title: Improved water table dynamics in MODFLOW.
abstract: The standard formulation of a block-centered finite-difference model, such as MODFLOW, uses the center of the cell as the location of a cell node. Simulations of a dynamic water table can be improved if the node of a cell containing the water table is located at the water table rather than at the center of the cell. The LPF package of MOD-FLOW-2000 was changed to position a cell's node at the water table in convertible cells with a water table. Improved accuracy in the upper regions of an unconfined aquifer is demonstrated for pumping from a partially penetrating well. The change introduces a nonlinearity into the solution of the flow equations that results in slightly slower convergence of the flow solution, 7% slower in the presented demonstration. Accuracy of simulations is improved where vertical flow is dominated by a moving water table, but not when a large water table gradient dominates over the water table movement.
authors.affiliation: Center for the Geophysical Investigation of the Shallow Subsurface, Boise State University, Boise, ID 83725, USA. tomc@cgiss.boisestate.edu
authors.forename: Tom
authors.initials: T
authors.lastname: Clemo
mesh_terms: D055593:Geological Phenomena; D005844:Geology; D008962:Models, Theoretical; D012680:Sensitivity and Specificity; D012987:Soil; D014872:Water Movements; D014881:Water Supply
chemical_list: D012987:Soil