Water levels in Upper and Lower Lough Erne are managed by a control structures located at Portora in Enniskillen and by the hydro electric power station at Cliff between Belleek and Ballyshannon, in the Republic of Ireland. During the summer period it is aimed to keep the water level at the down steam side of Portora, at or above, 150 ft. to avoid the need for the gates to be closed requiring the use of the navigation lock. This is to prevent restriction to boat traffic using the navigation facilities at the peak tourist period.