Why does the Qiantang River tide come on August 18 every year

Why did the tide of money rise on 18 August?

Tides are caused by the attraction of the moon and the sun, mainly the moon, to the seawater on the earth's surface. Around the first day of the lunar month and around the fifteenth day of the lunar month, the sun, moon and earth are arranged in a straight line, and the gravitational pull of the sun and the moon is combined to attract the sea water on the earth's surface, so the tides on the first and fifteenth days of each month are particularly large. Every year around the Mid-Autumn Festival, the moon and the sun have the greatest attraction to the earth, so the autumn tide around August 15 of the annual calendar is relatively large.

The autumn tide of the Qiantang River, which is more spectacular than the autumn tide in other places, is due to the special topography of Hangzhou Bay. The place where the Qiantang River enters the sea is called Hangzhou Bay, Hangzhou Bay is wide on the outside and narrow on the inside, the width of the sea is up to 100 kilometers, it shrinks to about 20 kilometers to the west near Pengpu, and then it is only three kilometers wide to the west near Yanguan in Haining County. The tide has just entered Hangzhou Bay, the water surface is wide, the more west it is, the more it is constrained by the topography on both sides of the river, the tide can not be widened, it has to gush up, the tide head accumulates higher and higher, like an upright water wall, advancing to the west.

At the same time, due to the action of the tidal current, a large amount of sediment poured into the sea of the Yangtze River is constantly brought to Hangzhou Bay, and gradually forms a huge volume in the Qiantang River estuary, like a threshold"Estuary Shakan".When the sea pushes the river water to the mouth of the Qiantang River, the sand kan blocks the tide, forming a spectacular scene of the back wave catching up with the front wave, wave after wave.

The tide of Qiantang is eight to nine meters high, and it is fierce, and the tide end is erected. When the tide comes, it is like a galloping horse. The surging tide hits the sea pond (seawall), and the waves splash and roar like thunder. This is the world-famous Qiantang tide.

Here's why:August 18 here refers to the eighteenth day of August in the lunar calendar, that is, three days after the Mid-Autumn Festival, usually the Qiantang tide water level is the highest on this day of the year, the most spectacular, this time is also the autumn season, so it is also called "autumn tide". Of course, in fact, the Qiantang River can also see spectacular tides in other seasons, but the tide is the most spectacular on August 18 every year.

Introduction:

Qiantang River, known as Zhejiang in ancient times, the full name is "Zhejiang", also known as "Zhejiang", "Zhijiang", "Rakshasa River", generally the Fuyang section of Zhejiang is called Fuchun River, and the Hangzhou section of the lower reaches of Zhejiang is called Qiantang River. The Qiantang River was first named in the Classic of Mountains and Seas, and was named after the ancient Qiantang County (now Hangzhou), which is one of the main birthplaces of Wuyue culture.

The Qiantang River is the largest river in Zhejiang Province, the name of the Liangzhejiang Road in the Song Dynasty, and the name of the province when Zhejiang Province was established in the early Ming Dynasty. Calculated from the Xin'an River in the north, the river is thousands of kilometers long; Calculated from the Majin River in the upper reaches of the Qujiang River in the south, the river is thousands of kilometers long. From its source, it flows through the southern part of present-day Anhui Province and Zhejiang Province, with a basin area of 55,058 square kilometers, and flows into the East China Sea through Hangzhou Bay.

Every year on the eighteenth day of the eighth month of the lunar calendar, the tide of the Qiantang River is the largest.

1 From the 16th to the 18th day of the eighth month of the lunar calendar, the sun, the moon, and the earth are almost in a straight line, and the sea is subject to the greatest tidal force on this day.

2 During this season, southeasterly winds blow along the eastern coast and are generally in line with the direction of the tide, contributing to the tide.

3 This season is also the period when the Qiantang River has the greatest amount of water.

Hello dear, this is mainly due to the geographical advantage. The cause of the tide of the Qiantang River is due to the favorable time, location and wind: the time of the day

From the 16th to the 18th day of the eighth month of the lunar calendar every year, the sun, the moon and the earth are almost in a straight line, so the sea water is subject to the greatest gravitational force on this day. Geographical advantage: Qiantang River Zheshan to the outer 12 kilometers section is like a big belly mouth small bottle, the tide is easy to advance and difficult to retreat, the outer mouth of Hangzhou Bay is as wide as 100 kilometers, to the outer 12 sections are only a few kilometers wide, the riverbed in the eastern section of the estuary rises suddenly, the beach is high and the water is shallow.

When a large amount of tide water pours in from the mouth of the Qiantang River, due to the rapid shrinkage of the river surface, the tide does not have time to rise evenly, so it has to push the back wave to push the front wave, layer upon layer, the Qiantang River is related to the sedimentation of more sediment under the water, these sedimentation plays a role in blocking and friction against the tide, making the front slope of the tide steepen, and the speed slows down, so as to form the back wave to catch up with the front wave, and the wave is stacked and surging. Winds: Southeasterly winds often blow along the coast, and the direction of the wind is roughly the same as the direction of the tide, which contributes to the tide.