Numerical simulation of flow in a fishway of Karkheh-Hamidieh diversion dam and environmental considerations to investigate possibility of fishway use in Mazandaran Province

Pool and weir is a type of fishway that provides a route for fish to migrate to damupstream. The effective parameters for fish swimming include velocity, water depth andturbulence. Several rubber dams have been under construction in Mazandaran Province, butthe necessary structures have not been built around them yet. When constructing these rubberdams, numerical models can be used to evaluate flow velocity and currently in Iran there isalso the possibility of comparing the results with field measurements at Karkhe-Hamidiehdam of Khuzestan Province. In this paper, the three-dimensional equations governing shallowwater in the weir and orifice fishway were solved using the suitable models of turbulence, andthe flow pattern and turbulence were calculated. The results of flow simulation and fieldmeasurements using Micromollineh were also compared. The final result showed that thevelocity lines in submerged and non-submerged modes with constant velocity were similar tothose estimated by Micromollineh - about 0.469 mps. We suggest it is not necessary to reducethe flow rate in a submerged state using devices such as baffles. The small Cyprinidae fishesare able to cross the fishway due to the slow flow of non-submerged state. In case of nonsubmergedstate, there is a need to reduce the flow rate.