One aim of environmental education is fostering sustainable environmental action. Some environmental behaviour models suggest that this can be accomplished in part by improving people's knowledge. Recent studies have identified a distinct, psychometrically supported environmental knowledge structure consisting of system, action-related and effectiveness knowledge. Besides system knowledge, which is most often the focus of such studies, incorporating the other knowledge dimensions into these dimensions was suggested to enhance effectiveness. Our study is among the first to implement these dimensions together in an educational campaign and to use these dimensions to evaluate the effectiveness of a programme on water issues. We designed a four-day environmental education programme on water issues for students at an educational field centre. We applied a newly developed multiple-choice instrument using a pre-, post-, retention test design. The knowledge scales were calibrated with the Rasch model. In addition to the commonly assessed individual change in knowledge level, we also measured the change in knowledge convergence, the extent to which the knowledge dimensions merge as a person's environmental knowledge increases, as an innovative indicator of educational success. Following programme participation, students significantly improved in terms of amount learned in each knowledge dimension and in terms of integration of the knowledge dimensions. The effectiveness knowledge shows the least gain, persistence and convergence, which we explain by considering the dependence of the knowledge dimensions on each other. Finally, we discuss emerging challenges for educational researchers and practical implications for environmental educators.