From August 18 to 20, the Yangtze River No. 5 Flood in 2020 and the Jialing River No. 2 Flood in 2020 ran past Chongqing's central town. Compared with the previous four Yangtze River floods and one Jialing River flood, both the Yangtze River No. 5 Flood and the Jialing River No. 2 Flood have gained in intensity. Even before the arrival of the flood peak, hydrometric stations at many districts and counties have reported higher-than-warning-line or higher-than-safe-line water levels.
On the evening of August 18, on Changbin Road in Yuzhong District, floods spread over the road, and cars passed by the ship. Photo by Cui Li.
But why? Will there be more floods on more large rivers in Chongqing as this year's flood season hasn’t yet come to an end? With these questions, the reporter interviewed related experts from Chongqing Water Resources Bureau, Upper Yangtze River Bureau of Hydrology and Water Resources Survey, and Chongqing Municipal Hydrological Monitoring Station on August 18.
Why is this round of floods more intense?
Over the past more than a month from July 2 to August 15, four floods had run through the Three Gorges Reservoir, and Chongqing took a little hit during all of them. But how come the Yangtze River No. 5 Flood and the Jialing River No. 2 Flood are so intensely felt by Chongqing?
At 18:00 on August 19, the peak of the Jialing River flood merges into the Yangtze River and passes through Jiangbei City.
"A larger amount of incoming water with higher peaks from the upper reaches, short interval of flooding times, and the already high water levels of the Yangtze River and the Jialing River in the central town of Chongqing are the main reasons," said Song Gangyong, Director of the Flood Prevention and Relief Department of Chongqing Water Resources Bureau.
From August 14 to 18, major tributaries of the Yangtze River in the upper reaches including Minjiang River, Tuojiang River, Fujiang River, and Jialing River were hit by rainstorms and downpour. Such persistent precipitation is very rare and has caused floods in many places in Sichuan. Of them, the water levels of Minjiang River, Tuojiang River, and Jialing River exceeded the warning line, the water level of Fujiang River crossed the safe line, and the incoming water from the upper reaches of the Yangtze River suffered a sudden rise.
At 13:00 on August 16, the Jialing River No. 2 Flood was formed; at 14:00 on August 17, the Yangtze River No. 5 Flood was formed. As the Yangtze River No. 4 Flood and the Jialing River No. 1 Flood were just past Chongqing's central town on August 14, the water levels of the Yangtze River and the Jialing River in Chongqing are already quite high. But a new round of floods already starts to run through Chongqing at a very short interval. All these have made Chongqing's flood prevention and relief tasks more challenging and arduous. At 11:00 on August 18, the Bureau of Hydrology of the Changjiang Water Resources Commission elevated the flood warning grade for Minjiang River, a tributary in the upper reaches of the Yangtze River. The most intense flood in the history of Minjiang River has also greatly impacted Chongqing's flood prevention and relief work.
Due to these reasons, this round of floods is much more intense.
Slight possibility of more numbered floods in this month
This year along, five numbered floods happened on the Yangtze River and two on the Jialing River. Chongqing runs through by the two rivers has been put to the test of floods for many times. Will there be more floods on the Yangtze River and the Jialing River in Chongqing this year?
Xiao Zhong, Deputy Director of the Upper Yangtze River Bureau of Hydrology and Water Resources Survey, answered the question based on scientific analysis and judgment. From August 18 to 19, the rainy days of Minjiang River, Tuojiang River, and Fujiang River were coming to an end. Because the three are major tributaries of the Yangtze River in the upper reaches, incoming water will grow less and less with the end of their rainy weather. But medium to heavy rains will continue in Qujiang River, the upper reaches of Wujiang River, major tributaries of the Yangtze River in the upper reaches, and Chongqing's surrounding areas. Based on comprehensive judgment, the water level of Beibei hydrometric station of the Jialing River is expected to reach the peak on August 19, and that of Cuntan hydrometric station of the major tributaries of the Yangtze River on August 20, and afterward, the water levels of the Jialing River and the Yangtze River in Chongqing will decline bit by bit.
Citing some preliminary analysis and judgment, Xiao added that the water level of the Cuntan hydrometric station is predicted to be lower than the safe line of 183.5 meters by August 23, and the warning line of 180.5 meters by August 24. In conclusion, the possibility that Chongqing's large rivers or their tributaries will be hit by numbered foods more intense than the Yangtze River No. 4 and No.5 floods by the end of this month is very slight.
Possible flooding at medium and small rivers in northeastern Chongqing from September
As the flooding at large rivers like the Yangtze River and the Jialing River is subduing, what's the situation of medium and small rivers?
Qiu Peng, Deputy Director of Chongqing Municipal Hydrological Monitoring Station, answered that flooding of varying degrees may happen at medium and small rivers in central and northeastern Chongqing around August 20, and some main rivers in western Chongqing may face the same situation around August 23.
Moreover, the Huaxi autumn rain season will set in with the arrival of September. According to Qiu, Huaxi autumn rain is a special weather phenomenon that takes place in western China during autumn from September to November. As the rain season sets in, it will rain often but not hard, or rather drizzle. So either by rainfall or intensity, autumn rain cannot compare with summer rain. But as predicted by the meteorological authority, it will set in earlier and with enhanced intensity this year.
"In other words, this year's Huaxi autumn rain will be more 'violent'," Qiu added that it will lead to a more violent collision of cold and warm fronts and thus higher rainfall intensity. Therefore, as September arrives, flooding of varying degrees may happen at most medium and small rivers in Chongqing, especially northeastern Chongqing where water levels may cross the warning line and safe line.