Abstract
Abstract. Subsurface flow in peat bog areas and its role in the hydrologic cycle has garnered increased attention as water scarcity and floods have increased due to a changing climate. In order to further probe the mechanisms in peat bog areas and contextualize them at the catchment scale, this experimental study identifies runoff formation at two opposite hillslopes in a peaty mountain headwater; a slope with organic peat soils and a shallow phreatic zone (0.5 m below surface), and a slope with mineral Podzol soils and no detectable groundwater (> 2 m below surface). Similarities and differences in infiltration, percolation and preferential flow paths between both hillslopes could be identified by sprinkling experiments with Brilliant Blue and Fluorescein sodium. To our knowledge, this is the first time these two dyes have been compared in their ability to stain preferential flow paths in soils. Dye-stained soil profiles within and downstream of the sprinkling areas were excavated parallel (lateral profiles) and perpendicular (frontal profiles) to the slopes' gradients. That way preferential flow patterns in the soil could be clearly identified. The results show that biomat flow, shallow subsurface flow in the organic topsoil layer, occurred at both hillslopes; however, at the peat bog hillslope it was significantly more prominent. The dye solutions infiltrated into the soil and continued either as lateral subsurface pipe flow in the case of the peat bog, or percolated vertically towards the bedrock in the case of the Podzol. This study provides evidence that subsurface pipe flow, lateral preferential flow along decomposed tree roots or logs in the unsaturated zone, is a major runoff formation process at the peat bog hillslope and in the adjacent riparian zone.
Highlights
Hydrologic extremes in central Europe during recent decades have stimulated debates over sustainable solutions and suitable, cost-efficient strategies to prevent or mitigate the impacts of droughts and floods
In order to establish the relative roles of peat bog and Podzol in this type of catchment, this study focused on a comparison of runoff formation on contrasting soil types – namely a mountain Histosol/peat bog and a Podzol (PZ) on opposite hillslopes of the Published by Copernicus Publications on behalf of the European Geosciences Union
In extension to our hypothesis, which was based on the conceptual runoff formation model, HOST model A, (Boorman et al, 1995; Figs. 1 and 8) we found that additional lateral subsurface flow in deeper soil horizons occurred at the mineral hillslope PZ2 (Podzol)
Summary
Hydrologic extremes in central Europe during recent decades have stimulated debates over sustainable solutions and suitable, cost-efficient strategies to prevent or mitigate the impacts of droughts and floods. A system of dams and reservoirs, which was built in the Vltava catchment – the main drainage of the Šumava Mts. in the 1960s – failed to prevent major floods in 2002 (Hladný et al, 2005; Hladný, 2009) or 2013 These floods were mainly caused by heavy rainfall in summer or by rain on snow events. Streamflow in peaty catchments is characterized by its quick rise and fall, and huge volatility: very low baseflows during dry periods and spiky storm hydrographs caused by heavy rainfall events (Evans et al, 1999; Holden et al, 2001; Holden, 2005) Most of these studies have focused on pure peat areas only. In order to establish the relative roles of peat bog and Podzol in this type of catchment, this study focused on a comparison of runoff formation on contrasting soil types – namely a mountain Histosol/peat bog and a Podzol (PZ) on opposite hillslopes of the Published by Copernicus Publications on behalf of the European Geosciences Union
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