Qiantang Tide

Qiantang Tide

(Photography: Wang Feiqing)

Photo: Taken by Wang Feiqing on October 1, 2012

Dingqiao Tide and Meeting of Tides

Among the most famous tidal bores in Chinese history, there are three: the Qingzhou Tidal Bore in Shandong, the Guangling Tide, and the Qiantang Tide.

The Qing Dynasty’s Fei Xinghuang (1664–?) wrote in *Debating the Guangling Tide*: “During the Spring and Autumn period, tides were strongest in Shandong; during the Han and Six Dynasties, they were strongest in Guangling. After the Tang and Song dynasties, tides became strongest in Zhejiang, probably because the earth’s energy flows from north to south, as those who truly understand it know.”

The Qiantang Tide emerged slightly later than the Guangling Tide, forming no later than the Eastern Han Dynasty. Wang Chong’s *Lunheng·Shuxu Pian* mentions that “the Qiantang River, Shan Yin River, and Shangyu River all have tides.” It also states that at the time, the Qiantang section of the river “all had temples dedicated to Wu Zixu, probably to appease his resentment and calm its fierce tides.” However, Wang Chong only mentioned that “the Qujiang River in Guangling had tides, which literati wrote poems about,” but did not mention poems about the Qiantang Tide. This shows that during the Eastern Han Dynasty, the Qiantang Tide was far less famous than the Guangling Tide. It is estimated that the custom of tide-watching at Qiantang had not yet formed at the time.

CCTV Live Broadcast of the August 16 Haining Single-Line Tide

Causes of the Qiantang Tide

The majestic and spectacular Qiantang Tide is caused not only by the gravitational pull of the moon and sun but also by the trumpet-like shape of the Qiantang River estuary. Nearly 500,000 acres of reclaimed land east of Zheshan Mountain on the southern bank of the Qiantang River acts like a peninsula, blocking the river mouth. This makes the section from Zheshan to Waishiergong resemble a bottle with a large belly and a small mouth, where the tide flows in easily but retreats with difficulty. The outer mouth of Hangzhou Bay is as wide as 100 kilometers, but narrows to just a few kilometers at Waishiergong. Additionally, the riverbed in the eastern section of the estuary suddenly rises, with shallow water and high shoals. When a large volume of tidal water surges into the Qiantang River mouth, the rapidly narrowing river surface prevents the tide from rising evenly. As a result, the waves push forward in layers, with the back waves catching up to the front ones, stacking one upon the other. Furthermore, the presence of underwater silt and sediment in the Qiantang River plays a role in obstructing and frictioning the tidal flow, causing the front slope of the tide to become steeper and its speed to slow down. This leads to the formation of a tidal bore where back waves chase front waves, layer upon layer, each wave higher than the last.

Features of the Qiantang Tide

Crossing Tides

About 55 kilometers from Hangzhou Bay lies a place called Dakouque, an excellent spot to view the crisscrossing tidal bore. Due to long-term sediment accumulation, a sandbar has formed in the river, splitting the tidal wave coming from Hangzhou Bay into two — the eastern tide and the southern tide. After circling around the sandbar, the two tides meet like brothers crossing and embracing each other, creating a constantly changing and spectacular crisscrossing tide, presenting a breathtaking scene described as “thunder gathering on the sea surface, a waterfall cascading across the river center.” At the moment the two tides collide, a water column is sent high into the air, several zhang tall, with splashing waves and a thrilling spectacle. When the water column falls back onto the river surface, the two tides have already formed a cross shape on the river and swiftly race westward. Meanwhile, the collision point rapidly shifts northward like an avalanche, crashing into the straight seawall and sending up a massive splash of water that falls onto the top of the wall, startling onlookers who scream and scramble to avoid it.

Single-Line Tide

After viewing the crisscrossing tide at Dakouque, it is recommended that you quickly drive to Yanguan to wait for the single-line tide. Before seeing the tide itself, you first hear its sound. A thunderous roar reaches your ears while the river surface remains calm. The sound grows louder and louder, resembling the beating of tens of thousands of war drums, deafening to the ear. In the distance, a white line appears on the misty river surface, swiftly moving westward, like “a white silk ribbon stretched across the river, a white rainbow rising from the flat sand.” Closer up, the white line turns into a wall of water, gradually rising, “to know how high the tide is, look how the mountains are submerged within the waves.” As this white wall rapidly advances, the tidal bore arrives before your eyes, with the momentum of ten thousand galloping horses and the power of thunder, unstoppable.

The single-line tide is not exclusive to Yanguan. Anywhere along the river where the channel is straight and free of sandbars, the tide front appears as a single line. However, none are as spectacular as at Yanguan. The reason is that Yanguan is located not far from where the river channel width sharply contracts upstream. The convergence of the eastern and southern tides forms a perfect straight line here, concentrating the tidal energy and resulting in an exceptionally high tide front, usually 1–2 meters, sometimes reaching over 3 meters. The momentum is overwhelming, and the tidal scenery is magnificent.

Backflow Tide

The tide flowing upstream from Yanguan will reach the next tide-watching spot, Laoyancang. The geographical environment of Laoyancang differs from that of Yanguan. At Yanguan, the river channel is straight, allowing the tidal bore to surge westward unimpeded. However, at Laoyancang, a 660-meter-long spur dike was built across the river for reclamation and seawall protection purposes. When the roaring tide encounters this obstacle, it is reflected back. There, it violently crashes against the opposite embankment, then rolls back with the force of Mount Tai collapsing, falling onto the westward-flowing current and forming a row of “snow mountains.” These rush eastward at lightning speed, sounding like a lion’s roar, earth-shattering — this is the backflow tide.

The Qiantang River tidal bore has the grandeur of daytime and the poetic charm of nighttime. Watching the tide is a joy, and listening to it is a form of reverie. No wonder someone said, “Those who come to watch the tides at Qiantang City never tire of it, even until their hair turns white.”

Midnight Tide

At midnight, a faint “rustling” sound can be heard from the river surface — the tide is rising. On the misty water, a dark ribbon floats intermittently, appearing and disappearing. Soon, the sound intensifies, and the tide rushes forth with a thunderous roar, shattering the moonlight on the river into fragments of silver. The tide front resembles thousands of gray-maned steeds jostling and grappling, spraying foam, charging straight toward the seawall like an army of 100,000 at the city gates. The front waves lead…

…the back waves, and the back waves push the front waves, forming a towering peak of tides on the river surface, with waves connecting to the sky, as if charging toward the bright moon in the heavens. At this moment, many tourists toss bonfires and reed flowers into the great river, letting them drift westward with the current, symbolizing their heartfelt wishes…

The best place to watch the Midnight Tide with the sound of 100,000 soldiers is around Tianfenghaitao Pavilion, known as the “Tianfeng Moon-Viewing” scene. Its romantic and unique atmosphere attracts a large number of tide-watching tourists. The Northern Song poet Su Dongpo even wrote a poem about it: “I know the jade rabbit is perfectly round, the September frost wind is already cold; tell the gatekeeper not to lock the door, leave it open so we can watch the night tide under the moon,” expressing his sentiments.

T-shaped Tide

Two tides form a ‘T’ shape. We don’t know how such a wonder is formed. The cause of the “T-shaped Tide” is still under research.