The simplest and least expensive flow measurement device is a?

• A. Weirs
• B. Flumes
• C. Orifice meters
• D. Venturi meters

Answer: (B)

Measuring flow in wastewater often relies on devices that create a predictable relationship between a measurable height of water and the discharge, with minimal moving parts. A flume does exactly that in a straightforward, robust way. By shaping the channel to a throat, the flow accelerates and a head difference develops that relates directly to how much water is moving. This setup is simple to install—often in existing channels or pipes—and uses standard, readily available sizes. Because there are few or no moving parts and the measurement is based on a clear depth reading, maintenance is typically low and the overall cost stays down.

Compared with other options, a flume tends to be cheaper and less complex to implement in many wastewater applications. Weirs, while also simple, can clog or foul more easily with debris and sediment and may require additional setups to get stable head readings for larger flows. Orifice and Venturi meters rely on differential pressure measurements and specialized instrumentation, which adds cost and complexity. So, for a simple, economical, and reliable open-channel flow measurement in wastewater, a flume is a practical choice.