Yodo River, Yodo River system (Osaka City, Osaka Prefecture)

Osaka City Yodogawa Ozeki Project

The Yodo River is the only river that flows from Lake Biwa into Osaka Bay. Built in 1983, the Yodogawa Ozeki is a weir located at the downstream end of the river. The water quality of rivers in Osaka City had deteriorated due to delays in sewerage system development caused by Osaka’s rapid population growth. The weir was built to improve the situation of this so-called “sewage canal.” This time, CTI Engineering was in charge of the main body design and construction plan for the Yodogawa Ozeki. In fiscal 2004, we were also in charge of the maintenance and management of the weir, including the design of seismic and anti-tsunami reinforcements.

　

The Yodogawa Ozeki is one of the largest tidal and diversion weirs in Japan, with a span of 668 meters (the distance between the supporting members of the bridge structure) and a retractable gate to control the water level. It is jointly managed by the Kinki Regional Development Bureau of the Ministry of Land, Infrastructure, Transport and Tourism and the Japan Water Agency for the purpose of supplying water and industrial-use water to Osaka and Hyogo prefectures.

　

The weir’s current purpose is to supply water for domestic, industrial, and sewage use to Osaka and Hyogo prefectures. It supplies water, sewage, and industrial water at a rate of 20 tonnes per second. On the other hand, it releases water for unspecified use into Osaka Bay at a rate of 100 tonnes/second at high tide and 40 tonnes/second at low tide while making adjustments.

　

The Yodogawa Ozeki is also capable of handling flush discharges, which are artificial floods triggered by water volume control measures in order to improve water quality by flushing polluted water into Osaka Bay.