Kema Suimon, Canal lock between Yodo River and Okawa in Osaka, Japan.

Kema Suimon is a lock complex on the old Yodo River in Kita-ku, Osaka, separating the Yodo River from the Okawa. It comprises the Kema Lock, the Kema Pump Station, and the Yodo River Weir. The lock chamber is about 80 meters long and 10 meters wide, with brick side walls about 8 meters high.

The system originated during Japan's industrial modernization period as a solution to prevent river flooding and manage water levels across Osaka. This engineering project was vital for protecting the expanding city from the dangers of overflow.

The site holds recognition as an Important Cultural Property of Japan, reflecting engineering expertise that locals and visitors witness in daily operation. The structure tells of how water management shaped life and development in this part of Osaka.

You can watch the lock operations from several viewpoints around the facility, which remains active in daily operation. Choose a quieter time of day to observe the mechanics of the gates and understand how water passes through.

Beside the old first lock stands a monument to the Yodo River improvement works, erected in 1910, and nearby lie several large stones called the Kema zannen-ishi. These are said to be wall stones carried from Fushimi Castle for the rebuilding of Osaka Castle in the Edo period; they fell from a transport boat into the river and were hauled up during the later river works.