Lough Derg

Size and shape

The lake covers 130 square kilometres and is 36 metres deep at most. It is the southernmost of the Shannon's three big lakes, after Lough Allen and Lough Ree, and the second largest in the Republic; only Lough Neagh and Lough Corrib are bigger on the island. Just below its outlet are the falls of Doonass, the largest on the gently sloping river, and near them the Ardnacrusha power station, the biggest in the world when it was built in 1927. Islands dot the lake, Inis Cealtra, Holy Island, among them.

Boats, eagles and mussels

In the nineteenth century the lake was the artery between the port of Limerick and Dublin through the midland canals; today it belongs to cruisers and pleasure craft, sailors and anglers, and the University of Limerick keeps an activity centre north of Killaloe with canoes, kayaks, windsurfers and dinghies. The RNLI lifeboat at Dromineer was Ireland's first inland station; in June 2013 it helped bring 35 people to safety when bad weather hit an international rowing event. Dublin City Council proposed in 2011 to pipe up to 350 million litres a day from the lake to the capital.

A pair of white-tailed eagles nested on an island in 2012, the first success of the reintroduction begun in 2007. Less welcome arrivals: the invasive stonewort Nitellopsis obtusa, first recorded in Ireland here in 2016, and quagga mussels found in 2021. The north-east shore is a Special Area of Conservation.

From Portumna

Portumna is the northern gateway: the marina, the forest park along the shore, the castle and the bridge over the Shannon to Tipperary. Killaloe and Ballina, Dromineer, Terryglass, Mountshannon, Garrykennedy and Scarriff, where Waterways Ireland has an office, are the other harbours round the lake. The model on this page pins the shore below the town.