Closing the gap

The problem of fish going through turbines at hydroelectric power plants and the growing concern over the survival rate of salmon at the US Army Corps operated Bonneville lock and dam on the Columbia river in the Pacific Northwest is discussed. The protection of the fish, the assessment of the hazards facing fish passing through turbines, the development of a new turbine, and improved turbine efficiency that reduces cavitation, turbulence and shear flow are examined. The closing of the gap between the turbine blades, hub and discharge ring to increase efficiency and reduce the risk to fish, and the development of the minimum gap runner (MGR) are described, and the lower maximum permitted power output of MGR is noted. (UK)