��������

Advances in hydrology are greatly needed and approaches that employ hypotheses to guide research have the potential to contribute to future advances. One line of reasoning in the USGS research program where I started my career was to “never undervalue forward progress on a tough problem”, and in this context, hypotheses can be particularly useful and empowering. Hypotheses can serve a range of purposes.��Retrospective hypotheses that attempt to explain unexpected field observations or experimental results can provide a guide for designing further field studies.��Focused testable hypotheses can facilitate effective presentation of proposed research, and clarify alternative hypotheses.��Overarching hypotheses can provide a common integrating framework for collaborative research and can be revised as research progresses over time. Finally, the value of employing a hypothesis-based approach depends upon the research environment, which can act as an ‘‘environmental filter’’ in determining successful research outcomes.��