A protection strategy in environmental management such as groundwater vulnerability mapping is a powerful tool for decision making and land use planning. Groundwater vulnerability evaluates a multilayer system over a large basin. It has a large and complex data and variables. Geographical Information System (GIS) provides an easy means to analyze large and complex groundwater data. These complexities also necessitate a systematic approach such as Multi Criteria Decision Making (MCDM) for decision analysis in a framework that supports hydrogeological spatial attributes as well as facilitates the incorporation of knowledge, experience and judgments in the vulnerability assessment. In addition, statistical methods can be integrated with hydrogeological model to calibrate the original model and validate the results.