Dynamic domain kinematic modeling for predicting interflow over leaky impeding layers

Authors: Meles, Menberu; JACKSON, C.R. - University Of Georgia; Goodrich, David; YOUNGER S.E. - University Of Georgia; GRIFFITHS, N.A. - Oak Ridge National Laboratory; VACHÉ, K.B. - Oregon State University; RAU, B. - Us Forest Service (FS)

Submitted to: Hydrological Processes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/8/2020
Publication Date: 5/25/2020
Citation: Meles, M.B., Jackson, C., Goodrich, D.C., Younger S.E., Griffiths, N., Vaché, K., Rau, B. 2020. Dynamic domain kinematic modeling for predicting interflow over leaky impeding layers. Hydrological Processes. 34(13):2895-2910. https://doi.org/10.1002/hyp.13778.
DOI: https://doi.org/10.1002/hyp.13778

Interpretive Summary: Representing complex flow regimes and the effects of impeding layers in hydrologic models remains challenging. This study evaluated the downslope travel distance concept applied to a lateral subsurface flow model with a leaky impeding layer. The model includes a continuous and an event-based model structure for estimating the quantity of interflow at the hillslope scale. The approach was developed and tested using unique interflow and perched water table datasets from the R experimental hillslope in USDA-FS Upper Fourmile Creek experimental watershed at the Savannah River Site in South Carolina. The modeling approach realistically represents interflow dynamics in hillslopes with leaky impeding layers and has shown good potential for integration into catchment-scale hydrology models.

Technical Abstract: Traditional Boussinesq or kinematic simulations of interflow (i.e., lateral subsurface flow) assume no leakage through the impeding layer and require a no-flow boundary condition at the ridge top. However, recent analyses of many interflow-producing landscapes indicate that leaky impeding layers are common, that most interflow percolates well before reaching the toe slope, and therefore the downslope contributing length is shorter than the hillslope length. In watersheds featuring perched interflow over a low conductivity layer under permeable topsoil, interflow with percolation may be modeled with a kinematic wave model using a mobile upslope boundary condition defining the hillslope portion contributing interflow to valleys. Here, we developed and applied a dynamic interflow model to simulate interflow using a downslope travel distance concept such that only the active contributing length is modeled at any time. The model defines a variable active area based on the depth of the perched layer, the topographic slope, and the ratio of the hydraulic conductivity of topsoil to that of the impeding layer. It incorporates a two-layer soil moisture accounting water balance analysis, a pedotransfer function, and percolation and evaporation routines to predict interflow rates in continuous and event-based scenarios. We implemented the modeling concept on two sets of data (2-year dataset of rainfall observations for continuous simulation and a multi-day irrigation experiment dataset for event simulation) collected from a 121-m-long open interflow collection trench on an experimental hillslope at the Savannah River Site, South Carolina. The model simulation partially captured the observed interflow hydrograph and perched water depth in the experimental hillslope with correlation coefficients of 0.85 and 0.35, respectively. The modeling approach realistically represents interflow dynamics in hillslopes with leaky impeding layers and has shown good potential for integration into catchment-scale hydrology models.