The Tokyo metropolitan government operated its cloud seeding equipment to trigger rain for the first time in 12 years after water levels of dams supplying the metropolitan region have fallen below normal.
Two machines were activated at around 2 pm
The government said yesterday it rained about 10 millimeters upstream of the Ogouchi dam in Tamagawa River three hours later and about 11 millimeters downstream from 2 pm.
"The rain upstream (of the dam) could have been the work of the equipment," a Tokyo government employee in charge of the operation said.
The machines are located near the dam in a Tokyo suburb of Okutama and Koshu, Yamanashi Prefecture.
Silver iodide, which will become seeds for raindrops, was mixed with acetone and burned before it was sprayed into the sky through a blower.
The mixture is thought to freeze in the clouds at 4,000-5,000 meters high to produce rain.
The Tokyo government will decide whether or not to operate the equipment in full-scale after observing changes in water levels.
As of yesterday, water level in dams along the Tone River system stood at 47 % and the level in dams along the Tama River system stood at 69 per cent.
The metropolitan government has implemented a 10 % water pumping restriction in reservoirs along the Tone River since July 24.