Turn on a tap in south Dublin and there’s a fair chance the water set out from here. Vartry Reservoir (Irish: Taiscumar Fheartraí) is a twin-lake system in the foothills of the Wicklow Mountains, just outside Roundwood, about 50 km south of Dublin, and it has been storing and filtering the capital’s water since 1863. For a visitor it’s a quiet, traffic-free spot where Victorian engineering sits beside easy woodland trails, lake views and still water.
The 1863 waterworks
The reservoirs were born from a sanitation crisis. By the mid-1800s, Dublin’s reliance on polluted canal water had led to recurring outbreaks of cholera and typhus. The Dublin Waterworks Act of 1861 authorised the damming of the River Vartry, and construction of the lower reservoir ran from 1862 to 1868 under the Dublin Water Works Committee, chaired by Dr John Gray. The lower dam was formally opened on 30 June 1863, giving the city its first reliable supply of clean, filtered water and sharply improving urban public health.
As Dublin’s population grew, demand outstripped the original capacity. A second embankment, 3.5 km upstream, was completed in 1923 to form the upper reservoir. Together the two lakes hold 16.9 billion litres. The lower reaches a maximum depth of 18.3 m; the upper holds 5.6 billion litres at 13.4 m deep. The works were considered remarkable for their day, with a controlled spillway channelling water between the lakes before it heads to the filter beds. The scheme even earned a literary nod in chapter 17 of James Joyce’s Ulysses, where the lower reservoir’s capacity is mentioned in passing.
The Walking Trails
Three officially waymarked loops suit different paces and interests. All are graded easy, well-maintained, and fine for families, casual walkers and dogs. For a first visit, the Lower Vartry Trail is the one to pick – it’s the only loop that takes in both the ballaun stone and, in low water, the drowned bridge.
| Trail | Distance | Way-marker | Approx. time | Start point |
|---|---|---|---|---|
| Lower Vartry Trail | 7.2 km | Blue | 2 hours | Roundwood village T-junction (R755/R765) |
| Upper Vartry Trail | 6.4 km | Green | 1.5 hours | Knockraheen entrance, east side of upper lake |
| Woodland Trail | 3 km | Pink | 45 minutes | Knockraheen entrance |
Lower Vartry Trail follows a traffic-free loop around the lower lake, hugging the shoreline on compact paths and quiet country roads. Look out for a hollowed-out ballaun stone near the water’s edge, likely relocated from a nearby monastic site. When summer levels drop, the stonework of the original bridge that once crossed the River Vartry reappears just beneath the surface.
Upper Vartry Trail climbs gently around the higher lake, with clearer sightlines to the Sugar Loaf and Djouce. There are a few short, steeper banked sections, but the overall gradient stays manageable. The route is fully waymarked in green and passes through open pasture before dipping into mixed woodland.
Woodland Trail is a short, shaded circuit through a stand of century-old Scots pines that separate the two reservoirs. The path follows a steep-sided cutting and makes a cool, quiet alternative on warmer days. It’s a favourite with birdwatchers in spring and early summer.
The quiet roads around the lakes also draw road cyclists, with the Roundwood Loop (about 16 km, mostly flat) a common circuit.
Wildlife & Nature
The catchment is protected for water quality, and the surrounding plantations make stable habitats for a range of species. The open water attracts grebes, which build floating nests anchored to reeds and lily pads. Mute swans, little egrets, grey herons and black-headed gulls are regular, while the pine edges and clear-felled glades hold red squirrels, foxes and the occasional sika deer. Spring brings a chorus of songbirds to the canopy, and the reed beds along the lower shoreline give cover to otters and water voles.
Can you swim in Vartry Reservoir?
No. This is a working drinking-water reservoir supplying a large part of north Wicklow and south Dublin, and swimming is prohibited to protect the supply. Dogs should be kept out of the water for the same reason. The walking trails around it are free and open year-round, so the lake is very much worth the trip, just not for a swim.
If a swim is what you came to Wicklow for, Lough Bray off the Military Road is a recognised wild-swimming spot on public ground. Lough Tay, Lough Dan and Coon Beach are all private with no public right of way to the shore. Our guide to swimming in Ireland’s lakes sets out which lakes in the country are monitored bathing waters and which are closed.
Practical Information
Vartry Reservoir is freely accessible year-round with no admission charge or formal opening hours. The site is managed by the national water utility, Uisce Éireann, but there is no visitor centre. It’s a working drinking-water reservoir, so there’s no swimming, and dogs should be kept out of the water.
Parking & Facilities
- Upper Vartry Car Park – At the Knockraheen entrance. Free parking with basic signage and public toilets.
- Lower Vartry Car Park – Near the trailhead in Roundwood village. Free parking with access to village amenities. Both areas are dog-friendly. Leads are recommended near livestock and water edges.
Accessibility The Lower Vartry Trail is largely flat and manageable with strollers, though sections are gravel or compact earth. The Upper and Woodland trails have moderate inclines and uneven ground. Detailed trail maps are available via Sport Ireland’s walking portal.
Getting There By car, take the M50 to the N11 southbound, exit at Kilmacanogue and follow the R755 to Roundwood. The journey from Dublin takes about an hour. Public transport includes Bus Éireann routes 181 and 183, which stop in Roundwood village. From the bus stop it’s a short walk to the Lower Trail start, or a quick taxi to the Knockraheen car park for the Upper and Woodland routes.
Nearby Attractions
Roundwood village is a two-minute drive from the trailheads and has cafés, pubs and shops. The Sugar Mountain Café and Bistro serves specialty coffee and light meals, while An Tochar House is a reliable spot for a post-walk pint and traditional food.
For drivers, the Sally Gap circular route begins just west of Roundwood and winds through the Wicklow Mountains National Park, past Lough Tay, Ballinastoe Woods and Glenmacnass Waterfall. Mountain bikers can head to the nearby Ballinastoe MBT centre for purpose-built trails through the same forest. If you’re extending the day, Bray and Wicklow town are both within a 20-minute drive.
Check water levels before visiting if you want to see the submerged bridge on the Lower Trail; late summer and early autumn usually offer the best visibility. Bring a waterproof layer and sturdy shoes, as the pine trails can stay damp well into the day.