Facility
Llyn Llagi Catchment

Falling within the Snowdonia National Park, the Llyn Llagi catchment covers 152 ha and reaches a maximum altitude of 672 m. The lake and its catchment receive an annual rainfall of c. 3000 mm. The geology consists primarily of Ordovician slates and shales of the Glanarfon series. The backwall is composed of a large doleritic intrusion with small intrusions of fine microgranites and volcanic tuff. Away from the precipitous bare rock of the backwall the catchment soils are chiefly stagnopodsols interspersed with blanket peats. The catchment is unafforested and characterised by acid moorland species, The lake lies at 380 m beneath a steep backwall and comprises a deep, almost circular basin (maximum depth 16.5 m) bordered by an extensive shallow (1 m deep) rim. The lake covers an area of 5.67ha and the primary inflow constitutes the outflow stream from Llyn yr Adar. The lake drains to the north-west to the Nanmor valley. The lake and much of the catchment lie within a designated Site of Special Scientific Interest (SSSI). Llyn Llagi is classified as having high acid deposition. Llyn Llagi is part of the UNECE International Cooperative Programme on Assessment and Monitoring of Acidification of Rivers and Lakes and hosts a bulk deposition collector for the UK Eutrophying and Acidifying atmospheric Pollutants (UKEAP) network. UK Upland Waters Monitoring Network data from Llyn Llagi are contributed to the UK Environmental Change Network, the European Long-Term Ecosystem Research Network (LTER Europe) and the International Long Term Ecological Research (ILTER) programme. The lake has been designated as a site in the Environment Agency's Water Framework Directive Lake Surveillance Network.