Landscape controls of surface-water/groundwater interactions on shallow outwash lakes: how the long-term groundwater signal overrides interannual variability due to evaporative effects

Hokanson, K. J.; Rostron, B. J.; Devito, K. J.; Hopkinson, C.; Mendoza, C. A.

Landscape controls of surface-water/groundwater interactions on shallow outwash lakes: how the long-term groundwater signal overrides interannual variability due to evaporative effects | Contrôles du paysage sur les interactions eau de surface/eau souterraine des lacs fluvio-glaciaires peu profonds: comment le signal long-terme de l’eau souterraine oblitère la variabilité interannuelle causée par les effets de l’évaporation Controles del paisaje de las interacciones entre el agua superficial y el agua subterránea en lagos poco profundos: cómo la señal del agua subterránea a largo plazo prevalece sobre la variabilidad interanual debida a los efectos de la evaporación 浅层冰水沉积湖地表水/地下水相互作用的景观控制: 长期地下水信号如何覆盖蒸发效应引起的年际变化 Controles da paisagem das interações água superficial/subterrânea em lagos de saída rasos: como o sinal de longo prazo da água subterrânea substitui a variabilidade interanual devido aos efeitos evaporativos

2022

Hokanson, K. J. | Rostron, B. J. | Devito, K. J. | Hopkinson, C. | Mendoza, C. A.

The spatial and temporal controls on variability of the relative contributions of groundwater within and between flow systems to shallow lakes in the low-relief glaciated Boreal Plains of Canada were evaluated. Eleven lakes located in a coarse glacial outwash, of varying topographic positions and potential groundwater contributing areas, were sampled annually for stable O and H isotope ratios over the course of 8 years. It was demonstrated that landscape position is the dominant control over relative groundwater contributions to these lakes and the spatial pattern of the long-term isotopic compositions attributed to groundwater overrides interannual variability due to evaporative effects. Lakes at low landscape positions with large potential groundwater capture areas have relatively higher and more consistent groundwater contributions and low interannual variability of isotopic composition. Isolated lakes high in the landscape experience high interannual variability as they have little to no groundwater input to buffer the volumetric or isotopic changes caused by evaporation and precipitation. An alternative explanation that lake morphometry (area and volume) control long-term isotopic compositions is tested and subsequently refuted. Landscape position within coarse outwash is a strong predictor for relative groundwater input; however, surface-water connections can short circuit groundwater pathways and confound the signal. A hydrogeological case study for three of the study lakes is used to contextualize and further demonstrate these results.

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