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 spot where Victorian engineering sits beside woodland trails, lake views and still water. It is a working drinking-water supply, so follow the walking signs and stay out of the 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
Walking routes here have been affected by storm damage, so check what is open before you set out. The one to choose is the Upper Vartry Trail.
Upper Vartry Trail. Visit Wicklow describes this as a loop of about 6.5 km with clearer sightlines to the Sugar Loaf and Djouce. It starts at the Knockraheen entrance on the east side of the upper lake. Allow about an hour and a half, and follow the signs where the route passes through open pasture and woodland.
Lower Vartry Trail. Visit Wicklow lists the Lower Vartry Trail as closed. When it is open, it loops around the lower lake and passes a hollowed-out ballaun stone near the water’s edge, likely relocated from a nearby monastic site. In low summer water the stonework of the original bridge that once crossed the River Vartry reappears just beneath the surface, but do not use that as a reason to go around any barrier.
Woodland routes. The Woodland Trail is a short, shaded circuit through a stand of century-old Scots pines that separate the two reservoirs, a favourite with birdwatchers in spring and early summer. Storm damage also affected the smaller woodland routes. In its last reopening notice, Uisce Éireann listed the Upper Woodland Trail and the woodland routes around the lower reservoir as still closed. Check signs, choose the main Upper loop if it is open, and do not go around barriers.
The quiet roads around the lakes also draw road cyclists.
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, and Uisce Éireann advises against swimming in reservoirs, where the depth and currents can change. Keep out of the water and follow local signs about dogs. The lake is well worth the trip for a walk, just not for a swim.
If a swim is what you came to Wicklow for, choose a designated bathing spot and check the local notice for the day. 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 free to visit, but trail status can change, so check local notices before travelling. The site is managed by the national water utility, Uisce Éireann. It’s a working drinking-water reservoir, so there’s no swimming, and you should follow local signs about dogs.
Parking & Facilities Use the signed parking at the Knockraheen entrance for the Upper loop, and check on-site notices. Do not count on toilets or other facilities at the trailhead; Roundwood village has shops, cafés and pubs.
Accessibility Surfaces vary around the reservoirs, with gravel, compact earth and some uneven or sloping ground, so the trails are not reliably suitable for buggies. Check the current trail description and notices before bringing a pushchair.
Getting There By car, take the M50 to the N11 southbound, exit at Kilmacanogue and follow the R755 to Roundwood, then use the signed Knockraheen entrance for the Upper loop. St Kevin’s coach and Local Link route 183 serve Roundwood, but the village stops are separate from the Upper trailhead. Check how you will reach the entrance and get back before relying on the bus.
Nearby Attractions
Roundwood village is close to the trailheads and has cafés, pubs and shops for a post-walk meal.
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 easy reach.
Bring a waterproof layer and sturdy shoes, as the pine trails can stay damp well into the day.