Lough Neagh - United Kingdom

Lough Neagh covers 386 km2 and is by far the largest area of freshwater in the British Isles. Situated in north-east Ireland, it has a drainage basin of 4450 km2, which is shared between Northern Ireland (91%) and the Republic of Ireland (9%). The average water retention time is 15 months. Although large in area, the lake is relatively shallow with a mean depth of 8.9m (max. 25 m). This, combined with its great size and a mild and windy oceanic climate, ensures that the water column is generally well mixed. Lough Neagh is hypertrophic with a mean annual total phosphorus concentration of 160 mg P l-1. Attempts to lower P concentrations in the lough by curtailing point sources of P have been unsuccessful due to increasing inputs from diffuse sources. Levels of P in the lough support large phytoplankton populations with annual chlorophyll a concentrations typically in excess of 60 mg l-1.