UK ECN site. Loch Leven is the largest, shallow, relatively nutrient-rich, lowland loch (lake) in Scotland. It lies at an altitude of 107m. It has a surface area of 13.3km2 and has a mean depth of 3.9m. The Loch Leven catchment covers 145 km2, consisting mainly of arable crops and improved pasture. Loch Leven is particularly renowned for its large numbers of migratory, breeding and overwintering waterfowl and its world famous brown trout fishery. Although the overall quality of the site is good, the loch has suffered from periodic cyanobacterial (‘blue-green algal’) blooms for many years. These have occurred, largely, as a result of substantial amounts of phosphorus entering the loch, combined with a relatively low flushing rate and a favourable light-climate.