean water off the lower, non-peaty slopes fills the upper lake and stays clear; a stone-faced channel carries it into the lower lake, which holds the peatier water that once drove the mills. From there it runs about 7.5 km to the treatment works at Ballyboden. The valley’s steep U-shape is glacier’s work, cut during the last Ice Age.
Walking trails
The Dublin Mountains Partnership maps an 8.5 km circuit, the Upper Reservoir Loop, starting at the Bohernabreena waterworks car park near Fort Bridge. Follow the orange markers. The route passes the lower reservoir on its way to the upper one and is almost flat, so it suits most walkers. The partnership lists 15 spaces and no toilets at this trailhead.
The Dublin Mountains Way uses yellow markers along part of the valley. Check the route and transport notes if you plan to continue towards Kiltipper and Tallaght.
Keep to marked paths and leave the water to its working purpose.
Wildlife and St Ann’s graveyard
The early-20th-century planting has matured into a mix of larch, Scots and Corsican pine, Douglas fir, hazel, birch, ash and sycamore, and in spring the meadows carry wild orchids. Along the water you will often see kingfishers, dippers, grey wagtails, herons and moorhens; sika deer move through the valley too. The lakes hold trout, but fishing is by permit through the local angling club only.
Above the reservoirs stand the remains of St Ann’s, the church of Santan, in use until the mid-16th century. The Dublin Mountains Partnership lists access to St Anne’s graveyard, so check its Glenasmole page for the current route and follow the markers on site. It is a quiet place to stop.
Getting there and parking
By car – from the city, take the N81 toward Tallaght, then the Oldbawn exit (R113), right at the crossroads onto Bohernabreena Road (R114), and left just after Fort Bridge into the waterworks. It is signposted.
By public transport – check current TFI and Local Link timetables for services serving Glenasmole and Bohernabreena before you travel.
Parking – the waterworks trailhead has 15 spaces and no toilets, so it fills quickly on weekends and bank holidays. Come early or on a weekday, and do not park on the narrow access road, where cars are liable to be towed.
Practical information
- Access: the walks are free. Check the Dublin Mountains Partnership page above for current notices before you go.
- Dogs: follow the signs and any reservoir rules on site, and bring bags.
- Facilities: the partnership lists no toilets at the waterworks trailhead.
Nearby
A short drive brings you to Cruagh Wood, where the forest trails climb to Cruagh summit and long views over the city. South of that, the lakeside town of Blessington has cafés and the Blessington Greenway if you want to keep walking.
The Glenasmole valley is quiet and parking is limited, so a weekday or an early weekend morning gives you both a space and the still water, before the wind gets up and the kingfishers move.