The central and local governments have strengthened drought-management measures because climate change has widened the risk of prolonged dry spells around the country.

Global warming has led to increased instances of severe flooding in Japan.

But changing rainfall patterns have also raised the likelihood of drought-like conditions.

Officials from the central government, Tokyo metropolitan government and five prefectures located in basin zone of the Tonegawa river attended an April 20 meeting of a liaison council of drought management along the river.

Kenji Muto, an official of the land ministry’s Kanto Regional Development Bureau, raised the alarm at the meeting.

“The percentage of water storage at upper-stream dams dropped to 36 percent in March because the weather has been dry since fiscal 2022,” Muto said.

The percentage is close to past levels that have prompted officials to impose cuts in water intake.

This year, accumulated snow in the mountains has been around half the average amount at the river’s source, the Oze Marsh.

The snowmelt started earlier this year, so a water shortage crisis is expected for a wide range of the Kanto region, Muto said.

“It appears to be the impact of global warming,” he repeatedly said.

Yasuto Tachikawa, a water-resource engineering professor at Kyoto University, said rising global temperatures have changed and complicated rainfall patterns. The difference between times when rain falls and the times when it doesn’t has become extreme.

Heavy rainfalls that continue for days at a time have led to flooding of wide areas. But the number of prolonged periods with no precipitation has also increased.

High temperatures during the dry times have accelerated water evaporation, further raising the risk of drought.

PLUGGING LEAKS IN FUKUOKA

The municipality of Fukuoka on the main southern island of Kyushu has been particularly vigilant against drought risks because there is no Class-A major river in the city.

Fukuoka city has often been forced to restrict its water supply because of droughts. It is now implementing measures to conserve water, including preventing leaks from water pipes.

Toshinori Fuchigami, who heads the city’s water management center, said officials conduct around 3,000 manual valve manipulations a day on the water supply system.

Excessive hydraulic pressure on water distribution pipes accelerates the deterioration of the equipment, which will cause more water leaks, Fuchigami said.

Therefore, officials frequently adjust the hydraulic pressure according to the amount of water used.

For example, during the World Cup soccer tournament in Qatar last year, the amount of water used in Fukuoka significantly dropped during play in games involving Japan, likely because people were glued to their TV screens.

Officials expected water use would jump significantly during the 15-minute half-time breaks of the games, and remotely conducted valve manipulation in many locations of the city.

Water pressure adjustments prevent about 4,000 tons to 5,000 tons of water from leaking a day, according to the city. Officials thoroughly inspect the water pipes to maintain a water leakage ratio under 2 percent.

Fukuoka is also making efforts to reuse water through two special sewage treatment facilities in the city.

The water is recirculated for use in toilets and to nourish plants in seven areas, including near JR Hakata Station.

The daily capacity of such recirculated water is 11,600 tons, the largest volume in Japan, a city official said.

WATER SHORTAGES IN SHIKOKU

Drought has become a frequent problem in areas along the Yoshinogawa river on the main island of Shikoku. Kagawa Prefecture, in particular, has seen a rainfall shortage.

In spring this year, the prefecture temporarily limited water intake because of dwindling water storage levels at Sameura Dam in Kochi Prefecture.

In 2021, the central and local governments devised drought-response measures.

They now use the percentage of water storage at Sameura and other dams as barometers to determine when to restrict water intake and when to call a drought an “extraordinary one.”

For such emergencies, the measures spell out when and how to set up a headquarters and when to ask residents and companies to restrict water use.

Tachikawa of Kyoto University, as a special member of the National Land Development Council, has been involved in reviewing the master plans to develop water resources along the Yodogawa river in the Kinki region and the Chikugogawa river in northern Kyushu.

He said both plans include drought measures, such as using rainwater, reusing wastewater and promoting water-saving equipment.

“We must be vigilant in developing infrastructure, such as dams, to prepare for droughts, but that is not enough. What is required is to take steps that thoroughly combine ‘soft’ measures,” Tachikawa said.