Groundwater flow models have been increasingly used to support policy making. A substantial amount of research has been dedicated to improving, validating and calibrating models and including stakeholders in the modelling process. However, little research has been done to analyze how the choices of model makers and steering by policy makers result in models with specific characteristics, which only allow specific modelling outcomes, and how the use of these modelling outcomes leads to specific social, economic and environmental consequences. In this study, we use the social construction of technology framework to explore the development, characteristics and uses of the groundwater model of the Mancha Oriental aquifer in Spain. The specific characteristics and functioning of this model influenced the policy implementation, implying that involving stakeholders in the development and use of models is crucial for improved democratic policy making.