Which type of water measurement device is typically used for open channel flow?

The Parshall flume is specifically designed for measuring flow rates in open channels. It operates based on the principle of fluid mechanics, utilizing a constriction in the channel that creates a distinctive hydraulic condition where the water level rises as flow increases. The dimensions and shape of the flume are calibrated to relate the water depth (head) upstream of the flume to the flow rate, allowing for accurate flow measurements without the need for mechanical parts that could wear out or require maintenance.

In contrast, a flow meter generally measures the flow of water in closed pipes, not open channels. A pressure gauge is used to measure the pressure of fluids in a system but is not suited for measuring flow rates directly. A piezoelectric sensor measures pressure changes which could be in various systems but isn't specifically tailored for open channel flow measurement. The Parshall flume’s design and calibration make it a reliable and efficient choice for accurately estimating flow in open channel applications.