Undulating - undulating

...In the past, there were many cases where villages in different villages built weirs on both sides of a river and competed for water intake, but since the end of the Taisho period, the construction of a unified weir (a joint weir) at a good location upstream has become more common. In addition, the undulating weir imported in modern times is a line of iron gates lying down in the water connecting a fixed point on both sides of the river, and the amount of water flowing is adjusted by mechanically raising and lowering the iron gates depending on the amount of water held up upstream and the amount of water needed downstream. There are also modern types of wash weirs. ...

*Some of the terminology explanations that refer to "undulating weirs" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…一河川の上流から下流へ，両岸に別々の村々の仲間の造営したせきが並立し，取水を争った場合もかつてははなはだ多かったが，大正末以降の，最上流の好位置へのせきの統一設置(合口（あわせぐち）)が近年著しく行われるようになった。　なお，近代に至って輸入された起伏ぜきは，河川の両岸の1定点を結んで水中に一列に鉄扉を連ね伏せ，その上流部の湛水（たんすい）量や，下流部の必要とする水量を考慮して機械操作によって鉄扉を起立，伏臥（ふくが）させて流水量を調節する。洗いぜきにも近代的なものがある。…

※「起伏ぜき」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報