Parshall Flume Calibrations Approach Studies 12-inch Throat

The Metro Waste Control Commission (MWCC) of St. Paul has installed Parshall flumes in sewer manholes at various locations to. monitor the discharges. The Parshall flume is an accurate measuring device for open channel flow when installed as specified in the standard manuals. This calls for ideal approach conditions, which may not always be possible in manhole installations. The MWCC proposed to investigate the accuracy of Parshall flumes in these installations. A literature search revealed very little definitive information on the effect of adverse approach flow conditions on the accuracy of discharge· measurements. A study of Parshall flume calibrations for various approach geometries was initiated. A commercially available reinforced plastic flume with a 12-inch throat was used. This report summarizes the studies.