Articles | Volume 19, issue 4
Hydrol. Earth Syst. Sci., 19, 1857–1869, 2015
https://doi.org/10.5194/hess-19-1857-2015
Hydrol. Earth Syst. Sci., 19, 1857–1869, 2015
https://doi.org/10.5194/hess-19-1857-2015

Research article 21 Apr 2015

Research article | 21 Apr 2015

Gravitational and capillary soil moisture dynamics for distributed hydrologic models

A. Castillo1,3, F. Castelli2, and D. Entekhabi1,3 A. Castillo et al.
  • 1Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
  • 2Department of Civil and Environmental Engineering, University of Florence, Florence, Italy
  • 3Center for Environmental Sensing and Modeling, Singapore–MIT Alliance for Research and Technology, Singapore, Singapore

Abstract. Distributed and continuous catchment models are used to simulate water and energy balance and fluxes across varied topography and landscape. The landscape is discretized into computational plan elements at resolutions of 101–103 m, and soil moisture is the hydrologic state variable. At the local scale, the vertical soil moisture dynamics link hydrologic fluxes and provide continuity in time. In catchment models these local-scale processes are modeled using 1-D soil columns that are discretized into layers that are usually 10−3–10−1 m in thickness. This creates a mismatch between the horizontal and vertical scales. For applications across large domains and in ensemble mode, this treatment can be a limiting factor due to its high computational demand. This study compares continuous multi-year simulations of soil moisture at the local scale using (i) a 1-pixel version of a distributed catchment hydrologic model and (ii) a benchmark detailed soil water physics solver. The distributed model uses a single soil layer with a novel dual-pore structure and employs linear parameterization of infiltration and some other fluxes. The detailed solver uses multiple soil layers and employs nonlinear soil physics relations to model flow in unsaturated soils. Using two sites with different climates (semiarid and sub-humid), it is shown that the efficient parameterization in the distributed model captures the essential dynamics of the detailed solver.

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Short summary
Using two sites with different climates, we show that a 1-pixel version of a distributed hydrologic model that uses a single soil layer with a novel dual-pore structure and employs linear parameterization for infiltration and other fluxes and has comparable performance to a benchmark detailed soil water physics solver in capturing the essential local-scale soil moisture dynamics.