Intermittent rivers and ephemeral streams are the world's dominant type of river ecosystem and are becoming more common because of global change. However, the inclusion of intermittent rivers and ephemeral streams in water policies and management plans remains largely limited because monitoring schemes and tools are designed for perennial rivers. In the present article, we discuss how smartphone applications used by citizen scientists can quantify the extent and occurrence of intermittent rivers and ephemeral streams. We also introduce a new app, DRYRivERS, specifically designed to monitor intermittent rivers and ephemeral streams. After a year of use, we counted more than 3600 observations from more than 1900 river reaches across 19 countries and four continents. Through three case studies, we then show that citizen science can improve our knowledge of the prevalence of intermittent rivers and ephemeral streams in the landscape, enhance hydrological modeling and calibration, and guide managers in setting water abstraction restrictions. Together, our approach demonstrates how citizen science can be incorporated into environmental monitoring to better inform river management and policy.