V‐Notch Weir Calibration Using New Parameters

Abstract

Monitoring of wastewater discharge requires measurements of both quality and quantity to satisfy federal regulations. The use of 90-degree V-notch weirs to measure discharge at outfalls is common. In many instances the weirs are placed in culverts or other space-limited locations such that the traditional calibration parameter, head over the weir notch, is difficult to measure. Two other parameters can be specified, which involve measurements at the weir plate. These have the advantage of not requiring that an elevation datum be established. The first is measurement of depth of flow over the weir notch using a common meter stick. The second is the measurement of width of flow at the weir crest using a modified machinist's caliper. Both techniques yielded reliable measurements using a sample data set obtained from 12 students asked to perform the measurements. Measured discharge varied no more than ± 5% from actual at one standard deviation, and no more than ± 10% at two standard deviations. It was concluded that the two new parameters were adequate substitutes for traditional weir head measurements.