Abstract
AbstractLateral subsurface stormflow (SSF) is the most important runoff generation mechanism for most hillslopes in temperate climates. It is influenced by pedological, biological, and topographic factors that change during landscape evolution, but so far little is known about how SSF changes over long‐time scales. Therefore, we conducted sprinkling experiments on a silicate and carbonate moraine chronosequence in the Swiss Alps. Each chronosequence consisted of four moraines ranging between a couple of decades and ∼13,500 years in age. On each moraine, we installed three plots and measured shallow SSF in a trench. We added tracers (δ2H and NaCl) to the sprinkling water to identify mixing and flow pathways in the subsurface. The coarse and drainable sediments on the young moraines provoked more frequent and larger SSF responses than for the old moraines. There was no SSF during the sprinkling experiments on the older moraines at the calcareous study area, but SSF occurred during larger natural rainfall events. The pre‐event water fractions in SSF were higher for the old moraines than the young moraines due to the increase in silt, clay, and soil organic matter content, and subsequent increase in the amount of water stored in the soil. The results of this study suggest that soil and vegetation development affect SSF characteristics and help—together with the results for overland flow (companion paper; Maier & van Meerveld, 2021, https://doi.org/10.1029/2021WR030221)—to improve hydrological models and our understanding of the changes in near‐surface runoff generation processes during the first millennia of landscape evolution in Alpine areas.
Highlights
Rainfall either infiltrates into the soil or is stored in puddles on the surface and runs off as overland flow (OF)
The median Ksat values were higher at Klausenpass than Sustenpass but this difference was only significant for the second oldest
A similar effect of soil development on subsurface flow (SSF) has been reported by Lohse and Dietrich (2005), who describe the development of a clay layer at 20–50 cm depth and related deceases in Ksat for a 4.1 million year-old Oxisol compared to a young (300 years) Andisol (Ksat of 0.8 and 140 mm hr−1 for the old and the young soil, respectively)
Summary
Rainfall either infiltrates into the soil or is stored in puddles on the surface and runs off as overland flow (OF). The effects of these changes in near-surface conditions on the partitioning of rainfall and SSF generation are still poorly documented Better knowledge of this partitioning and lateral SSF is important because it affects the runoff response at the hillslope scale (Bachmair & Weiler, 2011) and catchment scale, and affects floods (Hümann et al, 2011; Weingartner et al, 2003), hydropower production (Huss et al, 2008; Romerio, 2008; Schaefli et al, 2007), and water resources availability for agriculture and tourism (Beniston, 2012; Viviroli et al, 2003, 2011). It affects water residence and transit times and transport of labile nutrients into surface water bodies (Li et al, 2017; McGlynn & McDonnell, 2003), weathering rates (Brantley et al, 2013; Xiao et al, 2021), and in steep terrain the risk for landslide initiation (Montgomery et al, 1997), and landscape evolution
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