Loch Coire nan Arr - United Kingdom

Loch Coire nan Arr lies in a deep sandstone corrie at 125 m altitude. The loch covers an area of 11.6 ha and receives drainage at its northern end from the Allt Coire nan Arr and elsewhere along the loch from a series of small precipitous inflows. The loch drains 2 km to the sea via the Russell Burn. The loch has a very simple bathymetric profile with a single basin reaching 12 m at the deepest point. In 1991 a temporary dam was placed on the outflow in order to preserve the water supply for a fish farm located downstream from the loch. This structure was replaced by a permanent sluiced dam that has raised water levels within the site by at least 0.5m. Since this dam was constructed water levels have fluctuated far more than in the past, resulting in significant changes in the loch's aquatic macrophyte communities. This disturbance is the reason that a second site in the same remote area of north west Scotland was chosen for monitoring, Loch Coire Fionnaraich, which has now fully replaced Loch Coire nan Arr.