Why did 20 reservoirs in Shandong urgently raise gates to divert floods?
It was reported on August 31, 2018 that it was learned from the Shandong Provincial Flood Control and Drought Relief Headquarters that in response to the rainfall from August 27 to 28, the Shandong Provincial Flood Control and Drought Relief Headquarters promptly adopted a series of adjustments to the province’s reservoirs. To take measures, the "Emergency Notice on Reducing the Water Level of Over-Lined Reservoirs" was issued, requiring 20 reservoirs operating beyond the flood limit in Shandong Province to reduce the water level to below the prescribed indicators as soon as possible, strictly implement the approved reservoir flood season dispatch and operation plan, and ensure that Reservoir flood safety.
Lin Rongjun, chief engineer of the Shandong Provincial Defense General Office, said that previously, the Shandong Provincial Department of Water Resources sent a supervision team to investigate weak links in water conservancy projects and went to various parts of Shandong. Shandong Province has inspected 3,132 reservoirs, 596 rivers, 110 sluices, and 3,097 dams.
As for the dispatching and operation of the Weifang Reservoir during Typhoon "Wembia", which was of great concern to the public, Lin Rongjun said: "National laws have strict regulations on the dispatching and operation of reservoirs. Human lives are at stake, and there is no room for any mistakes." Shandong Province always adheres to safety first and regulates reservoirs in strict accordance with flood control plans. This has been done in response to heavy rainfall caused by typhoons such as 'Ambi', 'Capricorn' and 'Wumbia' since the flood season."
Today, an expert team from the Office of the National Flood Control and Drought Relief Headquarters gave clear opinions on the dispatch of the Weifang Reservoir during Typhoon "Wembia". The expert group believes that two consecutive extremely heavy rainfalls within a week are the main cause of floods. From August 13 to 16, the average rainfall in Weifang City was 94.1 mm. The rainfall that started on the 18th was more intense and heavier. The average rainfall in Shouguang City was 222 mm, the average rainfall in Qingzhou City was 259 mm, and the average rainfall in Linqu County was 229.8 mm. The total drainage area of the Mi River is 3,863 square kilometers. The reservoir-controlled drainage area accounts for nearly 30% of the total drainage area of the Mi River. Heavy rain floods in the remaining areas are not controlled by the reservoir and flow into the river along the natural terrain, flowing into the lower reaches of the Mi River and into the sea. Two typhoons overlapped within a week, and continuous heavy rainfall was the main cause of this flood disaster.
Expert analysis believes that the reservoir operation is in compliance with the regulations of the operation plan. Before the rainfall, the water levels in each reservoir were lower than the flood season limit levels. After the heavy rain and flood occurred, Weifang City dispatched the reservoir in accordance with the reservoir flood control plan, taking into account the upstream and downstream, and the left and right banks. On the premise of ensuring the safety of the reservoir dam, in order to reduce the flood pressure on the downstream river, the upstream reservoir adopted flood control measures. Peak-cutting scheduling. The maximum incoming flood peak of Heihushan Reservoir is 1,780 cubic meters per second, and the maximum outgoing flow rate is 960 cubic meters per second. The maximum incoming flood peak of Yeyuan Reservoir is 2,000 cubic meters per second, and the maximum outgoing flow rate is 700 cubic meters per second. Songshan Reservoir has the largest The flood peak is 278 cubic meters per second, and the maximum flow rate out of the warehouse is 120 cubic meters per second. If the reservoir does not release floods during heavy rains and floods, the floods from the Heihushan Reservoir will overflow the top of the earth dam, causing the dam to collapse, causing immeasurable major disasters to the downstream; the water level of the Yeyuan Reservoir is close to the top of the dam, and there is a great risk of dam collapse. ; The water level of Songshan Reservoir will exceed the flood limit level by nearly 2.4 meters, which is very likely to cause major dangers and endanger the safety of the dam.