UK ECN site. Nant Teyrn is a small upland stream in Yr Wyddfa/Snowdon National Nature Reserve. This ECN freshwater site is co-located with the Yr Wyddfa/Snowdon terrestrial ECN site, which has been in existence since 1997. The site is on the out flow from Llyn Teyrn (an upland lake). The geology of the catchment is nearly all highly acidic rhyolite and dolerite with a small amount of bedded pyroclastics. Some of the water chemistry data are available since 1997 with discharge data collected from the weir since 2000. 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.