A canal reservoir gone wild
Ballynafagh Lake isn’t natural. It was dug in the 1780s as the Blackwood Reservoir, a header pool to keep the Grand Canal topped up as it crossed the midland bogs, and it still turns up as Blackwood Lake or the Prosperous Reservoir on older maps. When the canal trade wound down last century the sluices were left, the water spread, and reeds and fen closed over the engineering. What remains is a 45-hectare wetland (about 112 acres) that the National Parks and Wildlife Service now manages as a Special Area of Conservation, designated under S.I. No. 493 of 2018. It’s Kildare’s only national wildfowl sanctuary, and there’s no shooting anywhere on the site.
If you have an hour, walk the loop and bring binoculars. Almost everything worth seeing here is on the water or passing over it.
The walk
The loop is short: 1.4 miles, about 2.25km, and most people are round in half an hour. It’s rated easy and it is flat, but flat and dry aren’t the same thing here. The grassy path holds water and turns to mud after rain, so this is a boots-not-trainers walk from autumn through spring; February to August is the better window, when the ground has a chance to firm up. There’s no real waymarking, but the lake keeps you honest, since the path just circles it.
Birds
The shallow water and reed beds are the whole draw. On their first outing here the Kildare branch of BirdWatch Ireland logged 37 species in a single morning, Hen Harrier included. Year-round you’ll see Little Grebe, Mallard, Moorhen, Coot, Snipe and Water Rail, with a Kingfisher working the open water. Winter is when the numbers climb, as Whooper Swan come in off the bog alongside Teal, Golden Plover, Curlew and Lapwing. Come at first light, and in the cold months, if birds are what you’re after.
Fen, snail and butterfly
The lake edge is alkaline fen, a base-rich peatland rare enough to be one of the reasons the site is protected at all. Among the black bog-rush and great fen-sedge live the two species the SAC is legally bound to safeguard: Desmoulin’s whorl snail, a tiny mollusc that needs stable water levels and tall vegetation, and the Marsh Fritillary, the only insect in Ireland with legal protection. Water levels are managed with both in mind, which is why the reserve is left deliberately undisturbed.
Canal remains
The loop passes the ruins of the 18th-century gatehouse that once controlled the flow, its culvert still running under the masonry, and a stone arch survives where the old feeder crossed the low ground. It’s a quiet spot, and the best piece of built history on the walk.
Getting there
From Prosperous, follow the Staplestown road north for roughly 2.5km and turn at the sign for the lake. Mind the approach: it’s narrow, with deep ditches either side and little room to pass, so take it slow. There’s a free car park at the north-east entrance, and the information boards sit just to the left of the entrance gate, worth a read before you set off. No toilets, no shop, no staffed gate; it’s an open reserve, accessible at any reasonable hour.
Without a car it’s harder. The nearest bus stop is in Prosperous, about a 3km walk away, so check Local Link times and factor the road walk in.
Nearby
- Four Potts Well – a Grand Canal overflow with a stone arch, a few kilometres north.
- Donadea Forest Park – woodland trails, a lake and a ruined medieval castle.
- Prosperous – the closest village for a coffee, a shop and a refuel.