Wang Shuhan, vice-manager of the Wuhan-based Changjiang Shipping Company, estimates that his firm alone stands to lose as much as 60 million yuan RMB (US$7.3 million) during the 67-day closure.

With the temporary shiplock at the dam taken out of service on April 10, China’s longest river is effectively blocked until the permanent shiplock that will allow vessels to get through the dam is put into operation on June 15.

Xie Fukang, vice-manager of the Chongqing-based Minsheng Shipping Corp., said the closure of the Yangtze at the dam will inevitably have "a huge impact" on his industry, with freight transport costs likely to be up to 30 per cent higher than usual.

Most of the goods transported out of the Chongqing area, including minerals, coal, steel, automobiles, fertilizer and agricultural produce, normally travel on the "golden waterway," as the Yangtze is called.

For the next two months, all cargo must be unloaded and transported overland around the dam, but much less freight than normal will be able to make it to the other side every day.

The water level behind the dam, which was 70.14 metres above sea level when the shiplock was closed on April 10, rose 0.6 metres within 18 hours, and is expected to reach 80 metres by the end of the month.

When the formal filling of the reservoir begins on June 1, the water will begin to rise by about four metres a day, until it reaches 135 metres above sea level by mid-June.

Up to 70 per cent of the goods that normally would have been shipped on the Yangtze will be transported by other means or be held back during the 67-day interruption, the Chongqing Morning Post (Chongqing chenbao) reported on April 14.

More than a million people have been transported around the dam by bus since Nov. 1, when a single temporary shiplock was left in operation. Now that even that passageway is closed, everyone must disembark to get to the other side of the dam. Passengers travelling to Shanghai from Chongqing leave their boats at Maoping upstream of the dam, and continue their journey by bus to Wuhan, where they can board another boat to Shanghai.

Officials say that the "cross-dam" transport operation will be severely tested in the first week of May, when a surge of passenger traffic is expected during the weeklong national May Day holiday.

Safety is a concern during all this loading and unloading of passengers and freight. On April 7, for instance, a truck overturned as it was being unloaded at the port of Maoping. "It was a dangerous situation, but fortunately nobody was hurt," the Chongqing Morning Post (Chongqing chenbao) reported on April 10.

Officials are also putting an emergency rescue plan in place to respond to accidents they expect will occur on the river as the water level rises in the reservoir.

"With the rising of the water, mountain slopes, cliffs, rocks and the mouths of Yangtze tributaries will be inundated. This could lead to new submerged reefs and dangerous shoals, and undercurrents in some sections of the river," China News Service (Zhongguo xinwen she) warned on March 24.

This is the second time that dam-building has halted traffic on the Yangtze. Navigation was interrupted for more than seven months (Nov. 11, 1980 to June 27, 1981) during construction of the Gezhouba dam, 40 kilometres downstream of the Three Gorges project.