More downpour and floods in South China are expected by Wednesday after regional flooding and landslides triggered by torrential rains killed at least 50 people since the start of July.

Since July 1, flooding, landslides and torrents of mud in South China have killed at least 50 people. Another 15 are missing, the Ministry of Civil Affairs said late Saturday.

More than 17 million people in nine provinces have been affected and about 597,000 people relocated since the start of July, according to the ministry.

About 42,000 homes have collapsed and another 121,000 have been damaged. About 946,500 hectares of farmland were damaged or destroyed, with economic costs estimated at up to 8.9 billion yuan ($1.3 billion), the ministry said.

The National Meteorological Center said on Sunday that more rains are expected before Wednesday.

The weather center expanded its orange alert for rainstorms, the second highest level for heavy rains, on Sunday. It forecast middle to strong rains for Sichuan, Chongqing and Guizhou provinces with the highest rain volume expected to reach 300 mm in some parts.

The heavy rains will last until July 20 in some parts of the southern region, the center predicted.

Hui Liangyu, vice-premier and director of the Office of State Flood Control and Drought Relief headquarters, urged local governments on Saturday to prepare for severe floods, especially along the middle and lower reaches of the Yangtze River, Poyang Lake, Dongting Lake and Huaihe River.

He said China has been facing "very complicated" weather conditions since the beginning of the year, adding that the frequent rainstorms and massive floods are "very rare".

He called for government departments to closely monitor the weather information and reinforce dams and dikes to minimize casualties and losses.

In Hubei, the local weather forecast bureau said storms or thunderstorms could hit the province before Tuesday. The bureau warned that rainfall would exceed 300 mm in some areas and trigger another round of heavy floods.

In Guizhou, several counties and villages were submerged in more than a meter of water. About 7,500 residents were evacuated from the region.

Meanwhile in Qinghai, more than 9,000 people had been evacuated on Sunday from Golmud as the water level continued to rise in nearby Wenquan Reservoir, municipal authorities said.

Several leaks had been reported in the embankment of the reservoir, about 127 km from urban Golmud. If the reservoir sustains further damage, it could threaten a population of 205,700 and endanger the city's power and water plants.

The Qinghai-Tibet railway, the world's highest railway and located about 40 km from the reservoir, could also be hit by floodwaters, authorities said.

Wenquan Reservoir now holds more than 230 million cubic meters of water but it was designed only to safely hold 70 million cu m, experts with the provincial drought relief and flood control headquarters said.

And the Three Gorges Dam, in the middle reaches of the Yangtze River in Hubei, on Saturday released water for the first time this year.

Engineers opened three sluice gates to discharge some 32,000 cu m of water per second and another sluice gate to release floating objects.

The flood from the upper stream reaching the dam was measured at 38,500 cu m of water per second on Sunday morning, the highest level since the flood season began, dam officials said.

Authorities said water levels in many branches of the 6,397-km-long Yangtze River have gone above warning lines.

At Wulong monitoring station in Chongqing, the water level was three meters above the warning line.