Numerical simulation of flow 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 dam upstream. The effective parameters for fish swimming include velocity, water depth and turbulence. Several rubber dams have been under construction in Mazandaran Province, but the necessary structures have not been built around them yet. When constructing these rubber dams, numerical models can be used to evaluate flow velocity and currently in Iran there is also the possibility of comparing the results with field measurements at Karkhe-Hamidieh dam of Khuzestan Province. In this paper, the three-dimensional equations governing shallow water in the weir and orifice fishway were solved using the suitable models of turbulence, and the flow pattern and turbulence were calculated. The results of flow simulation and field measurements using Micromollineh were also compared. The final result showed that the velocity lines in submerged and non-submerged modes with constant velocity were similar to those estimated by Micromollineh - about 0.469 mps. We suggest it is not necessary to reduce the flow rate in a submerged state using devices such as baffles. The small Cyprinidae fishes are able to cross the fishway due to the slow flow of non-submerged state. In case of nonsubmerged state, there is a need to reduce the flow rate.