HR: 0800h
AN: H51D-0749    [Abstracts]
TI: Characterization of hyporheic exchange, infiltration and exfiltration patterns at the catchment scale
AU: * Szeftel, P
EM: pszeftel@interchange.ubc.ca
AF: Faculty of Forestry, UBC, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada
AU: Weiler, M
EM: markus.weiler@ubc.ca
AF: Faculty of Forestry, UBC, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada
AU: Falda Buscaiot, M
EM: m.falda@hotmail.fr
AF: Faculty of Forestry, UBC, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada
AU: Alila, Y
EM: younes.alila@ubc.ca
AF: Faculty of Forestry, UBC, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada
AB: Field experiments have highlighted runoff contribution and nutrient and pollutant mobilization from hillslopes during rainfall events. This mobilization reduces the amount of minerals availability for plant and tree growth and soil ecosystems in general or affects stream ecosystems by transporting pollutants to the stream network. The saturated zone surrounding the stream network, or hyporheic zone (HZ), has the ability to mix with stream water. This mixing plays a critical role in reducing the effects of the pollutant or nutrient mobilization occurring during infiltration and runoff processes and provides stream organisms with nutrients and minerals. The hyporheic exchanges have been broadly described, highlighting processes occurring from the pore scale to few tenths of kilometers in length. Investigating in the HZ usually involves tracer experiments that are time and labor intensive and the outcome might have limited value across variable systems due to site specificity of these experiments. We propose a systematic approach based on reach scale tracer experiments to assess the ability of a given hyporheic system to retain nutrients released by its surrounding hillslopes, using readily available DEM-derived topographic parameters. The stream network of a 3.3km2 snow-dominated watershed has been split into 20 reaches each roughly 200m in length to investigate short time-space scale subsurface flow-paths within the HZ. For every reach, NaCl was injected into the stream at the upper boundary, following the slug injection method and the resulting breakthrough curve was recorded at its lower boundary. Three runs each consisting of 20 reach scale experiments were carried out at various hydrological regimes in order to investigate the influence of stream discharge on hyporheic exchanges. The OTIS model, based on a first order mass transfer between the HZ and the stream water was applied and Monte Carlo simulations were carried out to derive the best set of parameters and their related uncertainty that would characterize the hyporheic exchanges for a given reach (i.e. cross section of the HZ and mass transfer coefficient). The first step of the analysis highlights the spatiotemporal variability of the hyporheic exchanges from the headwaters to the outlet of the whole basin. In a second step, a potential correlation is investigated between the hyporheic exchange parameters output of OTIS and the topographic parameters derived from a DEM.
DE: 1830 Groundwater/surface water interaction
DE: 1847 Modeling
DE: 1856 River channels (0483, 0744)
DE: 1879 Watershed
SC: Hydrology [H]
MN: 2007 Fall Meeting