 |
| Titel |
Investigating riparian groundwater flow close to a losing river using diurnal temperature oscillations at high vertical resolution |
| VerfasserIn |
T. Vogt, M. Schirmer, O. A. Cirpka |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1027-5606
|
| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 16, no. 2 ; Nr. 16, no. 2 (2012-02-14), S.473-487 |
| Datensatznummer |
250013177
|
| Publikation (Nr.) |
 copernicus.org/hess-16-473-2012.pdf |
|
|
|
|
|
| Zusammenfassung |
| River-water infiltration is of high relevance for hyporheic and riparian
groundwater ecology as well as for drinking water supply by river-bank
filtration. Heat has become a popular natural tracer to estimate exchange
rates between rivers and groundwater. However, quantifying flow patterns and
velocities is impeded by spatial and temporal variations of exchange fluxes,
insufficient sensors spacing during field investigations, or simplifying
assumptions for analysis or modeling such as uniform flow. The objective of
this study is to investigate lateral shallow groundwater flow upon
river-water infiltration at the shoreline of the riverbed and in the
adjacent riparian zone of the River Thur in northeast Switzerland. Here we
have applied distributed temperature sensing (DTS) along optical fibers
wrapped around tubes to measure high-resolution vertical temperature
profiles of the unsaturated zone and shallow riparian groundwater. Diurnal
temperature oscillations were tracked in the subsurface and analyzed by
means of dynamic harmonic regression to extract amplitudes and phase angles.
Subsequent calculations of amplitude attenuation and time shift relative to
the river signal show in detail vertical and temporal variations of heat
transport in shallow riparian groundwater. In addition, we apply a numerical
two-dimensional heat transport model for the unsaturated zone and shallow
groundwater to obtain a better understanding of the observed heat transport
processes in shallow riparian groundwater and to estimate the groundwater
flow velocity. Our results show that the observed riparian groundwater
temperature distribution cannot be described by uniform flow, but rather by
horizontal groundwater flow velocities varying over depth. In addition, heat
transfer of diurnal temperature oscillations from the losing river through
shallow groundwater is influenced by thermal exchange with the unsaturated
zone. Neglecting the influence of the unsaturated zone would cause biased
interpretation and underestimation of groundwater flow velocities. The
combination of high resolution field data and modeling shows the complex
hydraulic and thermal processes occurring in shallow riparian groundwater
close to losing river sections as well as potential errors sources for
interpreting diurnal temperature oscillations in such environments. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|