Surface water–groundwater exchanges in three dimensions on a backwater of the Rhône River

Abstract

1. Hydrological exchange between the surface stream and the hyporheic zone is well documented in the main channel of rivers, especially at the reach scale. Hydrological processes of advection/convection occur at different scales, and in secondary channels of large rivers little is known about these exchanges in the hyporheic zone on a broad scale (i.e. kilometres). This work studied exchanges of water and biota in a secondary channel on a large scale (4 km), using a three‐dimensional framework. 2. The exchanges of water were described using physicochemical indicators of surface and groundwaters. Samples of water and biota were taken in three dimensions: (i) vertically from benthic (i.e. 0.20 m below the surface of the substratum) to hyporheic (0.50 m) and deep interstitial (1.0 m) zones; (ii) laterally from the right to the left bank (i.e. right, middle and left positions); and (iii) longitudinally from upstream to downstream (seven stations regularly distributed along the channel). 3. The physicochemical indicators clearly revealed hydrological heterogeneity in the longitudinal and vertical dimensions, whereas lateral variability was not significant. 4. Spatial distribution of biota exhibited strong longitudinal variations that were not gradual as predicted by an upstream/downstream continuum, but patchy and discontinuous. No significant differences were found between the three positions across the channel. 5. Analyses of both physicochemical and faunal data sets produced matched ordination of samples and stations, indicating that interstitial–surface flow relationships appear to be an important governing factor in the distribution of interstitial biota at this broad scale. 6. Results are discussed in relation to the hypothetical three‐dimensional models of the hyporheic zone in rivers. Contrasting with other observations on the main channel (where advection/convection patterns are dominated by morphological changes of the river‐bed morphology), it is proposed that water exchanges in backwaters are more likely to be related to local modifications of stream‐bed porosity.

Impact of hydropeaking on hyporheic invertebrates in an Alpine stream (Trentino, Italy)

“…Such variations are confirmed by this study and are shown to propagate to the hyporheic zone, although slightly attenuated, as already demonstrated in several studies in Alpine and other rivers (e.g. Brunke and Gonser, 1997;Dole-Olivier, 1998;Fowler and Scarsbrook, 2002). The thermal alterations related to the hydropeaking waves probably affect the composition of hyporheic assemblages in the Noce Stream.…”

“…In fact, the hyporheic zone may provide a temperature refuge for epigean taxa (Boulton et al, 1998), and high surface water temperature may initiate the movement of some taxa into the hyporheic zone (Fowler and Scarsbrook, 2002). On the other hand, because in natural conditions, hyporheic temperatures are cooler in summer and warmer in winter relative to the water in the channel and less variable (Williams, 1984;Ward, 1994;Dole-Olivier, 1998), the imposed variation to the hyporheic thermal regime might limit the distribution of stygobite taxa.…”

Benthic and hyporheic macroinvertebrate distribution within the heads and tails of riffles during baseflow conditions

“…Dole-Olivier, 1998;Davy-Bowker et al, 2006;Mathers & Wood, 2016), the consequences of flow dynamics at small spatial scales and the associated sedimentary characteristics upon benthic and hyporheic invertebrate assemblages remain poorly quantified (Marmonier et al, 2010(Marmonier et al, , 2012Descloux et al, 2014;Jones et al, 2015). Despite several seminal papers over multiple decades which identified the potential importance of vertical hydraulic connectivity (Orghidan, 1959;Tilzer, 1968;Hynes, 1983), linkages between surface and groundwater and its influence on instream communities remain poorly studied (Boulton et al, 1999;Krause et al, 2011a).…”

Do benthic invertebrates use hyporheic refuges during streambed drying? A manipulative field experiment in nested hyporheic flowpaths

“…These variations in the impact channel were mostly linked to higher specific conductance and VHG as well as lower water oxygenation at the downstream position compared to the upstream position (Figure 3a). Nevertheless, the differences between surface and interstitial water were very weak, and the amplitude of vertical changes in the parameters (Table 2) was minimal compared to other studies in which hyporheic water upwelled mixed with deep groundwater (e.g., the amplitude of vertical change between surface and hyporheic water may reach 200 and~400 μS/cm of specific conductance in two different water bodies of the Rhône River system; Dole-Olivier, 1998;Dole-Olivier et al, 1997).…”