The applicability and effectiveness of integrating an expert system with a geography information system (GIS) are examined. The knowledge base, including indicators related to application, development and evaluation of a water\|saving city, is developed with the C Language Integrated Product System, a knowledge inference engine developed by NASA, USA. The knowledge base is subsequently coupled, through a platform independent language Qt/C++, with a GIS application, in which a GIS component library, ArcEngine, is used to display the administrative boundaries of the study area. The integrated water\|saving evaluation system, along with a case study in the Zhangye Municipality of China, demonstrates that how an expert system can be applied to water resources management and how easily an expert system can be coupled into a GIS application as well as other applications. The proposed prototype may be helpful and prospective in solving unstructured and uncertain questions in geo\| and hydro\|sciences.