XINZHOU, China - As deputy Communist Party secretary of the Yangtze River management station in Xinzhou, Ba Qiansheng is supposed to keep a close eye on rising waters. A sign across the street from his office lists flood-warning levels, and large red characters say that swimming is prohibited.

But these days, the idea of a flood seems ludicrous. On one side of the giant sluice gate at Xinzhou, the water is shallow; on the other side, there's almost no water at all. The channel that is supposed to connect with the Yangtze is filled with foot-deep cracks baking in the sun where the river used to be.

"It's the lowest it's been in 70 years," Ba said.

Asked why that would be, he shifted nervously for a moment. "We don't yet know the reason," he said.

Pushed for an answer, Ba said there's been no rain and then, with considerable hesitation added, "It's possible that the dam is part of the reason."

He was referring to the Three Gorges Dam, the largest hydroelectric project in the world, which sits to the west of this town in southern China's Hubei province. Designed to generate electricity and tame the Yangtze, the longest river in Asia, the controversial dam cost at least $23 billion.

It was seen as a testament to the dramatic power of China's state planning when it was finished in 2006.

Now that legacy is being chipped away as the worst drought in at least half a century unfolds across the Yangtze River region.

The government says that the least rainfall in at least 50 years has affected 3.2 million-plus acres of farmland in seven provinces. In five provinces, 4.2 million people are having trouble finding drinking water. In one province, Hunan, which borders Hubei, rain hasn't been so scarce since 1910, a provincial official told the state Xinhua newswire.

"This is the worst I've ever seen," said Luo Baoqing, 70, a farmer in Hubei who said that if the rains don't come soon, he won't plant rice this season. "Before when there were droughts, we could dig a well, but we've tried drilling two wells this year and there's no water."

State media ran a report last month insisting that rice crops would be fine overall. But it acknowledged that more than 494,000 acres of rice paddies have been affected in Hubei alone, citing the Ministry of Agriculture.

Xinhua quoted specialists saying that the dam had "very little" impact on regional climate conditions and that there is "no evidence that the drought was caused by the dam."

Others disagree. Fan Xiao, a senior engineer with a provincial geological survey team in the area, said that in addition to the lack of rain, the drought conditions are "related to the Three Gorges Dam."

Chinese officials pushed for water levels to hit a height of 574 feet at the dam in 2008 and 2009 - seeking maximum power-generation capacity - and finally succeeded last October. That campaign, Fan said, came "at the cost of the downstream water supply."

The areas regularly cited as being hardest hit by the drought all sit downriver from the dam.

With reports of shipping barges having trouble navigating some spots of the Yangtze, and bone-dry rice fields in a nation already concerned about food prices, Chinese leaders decided to release more water from the reservoir.

Although hundreds of thousands of cubic feet of water are now leaving the dam every second, the scenes in Hubei suggest the government's challenges are far from over.

Sun Chufeng was plopping along behind a water buffalo, which snorted and strained as it dragged a metal blade through a thick patch of mud he was trying to turn into rice paddy. Asked how the planting season had gone, Sun, 72, paused to wave his hand at the dry fields all around him - "everything you see is usually under water."

Sun expects his crops to drop by half or more this year.

"There's no water," said Sun, who got the small amount he has to work with by pumping from a canal that has been withering away. "It has all dried up."

A few minutes later, the farmer was back to trudging through the only wet patch of land he had, and hoping for rain.