CHONGQING: The Three Gorges Dam has opened its flood discharge gates for the first time this year, with the aim of alleviating flood control concerns upstream of the world’s largest hydropower project as the rain shifts westward along the Yangtze River.

The speed of discharge from two sluice gates of the dam in Yichang, Hubei province, which were opened on Wednesday, will gradually increase from 27,000 cubic metres per second to 31,000 cubic m/s, according to the Ministry of Water Resources.

A forecast on Wednesday said the upper reaches of the Yangtze would swell remarkably in the following week due to continuous downpours in the next 10 days in Sichuan province and Chongqing.

A forecast from the National Meteorological Centre shows that a vast stretch of regions in the Yangtze’s upper reaches, including the Sichuan Basin and the south-eastern part of the Qinghai-Tibet Plateau, will receive 60 to 120 millimetres of rainfall in mid-July, and the precipitation in some areas in the basin, which covers Sichuan and Chongqing, may exceed 300 mm.

The expected accumulated precipitation in many areas in the basin during that time will be 50 to 90 percent higher than normal for the same period.

The ministry said rainfall in the upper stretches of the Yangtze since Monday had increased the speed of water flow into the Three Gorges Reservoir to 50,000 cubic m/s as of 6 pm on Thursday, raising the water level to a record high of 161.1 metres for this time of the year.

This means that the second major flood has formed in the Yangtze this year. The first major flood in Asia’s longest watercourse was reported in late June in its lower reaches.

The Changjiang Water Resources Commission, an affiliate of the ministry that governs the Yangtze basin, will assess the situation continuously and may increase the water discharge from the reservoir accordingly, the ministry said.

“When adjusting the flood discharge, the commission will thoroughly assess the flood control conditions in the middle and lower reaches of the Yangtze to prevent the reoccurrence of alerts in some Yangtze sections where water levels have recently receded below their danger marks,” it said.

After entering their rainy season, many areas in the middle and lower reaches of the Yangtze have experienced persistent torrential rains. That led to water levels at 185 hydrological stations surpassing their flood warning marks on July 2.

During that time, the Three Gorges Dam played a crucial role in mitigating the impact of water from the upper reaches of the Yangtze, significantly alleviating the flood control situation downstream, the ministry said.

However, that resulted in the water level in the Three Gorges Reservoir reaching 159.9 metres as of Wednesday, 15 metres above its normal level.