The impact of hillslope groundwater dynamics and landscape functioning in event-flow generation: a field study in the Rietholzbach catchment, Switzerland

von Freyberg, Jana; Rao, P. Suresh C.; Radny, Dirk; Schirmer, Mario

The impact of hillslope groundwater dynamics and landscape functioning in event-flow generation: a field study in the Rietholzbach catchment, Switzerland | Incidence de l’hydrodynamique souterraine des pentes et des fonctionnalités du paysage sur la génération d’un évènement hydrologique: étude de terrain dans le bassin versant du Rietholzbach, Suisse El impacto de la dinámica del agua subterránea de las laderas y el funcionamiento del paisaje en la generación de eventos de flujo: un estudio de campo en la cuenca de Rietholzbach, Suiza 事件流生成中山坡地下水动力学和地形功能的影响:瑞士Rietholzbach流域的一个研究实例 Impacte da dinâmica hidrogeológica em vertentes e do funcionamento da paisagem na geração de eventos de escoamento: um estudo de campo na bacia hidrográfica de Rietholzbach, Suíça

2015

von Freyberg, Jana | Rao, P. Suresh C. | Radny, Dirk | Schirmer, Mario

A reliable prediction of hydrograph responses in mountainous headwater catchments requires a mechanistic understanding of the coupled hydro-climatic processes in these regions. This study shows that only a small fraction of the total area in a pre-Alpine headwater catchment actively regulates streamflow responses to hydro-climatic forcing, which facilitates the application of a parsimonious framework for hydrograph time-series prediction. Based on landscape analysis and hydrometric data from the Upper Rietholzbach catchment (URHB, 0.94 km², northeast Switzerland), a conceptual model was established. Here, the rainfall-event-driven contribution of surface runoff and subsurface flow (event flow) accounts for around 50 % of total river discharge. The event-flow hydrograph is generated from approximately 25 % of the entire area consisting of riparian zones (8 %) and adjacent hillslopes (17 %), each with characteristic streamflow-generating mechanisms. Baseflow generation is attributed to deep groundwater discharge from a fractured-rock aquifer covering ∼75 % of the catchment area. A minimalistic model, that represents event flow as depletion of two parallel linear reservoirs, verified the conceptual model of the URHB with adequate hydrograph simulations (R ² = 0.67, Nash-Sutcliffe efficiency (NSE) = 0.64). Hereby, the expansion of the event-flow contributing areas was found to be particularly significant during long and high-intensity rainfall events. These findings provide a generalized approach for the large-scale characterization of groundwater recharge and hydrological behavior of mountainous catchments with similar landscape properties.

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