Residents from Jiande city in Zhejiang province watch as water is released from the Xin'an River Reservoir on Tuesday morning. [Provided to China Daily]

SHANGHAI - Water was discharged from Xin'an River Reservoir in West Zhejiang on Tuesday morning in a bid to release pressure on the dam that had been holding back the swollen waters of Qiantang River.

Decision-makers from the flood control and drought relief headquarters in Zhejiang province ordered the opening of three of the reservoir's nine floodgates at 9:30 am.

It was the first time the reservoir's operators had been forced to discharge water since 1999.

The Xin'an River Reservoir, which was built on the Qiantang River in 1959, is the largest in East China and can hold about 21.6 billion cubic meters of water.

Heavy rain that started falling on Zhejiang on June 3 left the reservoir at bursting point and triggered the need to release some of the water.

The deluge stopped on Monday but the upper reaches of QiantangRiverwas still carrying a huge amount of water and its level had risen to 33.75 m on Monday,its highest since1955.

When the reservoir's floodgates were opened, water spewed out at between 2,800 and 3,000 cubic metersper second. Experts expect to leave the gates open for between 32 and 44 hours in a bid to lower the reservoir's level to less than 106.7 m.

At 3 pm on Monday, the water level had reached 107.2 m, almost 0.7 m higher than its supposed maximum.

People living downstream of the reservoir were evacuated before the water was released.

The Xin'an River Reservoir has discharged water five times in its history - in 1983, 1994, 1995, 1996 and 1999. During the biggest discharge - in 1999 - the reservoir's water level reached 108 m and eight of its nine floodgates were opened.

According to Liu Guohua, director of the hydraulic structuresand water environmentresearch institute at Zhejiang University, the reservoir's operators had been putting off the discharge in the hope that the level of the Lanjiang River, a tributary of the Qiantang River, would fall.

"But, because the flood season in Zhejiang stretches from April 15 to Oct 15, it is best that the reservoir discharges water at this time, in case another round of heavy rain hits the province," said Liu.

According to the Zhejiang meteorological bureau, showers and thunderstormsare expectedin the coming days.

While some people living on the banks of Xin'an River expressed concern that there could be some flooding downstream, many understood that there was no alternative and watched the surging water from a safe distance.

"More than 100 people gathered near to where we set up our camera to watch the water discharged," said Li Li, a reporter from the Zhejiang Online website.

Rain-triggered floods have hit 10 cities in Zhejiang in recent days. More than 4.41 million people have been affected and about 1,846 companies have stopped production. The floodshave caused directeconomic losses of7.69 billion yuan ($ 1.19 billion).

Rain-triggered floods have caused problems throughout eastern and southern China this month, claiming at least 175 lives and leaving 86 people missing, the Ministry of Civil Affairs said on Monday.

Xinhua contributed to this story.