This research report summaries and details the first year of work on a multi-year karst modeling project organized to develop enhanced groundwater modeling capabilities that can be used to effectively manage karst aquifers. Discussed are the three key considerations for modeling karst systems were identified: representation of conduits in flow models, representation of flow dynamics in conduits, and representation of partially filled conduits and the numerical experiments used to identify the limitations and advantages of the three general representations of conduits within groundwater models. A new dual-conductivity MODFLOW-2000 package (DCM) was developed for testing the dual-conductivity approach. A turbulence model was added, the software was validated using simple benchmark problems, and code documentation was completed. Simultaneous demonstrations showed that the modeling tool can be successfully applied in complex applications.