Yatsumen-gawa River, which flows through Yuza Town, is supplied by spring water from nearby artesian wells. It maintains a low water temperature even in summer, making it a habitat for the ninespine stickleback (Pungitius pungitius), a relict species of fish that survived the last glacial period. The waterway was once polluted by household wastewater, but has since been repaired and maintained by national, Yamagata Prefectural, and Yuza Town waterway maintenance.

The local community considers Yatsumen-gawa River to be a community asset and has established an association dedicated to maintaining the waterway, as well as preserving and improving its ecosystem.