As the water level of the world's largest hydropower project rises to its planned height, many people see it as a symbolic culmination that will not only attract the world's attention, but commercial opportunities in tourism and shipping as well.

An overall view of the Three Gorges Dam, on Tuesday, when the reservoir finally reached its target level of 175 meters. [Du Huaju / Xinhua]

Shi's company started a sightseeing program near the dam in July that has pulled in more than 10,000 tourists, according to company statistics.

When the reservoir's water hit the maximum height of 175 meters at around 9 am on Tuesday, it had the effect of shortening transportation routes.

The reservoir will stick to the 175-meter mark until early next year, when the water will be gradually discharged, falling to 145 meters by June 10, leaving more than 22 billion cubic meters for flood control, China Central Television reported on Tuesday.

"It's a great season for Three Gorges tourists," Shi said. They can take a three-hour cruise to see the dam close-up for only 90 yuan ($13).

There are other sightseeing venues in addition to that, as well as the obviously not-to-be-missed underwater wedding, according to Tang Youjin, general manager of the Chongqing Kingvista Tourist Agency, who was quoted by Chongqing Evening News, on Tuesday.

An average of 6,000 tourists, many of them from foreign countries, have traveled to the Three Gorges area for sightseeing since Oct 1, an increase of about 25 percent over the same period last year, the Three Gorges Tourist Agency records show.

Cui Bangjian, a 60-year-old man who lives close to the dam and likes to take a stroll along the embankment after meals, said the scene is becoming more beautiful with more boats going back and forth.

Shipping times cut but silt build-up is a threat

One important result of all that activity is that the water is shortening the shipping time between Chongqing and Yichang, Hubei province, from 6 days to less than 4 days. Chongqing Kingvista's Tang Youjin said.

That water level will also allow cargo ships with 5,000-ton capacity to enter Daning River, a Yangtze tributary, promoting local economic development, Chongqing Evening News quoted local transportation bureau officials as saying on Tuesday.

Meanwhile, other experts worry about travel on the new waterway since the heights of existing bridges are lower than what they were because of the rising waters, not to mention the rising silt levels.

The Wanxian Bridge over the Yangtze, in Chongqing's Wanzhou district, built in 1997, used to rise about 140 meters above the water, but now its highest point is a mere 30 meters from the water, posing a threat to ships passing underneath, eastday.com, a Shanghai news portal, reported on Tuesday.

The rising waters are also soaking the bridge piers, which spells danger for the bridges if a ship hits the piers, Wen Guanghua, head of the Wanzhou waterway bureau, told China Business News on Monday.

But bridges are not the only problem. There is that silt. Wen warned that the increasing amounts of silt are "severe".

The depth of that sludge reaches 26 meters in some parts of the river, causing the water depth to be near 5 meters, the minimum for water transportation, he said.

"If things get worse, transport will have to be suspended during the dry season of March and April," Wen said.

So there is a balance or trade-off between the reservoir's water level and its silt volume: if the high water levels are kept for flood control, the silt will increase and threaten the security of ships and the dam. If, on the other hand, water levels are kept low, the reservoir will not be able to play its flood control role, Wang Guixian, a Tsinghua University professor of water resources, told China News Weekly in July.

Xinhua contributed to this story.