Delineation of spatial-temporal patterns of groundwater/surface-water interaction along a river reach (Aa River, Belgium) with transient thermal modeling

Anibas, Christian; Tolche, AbebeDebele; Ghysels, Gert; Nossent, Jiri; Schneidewind, Uwe; Huysmans, Marijke; Batelaan, Okke

Delineation of spatial-temporal patterns of groundwater/surface-water interaction along a river reach (Aa River, Belgium) with transient thermal modeling | Délimitation des modalités spatio-temporelles d’interactions entre eaux souterraines et eaux de surface le long d’une rivière (rivière Aa, Belgique) à l’aide d’une modélisation thermique en régime transitoire Delimitación de los patrones espacio-temporales de la interacción agua subterránea/agua superficial a lo largo de un río (Aa River, Bélgica) con un modelado térmico transitorio 采用瞬时热建模描述沿河段(比利时Aa河)地下水-地表水相互作用时空模式 Delineamento de padrões espaço-temporais de interação águas subterrâneas/águas superficiais ao longo de um trecho de rio (Rio Aa, Bélgica) com modelagem termal transiente

2018

Among the advances made in analytical and numerical analysis methods to quantify groundwater/surface-water interaction, one methodology that stands out is the use of heat as an environmental tracer. A large data set of river and riverbed temperature profiles from the Aa River in Belgium has been used to examine the spatial-temporal variations of groundwater/surface-water interaction. Exchange fluxes were calculated with the numerical heat-transport code STRIVE. The code was applied in transient mode to overcome previous limitations of steady-state analysis, and allowed for the calculation of model quality. In autumn and winter the mean exchange fluxes reached −90 mm d⁻¹, while in spring and early summer fluxes were −42 mm d⁻¹. Predominantly gaining conditions occurred along the river reach; however, in a few areas the direction of flow changed in time. The river banks showed elevated fluxes up to a factor of 3 compared to the center of the river. Higher fluxes were detected in the upstream section of the reach. Due to the influence of exchange fluxes along the river banks, larger temporal variations were found in the downstream section. The exchange fluxes at the river banks seemed more driven by variable local exchange flows, while the center of the river was dominated by deep and steady regional groundwater flows. These spatial and temporal differences in groundwater/surface-water exchange show the importance of long-term investigations on the driving forces of hyporheic processes across different scales.

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