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. Dublin City Council manages the lakes, which still serve around 35,000 households in the southern part of the city. They sit between the Dublin Mountains and the edge of Wicklow’s uplands, with views to Seefingan, Corrig and Kippure, and the surrounding land is a conservation area. It’s a quiet walk, close in, without a long drive.
If you’ve only time for one loop, take the lower one from the paid car park. It’s the shorter walk and gives you the best of the water for the least effort.
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 enough to drink; 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
Two loops, both well-surfaced and manageable for most:
Upper Reservoir Loop (8.5 km) – starts at the original car park off the Ballinascorney Road, follows the Dodder past the lower lake and around the upper reservoir. Waymarked orange, 60 to 90 minutes, and almost flat, with about 15 metres of climb across the whole circuit.
Lower Reservoir Loop (about 4 km) – starts from the newer paid car park, circles the lower lake and passes St Ann’s graveyard before returning. Allow an hour to an hour and a half. This is the one to do if you want the views without the longer approach road.
Both link into the Dublin Mountains Way, which runs along the shoreline and out into the wider network of mountain paths.
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’ll 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 from the local clubs only.
On the western shore of the upper lake stand the remains of St Ann’s – the church of Santan, in use until the mid-16th century. Follow the yellow Dublin Mountains Way markers down toward Castlekelly and back along the road to reach it. It’s 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’s signposted.
By public transport – the TFI Local Link SD3 runs between Tallaght Luas and Ballinascorney, stopping at Glenasmole and the upper reservoir. Bus 49 from the city centre terminates near Bohernabreena Pitch and Putt, about a 15-minute walk from the lower reservoir.
Parking – two options, and the choice matters:
- Original car park (Bohernabreena North): free, but only 15 spaces, and it fills fast on weekends and bank holidays. Come early or on a weekday. Don’t park along the narrow access road – cars are liable to be towed.
- Upper car park (recommended): newer, secure, €5, with toilets and a weekend coffee stand (Goughie’s). It’s the start of the shorter loop and far less stressful to get into.
Practical information
- Opening hours: open year-round with unlimited access – no gates, no formal closing time.
- Admission: free to all the walks, picnic areas and viewpoints; you only pay to park at the upper car park.
- Dogs: welcome, but the reservoir rules ask that they’re kept on a lead for the whole walk, not just near the farm and water. Bring bags.
- Facilities: picnic tables around both lakes; toilets and the weekend coffee stand at the paid car park; nothing permanent at the original car park.
Nearby
A 20-minute 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, a chipper and the Blessington Greenway if you want to keep walking.
Get there early. The Glenasmole valley is quiet and the good parking is scarce, so a weekday or an early weekend morning gives you both the spaces and the still water – the reservoir is at its best before the wind gets up and the kingfishers move.