2000), Groundwater in headwaters: Hydrological and ecological

Abstract: The hydrological and ecological significance of groundwater has generally been under-estimated in headwater catchment studies within the Celtic regions. The paper presents data from headwater catchments in both upland and lowland settings in northern Scotland to address this gap in our understanding. Research in the 10 km 2 Allt a ' Mharcaidh catchment in the western Cairngorms has demonstrated that a range of groundwater sources in various drift deposits can a count for c. 50 % of annual runoff, even in a high altitude headwater stream. Despite the traditional ssumption that upland catchments have limited aquifer storage, oxygen isotope studies of groundwater imply mean water residence times of up to five years which indicate a range of groundwater sources in montane nvironments. Moreover, hydrogeochemical reactions in the saturated zone appear to regulate stream water chemistry at moderate and low flows. In such montane nvironments, groundwater discharges at springs create unique wetland habitats which often form the source of headwater streams and affect riparian areas. In lowland catchments he hydrological significance of groundwater is equally important. In addition, recent studies in a salmon spawning stream in the Newmills Burn, Aberdeenshire has shown that aquifer-strea