Gage ruler

To measure river stage using a gage ruler, look for the ruler installed vertically along the riverbank or a structure like a bridge. The bottom of the ruler is set at a known reference point. Simply read the number at the water’s surface level on the ruler. That number tells you the river’s stage, or height, in meters. The higher the water reaches on the ruler, the higher the river stage. This is a quick and easy way to track how much the water level changes over time, especially during storms or floods.