The present study aims to acquire deeper understanding of the runner blade channel vortices phenomenon by numerical simulations of the whole turbine passage. Several operating points along different specific discharge were calculated by a hybrid turbulence model, Very Large Eddy Simulation, which was proved that it was able to capture the blade channel vortices similarly. The results showed that the blade channel vortices structure and intensity were various for different runners at incipient point. The flow pattern revealed that the direct relationship of a backflow region and the blade attacking angle near the hub had a distinct variation in vortex structure and intensity. Furthermore, this paper referred a new method to evaluate the strength of blade channel vortex quantitatively, basing on the evolution of specific energy gradient over the stream-wise location. Therefore, this new method enabled the researchers to understand deeply the flow characteristics associated with the blade channel vortices formation and carry out efficiently the hydraulic optimization design. (C) 2020 Elsevier Ltd. All rights reserved.