Slotted separation pillars for improved tailwater design at run-of-river plants

Run-of-river plants often use longitudinal separation pillars between turbine outlets and downstream weirs to manage sediment transport effectively. However, these pillars can narrow water flow, leading to higher water levels in the turbine section compared with the downstream weir. One method to reduce the flow restrictions created by conventional pillars is the installation of slotted separation pillars. This paper introduces a separation pillar design investigated as part of detailed model tests for the construction of the new Stegenwald run-of-river plant on the Salzach river in Austria, which is nearing completion. The new slotted separation pillar design allows sediments to flow through the tailwater at run-of-river plants, while maintaining the lowest possible water levels at the turbine outlet.