『Abstract
　MODFLOW is a groundwater modeling program. It can be compiled and remedied according to the practical applications. Because of its structure and fixed data format, MODFLOW can be integrated with Geographic Information Systems (GIS) technology for water resource management. The North China Plain (NCP), which is the politic, economic and cultural center of China, is facing with water resources shortage and water pollution. Groundwater is the main water resource for industrial, agricultural and domestic usage. It is necessary to evaluate the groundwater resources of the NCP as an entire aquifer system. With the development of computer and internet information technology it is also necessary to integrate the groundwater model with the GIS technology. Because the geological and hydrogeological data in the NCP was mainly in MAPGIS format, the powerful function of GIS of disposing of and analyzing spatial data and computer languages such as Visual C and Visual Basic were used to define the relationship between the original data and model data. After analyzing the geological and hydrogeological conditions of the NCP, the groundwater flow numerical simulation modeling was constructed with MODFLOW. On the basis of GIS, a dynamic evaluation system for groundwater resources under the internet circumstance was completed. During the process of constructing the groundwater model, a water budget was analyzed, which showed a negative budget in the NCP. The simulation period was from 1 January 2002 to 31 December 2003. During this period, the total recharge of the groundwater system was 49,374×10⁶ m³ and the total discharge was 56,530×10⁶ m³ the budget deficit was -7,156×10⁶ m³. In this integrated system, the original data including graphs and attribution data could be stored in the database. When the process of evaluating and predicting groundwater flow was started, these data were transformed into files that the core program of MODFLOW could read. The calculated water level and drawdown could be displayed and reviewed online.

Keywords: Groundwater model; MODFLOW; GIS; Integration; North China Plain; Water resources 』

Introduction
Integration process of groundwater model and GIS
　Features of MODFLOW
　Integration idea of groundwater model and GIS
　Technical realization of integration groundwater model with GIS
A case study of dynamic evaluation system of water resources for the NCP
　Background of the NCP
　Constructing the groundwater model of the NCP
　　Basic conditions description of the NCP
　　Conception model and mathematic model
　　Numeric model
　　　Model discretization
　　　Solution conditions
　　　　Boundary conditions
　　　Sources and sinks
　Calibration and identification of the model
　　Application of the integration system of groundwater model and GIS
Conclusions
Acknowledgments
References