When Emperor Saga abdicated and used the opportunity to move from his mansion named 'Reizeiin' to his new mansion, he expanded the channel to approximately 12 m at its widest and 1 m at its deepest.
嵯峨天皇が譲位を契機として冷然院からこの新院へと遷御した時期に最大幅約12メートル、深さ約1メートル規模拡張された。