Identification of runoff formation with two dyes in a mid-latitude mountain headwater
Lukáš Vlček1, Philipp Schneider2, and Kristýna Falátková11Department of Physical Geography, Charles University, Prague, Czech Republic 2Department of Geography, University of Zurich, Switzerland
Received: 11 Feb 2017 – Accepted for review: 13 Feb 2017 – Discussion started: 17 Feb 2017
Abstract. Subsurface flow in Peat Bog areas and its role in the hydrological 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 flowpaths between both hillslopes could be identified by sprinkling experiments with Brilliant Blue and Sodium-Fluorescein. To our knowledge, this is the first time these two dyes have been compared in their ability to stain preferential flowpaths 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 pipeflow 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 pipeflow, 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.
Vlček, L., Schneider, P., and Falátková, K.: Identification of runoff formation with two dyes in a mid-latitude mountain headwater, Hydrol. Earth Syst. Sci. Discuss., doi:10.5194/hess-2017-77, in review, 2017.