HR: 08:00h
AN: H51J-01 INVITED    [Abstracts]
TI: Monitoring and Modelling the Influence of Overland Flow on Hydrology and Hydrochemistry at Different Scales in Montane Watershed
AU: * Soulsby, C
EM: c.soulsby@abdn.ac.uk
AF: University of Aberdeen, School of Geosciences Elphinstone Road, Aberdeen, AB24 3UF, United Kingdom
AU: Tetzlaff, D
EM: d.tetzlaff@abdn.ac.uk
AF: University of Aberdeen, School of Geosciences Elphinstone Road, Aberdeen, AB24 3UF, United Kingdom
AU: Dunn, S
EM: S.Dunn@macaulay.ac.uk
AF: The Macaulay Institute, Craigiebuckler, Aberdeen, AB15 8QH, United Kingdom
AB: Overland flow is often a significant hydrological process in montane watersheds; however, its contribution to quantity and quality of stream flow during storm responses depends upon factors such as soil cover, topography and precipitation characteristics. Recent work in 18 contrasting mesoscale catchments in the Scottish highlands compared input-output relationships for natural conservative tracers and hypothesised that greater tracer damping largely reflects the diminishing importance of overland flow and other near-surface hydrological flow paths. This hypothesis is supported by very good predictive relationships between the percentage cover of soils likely to generate overland flow (histosols, regosols, sealed surfaces etc.) and tracer-derived descriptors of catchment-scale hydrological function such as mean residence time and annual percentage groundwater contribution to stream flow. Put simply, the greater the coverage of overland flow-dominated soils, the shorter the mean residence times and the lower the groundwater contributions. In this contribution, the hypothesis is further tested by analysis of tracer data and digital soils maps) from the UK Hydrology of Soil Types (HOST) system) of 20 different validation catchments varying between 1km2 and 240km2. Moreover, it is hypothesised that stronger predictive relationships might be derived by considering the distribution of riparian soils that are highly connected to the river channel network. Preliminary results indicate that, in general, the relationships hold; though riparian soil cover is no better a predictor of tracer damping than total catchment soil cover. This may, however, reflect inadequacies in the readily available soil maps or the need for a more sensitive, topographically-based definition of riparian areas. The results of these field campaigns are now being integrated in tracer-aided, semi-distributed hydrological models. The modelling work confirms that fundamentally different mixing relationships need to be considered in catchments where overland flow is a dominant mechanism of storm runoff generation.
DE: 1806 Chemistry of fresh water
DE: 1815 Erosion
DE: 1826 Geomorphology: hillslope (1625)
DE: 1850 Overland flow
SC: Hydrology [H]
MN: 2007 Fall Meeting