Heterogeneity of groundwater-surface water ecotones

Vaněk, V.

doi:10.1017/cbo9780511753381.020

Cited by 15 publications

(15 citation statements)

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“…The depression of the water table that occurred in the centre of the meander bends is probably the result of evapotranspiration by the dense vegetation cover exceeding the advection of stream water. Local lowering of the water table and changes in groundwater flow direction resulting from evapotranspration has also been reported by Vanek (1997). Consistency in chloride patterns between the two distinct flow patterns also suggests a low lateral seepage of stream water because the increase in advection of stream water into the meander bends expected from the shift in flow patterns did not translate into a change in the pattern of chloride concentrations.…”

Section: Discussionsupporting

confidence: 63%

Instream restoration: its effects on lateral stream–subsurface water exchange in urban and agricultural streams in Southern Ontario

Kasahara

Hill

2007

River Research & Apps

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Instream restoration strategies do not generally consider the subsurface environment. The study of recently restored stream reaches can provide an opportunity to assess the impacts of restoration on surface-subsurface exchange. In this study, lateral hyporheic zones occurring in a constructed gravel bar and re-meandered stream reach were examined, using hydrometric data in combination with differences in background conservative ion and tracer injection experiments. Both the constructed gravel bar and the meander bends induced lateral hyporheic exchange flow. In the gravel bar, lateral hyporheic exchange increased after a riffle-pool sequence was constructed in the channel adjacent to the bar. The substrate in the meander bends had low saturated hydraulic conductivity, and the stream-subsurface exchange was limited despite the large change in channel configuration. These results suggest that to enhance and maintain stream-subsurface water exchanges, restoration projects that modify horizontal geometry should involve construction of vertical morphologic features, and where floodplain sediments are fine-grained, the addition of coarse sediments should also be incorporated in the design.

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Section: Discussionsupporting

confidence: 63%

Instream restoration: its effects on lateral stream–subsurface water exchange in urban and agricultural streams in Southern Ontario

Kasahara

Hill

2007

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“…The restoration also improved the quality of bottom sediments, with an increase in the depth of hypoxia, low nitrite and low ammonium contents inside sediments. Vanek (1997) and Gayraud and Philippe (2003) have already observed that a decrease in fine sediment contents (and the resulting increase in gravel porosity) induced increasing exchanges between surface and interstitial waters and changes in biological processes (Hendricks and Rice, 2000). In agricultural areas, inputs of fine sediments and organic matter increase in rivers (Vitousek et al, 1997), which induces a physical clogging of interstices and a biological colmation through excessive growth of biofilm (Dahm et al, 1998;Brunke, 1999).…”

Section: Effects Of the Restoration On The Surface-sediment Connectivitymentioning

confidence: 99%

Effects of bottom sediment restoration on interstitial habitat characteristics and benthic macroinvertebrate assemblages in a headwater stream

Sarriquet

Bordenave

Marmonier

2007

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The restoration of in-stream habitats by structural improvement of stream beds is more and more frequent, but the ecological consequences of such works are still little known. We have examined the influence of the deposit of a 15 cm gravel layer over the stream bottom on the chemical characteristics of the interstitial water, the sediment grain size and the composition of the benthic assemblages. We have compared a restored reach to an upstream control over three years and at three seasons each year. Dissolved oxygen, ammonium, nitrite and nitrate contents were measured in both surface and interstitial (À15 cm deep) waters, together with the depth of anoxia estimated using wooden stakes and fine sediment content at the surface. During the same period and seasons, benthic invertebrates were sampled at five points in each reach. The restoration induced an increase in vertical exchanges of water between surface and interstitial habitats, with an increase in the depth of hypoxia. Changes were observed in the composition of invertebrate communities, but not in the density or in the taxonomic richness of assemblages. These changes in assemblages were fragile: a local disturbance (such as a drying period) diminished the beneficial effect of the restoration with the disappearance of several organisms. The viability of such restoration works may be associated with catchment management designed to reduce fine sediment inputs to the river.

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“…For example, a rise in river level can result in water infiltrating a previously unsaturated region, which may not exhibit the same removal properties as the permanently saturated zone (44). Variability in pore water velocity and the corresponding retention time, caused by changes in both the hydraulic gradient and the alluvial hydraulic conductivity, may also limit biogeochemical activity in the hyporheic zone (45). Furthermore, in a study conducted in the riverbed of the Rhine River at the Flehe waterworks in central Germany, Schubert et al found that the river flow dynamics influenced the breadth and permeability of the clogged regions (44).…”

Section: Hydrology Influences Performancementioning

confidence: 99%

“…Diurnal or seasonal fluctuations in surface water temperature also contribute to the temporal heterogeneity of alluvial aquifers (45). Because the rate of most biogeochemical processes is highly sensitive to temperature, variations in water temperature may lead to decreased microbial activity.…”

Section: Hydrology Influences Performancementioning

confidence: 99%

“…Changes in water temperature can also affect the rate of infiltration into the alluvial aquifer (46). With a rise in temperature, water viscosity decreases, and therefore, hydraulic conductivity increases (45,47 ). The dynamic nature of conditions and processes at the surface watergroundwater interface suggests that feasibility and performance studies of a riverbank filtration facility should be conducted over extended time periods (44).…”

Section: Hydrology Influences Performancementioning

confidence: 99%

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