MODFLOW-2000, The U.S. Geological Survey modular ground-water model: User guide to modularization concepts and the ground-water flow process

TLDR

MODFLOW numerically solves the 3‑D groundwater flow equation with a finite‑difference method and was designed for easy enhancement, though its architecture primarily supports flow‑equation extensions, prompting the need for additional equations such as transport and parameter‑estimation. The report introduces MODFLOW‑2000, a new version designed to accommodate equations beyond the groundwater flow equation. It provides an overview of the original and new design concepts, documents a new package, and gives input instructions for using the model to solve the groundwater flow equation. This report serves as a user’s manual.

Abstract

MODFLOW is a computer program that numerically solves the three-dimensional ground-water flow equation for a porous medium by using a finite-difference method. Although MODFLOW was designed to be easily enhanced, the design was oriented toward additions to the ground-water flow equation. Frequently there is a need to solve additional equations; for example, transport equations and equations for estimating parameter values that produce the closest match between model-calculated heads and flows and measured values. This report documents a new version of MODFLOW, called MODFLOW-2000, which is designed to accommodate the solution of equations in addition to the ground-water flow equation. This report is a user's manual. It contains an overview of the old and added design concepts, documents one new package, and contains input instructions for using the model to solve the ground-water flow equation.