Design Problems of Fish Passes at Water Level Fluctuation at Upstream of Intake Structure

Abstract

During recent years small hydropower sector is being rapidly developed, especially in the mountainous countries with extensive network of small rivers. Investigation of many fish passes built on water intakes in some CIS countries, have shown that they usually do not work effectively. Normative documents regulating work of fish passes, usually developed for a constant water level in the upstream of intake structures. That is why even water level minor fluctuations at upstream, disrupt of hydraulic regime of the fish pass stream, which prevents the fish migration. The article provides performance of fish passes at a constant velocity in the fish pass stream regardless of water level fluctuations in the upstream. For this purpose it is recommended to construct the walls of fish pass stream with a variable roughness. The equation derived, describing the dependence of the relative roughness of the walls of a rectangular stream from the water level in it. A calculation algorithm for the design of the fish pass provided.