It has been a long-standing tradition for people living near the mouth of the Qiantang River to celebrate the Mid-Autumn Festival by watching the tidal bore*, which they enjoy from a safe distance while enjoying another staple of the Mid-Autumn Festival: moon cake.** The International Qiantang River Tidal Bore Watching Festival, as it is now called, has also become a popular attraction for tourists.
Tourists Watching Qiantang River Tide
Yanguan Town in Haining County, Zheijiang Province, just north of Hangzhou Bay (and some 50 kilometers northeast of the city of Hangzhou), into which the Qintiang River empties, has long been regarded as the best place to watch the Qiantang River Tidal Bore. The annual International Qiantang River Tidal Bore Watching Festival is held in Yanguan Town on 18th day of the eighth lunar month.
When the tide approaches, the sight of its mighty surge has been compared to the sight of ten thousand horses racing side by side across an open plain. The height of this special tidal wave can reach 9 meters. Its earthshaking sound rumbles across the water like muffled thunder, its crushing force eerily reminiscent of that of an avalanche which gains speed as the momentum of its cumulative weight propels it forward.
The scene of the Qiantang River is ever-changing, as is the height of its waters where they empty into Hangzhou Bay. When the frothy tide appears in the distance, it initially looks like a white rainbow, given its natural curvature, rising from a plain. As it surges forward, the tidal bore gains speed. Some of the local observers of this regularly recurring phenomenon even race it in their automobiles during the final stages to see if they can keep abreast of it as it gains speed. As the tidal bore proceeds up the Qiantang River, the aftermath of the surge remaining in Hangzhou bay continues to make its presence felt. The "boiling waters" underneath the surface of the bay, depending on the strength of the tidal bore, can sometimes form a huge circular "ribbon" on the surface of Hangzhou Bay, a sight that is particularly majestic to behold at nighttime.
A word of caution: Since the forces involved in producing a tidal bore, as well as its "after shocks", are immensely powerful, warning signs have been posted to caution onlookers to remain behind a designated perimeter in order to avoid danger, especially since the "ribbon" effect can create an undertow that is life-threatening (one can be sucked underwater and transported for hundreds of meters before being released). Alas, in spite of these clearly posted warnings, a certain number of foolhardy individuals perish every year during a tidal bore at Hangzhou Bay!
* A tidal bore is the term used to describe the phenomenon of the leading wave of a rising/ incoming tide as it rushes up a river or a narrow inlet from a larger bay (think of a funnel). It is a dramatic sight that is the more dramatic the greater the funnel effect, i.e., the greater the size of the bay and the smaller/ narrower the river/ inlet. If the difference between the two is great, then not only will the incoming wave be high (in France and in certain other parts of the world where the "funnel" is exaggerated, surfers sometimes ride the tidal bore, though not without risk to life and limb), the water level will rise significantly, and can remain at this height for a half-hour or more.
The largest, or most forceful, tidal bores occur during spring tides (aka springs), when the sun, moon and earth all line up (in any order), thus increasing the gravitational pull on the earth. This occurs during a new moon or during a full moon. The tidal bore is at its weakest at neap tides (aka neaps), when the sun and moon are separated by 90 degrees (during the first-quarter or third-quarter moon), for the gravitational pull from the one tends to cancel the pull from the other.
The most famous tidal bore is the Mascaret which ascends the Seine. Other famous tidal bores, besides the impressive tidal bore on the Qiantang River (aka the Hangzhou bore), include the Benak on the Batang Lupur River in Malaysia, the Pororoca on the Amazon River in Brazil, and the Hooghly on the Hooghly River, a canal-like tributary to the Ganges River in Murshidabad, in India. There are smaller tidal bores elsewhere, as well as large, nameless tidal bores on other rivers of the world, such as on the Pungue River in Mozambique and on the Mekong River in Vietnam.
** Moon cake is a Chinese pastry that is considered an exquisite delicacy. The pastry-like moon cake, in contrast to traditional Western pastries, is dense, and therefore quite heavy. It has a relatively thin crust with a rich filling commonly consisting of a paste of lotus seed and duck egg yolks. The cake is usually round, but may occasionally be rectuanglar. It is about two inches (4-5 centimeters) high. Brushed with egg whites before baking, the cake's shiny exterior is very appealing, nor does interor disappoint, of course. Moon cake is usually eaten in small wedges served with a traditional Chinese tea. It is a staple of the Chinese Mid-Autumn Festival.