Abstract. Teaching hydrogeology in the field presents unique cognitive difficulties, including the multidisciplinary and hidden nature of the processes. Lecturers commonly encounter large heterogeneity in student backgrounds, and many students harbor pre-existing mental models of the subsurface that differ from reality. In this study, we assess the influence of a student’s prior knowledge on his/her outcome in an inquiry-based learning strategy designed for a hydrogeology field course. We also assess the effectiveness of this strategy in the students’ conceptual model expression for the field site. Statistical results showed that in general lower scores were obtained in the conceptual model expression than in the inquiry-based learning. However, students with a high prior knowledge showed in average a better performance in the conceptual model expression, although with a larger variability, indicating that the prior knowledge is not a guarantee for an adequate conceptual model conception. In general, a learning bottleneck was identified: going from the split information to the integration of it. In the light of these findings, and in order to improve the student’s ability for conceptual model expression, we recommend the inclusion of specific prior-to-field lessons in the classroom to introduce methodologies for the expression of hydrogeological conceptual models to identify and dispel any prior misconceptions.