Kagawa and Tokushima prefectures filed a formal request Tuesday with the Shikoku Regional Development Bureau to divert water earmarked for hydroelectric power to human use.
The move comes amid a drought in Shikoku that has seen the water level in the Sameura Dam reservoir on the Yoshino River drop to just 6.2 percent of capacity as of 10 a.m. Tuesday.
According to the bureau, which manages the river, the reservoir is expected to dry up completely around Saturday if doesn't rain. Kagawa and Tokushima prefectures depend heavily on the dam for water.
"The livelihoods of the people of Kagawa Prefecture will fall into a crisis if the (Kagawa) water supply is stopped," Kagawa Gov. Takeki Manabe warned bureau chief Koji Yokota during a morning meeting.
Tokushima Vice Gov. Masahiro Kimura made a similar visit about an hour later.
Yokota promised the governors that authorities would cooperate in handling the crisis.
At the same time, however, he told Kimura it was "deeply regrettable" that Tokushima Prefecture refused to reduce reliance on the special water supply it gets from the dam when authorities were trying to reduce water consumption.
The bureau has already received permission from Electric Power Development Co. to use some of its supply as regular water.
Exactly how much will be allocated to Kagawa and Tokushima prefectures will be decided by the liaison committee for the Yoshino River water system.