The article explores historical documents on waterworks in Nagaoka city during the Taisho era. A waterworks plan from 1920, created by Mr. Jiro Inoue, revealed differences from a later plan in 1922. The 1920 plan suggested drawing water from the Shinano River and placing a reservoir at Yukyusan mountain. Due to technical and budget challenges, a revised plan was developed in 1922. Mr. Inoue was chosen for his expertise in cold region waterworks and freelance status at the time.