There are over 12,000 lakes in Ireland. Due to past glaciation activity these are primarily located along the western seaboard and in the centre of Ireland, with relatively few in the east of the country. They are mostly shallow (<5m mean depth) well-mixed lakes and, due to their proximity to the Atlantic Gulf Stream, they are not exposed to extremes of temperature.

High rainfall and relatively little disturbance has ensured that our lakes are overall of good ecological quality. Recently, however, nutrient loading pressures have become more noticeable and increased research and monitoring of lakes has been undertaken in response.

Irish lakes are predominantly natural salmonid (salmon and trout) waters indicative of good ecological status. The large limestone lakes of the midlands hold good stocks of brown trout and the many thousands of smaller lakes in the upland blanket bog regions along the west coast hold stocks of brown trout, sea trout and salmon. Arctic char are present in a few of these lakes.  The good or high ecological quality required to sustain salmonid fish stocks in these lakes also favours other water uses such as abstraction for drinking water supplies, water contact sports and other recreational uses.