Lough Derg reaches depths of up to 36 meters in its southern section near Killaloe.
The lake contains numerous islands, the most historically significant being Holy Island (Inis Cealtra), which hosts a monastic site dating back to the 7th century.
The water levels are artificially regulated to support the Ardnacrusha Power Station, the first major hydroelectric scheme in Ireland.
The lake is part of the Lough Derg Way, a long-distance walking trail that traverses the Shannon valley.
Lough Derg is internationally recognized as a major site for pike fishing, consistently yielding specimens exceeding 20 pounds.
The lake serves as a primary reservoir for the Shannon River basin, playing a role in flood mitigation for the midlands.
Lough Derg is the third-largest lake on the island of Ireland, stretching 40 kilometers long as the southernmost of the River Shannon's three main lakes. It functions as a critical navigational artery for the Shannon-Erne Waterway system, connecting Killaloe and Ballina in the south to Portumna in the north. The lake is a premier destination for coarse and game angling, particularly noted for its pike, brown trout, and perch populations. Geological features include a mix of limestone landscapes and extensive reed beds that provide habitats for diverse bird species. The shoreline spans three counties: Tipperary, Galway, and Clare. Recreational infrastructure includes numerous marinas and public harbors designed for cruiser and sailboat access. The surrounding terrain is characterized by the Slieve Aughty Mountains to the west and rolling agricultural land to the east. Water levels are strictly managed by the ESB for hydroelectric power generation at the Ardnacrusha plant.
The lakeside pier at Mountshannon overlooking the monastic ruins on Holy Island.
Ensure you have a current permit if planning to fish, as inland fisheries are strictly regulated.
Check the official Waterways Ireland navigation charts if operating a private vessel, as shifting sandbars exist.
Wear layered, waterproof clothing even in summer, as weather conditions on the water change rapidly.
Attempting to navigate shallow regions without local knowledge or an accurate depth sounder.
Navigation routes remain open year-round, but rental boat services and seasonal tourist amenities typically operate from late spring through early autumn.
Practice 'Leave No Trace' principles; follow local boating speed restrictions to prevent shoreline erosion.
