In hydrography, what does the term 'stage' refer to?

In hydrography, the term 'stage' specifically refers to the height of the water surface above a specific datum, typically a reference point such as sea level or the bottom of a riverbed. This measurement is fundamental for understanding water dynamics, flood risk assessments, and many aspects of hydraulic engineering. It indicates not just the current level of the water, but also provides essential data for monitoring changes over time, which can be critical for flood management and environmental studies.

While the speed of water flow addresses how quickly water moves, the depth of the riverbed pertains to the underwater topography, and the volume of water in a reservoir focuses on capacity rather than surface height, none of these definitions capture the essence of 'stage' in hydrography. Understanding 'stage' is crucial for hydrologists, engineers, and surveyors who deal with water bodies.