model gives the basic idea or constructed understanding of how systems and processes operate (Bredehoeft, 2005).As with all models, the quality of hydrogeologic models depends on the quality of the information that can be gathered for its construction, which in turn depends on the availability of financial resources.It is important to note that a hydrogeological model contains many qualitative and subjective interpretations and proof of its validity can only be achieved by implementing specific research techniques and then constructing a numerical model and comparing the results from the simulation with observations from the field.Bredehoeft (2005), referring to the certainty of conceptual models, uses the term SURPRISE and relates it to the situation in which the collection of new data invalidates an original conceptual model.Surprise may come from revision of the scientific theory or as a result of new information obtained on a particular site.According to Bredehoeft, surprise occurs in 20-30% of cases studied, indicating that it is not easy to build an appropriate hydrogeological MonitoringAnalysis of data quality.