Tide of Qiantang River

In ancient times, the Qiantang River only had general tidal fluctuations from the Gushan estuary in Fuyang. Over time, the Yangtze River in the north gradually carries sediment from the upper reaches, forming the Taihu alluvial plain on the north bank of Hangzhou Bay, and forming a unique estuary form with the relatively stable south bank. At present, the mouth of Hangzhou Bay is 100 km from Nanhuizui on the north bank to Zhenhai on the south bank, but it reaches Yan Guan at 132 km upstream, and the river surface is actually reduced to 2.5 km wide, forming a huge trumpet-shaped estuary on the plane. The trumpet-shaped estuary structure makes more tides flow into Hangzhou Bay in the diurnal tide, which pushes the sediment deposited near the estuary to move into the bay and slowly forms a sand bar at the estuary. Similarly, due to the constraint of the shape of the bell mouth, the estuary shrinks inward and the tide

The greater the difference between the water surface and the river surface, the tidal bore will form. Under the influence of the moon's gravity, when the incoming tide reaches the vicinity of Yan Guan in Daxinganling, the highest tidal head can reach more than 3 meters, and it pushes upstream at a speed of 5-7 meters per second, just like a bamboo, which is spectacular.

The story of high tide in Qiantang River

When the Qiantang River is at high tide, like other rivers, there is neither tide nor sound.

One year, a giant came by the Qiantang River. The giant was so tall that he crossed from one side of the river to the other. He lives in Shushan, Xiaoshan County, and sets fire to salt. People don't know his name, because he lives by the Qiantang River, so they call him Qian Wang. Qian Wang has great strength. He often used his iron pole to pick some big stones and put them on the river. Soon, he piled up one mountain after another.

One day, he went to pick the salt he had burned in Shushan for three years and three months. However, the salt was only enough for him to hold one end, so he tied a big stone to the other end of the pole, tried it on his shoulder, and picked it up and crossed the north bank of the river.

It was hot at this time, and Qian Wang was a little tired because he had just had lunch, so he put down his burden and had a rest. Unexpectedly, he dozed off Just then the Dragon King of the East China Sea came out to patrol the river, and the tide came in. Up and up, even up to the shore, slowly melting all the salt on Qian Wang. When the Dragon King of the East China Sea heard that there was no such salty taste in the water, it became more and more salty. He couldn't take it anymore, so he turned around and ran away. He doesn't want to escape to the ocean and make the sea salty. King Qian slept, opened his eyes and found that the stone at one end of the pole was still on Shixia Mountain (now Shixia Mountain), but the salt at the other end was gone!

Qian Wang looked everywhere, but he couldn't find salt. As soon as he looked down, he smelled the salty taste in the river. He thought, oh, no wonder the salt is gone. Stolen by the East China Sea Dragon King. So he raised his pole and smashed it into the sea. A pole hit the big fish and they all died; Two poles turned over at the bottom of the river; The three poles brought the Dragon King of the East China Sea to the surface, begging for mercy.

The Dragon King of the East China Sea asked Qian Wang why he lost such a big temper. Qian said, "Where did you steal my salt?" The Dragon King of the East China Sea realized the reason why the seawater became salty. Make amends at once, and tell me how to patrol the river, how to melt the salt of Qian Wang unintentionally, and make the sea water salty.

The king of money was so angry that he really wanted to lift the iron pole and smash the dragon king of the East China Sea to death. The Dragon King of the East China Sea repeatedly kowtowed in panic and begged for mercy, promising to compensate Qian Wang with the salt in the seawater. Call it up when the tide rises in the future, so that the rich king won't fall asleep and can't hear it. Hearing that these two conditions were not bad, Qian Wang spared the Dragon King of the East China Sea, put the pole at the mouth of Hangzhou Bay and said, "Call from here when the tide is high!" The Dragon King of the East China Sea promised again and again, and the money king left happily.

From then on, as soon as the tide entered Hangzhou Bay, it stretched out its neck and cried noisily until it rose to the place where Qian Wang had sat, and its neck stretched out to the top and shouted loudly. This place is now Haining. This is the origin of the world-famous Qian Jiangchao.

August and a half is the best time to watch the tide. 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. In fact, the first half and the second half of the lunar calendar are good times to watch the tide, and it is not necessary to choose August and a half. 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.

Tide of Qiantang River

On August 18 of the lunar calendar, people flocked to Haining, Zhejiang Province to watch the tide. At this time, the shore was crowded with people, and people were anxiously waiting for the exciting moment. After a while, I suddenly saw the crowd stir up and saw a white line in the distance, from far to near; In an instant, the wall stood on the tide, like a tall water wall, roaring and sweeping in, making a thunderous roar, which was deafening. This is really: "the sky is full of turbid waves, and rivers and mountains are destroyed." This is the world-famous tide of Qiantang River. The magnificent Qiantang River is known as the "Wonder of the World". People usually call this tide "tidal bore", and some people call it "tidal bore". Many estuaries in the world also have tidal bore. For example, the Amazon River in Brazil and the Seine River in France. The spring tide of Qiantang River in China is also world-famous.

Why is there such a spectacular tidal bore?

First of all, this is related to the shape and special topography of Hangzhou Bay where Qiantang River enters the sea. Hangzhou Bay is trumpet-shaped with a big mouth and a small belly. The channel of Qiantang River narrows and rises sharply from the west of Ganpu, which leads to the sudden decrease of riverbed capacity, and a large number of tides flood into the narrow and shallow channel, and the tidal head is blocked, and the tidal head behind it advances rapidly, forcing the tidal head to stand, break and roar, forming a breathtaking and spectacular scene. Secondly, there is a huge sandbar in the estuary. When the tide rushes in and meets with strong resistance, it will definitely lift the sky. The front wave was suppressed and the back wave rose again. Waves push waves, and waves overlap. The tide naturally surges and growls, coming like an avalanche. The height of tidal head can reach more than 3.5m, and the tidal range can reach 10m. Third, the spring tide is related to the gravity of the moon and the sun. Tide is a periodic fluctuation phenomenon of seawater under the gravity of the moon and the sun. The tide in Qiantang River is mainly caused by ebb tide, so it is also related to the gravity of the moon and the sun.

Qiantang river tidal bore

Scientists believe that the generation of tidal bore is also related to the ratio of water velocity to tidal wave velocity in rivers. If they have the same or similar speed and are evenly matched, it will be beneficial to the generation of tidal bore. If the speed difference between the two is far, even if there is a trumpet-shaped estuary, there will be no tidal bore.

In addition, tidal bore can be formed in the estuary, which is related to tidal range in other places. Because Hangzhou Bay is located on the west coast of the East China Sea, the tidal range between Hangzhou Bay and the East China Sea is larger than that of the East China Sea. The tidal waves in the Pacific Ocean enter the East China Sea from the northeast, and are deflected to the right by the geostrophic bias in the process of going south, so that the tidal range between the two sides of the Taiwan Strait is greater than that on the east coast.

Hangzhou Bay is located in the place where the Pacific tidal waves come straight from the east, and it is also the position with the largest tidal range on the west coast of the East China Sea. Therefore, various reasons come together and contribute to the tidal bore of Qiantang River.

Cross tide

55 kilometers away from Hangzhou Bay, there is a place called Daguan, which is an excellent place to watch the tide. Due to the long-term deposition of sediment, a sandbar is formed in the river channel, which divides the tidal wave from Hangzhou Bay into two waves: the east tide and the south tide. After bypassing the sandbar, the two tidal heads crossed and embraced like two brothers, forming a varied and spectacular cross tide, showing a spectacular scene of "thunder gathering on the sea and waterfalls crossing the river". At the moment when the two tides collided, a water column was stirred up, which was as high as several feet, splashing and stirring. By the time the water column fell back into the river, there were already two tidal heads on the river, which were cross-shaped and quickly ran west. At the same time, the intersection moved northward like an avalanche, hitting the straight seawall, causing huge splash and landing on the top of the pond, scaring tide watchers to scream and avoid.

Yixianchao

After seeing the tide crossing in the Great Gorge, I suggest you drive to Yan Guan as soon as possible and wait for the first tide. No tide shadow, smell the tide first. There was a loud noise in my ear, and the river remained calm. The noise is getting louder and louder, like drumming on all sides, which is deafening. In the distance, a white line appeared on the foggy river, which moved rapidly to the west, just like "Pingchuan crossing the river, Changpingsha starting from Bai Hong". Closer, the white line becomes a water retaining wall and gradually rises. "If you want to know how high the tide is, you must cross the mountains and waves first." With the rapid advance of a white wall, the tidal bore came to our eyes. With the trend of Ma Benteng, the power of thunder was unstoppable.

The first-line tide is not unique to salt officials. Where the river is straight and there is no sand, the tides are all on the same line, but it is not as good as the salt official. The reason is that the position of the upstream Yan Guan and the width of the river channel shrink sharply, and the east and south tides meet in a straight line, so the tidal level energy is concentrated, and the tidal range is particularly large, usually 1-2 meters, and sometimes it can reach more than 3 meters. Magnificent and spectacular tidal scene.

Huitouchao

The tide in the upper reaches of Yanguan will reach the next tidal spot, Laoyancang. The geographical environment of the old salt warehouse is different from that of the dry salt official. The river is straight and the tidal bore advances westward without any obstacles. For the purpose of reclamation and seawall protection, a 660-meter-long groin was built on the river course of the old salt warehouse. After encountering obstacles, the roaring tide will be reflected and turned back, where it will violently hit the opposite dam, and then turn back with the trend of Mount Tai topping, and fall on the rapids moving westward, forming a row of "snow mountains".

The spring tide of Qiantang River is magnificent during the day and poetic at night. Watching the tide is a kind of enjoyment, and listening to the tide is a daydream. No wonder some people say that "the Qiantang national ceremony is not enough to see the hipsters until they are bald."