The Landmarks of Tokyo Waterworks
Hamura Intake Weir
Hamura Intake Weir is located about 54km upstream from the estuary of Tama River. It consists of “Nagewatashi Weir” and “Fixed Weir” that dams up the water from the river, fishway where fishes can freely swim, and the first Water Gate to intake the dammed water.
Hamura Intake Weir was built at the same time as Tamagawa Josui, and it was completed in 1653,when the Shogunate (Japan’s feudal government) was concerned about the population increase of Edo. As for the Tamagawa Josui, the Shogunate made a plan to intake the water from Tama River into Edo. They initially tried to build an intake in the vicinity of Aoyagi in Kunitachi, then in the vicinity of Kumakawa in Fussa but both failed. After all, it was established at the current location in Hamura.
Up to this day, the weir has undergone remodeling and expansion in 1900 and 1924. Due to the structure of the weir, it normally intakes the water as much as possible and discharges 2㎥ of it every second from the small flushing gate. However, to ensure the safety of the weir we remove the Nagewatashi Weir to avoid the water level from rising when it floods, like when there is a typhoon.
Nagewatashi Weir is an extremely rare type; fistly, a steel girder is placed at a right angle to the river. Secondly, the log piles are leaned against them. Then logs are inserted horizontally, and finally items such as fascine (bundled branches of trees) and gravel are used to complete the weir. When the water level of the river exceeds a certain level due to heavy rain such as a typhoon , the girder is removed so that the weir can flow itself downstream. This is called “ Nagiharai”. After the water level drops, the weir is rebuilt. This is called “Shitsuke”, and these traditional techniques are still continued even to this day.
Raw water that has been withdrawn are conveyed to Murayama and Yamaguchi Reservoirs. Also, after passing through Tamagawa Josui it is conveyed to Higashi Murayama Purification Plant.
|Name||Hamura Intake Tower|
|Location／Access||3-8-32 Hanehigashi,Hamura City
10-minute walk from JR Ome Line “Hamura” station.