Modeling of Groundwater Flow with MODFLOW in a Fractur-Karst Aquifer in the Big Spring Basin, Iowa

摘要

Groundwater flow in a fractured-karst ormation, the Galena aquifer, at the Big Spring Basin, Iowa is modeled with MODFLOW. The aquifer consists of limestone and dolomite that contain many fractures, sinkholes, and solutional conduits, which determine the pattern of groundwater flow. First, a stead-state model was calibrated against the long-term average of the observed data. Then, the model was calibrated against the observed hydraulic head changes at three observation wells and the observed discharge rate at the Big Spring during 1989. Finally, the model was verified with the observation data in 1990. The simulated heads and Big Spring discharge rates matched well with the observed in both calibration and verification.