Basic Wastewater Operator Practice Exam

Where is a manual flow reading taken in a Parshall flume?

1. 4x the throat width back

2. At the beginning of the throat

3. At the end of the throat

4. 2/3 the length of the converging wall measured back from the throat

The correct answer is: 2/3 the length of the converging wall measured back from the throat

Taking a manual flow reading in a Parshall flume typically occurs at a specific point to ensure that measurements are accurate and reliable. The correct practice is to take the reading 2/3 the length of the converging wall measured back from the throat of the flume. This location allows for the most consistent and stable flow conditions, minimizing the effects of turbulence that can occur near the throat. Measuring at this position helps avoid any disturbances in the flow profile that might affect the accuracy of the reading, ensuring that the flow measurement reflects the true hydraulic conditions of the wastewater being assessed. It optimizes the point where the flow is fully developed and offers reliable data for operations. In contrast, measuring too close to the beginning or end of the throat could result in inaccurate readings due to transitional flow effects or turbulence that can distort the flow characteristics.