It is the second longest river in Shikoku (slightly shorter than the Shimanto), and is the only river whose watershed spreads over the four prefectures of the island.

This was considered unusual in a country where pork barrel public works projects were common and often welcomed by locals in provincial areas.

Ironically, one author has argued that because of earlier local reforms which required a 50% turnout rate for referendums to pass through, pro-dam lobbyists likely urged "yes" supporters to not turn out to vote in the hopes that the total turnout would be less than 50% and thus invalidate the inevitable "no" vote.

The entire episode led to a heated struggle between opposed locals and pro-dam lobbyists over the project.

[1] Reconstruction of the Yoshino Daiju Dam (吉野川第十堰 Yoshino-gawa Daijūzeki) near its mouth provoked much controversy among environmentalists.