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Titel |
Investigating temporal and spatial patterns of groundwater-surface water
interaction on a river reach by applying transient thermal modelling |
VerfasserIn |
Christian Anibas, Abebe Debele Tolche, Gert Ghysels, Uwe Schneidewind, Jiri Nossent, Syed Md Touhidul Mustafa, Marijke Huysmans, Okke Batelaan |
Konferenz |
EGU General Assembly 2017
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Medientyp |
Artikel
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Sprache |
en
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 19 (2017) |
Datensatznummer |
250143087
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Publikation (Nr.) |
EGU/EGU2017-6783.pdf |
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Zusammenfassung |
The quantification of groundwater-surface water interaction is an important challenge for
hydrologists and ecologists. Within the last decade, many new analytical and numerical
estimation methods have been developed, including heat tracer techniques. In a number of
publications, their sources of errors were investigated, and future directions for the research
in groundwater-surface water exchange were discussed. To improve our respective knowledge
of the Belgian lowland Aa River we reinvestigate temperature data which was gathered in the
river bed and used for the quantification of the 1D vertical groundwater-surface water
exchange. By assuming a thermal steady state of the river bed temperature distribution,
Anibas et al. (2011) were unable to use the full potential of the entire large data set. The
analysis tool STRIVE is modified to use the river water temperature time series as
the upper model boundary. This transient thermal set up overcomes many of the
limitations of the steady state assumption and allows for the analysis of vertical 1D
exchange fluxes in space and time. Results of about 380 transient simulations covering
a period of more than 1.5 years show high absolute changes in exchange fluxes
in the upstream part of the river. However, in the downstream part, the relative
changes in fluxes are larger. The 26 spatially distributed thermal profiles along the
river reach are interpolated using kriging based on variograms calculated from the
temperature dataset. Results indicate gaining conditions for most locations and
most of the time. Few places in the downstream part show losing conditions in late
winter and early spring. While in autumn and winter the mean exchange fluxes
can be -90 mmd−1, in spring to early summer fluxes are only -42 mmd−1. The
river bed near the banks shows elevated fluxes compared to the center of the river.
Probably driven by regional groundwater flow, the river bed near the left and right bank
shows fluxes respectively a factor 3 and 2 higher than at the center of the river. The
transient model allows for the calculation of model quality (like the RMSE) and can be
used for data sets collected at any time during the year. The flux results represent
integrations over the simulated period (i.e. weeks or month); short time changes in
groundwater-surface water interaction cannot be estimated. With the adapted STRIVE
model, future research can focus on the role of heterogeneity of the riverbed and
better integration of riverbed parameters like hydraulic and thermal conductivities. |
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