Qiandao Lake is the first time to fully open 9 holes for flood discharge. What does this mean?

Undoubtedly, this shows that the continuous rainstorm this summer has seriously affected the lives of residents, the water situation in the middle and lower reaches of the Yangtze River is in a hurry, and the flood control work in Hangzhou is not easy. Since the beginning of July this year, heavy rains have occurred frequently in the middle and lower reaches of the Yangtze River. Most of the middle and lower reaches of the Yangtze River have reached a record high in July, and the water levels of rivers and lakes are rising. The streets of many cities are seriously flooded, and China soldiers risk their lives to save people every day. Qiandao Lake has also increased from 3 holes to 5 holes and then to 7 holes, but the water level in Qiandao Lake is still rising. At 9 o'clock on the morning of July 9, the water level of Qiandao Lake exceeded the flood limit level, and Qiandao Lake opened 9 holes for flood discharge for the first time. But this does not mean that the flood is too serious to control. Although there are statistics, after the flood discharge of 9 holes in Qiandao Lake is opened, the flood discharge is close to 8000 cubic meters per second, and a West Lake can be discharged in half an hour. The water level of Qiandao Lake has been gradually decreasing within one hour after the flood discharge of 9 holes was opened. This has greatly alleviated the flood hazard in the upper reaches of the Yangtze River.

It is worth mentioning that this year, the flood limit water level of Qiandao Lake is set at106.5m, while only two of the seven flood discharges in Qiandao Lake's history are lower than107m. This means that the subsequent rainfall will still make the water level of Qiandao Lake rise, setting off the seriousness of this rainstorm.

The more spillway tunnels, the more serious the impact on the cities along the Xin 'anjiang River, and the street water level in these cities will rise rapidly. Before deciding whether to increase the number of flood discharge holes in Qiandao Lake, the municipal defense department needs to weigh the risk of flood disaster with the convenience of urban residents along Xin 'an River and the losses caused by flood discharge to these cities.

The opening of the 9-hole flood discharge in Qiandao Lake also represents the unusually long stay time of the quasi-static front in the middle and lower reaches of the Yangtze River this year. Because the precipitation type in the middle and lower reaches of the Yangtze River is mainly Meiyu.