Flow-measuring structure.

Weirs, flumes and gates have been used for centuries to determine discharges in open channels. In this paper the distinct flow types, modular flow and non-modular flow, are described and applied to derive the head-discharge relations of weirs with a horizontal crest. The flow measurement structures are classified according to international rules. For a number of decades, the ability of flow measurement structures to allow fish migration has also been judged. On the other hand, some well-known fishways have been considered to act as an alternative flow measurement structure. The presentation of the Venturi gate, which combines the functions of flow measurement structure and fishway, concludes the pape