Basic introduction
Qianjiang Guanchao is located in Yan Guan Town, Haining, 45km northeast of Hangzhou. It is caused by the gravity of celestial bodies and the centrifugal effect of the earth's rotation, as well as the special terrain of the bell mouth of Hangzhou Bay. Every year on the 15th day of the eighth lunar month, the tidal bore in Qianjiang River is the largest, and the tidal head can reach several meters. When the tide came, the sound was like thunder, and the avalanche was spectacular. Tide-watching began in the Han and Wei Dynasties (1 6th century) and flourished in the Tang and Song Dynasties (7th century to13rd century). After more than two thousand years, it has become a local custom.
cause
in time
From August 16 to August 18 of the lunar calendar, the sun, the moon and the earth are almost in a straight line, so the tidal gravity (the difference between the gravity of the moon, the sun or other celestial bodies on the earth and the gravity of the earth per unit mass, or the resultant force of the inertial centrifugal force generated by the movement of the earth around the center of mass and the gravity of the moon (the sun)) is the largest.
Geographical advantage
It is related to the trumpet-shaped estuary of Qiantang River. Nearly 500,000 mu of land was reclaimed to the east of Zheshan Mountain on the south bank of Qiantang River, which blocked the estuary like a peninsula, making the section from Zheshan Mountain to Qiantang River 12 like a small belly bottle, which is easy to retreat when the tide rises. The width of the outer mouth of Hangzhou Bay is 100 km, which is only a few kilometers away from the outer 12 section. The riverbed in the eastern part of the estuary suddenly rises and the beach is shallow. When there is a large number of tidal bore in the mouth of Qiantang River, it is difficult to ebb because of the rapid contraction of the river surface. Secondly, it is related to the sediment deposition under the Qiantang River, which blocks and rubs the tidal current, making the front slope of the tidal current steep and gentle, thus forming a wave after catching up with the front wave, and one wave overlaps with another.
wind power
Southeast winds are often blown along the coast, and the wind direction is roughly the same as the tide, which is helpful to the tide.
The tidal water in Qiantang River is related to the peak discharge and total flood volume in the first three or four months of tide. According to the values of peak discharge and total flood volume, the tide can be estimated. Han Zengcui, a professor-level senior engineer and consultant of the Institute of Water Conservancy and Estuary, said, "The tide at 20 12 may be slightly smaller than that at 20 1 1, but it is definitely larger than that in 2004, 2007 and 2008."
Zhou, director of Hangzhou Water Conservancy Facilities Supervision Center, said that many people don't know the power of the tide, and they think they can run back to the levee before the tide comes. Zhou said that this idea is seriously wrong. He took out a set of data: the average person runs only 6-8 meters per second, but in the spring tide, the tide speed can reach 12 meters per second, and only Liu Xiang, an Asian flier, can go with the flow.
Best viewing period
The middle of August in the lunar calendar is the best time to watch the tide. It has the reputation of "August 18th Tide, without it in the spectacular world". In fact, the tidal bore of Qiantang River changes regularly, and the tide is restricted by many factors, such as astronomy, geography, river bed elevation, runoff, the direction of the main channel (channel), climate and so on.
Except for the first half and the second half of the lunar calendar, August and a half are not necessarily chosen. But the autumn tide is bigger than the spring tide, because the rainfall in Qiantang River basin is mainly concentrated in the rainy season and typhoon season from mid-March to mid-September; The rainfall from June 65438 to February of the following year is relatively small. In different places, you can enjoy different tidal scenes, such as "first-line tide" in the tower, "confluence tide" in the babao and "ebb tide" in the old salt warehouse.
The most dangerous viewing spot
Zhou, director of Hangzhou Water Conservancy Facilities Supervision Center, believes that the north and south banks of Qiantang River have different degrees of danger according to different topography, and the downstream is generally more dangerous than the upstream. There are eight specific danger points, which should be paid special attention to when watching the tide: Haining Daxia, Haining Laoyancang, Qibao, Xiaoshan No.9 Dam, Xiasha No.7 Grid, Xiaoshan Meiren Dam, Sanbao and Jiuxi.
Zhou particularly stressed that you must not enter the dangerous area in the early hours of the morning, flood season and other dangerous periods, otherwise you will lose the opportunity to escape because you can't see clearly or handle it calmly. According to the characteristics of tidal bore in Qiantang River, the spectacular tidal scene is often the most dangerous place, so tourists should never go down to the beach and groin to watch the tide.
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