Analysis of Slot Orifice Fishway


P Dass




culverts, design, design criteria, entrance, fish passage, horizontal, instream flow, mathematical models, model studies, models, orifices, slope, slot orifice, spacing


University of Idaho Graduate School


The object of this study was to develop design criteria for a slot orifice fishway. Sizing and spacing of slot orifices inside the fishway can be designed to create flow conditions satisfactory for fish passage. The slot orifice fishway will function well in a wide range of discharges and should not have any serious silting problems. Values of drag coefficients for the slot orifice constrictions were evaluated by model studies for a range of slot openings varying form 0.6 to 0.85 of fishway width and culvert slope varying from horizontal to five percent. Three longitudinal spacings, 4, 5, and 6 times the fishway width, were considered for the slot orifices in the fishway. The effect of tailwater on the flow conditions at the fishway entrance was studied. The backwater relation of the slot orifice also was developed in the above range. Nondimensional curves are given for the values of the drag coefficients of the slot orifice constrictions and also for the backwater relations for the slot orifices. An equation, based on momentum principle, is developed which enables the designer to find the rate of flow through the fishway. Necessary criteria regarding suitability of flow for fish passage are also developed.



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