@article{22523,
  abstract     = {In hydrological models, variably saturated flow is often described using the Richards equation, either in a fully three-dimensional (3D) implementation or using a quasi-3D framework based on the 1D Richards equation for vertical flow and a flow-approximation for the other two dimensions. However, it is unclear in which configuration or under which boundary conditions these approximations can produce adequate estimates. In this study, two formulations with a quasi-3D approach are benchmarked against a fully 3D model (HYDRUS-3D). The formulations are: the Real-time Integrated Basin Simulator + VEGetation Generator for Interactive Evolution (tRIBS + VEGGIE) model that uses the Dupuit–Forchheimer assumption and the Tethys & Chloris (T&C) model that implements the kinematic approach. Effects of domain slope, hillslope size, event size and initial moisture conditions on simulated runoff and soil moisture dynamics are examined in event-based simulations at the hillslope scale. The Dupuit–Forchheimer assumption (tRIBS-VEGGIE) produces deviations from the HYDRUS-3D solutions only for simulations with initially dry soil. Using the kinematic approach (T&C) results in deviations from the 3D solution primarily for the small hillslope domain in combination with a gentle slope angle. This applies especially to the partition between subsurface and surface runoff production, with T&C being biased towards the latter. For all other cases investigated, the simpler formulations provide reasonable approximations of the 3D model.},
  author       = {Hopp, Luisa and Fatichi, Simone and Ivanov, Valeriy Y.},
  issn         = {2224-7955},
  journal      = {Hydrology Research},
  keywords     = {hillslope hydrology, hydrologic modeling, parsimonious approximation, surface-subsurface hydrology},
  number       = {2},
  pages        = {274--290},
  publisher    = {IWA Publishing},
  title        = {{Simulating water flow in variably saturated soils: A comparison of a 3D model with approximation-based formulations}},
  doi          = {10.2166/nh.2015.126},
  volume       = {47},
  year         = {2016},
}