site on a stream, canal, lake, or reservoir where systematic observations of gauge height (water level) or discharge are obtained. From the continuous records obtained at these stations, hydrologists make predictions and decisions concerning water level, flood activity and control, navigation, and the like. Among the measuring devices used are a staff gauge, which is a graduated scale anchored in the water and read by observing the level of the water surface in contact with it; and a recording gauge, which continuously monitors water level, sensed by a probe or a float and recorded by a pen or printer on a moving sheet of paper.