UK ECN site. Allt a'Mharcaidh is a stream site on the western flank of the Cairngorm Mountains. The catchment area is 998ha and it drains to the River Feshie, a tributary of the River Spey. The catchment rises from 325m at the sampling site to 1111m and is covered by alpine and peaty podsols (60%) and blanket peat (40%). The underlying geology is intrusive biotite-granite of the Lower Old Red Sandstone age. Vegetation is characterised by a heather/fescue grass mixture (90%) with native pinewoods (c. 2%) interspersed along the lowest reaches. The catchment comprises part of the Cairngorm National Nature Reserve and land-use is confined to deer grazing. The stream gradient is steep and exposed bedrock, rapids and waterfalls and large boulders characterise the monitored channel section. Note: this site is a single point sampling location (gauging station) on a river (hence size: 0 ha). The shape file indicates the whole river catchment.The stream site is nested within the Cairngorms National Park LTSER site (http://data.lter-europe.net/deims/site/LTER_EU_UK_059), which also contains the Cairngorms terrestrial ECN site.