Why does the Qiantang River have such big waves?

The reasons for the formation of spring tides in the Qiantang River are as follows:

1. Every time the earth rotates once (24 hours), a certain point must face the moon once and face away from the sun. When facing the moon, the moon's gravity is greater than the earth's centrifugal force, causing the sea water to rise. When the moon is behind the moon, the centrifugal force of the earth is greater than the gravitational pull of the moon, and the sea water rises again, resulting in the natural phenomenon of sea water rising twice a day.

2. On the first and fifteenth day of the lunar calendar, the positions of the sun, moon, and earth are basically aligned, and the gravitational pull of the sun and the moon is consistent, forming a spring tide. But in the Mid-Autumn Festival in the eighth month of the lunar calendar, because the earth's revolution around the sun is on the short axis of the elliptical orbit, the sun and the moon are closest to the earth, and the energy to attract tides is the greatest, thus forming an annual extremely large tide.

From September 17th to 23rd, there will be spring floods, especially the tide on August 18th (September 21st) is the most spectacular, and it is also the best time to watch the tide on the Qiantang River.

Extended information:

The Qiantang River is located in Zhejiang Province, my country, and eventually flows into the East China Sea. The tide at its mouth is famous all over the world, and many tourists come to watch this spectacle every year. Before the arrival of the tide, a tiny white dot first appeared in the distance, and in a blink of an eye it turned into a wisp of silver, and accompanied by bursts of thunderous tide sounds, the white line rolled in.

With almost no time for people to react, the surging tide has roared in. The peak of the tide is 3-5 meters high. The waves behind are catching up with the waves ahead, one layer after another, like a long white belt. It has the potential to overwhelm mountains and seas.

The poem goes: "As soon as I look at Qiantang, there are endless waves, and suddenly the waves are in front of me; the energy contained in the seemingly ordinary river water is astonishing." The tide comes from far and near, speeding in, and the tide pushes and embraces, The sound is like thunder, the beads are sprayed and the jade is splashed, and the momentum is like ten thousand horses galloping. Tide watching began in the Han and Wei dynasties and flourished in the Tang and Song dynasties. After more than 2,000 years, it has become a local custom.

Baidu Encyclopedia-Qiantang River Tide