HR: 0800h
AN: H31H-0762    [Abstracts]
TI: Richards' Equation and its Constitutive Relations as a System of Differential-Algebraic Equations
AU: * Murray, S K
EM: shannonmurray@mail.boisestate.edu
AF: Mathematics Department, Boise State University, 1910 University Dr, Boise, ID 83725, United States
AU: Mead, J L
EM: jmead@boisestate.edu
AF: Mathematics Department, Boise State University, 1910 University Dr, Boise, ID 83725, United States
AB: Richards' Equation is commonly used to understand how water flows in unsaturated soils. We present a new formulation of Richards' Equation which will allow us to incorporate model and observation errors. In addition, we can address spatial and temporal inconsistencies existing between the model and observations. There are two basic formulations for Richards' Equation: the pressure head form and the mixed form, the latter of which explicitly incorporates soil moisture content. The mixed form is typically solved using HYDRUS, a freely available program that uses finite elements with Picard iteration to handle the nonlinearities. However, recent results suggest considering Richards' Equation as a differential-algebraic equation (DAE), where the algebraic models for soil moisture content (van Genuchten's equation) is solved simultaneously with Richards' Equation (Kees, et. al., 2002). This formulation can give more accurate forward model solutions, however, we note that it also allows us to consider the uncertainties in the pressure head ψ and the soil moister content θ during the inversion process. We extend the DAE formulation to include the algebraic constraint for hydraulic conductivity K, so that its uncertainty can also be considered in an inversion. This poster focuses on the efficiency and accuracy of the forward numerical solution of this particular DAE formulation of Richards' Equation and how it compares to other forward solutions, such as HYDRUS.
DE: 1805 Computational hydrology
SC: Hydrology [H]
MN: 2007 Fall Meeting