As a cannon sounds in the distance to signal the start of celebrations, a dozen men get to work on the banks of the Min River. The team pulls on a bamboo rope, hauling up a ma cha - a tripod-shaped wooden frame filled with rocks secured by bound rope.
These are strung together in rows to hold back the water, functioning as a temporary floodgate.
Once the rows of ma cha are removed, fresh water rushes back into the river. This cascade signals the start of the biggest festival of the year, Fang Shui Jie - which literally means "Release the Water Festival" in Dujiangyan city, 50 kilometers from Chengdu.
The springtime festival, which evolved from ancient traditions and can be dated back at least 1,000 years, features various kinds of performance, plus acts of worship to the man who created the feat of hydrological engineering after which the city is named.
The Dujiangyan Irrigation System by engineer Li Bin was completed in 256 BC and is renowned for using no dams or flood gates to regulate water flow.
Some 2,300 years on, the system still works, providing irrigation, controlling the water level and preventing flooding. The area around has been built into a park where visitors can learn more about this marvel of hydrology.
Such is the esteem in which Li and his son, who worked with his father, are held, some people worship them at the water god temple there.
Although only 50 kilometers from Chengdu, Dujiangyan is 273 meters higher than the city. In ancient times, it was recorded that Chengdu would flood during the rainy season and suffer from drought the rest of the year.
This was before the area was known as tian fu zhi guo, literally meaning "heavenly kingdom." A solution had long been sought, but it was engineer and official Li who provided one, paving the way for the area to become one of the most affluent in the country.
Li worked during a period of warfare and was ordered to keep the waterway open as a supply line for troops, thus ruling out dams or floodgates.
Taking suggestions from local engineers, Li instead had rocks piled up in the shape of a fish's mouth in the middle of the Min River. This divided its flow into eastern and western channels.
The western part is used to release excess water to prevent flooding, while the eastern canal provides irrigation for the Chengdu Plain.
Confronting an obstacle in the shape of Yulei Mountain on the western side, Li decided to tunnel his way through. The engineer shattered the rock through repeated expansion and contraction, heating it with fire then dousing it with cold water. This channel became a water gate, able to divert some flow into the eastern river.
In ancient times, the banks of both forks of the river were lined bamboo baskets filled with rocks. In winter, when the water level is at its lowest, locals repaired baskets and removed silt. Rows of ma cha running across the rivers created a floodgate so maintenance could be carry out. In spring, these were removed and water flowed back.
Bamboo-lined river banks have long given way to cement banks, but the tradition continues. It commemorates what was once a harsh landscape becoming a "heavenly kingdom." Many people say Li's engineering achievements created the conditions for a laid-back lifestyle associated with the Chengdu Plain, as it's easier to lead a reflective life if a perennial threat of natural disaster has been removed.
This may also explain why the area is a significant spot for Taoism, China's home-grown religion and philosophical school. Experts are divided on the origins of Taoism but Qingcheng Mountain in Dujiangyan city is considered a sacred place by Taoist believers.
Many experts consider it the birthplace of the religion, because its founder Zhang Daoling was confirmed to have taught there. According to some accounts, Zhang died on the mountain at the age of 123, while others say he achieved a Taoist "nirvana" there. The cave where Zhang taught, halfway up the mountain, is now a tourist attraction.
And all perhaps thanks in no small way to an engineer whose own contemplations helped make the area great.