Abstract: This research is aimed at problems occurred in the water release operation of five-step shiplocks of the Three Gorges Project (TGP). By using numerical modeling and prototype measurements, we present the operation mode of controlling the valves of shiplocks’ tank under water level fluctuation condition according to the difference between observed water level at the outlet of water tank and at the downstream approach channel. In the meanwhile the present operation schemes were rarely disturbed. By adopting this new mode, problems that valves of the sixth-step shiplock head cannot be closed to a small opening during dry season and lock-sills cannot be opened normally during flood season with large discharge are solved. The operational parameters for closing the lock heads in the presence of different water discharges are given in which case the auxiliary valves needs not to be enabled and the necessary navigation discharge can also be guaranteed. The navigation efficiency could be improved by using the new operational mode.

Key words: Three Gorges shiplock, sixth-step ship lock head, main valve, auxiliary valve, operational mode