JWA constructs and manages many water-related facilities in the designated seven river systems in Japan, namely, Tone, Ara, Toyo, Kiso, Yodo, Yoshino, and Chikugo River System to ensure stable water supply.

In these areas, population and industry are concentrated, and water demands are quite high. The total basin area of the designated seven river systems accounts for approx. 17% of the entire national land, approx. 52% of the national population and approx. 46% of the nation's industrial shipments. Water resources developed by JWA's projects totals approx. 348m³/s, accounting for approx. 79% of the total developed water in the seven river systems of approx. 439m³/s.