This research tested the hypothesis that students' erroneous mental models about groundwater will change towards more valid concepts if they are taught on the basis of a mental model-building strategy that focuses on the clarification of students' misconceptions. To examine the hypothesis a quasi-experimental research design was chosen. The methodology adopted in the study used both qualitative and quantitative methods. To promote conceptual change, a teaching and learning approach aiming at mental model building developed by Taylor et al. (2003) was adopted in the experimental group, while the control group was taught in a traditional lecture style. The procedure was applied to investigate the mental models of 30 German undergraduate teacher education students in geography. More than 75% of the students' conceptions were either unclear or incorrect, based on simple, "common sense" views of groundwater deposits. After the intervention the experimental group revealed significantly fewer misconceptions in their mental models about groundwater than did the control group. Teaching and learning by the mental model-building approach therefore seems to help undergraduate students to improve and refine their mental models of the abstract concept of groundwater occurrence in natures. The findings also suggest that the mental model-building approach could be a feasible strategy to induce conceptual change of other natural and cultural phenomena in geography and environmental sciences. (Contains 5 figures and 5 tables.)