Evaluation of free and submerged flow data for large parshall flumes

Because the accurate measurement of water plays such an important part in water management, such structures as weirs, orifices, calibrated gates f and flumes have been developed. These structures provide the means for reasonable measurement of the smaller flows (1: .. 100 cfs), but for the large flows (100-3,000 cfs) the current meter, large Parshall flume, and various other flumes are commonly used. Where a permanent structure is required, the most widely accepted and utilized method for measurement of large flows is probably the Parshall flume. The purpose of this report has been to collect the existing flow data for large Parshall flumes having throat widths of 10, 12, 15, 20, 25, ,30, 40, and 50, feet, and evaluate from the data certain free flow and submerged flow relationships. The free flow relationships of large Parshall flumes as listed by R . L. Parshall (1932) are verifieq. from the data. The study reported herein was further made to illustrate that the analysis of submergence developed at Utah State University for smaller Parshall flumes (Skogerboe, Hyatt. Johnson, and England, 1965) is also applicable to large Parshall flumes