ABSTRACT
Freshwaters in the form of headwater stream systems and lakes are an intrinsic part of the upland landscape. These waters are characterised by generally dilute, nutrient-poor, well-oxygenated chemical conditions with high biodiversity values including species and communities distinct from those found in lowland systems. They also contribute a range of important ecosystems services including recreation and water supply, with some 60 per cent of UK water supply sourced from the uplands. Surface waters in upland environments are often assumed to be pristine and minimally impacted by anthropogenic pressures or pollution, and this can indeed be the case in remote regions. Nevertheless, upland waters are highly sensitive to environmental change in general, and atmospheric processes in particular, and in many regions have experienced significant levels of environmental degradation.
