Accuracy for measuring a hydrograph at a particular stream location depends on the method used. Visual observation of stage through high and low water marks or vegetation growth. Current Meter Is a device for sensing velocity. Changes in voltage are translated to velocity. Velocity varies with location and time in a river.
Velocity varies within the same cross section.
It is also called rating curve. Float Used especially during floods. Two stations are marked along the stream and the distance between them is measured along the stream centerline. The time it takes for the float to travel through the marked distance is recorded. Velocity is then calculated.