HR: 08:20h
AN: H21F-02    [Abstracts]
TI: Influence of Catchment Scale and Landscape Controls on Runoff Sources and Mean Residence Times in Montane Watersheds
AU: * Soulsby, C
EM: c.soulsby@abdn.ac.uk
AF: School of Geosciences, University of Aberdeen, Elphinstone Road, Aberdeen, AB24 3UF United Kingdom
AU: Tetzlaff, D
EM: d.tetzlaff@abdn.ac.uk
AF: School of Geosciences, University of Aberdeen, Elphinstone Road, Aberdeen, AB24 3UF United Kingdom
AU: Waldron, S
EM: s.waldron@geog.gla.ac.uk
AF: University of Glasgow, University Avenue, Glasgow, G12 8QQ United Kingdom
AU: Dunn, S
EM: s.dunn@macaulay.ac.uk
AF: Macaulay Institute, Craigiebuckler, Aberdeen, AB15 8QH United Kingdom
AB: The influence of catchment scale and landscape controls on hydrological sources and mean residence times were assessed in nested sub-basins of 3 separate montane watersheds (30-230km2) in northern Scotland. Geochemical and isotopic tracers were used to carry out chemical hydrograph separations to quantify the relative contribution of different hydrological sources to annual runoff and estimate mean residence times in 24 individual catchments at scales ranging from 0.9km to 230km2. Mean annual groundwater contributions varied between 23 and 54% of annual runoff, and mean residence times varied between 83 days and 443 days. A GIS was used for watershed analysis to assess the relative importance of landscape controls on hydrological sources and residence times. Neither of these hydrological descriptors exhibited significant correlations with catchment scale. Both were influenced by various topographic indices (eg mean slope and flowpath length), but were most strongly related to catchment soil cover mapped using the UK HOST (Hydrology Of Soil Types) national digital data base. Soils could be sub-divided between more hydrologically "responsive" montane soils (eg peats, regosols, and gleysols), which generate storm runoff by overland flow and shallow subsurface storm flow and more "free-draining" soils (eg podsols and inceptisols) that facilitate groundwater recharge. For the 24 catchments, the percentage cover of "responsive soils" was negatively correlated with groundwater contributions to annual flows were (r2 0.58, p <0.0001) and mean residence times (r2 0.82, p<0.0001). The study shows that accurate digital soil maps can provide excellent insights into hydrological functioning in catchments at a range of scales in montane environments. Despite their significance in water resource management as river headwaters, such catchments are often remote and logistically difficult to instrument, particularly at large scales. As soils integrate the effects of heterogeneities in catchment topography, geology, climate and vegetation, the paper will stress that soil maps have considerable potential for rapid impact assessment and modelling studies in ungauged basins in montane areas.
DE: 1625 Geomorphology and weathering (0790, 1824, 1825, 1826, 1886)
DE: 1806 Chemistry of fresh water
DE: 1836 Hydrological cycles and budgets (1218, 1655)
DE: 1860 Streamflow
DE: 1871 Surface water quality
SC: Hydrology [H]
MN: Fall Meeting 2005