EGU2020-646
https://doi.org/10.5194/egusphere-egu2020-646
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Simulating preferential flow in a two water worlds framework

Jesse Radolinski1, Luke Pangle2, Julian Klaus3, Durelle Scott4, and Ryan Stewart5
Jesse Radolinski et al.
  • 1University of Innsbruck, Institute of Ecology, Austria (jesse.radolinski@uibk.ac.at)
  • 2Georgia State University, Geosciences Department, USA (lpangle@gsu.edu)
  • 3Luxembourg Institute of Science and Technology, Environmental Research and Innovation, Luxemburg (julian.klaus@list.lu)
  • 4Virginia Polytechnic Institute, Department of Biological Systems Engineering USA (dscott@vt.edu)
  • 5Virginia Polytechnic Institute, School of Plant and Environmental Sciences, USA (rds@vt.edu)

Ecohydrological separation has been observed across climates and biomes, and at a fundamental level suggests that water in mobile versus immobile domains may resist mixing over varying periods of time; however little mechanistic evidence exists to explain this separation at a process scale. Non-equilibrium flow in the vadose zone may partially account for widespread perception of distinct hydrological domains yet no studies have weighed its contribution. Using a simple isotope mixing technique, we sought to determine the amount of preferential flow necessary to maintain a two water worlds scenario (i.e., physical separation between mobile and immobile water pools). We constructed 60 cm soil columns (20 cm-ID PVC) containing low soil structure (sieved soil material), subsoil structure (intact B horizon), and soil structure without matrix exchange (tubing reinforced macropores) to simulate multiple preferential flow scenarios. Columns were subjected to 3 rain storms of varying rainfall intensity (~2.5 cm h -1, ~5 cm h -1, and ~11 cm h -1) whose stable isotope signatures oscillated around known baseline values. Isotopic analysis was performed on collected leachate and matrix water sampled via direct vapor equilibration. Preliminary estimates of matrix water indicate up to 100% mixing with infiltrating rain water under low rainfall intensity (2.5 cm h -1) in subsoil structure columns, whereas high intensity rain (11 cm h-1) produced clear separation between columns with intact or artificial soil structure and those controlled for structure (low structure treatment). This separation was confirmed by preferential flow estimates; however minimizing matrix exchange (via artificial macropores) reduced preferential flow by a factor of 4 compared to soil with intact structure. These data suggest that distinct domain separation may only be possible under extreme precipitation intensity; and that exchange with less mobile storage in the soil matrix produces more preferential flow. We intend to use these estimates of preferential flow as a benchmark to understand the prevalence, persistence, and plausibility of ecohydrological separation. As a next step, we will use this conceptual framework to define how recurrent drought, elevated CO2, and warming may alter the partitioning of mobile and immobile water in mountain grasslands.

How to cite: Radolinski, J., Pangle, L., Klaus, J., Scott, D., and Stewart, R.: Simulating preferential flow in a two water worlds framework, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-646, https://doi.org/10.5194/egusphere-egu2020-646, 2019

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