Lough Neagh
The Lough Neagh catchment drains 43% of the landmass of Northern Ireland, as well as some border areas in the Republic of Ireland, all in Ulster. The Rivers Agency manages the water level in the lough using a barrage at Toome. The current drainage scheme was engineered by Major Percy Shepherd and was enabled by the Lough Neagh and Lower Bann Drainage and Navigation Act (Northern Ireland) 1955. The levels are regulated between 12.45 metres to 12.6 metres above Ordnance Datum, as defined in the Lough Neagh (Levels) Scheme 1955 (as amended).