River Shannon - Geography

Geography

By tradition the Shannon is said to rise in the Shannon Pot, a small pool on the slopes of Cuilcagh Mountain in County Cavan, from where the young river appears as a small trout stream. Surveys have defined a 12.8 km² immediate pot catchment area covering the slopes of Cuilcagh. This area includes Garvah Lough, Cavan, 2.2 km to the northeast, drained by Pollnaowen. Further sinks that source the pot include Pollboy and, through Shannon Cave, Pollahune in Cavan and Polltulyard and Tullyrrakeeragh in County Fermanagh, Northern Ireland. The highest point in the catchment is a spring at Tiltinbane on the western end of the Cuilcagh mountain ridge.

From the Shannon Pot, the river subsumes a number of tributaries before replenishing Lough Allen at its head.

The river runs through or between 11 of Ireland's counties, subsuming the tributary rivers Inny, Suck and Brosna, before reaching the Shannon Estuary at Limerick. At a total length of 360.5 km (224 miles), this means it is the longest river in both Ireland and the wider British Isles.

There are some tributaries within the River Shannon system which may have headwaters that are further in length (from source to mouth) than the Shannon Pot source. Most notably the Owenmore river in Co. Cavan, which flows west through the valley of Glengavlin, joining the Shannon about 2 miles below Lugnashinna.

Lakes on the Shannon include Lough Allen, Lough Ree and Lough Derg.