Hydrological modeling of transport phenomena at the Landscape Evolution Observatory
Monday, October 5, 2015
Carlotta Scudeler1,2, Luke A Pangle3, Damiano Pasetto1, Guo-Yue Niu3, Claudio Paniconi2, Mario Putti1 and Peter A A Troch3, (1)University of Padua, Department of Mathematics, Padua, Italy, (2)Institut National de la Recherche Scientifique-Eau Terre Environnement INRS-ETE, Quebec City, QC, Canada, (3)University of Arizona, Tucson, AZ, United States
Abstract:
Accurate description of flow and transport phenomena in unsaturated soils is a challenging problem in hydrological modeling, in particular when trying to capture both integrated fluxes over the entire control volume and spatially distributed response variables. Here we report on a modeling analysis of the second experiment (first tracer experiment) at the Landscape Evolution Observatory (LEO) of the Biosphere 2 facility in Oracle, Arizona. The experiment included three irrigation applications over one of the LEO landscapes - the second application utilized deuterium-enriched water (60‰ enrichment) as a tracer. Data collection included spatially-distributed measures of the volume and tracer concentration within the soil water, total water storage within the landscape, and integrated fluxes of water and tracer through the seepage face at the downslope boundary. Even with the rain pulses, quite dry conditions prevailed over the landscape for the duration of the experiment. Numerical simulations were performed with the CATHY (CATchment HYdrology) model, a distributed physically-based model that solves the three-dimensional Richards equation for flow and the advection-dispersion equation for solute transport under variably saturated conditions. For the first LEO experiment the modeling analysis, performed in a systematic way via Monte Carlo simulations, showed that using just integrated flow measurements (seepage face flow, total storage, and overland flow), satisfactory results are obtainable with a parameterization which is not overly complex [Niu et al., 2014]. For the second experiment, on the other hand, when simultaneously looking at integrated and point-scale flow and transport responses, the task became much more complicated. This study allowed us to analyze how model complexity envolves with process complexity. We found that in passing from integrated to point-scale response it was necessary to augment the degree of heterogeneity of the soil hydraulic parameters and that the heterogeneous parameterization used for the point-scale response did not satisfy the integrated (flow) observation dataset. There is also evidence that the model used is not adequate to simulate the full complexity of solute transport response for this second LEO experiment involving tracer injection into a dry soil.
