Three Dimensional Modeling of Watershed Hydrologyby M. N. Saquib, James M. Montgomery, Consulting Engineers, Inc, Sacramento, United States,
M. L. Kavvas, James M. Montgomery, Consulting Engineers, Inc, Sacramento, United States,
Abstract: A three dimensional finite element numerical model is developed for the first order watershed hydrology using 8-noded isoparametric brick elements. The 3-D subsurface flow in a hillslope is coupled with the 1-D channel flow in the adjoining stream. The upstream converging section of the hillslope is also incorporated into the flow domain to replicate the physical environment in its entirety. The saturated-unsaturated flow problem is solved using the Galerkin's finite element method. The soil characteristics functions in the unsaturated flow domain are taken to be highly nonlinear to represent the field conditions. The diffusion wave approximation of Saint Venant's equation is used to solve the channel flow. An innovative discrete numerical approach using Penman-Monteith combination equation is taken to model the evapotranspiration from the land surface as a time space varying nonlinear boundary condition that is governed by the matric potential at the soil surface and by atmospheric conditions. This integrated hydrologic model is used in numerical simulation of hydrologic responses of the watershed under different physical settings (e.g. slopes) and different initial and boundary conditions. The 3-D hillslope model provides comprehensive insight into the nonlinear soil moisture dynamics as it incorporates the related hydrologic components in a detailed manner.
Subject Headings: Hydrologic models | Three-dimensional models | Finite element method | Numerical models | Three-dimensional flow | Channel flow | Watersheds | Hydrology
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