The annual flood-control benefits of the Longtan Hydropower Station can reach 1.02 billion yuan ($149.34 million), Dai said. Should floods like the ones in 1994 and 1998 occur again, the flood-control benefits of the Longtan Reservoir may be more considerable, reducing flooded land by 70,000 hectares and saving 3.04 million lives; hence the hydropower station will become a strategic flood-control project in southwest China, Dai said.
Four world records
LHDC said the Longtan Hydropower Station, the third largest of its kind in China, has set four world records. First, the 216.5-meter-high concrete rolled dam is the tallest of its kind in the world. It is 31.5 meters higher than the Three Gorges Hydropower Station Dam on the Yangtze River.
Underneath the Longtan Hydropower Station Dam is the world's largest underground power-generating workshop, which is 388.5 meters long, 28.5 meters wide and 74.4 meters high. It contains seven generating units, each having an installed capacity of 700,000 kw, the largest single installed capacity in the world equalling that of the Three Gorges Hydropower Station and the Itaipu Hydropower Plant in Brazil.
According to LHDC, the design of the Longtan Hydropower Station has taken into account the shipping value of the Hongshuihe River. Because the river valley where the hydropower station is located has a steep decline in elevation, the designers have installed a ship lift on the dam, with the world's highest lifting capacity. The ship lift, which is 1,650 meters long, has a maximum lifting height of 179 meters.
LHDC has created another record with the fastest construction of a large-scale hydropower station in the world. It will take only one and a half years from the time when the first unit began to generate electricity in May 2007 to the time when the No.6 and No.7 units will generate electricity by the end of this year.
Besides its major function of generating power, the Longtan hydropower project also prevents floods and protects the environment. The station has already produced some ecological benefits. After the station's dam began to store water in 2006, it greatly improved the flow of salt tide to cities in the Pearl River Delta area, including Macao, Zhuhai and Guangzhou.
Winter and spring are the Pearl River's low-water seasons, when the river's water levels drop, causing seawater to flood the land alongside the estuary and form a salt tide. As it flows upstream, the salt tide has a negative impact on agricultural and industrial production and residents' lives.
China's water quality standards stipulate that the amount of chloride in drinking water must be less than 250 milliliters per liter; but when the salt tide flows upstream, it increases the amount of chloride in the drinking water of Pearl River Delta cities to higher than standard levels. Sometimes local tap water facilities must be closed, and the safety of drinking water is seriously threatened. According to figures released by the Pearl River Water Resources Commission of the Ministry of Water Resources, drinking water could not be taken from the Pearl River for 28 consecutive days between the end of 2003 and the beginning of 2004 after an extraordinarily strong salt tide hit Macao, Zhuhai, Zhongshan and Guangzhou.
From November 26, 2005, to January 15, 2006, another extraordinarily strong salt tide hit the Pearl River Delta, and Zhuhai and Macao could not take water from the Pearl River for 48 days. The chloride content at the Guangchang Pumping Station in Zhuhai reached 10,000 milliliters per liter during the strongest salt tide on record. Some residents had to fetch water from nearby hills or buy pure water to drink. In some riverside villages, large patches of crops were wiped out, and farmers had to stop using the land. In some factories, equipment eroded, and production had to be suspended.
In November 2006, Longtan Hydropower Station began to store water. The local media in Guangdong reported that this would modulate the waterline of the Pearl River in the low-water season. In 2007 and the first half of 2008, the water level of the Pearl River did not fluctuate seriously, and water supply in the Pearl River Delta was not threatened by salt tides.