円筒分水 (entō bunsui) えんとうぶんすい = cylindrical diversion
An ento-bunsui is a structure that regulates a river or stream, diverting water towards multiple irrigation channels, which differ in size according to the size of the land they serve. The English word for 円筒分水 is practically non-existent. The best translation is probably “cylindrical water diversion”, but I’ve seen cylindrical water splitter, diversion cylinder, watershed cylinder, cylindrical diversion, and others. I can find no evidence of similar devices outside of Japan.)
For more photos of ento-bunsui throughout Japan, do a Google image search for 円筒分水.
Read more about water infrastructure in Tokyo:
Read more for information about the Shimokuzawa diversion pond:
- 春の円筒分水ツアー （下九沢分水池～久地円筒分水へ） Spring of the cylindrical water diversion tour (to the watershed pond – lottery cylindrical diversion Shimokuzawa)
A map of all the identified ento bunsui in Japan (per entoubunsui.com):
Another version (unknown source):
- 可視化された公平性 Fairness visualized: this post claims that ento bunsui were invented at the end of the Meiji era.