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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Hyporheic Processes
A TEST OF THE HYPORHEIC CORRIDOR CONCEPT IN A HEADWATER RIVER FLOOD PLAIN.
F. Malard1, D. Ferreira1, S. Doledec1, and J.V. Ward2. 1Department of Fluvial Hydrosystems, University Claude Bernard, Lyon, France, 2Department of Limnology, EAWAG/ETH, 8600 Duebendorf, Switzerland
Following the predictions of the hyporheic corridor concept, we hypothesized that increased hydrological connection between surface water and groundwater would increase the diversity and density of the hyporheos at the downstream end of a glacial floodplain having an extensive upwelling zone and a distinct annual expansion – contraction cycle. Hyporheic water and invertebrates were collected during the 4 different phases of the expansion-contraction cycle in 28 channel sites. We used the STATIS multivariate method and ANOVA to test for differences in the concentration of nutrients and composition of the hyporheos between the upper and lower parts of the floodplain. Density and taxonomic richness were significantly higher in the upwelling zone, essentially because of an increase in the number and density of taxa belonging to the permanent hyporheos and true groundwater fauna. Despite downwelling of surface glacial water at multiple locations during the pulsing of discharge, the longitudinal pattern of hyporheic assemblages was remarkably stable over time. We concluded that the strength of hydrological connections between surface water and groundwater had a major influence on the diversity and density of the hyporheos by controlling not only the degree of flow permanency but also the recolonization pathways of streambed sediments.
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