UK ECN site. This is a stream site located 80 kilometres from the source of the River Tweed. The catchment area above this site is 150,000 ha. The catchment rises from 92 m at the sampling site to 400 m and is mainly covered by peaty and humus-iron podsols. The underlying geology of the upper Tweed catchment is of shales, mudstones, slates and greywackes. Land cover types for the entire Tweed catchment are improved grassland (26%), rough grassland (16%), woodland (16%), heather/peatland (10%) and arable (18%) although almost all of the latter is found downstream of this site. The River Tweed has an international reputation both as a famous salmon river and an excellent trout water. The Tweed has been designated as a Site of Special Scientific Interest and is recognised as a nationally important example of a relatively nutrient-rich river system showing characteristic hydrological and biological sequences along its length. The upper Tweed has also been designated as a National Scenic Area by Scottish Natural Heritage and there is an Environmentally Sensitive Area designation covering that portion of the catchment in the central Southern Uplands.