HR: 0800h
AN: H21A-0174    [Abstracts]
TI: Runoff generation in SE Spain
AU: Dalen, E N
EM: e.n.dalen04@leeds.ac.uk
AF: School of Geography, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, United Kingdom
AU: * Kirkby, M J
EM: m.j.kirkby@leeds.ac.uk
AF: School of Geography, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, United Kingdom
AU: Chapman, P J
EM: p.j.chapman@leeds.ac.uk
AF: School of Geography, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, United Kingdom
AU: Bracken, L J
EM: l.j.bracken@durham.ac.uk
AF: Deaprtment of Geography, Durham University, South Road, Durham, DH1 3LE, United Kingdom
AB: We are working to improve a hydrological model for prediction of runoff in medium-scale semi-arid catchments in SE Spain. The aim is to develop and improve understandings of runoff generation in semi-arid areas and to improve modelling of runoff. Objectives are to investigate the influence of geology, landuse and seasonality on infiltration rates and use remonte sensing (RS) and GIS to classify an area into Hydrologically Similar Surfaces (HYSS) categories. The research includes investigating the impact of different landscape elements on runoff within two 150 km2 catchments, the Rambla Nogalte and the Rambla de Torrealvilla. Most storms within these catchments are of short duration. HYSS are defined as areas with similar1-D (vertical) partitioning of net rainfall between infiltration and overland flow. HYSS are identified from field measurements of soils, micro and macro- topography and infiltration rates; then combined with analysis of multi-spectral airborne RS images. HYSS are selected to minimise internal variability in the relationship between rainfall and local runoff generation and are scaled up to cover larger areas. The overall sampling strategy for measurements has been to undertake constant intensity rainfall simulator measurements within provisional HYSS categories, and to augment this with a large number of minidisk infiltrometer measurements. This strategy captures as much of the variability in the landscape as possible. The wide variability within even small areas has led to the final adoption of only a few large classes that can be effectively distinguished. The final part of the research is to link the spatial partitioning of the two catchments into HYSS with the detailed rainfall records for the areas, and combine these two sets of data into a grid-based model for runoff generation across the area. The applied Green-Ampt modelling approach gave 63 possible combinations of surface properties (9 HYSS) and areas in the Rambla Nogalte each represented by a raingauge (7). The model was initially run with uniform rainfall over the catchment, next the model was run for selected storms using collected rainfall data. Selected storms were either intense short duration rainfall, or records with several days of precipitation. Soil moisture was stored in the surface layer over days, since the evaporation needs time and temperature to be effective and dry the upper soil layer. The data from the model runs have been linked to the map of HYSS categories, and the resulting map of at a point runoff gave an indication of potential runoff in the catchments.
DE: 1809 Desertification
DE: 1826 Geomorphology: hillslope (1625)
DE: 1838 Infiltration
DE: 1850 Overland flow
SC: Hydrology [H]
MN: 2007 Fall Meeting