Do experts attach the same meaning as laypeople to terms often used in hydrology such as "river", "flooding" and "downstream"? In this study a survey was completed by 34 experts and 119 laypeople to answer this question. We found that there are some profound differences between experts and laypeople: words like "river" and "river basin" turn out to have a different interpretation between the two groups. However, when using pictures there is much more agreement between the groups.