Methods and applications of an unstructured grid version of MODFLOW: MODFLOW-USG

The classic MODFLOW uses a structured grid which has problems in the discretization of model boundaries with complex irregular shapes. A new version of MODFLOW,called MODFLOW-USG( for unstructured grid),supports a wide flexible unstructured grid type that offers advantage for modeling irregular boundaries,homogeneous geological framework and discontinuous layer,etc,and improves the reliability and accuracy of the simulation results. This paper utilizes the MODFLOW-USG method to study the groundwater flow model of the middle reaches of the Heihe basin. The accuracy of the simulation results in the focused zone nearby the river has been improved by generating a finer unstructured grid for the irregular and various sized river boundary.