In 1936, the union of Mikuriya Yosui managed to get 85,000 yen from Furukawa Mining as funds for the project to improve the intake; before the works, they had drawn water directly from Watarase-gawa River, however, after the works, they began to draw water from the undercurrent.
1936年に三栗谷用水は古河鉱業から事業資金の一部8万5千円を提供させ、取水口の改良工事を行い、それまでの渡良瀬川からの直接取水から、伏流水を主に取水する方式に変更した。