ABSTRACT
This chapter briefly reviews the conventional techniques for measuring discharges in closed-conduit and free-surface flow situations. It focuses on new instruments and methods for measuring discharges in natural streams. The chapter considers differing types of instruments and methods for discharge estimation. It reviews the well-documented conventional methods for discrete and continuous measurements of discharge used primarily in laboratories and fieldwork. Intrusive flowmeters involve the principle of conservation of energy in order to estimate discharge; Other devices, such as broad-crested weirs, measure flow velocity directly. Non-Intrusive Flowmeters indirectly measure flow velocity over the flow cross section. The acoustic Doppler current profiler use for river-flow measurements has profoundly changed the way that velocities and discharge are collected in streams and man-made channels. Near the coast, tides and wind at the seaward river boundary may affect water level and discharge variations. Hence, artificial neural networks may be employed to predict discharge.
