SHANGHAI, Aug 18 (Reuters) - China's water ministry warned that severe drought conditions in the upper and middle reaches of the Yangtze river could last well into September as local governments race to find new supply sources and irrigate crops ahead of the autumn harvest.
A severe heatwave across the basin of China's longest river, caused by a larger than usual Western Pacific subtropical high, has now lasted more than two months, slashing hydropower supplies and drying out large expanses of arable land.
Normal water flows could still be months away, with rainfall expected to remain low until the end of this month and beyond, said Liu Zhiyu, an official at the Ministry of Water Resources, speaking at briefing late on Wednesday.
"It is expected that in September, water inflows in the middle and lower reaches of the Yangtze will still be low, and the drought in Anhui, Hubei, Hunan and Jiangxi could develop further," Liu warned, referring to four major provinces on the middle reaches of the river.
Rainfall in the Yangtze basin has been around 45% lower than normal since July, and high temperatures are likely to persist for at least another week, according to official forecasts.
Authorities in the region also warned that temperatures would continue to exceed 40 degrees Celsius (104 Fahrenheit) on Thursday, with parts of Chongqing set to go beyond 44 degrees, putting further pressure on power supplies amid surging air conditioner use.
Water levels on the main trunk of the Yangtze and the vital flood basin lakes of Dongting and Poyang are now at least 4.85 metres (16 feet) shallower than normal, and the lowest on record for the period, officials said.
Rice and other autumn crops were now at a "critical period" when it comes to irrigation, warned Liu Weiping, Vice-Minister of Water Resources, at the same Wednesday briefing.
He said around 820,000 hectares (2 million acres) of arable land from Sichuan in the southwest to central China's Anhui have suffered damage, affecting 830,000 people as well as 160,000 head of livestock, mostly in areas relying on smaller reservoirs or mountain springs for irrigation.
Upstream reservoirs have opened their gates to replenish storage levels at the Three Gorges Dam, which will release 830 million cubic metres downstream over the coming days, Liu said.
Local governments are also being urged to ensure that enough water resources are stored for emergency use, and to make use of additional water sources, including mountain springs and streams, he said.