Velocity–discharge Relationships Derived From Dye Tracer Experiments in Glacial Meltwaters: Implications for Subglacial Flow Conditions

Mixing law versus discharge and electrical conductivity relationships: application to an alpine proglacial stream

“…This behaviour is consistent with a contribution of mineralised water during daily floods attributed to flow in the subglacial network or in the basal sediments (Fairchild et al, 1999b). Previous studies of suspended sediment concentration (Richards and Moore, 2003) and through-flow velocity (Nienow et al, 1996) have led to similar conclusions. Our results were similar to those reported by Brown et al (2006) for a glaciated Alpine river basin, in that the Baounet proglacial stream is supplied by a combination of groundwater, subglacial, and englacial flows.…”

Mixing law versus discharge and electrical conductivity relationships: application to an alpine proglacial stream

“…This behaviour is consistent with a contribution of mineralised water during daily floods attributed to flow in the subglacial network or in the basal sediments (Fairchild et al, 1999b). Previous studies of suspended sediment concentration (Richards and Moore, 2003) and through-flow velocity (Nienow et al, 1996) have led to similar conclusions. Our results were similar to those reported by Brown et al (2006) for a glaciated Alpine river basin, in that the Baounet proglacial stream is supplied by a combination of groundwater, subglacial, and englacial flows.…”

Diurnal variability of subglacial drainage conditions as revealed by tracer experiments

“…[45] In general, the values of transport parameters obtained from tracer injections into a moulin at Unteraargletscher, Switzerland, are within the range found in previous studies [e.g., Collins, 1982;Seaberg et al, 1988;Willis et al, 1990;Fountain, 1993;Hock and Hooke, 1993;Kohler, 1995;Nienow et al, 1996b] and indicate drainage through a hydraulically efficient channel system. However, our results display a pronounced diurnal variability in terms of transit velocity and tracer dispersion, which, if single tests are conducted at coarse temporal intervals, may lead to false conclusions about the structure of the drainage system.…”

“…[46] In line with findings of previous studies [Collins, 1982;Hock and Hooke, 1993;Nienow et al, 1996b], the inference of hydraulic conditions was complicated by the wide scatter in the observed vQ relationships that rendered conventional interpretation techniques inapplicable. However, the systematic pattern displayed by the scatter enabled us to infer two alternative explanations for our observations.…”

“…It is clear that the determination of such a function as done in previous studies [e.g., Seaberg et al, 1988;Hock and Hooke, 1993;Fountain, 1993;Kohler, 1995] would be highly sensitive to the choice of the function, thereby reducing the reliability of the result. Nienow et al [1996b] have observed similar scattering and found that if the chronological order of the data is taken into account, the sequence reveals a conspicuously systematic behavior. Figures 10b and 10d illustrate how the vQ relationship follows distinct trajectories through a discharge cycle.…”

Conduit roughness and dye-trace breakthrough curves: why slow velocity and high dispersivity may not reflect flow in distributed systems

“…These velocities are less than the criterion of <0.5 m s -1 assumed to indicate distributed systems (Nienow and others, 1998; Mair and others, 2002) but were generated in a conduit at Rieperbreen. Similar results of flow less than 0.5 m s -1 have been found in drainage systems that were presumed to have been conduit-dominated (Nienow and others, 1996;Schuler and others, 2004), but the decrease in velocities could not be unambiguously established since the conduit size and morphology were unknown. Possible causes of changes in BTCs in these studies are changes in hydraulic gradient, changes in roughness, or conduit enlargement and creep.…”

Mixing law versus discharge and electrical conductivity relationships: application to an alpine proglacial stream

“…This behaviour is consistent with a contribution of mineralised water during daily floods attributed to flow in the subglacial network or in the basal sediments (Fairchild et al, 1999b). Previous studies of suspended sediment concentration (Richards and Moore, 2003) and through-flow velocity (Nienow et al, 1996) have led to similar conclusions. Our results were similar to those reported by Brown et al (2006) for a glaciated Alpine river basin, in that the Baounet proglacial stream is supplied by a combination of groundwater, subglacial, and englacial flows.…”

Diurnal variability of subglacial drainage conditions as revealed by tracer experiments

“…[45] In general, the values of transport parameters obtained from tracer injections into a moulin at Unteraargletscher, Switzerland, are within the range found in previous studies [e.g., Collins, 1982;Seaberg et al, 1988;Willis et al, 1990;Fountain, 1993;Hock and Hooke, 1993;Kohler, 1995;Nienow et al, 1996b] and indicate drainage through a hydraulically efficient channel system. However, our results display a pronounced diurnal variability in terms of transit velocity and tracer dispersion, which, if single tests are conducted at coarse temporal intervals, may lead to false conclusions about the structure of the drainage system.…”

“…[46] In line with findings of previous studies [Collins, 1982;Hock and Hooke, 1993;Nienow et al, 1996b], the inference of hydraulic conditions was complicated by the wide scatter in the observed vQ relationships that rendered conventional interpretation techniques inapplicable. However, the systematic pattern displayed by the scatter enabled us to infer two alternative explanations for our observations.…”

“…It is clear that the determination of such a function as done in previous studies [e.g., Seaberg et al, 1988;Hock and Hooke, 1993;Fountain, 1993;Kohler, 1995] would be highly sensitive to the choice of the function, thereby reducing the reliability of the result. Nienow et al [1996b] have observed similar scattering and found that if the chronological order of the data is taken into account, the sequence reveals a conspicuously systematic behavior. Figures 10b and 10d illustrate how the vQ relationship follows distinct trajectories through a discharge cycle.…”

Conduit roughness and dye-trace breakthrough curves: why slow velocity and high dispersivity may not reflect flow in distributed systems

“…These velocities are less than the criterion of <0.5 m s -1 assumed to indicate distributed systems (Nienow and others, 1998; Mair and others, 2002) but were generated in a conduit at Rieperbreen. Similar results of flow less than 0.5 m s -1 have been found in drainage systems that were presumed to have been conduit-dominated (Nienow and others, 1996;Schuler and others, 2004), but the decrease in velocities could not be unambiguously established since the conduit size and morphology were unknown. Possible causes of changes in BTCs in these studies are changes in hydraulic gradient, changes in roughness, or conduit enlargement and creep.…”

Mixing law versus discharge and electrical conductivity relationships: application to an alpine proglacial stream

“…This behaviour is consistent with a contribution of mineralised water during daily floods attributed to flow in the subglacial network or in the basal sediments (Fairchild et al, 1999b). Previous studies of suspended sediment concentration (Richards and Moore, 2003) and through-flow velocity (Nienow et al, 1996) have led to similar conclusions. Our results were similar to those reported by Brown et al (2006) for a glaciated Alpine river basin, in that the Baounet proglacial stream is supplied by a combination of groundwater, subglacial, and englacial flows.…”

Diurnal variability of subglacial drainage conditions as revealed by tracer experiments

“…[45] In general, the values of transport parameters obtained from tracer injections into a moulin at Unteraargletscher, Switzerland, are within the range found in previous studies [e.g., Collins, 1982;Seaberg et al, 1988;Willis et al, 1990;Fountain, 1993;Hock and Hooke, 1993;Kohler, 1995;Nienow et al, 1996b] and indicate drainage through a hydraulically efficient channel system. However, our results display a pronounced diurnal variability in terms of transit velocity and tracer dispersion, which, if single tests are conducted at coarse temporal intervals, may lead to false conclusions about the structure of the drainage system.…”

“…[46] In line with findings of previous studies [Collins, 1982;Hock and Hooke, 1993;Nienow et al, 1996b], the inference of hydraulic conditions was complicated by the wide scatter in the observed vQ relationships that rendered conventional interpretation techniques inapplicable. However, the systematic pattern displayed by the scatter enabled us to infer two alternative explanations for our observations.…”

“…It is clear that the determination of such a function as done in previous studies [e.g., Seaberg et al, 1988;Hock and Hooke, 1993;Fountain, 1993;Kohler, 1995] would be highly sensitive to the choice of the function, thereby reducing the reliability of the result. Nienow et al [1996b] have observed similar scattering and found that if the chronological order of the data is taken into account, the sequence reveals a conspicuously systematic behavior. Figures 10b and 10d illustrate how the vQ relationship follows distinct trajectories through a discharge cycle.…”

Conduit roughness and dye-trace breakthrough curves: why slow velocity and high dispersivity may not reflect flow in distributed systems

“…These velocities are less than the criterion of <0.5 m s -1 assumed to indicate distributed systems (Nienow and others, 1998; Mair and others, 2002) but were generated in a conduit at Rieperbreen. Similar results of flow less than 0.5 m s -1 have been found in drainage systems that were presumed to have been conduit-dominated (Nienow and others, 1996;Schuler and others, 2004), but the decrease in velocities could not be unambiguously established since the conduit size and morphology were unknown. Possible causes of changes in BTCs in these studies are changes in hydraulic gradient, changes in roughness, or conduit enlargement and creep.…”