Flood control situation grim
Heavy precipitation has raised experts’ worries about small and midsize rivers
Stronger rainfall, a prolonged rainy season and uncertain weather conditions have merged to create a grim flood control situation in China this year, particularly along midsize and small rivers, according to experts.
As of Saturday, meteorological authorities had issued alerts for torrential rainfall every day for certain regions of China. Some observation stations along the Yangtze River witnessed the water levels exceeding those of 1998, when major floods killed more than 4,000 people in the country. Many are worried about another disastrous flooding year.
Risks loom, especially for the vulnerable midsize and small rivers where many dikes have not received adequate funding and maintenance for years, experts said.
Rainfall in China since June has far exceeded the average for the period, meteorological records show.
Between June 1 and July 7, the average precipitation along the Yangtze River Basin reached 347 millimeters, the second-highest amount since 1961. It even exceeded the 1998 level for the period by 15 millimeters, according to the National Meteorological Center.
Many areas have seen unprecedented daily precipitation this year. Thirty-one national meteorological monitoring stations in seven provincial regions, mostly in middle and lower reaches of the Yangtze, saw record high daily precipitation in July. Meteorological stations in 13 counties, 10 of which are in Jiangxi province, reported all-time high precipitation, according to the center.
In the most extreme circumstance, Xishui county, Hubei province, had 999 millimeters of precipitation from July 4 to 9, said Zhang Fanghua, chief forebefore caster at the center.
An extended Plum Rains season this year has also brought more rainfall. Plum Rains, often occurring in June and July, refer to the long period of continuous rainy or cloudy weather in the middle and lower reaches of the Yangtze River. The name is a reference to the time that plums ripen in the region.
This year’s Plum Rains season began five to seven days earlier than normal in the southern region and along the Yangtze, according to the China Meteorological Administration.
“The season has come earlier, and it’s expected to continue later this year,” said Wang Yongguang, chief forecaster at the National Climate Center.
Instead of ending as usual in the later part of the first 10 days of July, the season may linger until the middle of the month, putting great pressure on flood control efforts along the Yangtze River, he said.
Forecast bodes ill
Wang said that rainfall in the middle and lower reaches of the Yangtze, and in Yunnan and Guizhou provinces, will be heavier than normal in July.
The excessive rainfall has posed challenges to China’s flood control efforts, but experts are mostly concerned about small and midsize rivers.
“Currently, the flood control pressure in the country is more on midsize and small rivers,” said Cheng Xiaotao, a member of the expert committee of the National Disaster Reduction Committee.
Flood control capabilities in major rivers are “completely different” from those in 1998. While a series of water conservancy projects have begun operations since 2000, including the Three Gorges Dam on the Yangtze, the reinforcement of dikes along major rivers has been completed, said Cheng, also former head of the institute for flood control and disaster relief at the China Institute of Water Resources and Hydropower Research.
“We now have more confidence to say that we can better prevent extraordinary floods,” he said.
Wang, of the National Climate Center, said the Three Gorges Dam plays a big role in helping mitigate floods.
“The dam can discharge water as needed based on water levels in the middle and lower reaches of the Yangtze to help relieve the flood control pressure in the mainstream of the river. There was no Three Gorges Dam to facilitate flood control efforts in 1998,” he said.
The Yangtze’s first flood this year came at the dam on July 2 with a peak flow rate of 53,000 cubic meters per second, raising the reservoir’s water level to 149 meters.
“The current flood situation in the Yangtze’s main course is not particularly severe, so the reservoir’s flood storage capacity has yet to be fully utilized,” Bao Zhengfeng, an official at the Three Gorges Cascade Dispatch and Communication Center, was quoted as saying in a Xinhua News Agency report published on Wednesday.
The reservoir discharges water every flood season so that it will have more space to accommodate incoming water surges. It can handle a water level of up to 175 meters.
But “great uncertainties” remain in precipitation this year, and that will complicate the flood control situation along the midsize and small rivers, whose water control facilities lag behind.
Forecasts done at the beginning of the year all pointed to there being more precipitation this year. But opinions differ on which area will be affected more. “There are big uncertainties,” Cheng said.
It is also hard to predict what places are the center of downpours, even though forecasts can be increasingly accurate on what areas are to be affected as torrential rains approaches, he noted.
“People and materials for flood control are limited. If the forecasts can confirm the affected areas, we know where we should dispatch the people and materials. When there are uncertainties, we have to roll out precautionary measures here and there. The uncertainty itself is a kind of risk,” Cheng said.
He said COVID-19 epidemic control measures also complicated the flood-control situation this year. Previously, local governments were responsible for investing in flood control projects on midsize and small rivers, most of whose dikes are earthen. Some governments, however, were too financially overburdened to make adequate investments, Cheng said.
Though the central government has been investing in these projects since it initiated a national campaign to ramp up flood control management in key sections of these rivers in 2009, dike reinforcement there cannot be completed in the short term, he said.
In addition, the maintenance of dikes is mainly conducted in the winter and spring, which has also been hampered this year because social movement was restricted at that time for the control of COVID19 pandemic.