On the night of Aug. 8, 1975, a line of people frantically piled sandbags atop the Banqiao Dam, in the central Henan Province, while being battered by the worst storm ever recorded in the region.
They raced against the rapidly rising Ru River to save the dam and the millions of people that lay sleeping downstream.
Just after 1 a.m., the sky cleared and stars emerged from behind the storm clouds. There was an eerie calm as someone yelled, "The water level is going down! The flood is retreating!" Seconds later, recalled one survivor, it "sounded like the sky was collapsing and the earth was cracking." The equivalent of 280,000 Olympic-sized swimming pools burst through the crumbling dam, taking with it entire towns and as many as 171,000 lives.
Today, aside from Henan Province, if you ask Chinese people what they know about the Banqiao Dam collapse, you're not likely to hear much. What may have been the deadliest structural failure of all time occurred in an era when the state quickly covered the scale of such catastrophes.
In 2005, 30 years after the collapse, scholars started to re-examine the event as public records were being released; yet the majority of Chinese are still unaware of the disaster's scale and the missteps that led to it. As China now embarks on another binge of rapid dam development, some worry that factors that led to Banqiao's collapse are re-emerging.
The dam was completed in 1952 as part of a campaign to "Harness the Huai River" and its tributaries after severe flooding in previous years. During the 1950s, over 100 dams and reservoirs were built in the Zhumadian Prefecture of Henan Province, including the Banqiao Dam. When the Great Leap Forward began in 1958, the campaign was held up as a national model to give primacy to water accumulation for irrigation. A hydrologist named Chen Xing warned that an overbuilding of dams and reservoirs could raise the water table in Henan beyond safe levels and lead to disaster.
After the Great Leap Forward, many of the projects were re-examined and renovated, but dams continued to go up quickly. From the 1950s to the 1970s, about 87,000 reservoirs were built across the country.
More than 100 additional dams went up in Zhumadian in the 1960s, joining those that had gone up in the previous decade. They created reservoirs that claimed huge tracts of land previously reserved for flood diversion. The irresistible benefits of the dams ultimately drowned out the voices urging restraint.
The equivalent of seven Three Gorges Dams
Today, China is on the cusp of another dam-building binge.
By 2020, China hopes to increase its total energy capacity by 50 per cent, at the same time it tries to raise the non-fossil fuel proportion of that energy from 9 per cent to 15 per cent. With nuclear development being slowed in the wake of Japan's 2011 Fukushima disaster, dams have been left to do most of the heavy lifting. The twelfth five-year plan calls for the hydropower-producing equivalent of seven Three Gorges Dams to be built by 2015.
Nowhere is the aggressive dam push raising more eyebrows than in southwest China, where dozens of major projects are gearing up. On three river systems – the Nu (Salween), the Lancang (Mekong), and the Yangtse watershed – there are altogether 32 major dams. But in coming years these are likely to be joined by over 100 more.
While most worries associated with the planned projects focus on environmental effects and dislocation of local residents, serious safety concerns have also been raised. Last year, a report by the environmental group Probe International said that of the 130 proposed dams on these and other rivers in the region, nearly 50 per cent "are located in zones of high to very high seismic hazard." The report continues, "By constructing more than 130 large dams in a region of known high seismicity, China is embarking on a major experiment with potentially disastrous consequences for its economy and its citizens."
Earthquakes are only one of the concerns in this mountainous region with unstable terrain. In 2010, landslides in Gansu Province – which is similar to Henan Province – killed nearly 1,500 people. A prolonged drought followed by heavy rains were the official causes of the disaster, but experts like geologist Fan Xiao believed these factors were exacerbated by deforestation, mining and a binge of dam building that had occurred in the preceding years – issues that also plague southwestern China's river valleys.
At the time of the landslides, Fan Xiao told Hong Kong's South China Morning Post, "Local authorities have ignored daunting warnings about the severe consequences of dam-building and viewed dams as their key source of taxation. While officials may see dams as a clean and efficient way to boost local economies, they sometimes also see them as opportunities to line their own pockets."
The recently coined term "tofu construction" refers to structures built with substandard materials and unqualified contractors as a result of corruption. Since 2007, China has had at least 19 major bridge collapses resulting in over 140 total deaths. In one case, a collapsed bridge had been built by a blind contractor.
During the building of China's high-profile Three Gorges Dam, there were nearly 100 reported instances of corruption, bribery and embezzlement associated with the project. Most were related to resettlement funds for displaced residents, but at least 16 cases were directly related to construction.
Old dams raise even greater worries. Thousands that were built prior to Reform & Opening Up are still in use, many of which are badly in need of renovation. The central government has said that more than 40,000 dams are at risk of breach and allotted 62 billion yuan ($10-billion U.S.) to repair them. But that appears to be coming up short and local governments have been unwilling or unable to make up difference.
"There are so many endangered dams," Zhou Fangping from the Water Resources Department of Guangdong Province told China Economic Weekly in 2011. "We have so many rivers to manage and so many irrigation and water conservancy projects. If there's only one project, we can handle it, but there are so many. So the result is either we promise to complete all the projects but we don't actually meet the targets, or we finish them all but with sub-standard quality."
The China Economic Weekly reported that about 15,900 new small-sized dams would be built by the central government by the end of 2013 and 25,000 by local governments before the end of 2015.
As recently as Feb. 2 this year, a small dam in Xinjiang collapsed, flooding 70 homes and killing one man. According to a statement by a Water Resources Ministry official in 2006, in a given year around 68 (mostly small) dikes like this collapse in China.
Soon after the Banqiao Dam was completed in 1952, cracks began to emerge. So from 1955-56, the structure was reinforced using Soviet specifications (which the Water Resources Ministry would later admit were inappropriate for the region). After renovations, Banqiao was dubbed the "Iron Dam" to reflect its new-found invincibility.
However, on Aug. 5, 1975, a typhoon collided with a cold front over Henan and dropped the area's average yearly rainfall in less than 24 hours. The 106 centimetres of rain that fell that day dwarfed the 30-centimetre daily limit the dam's designers had anticipated. Witnesses said that the area was littered with birds that had been pummelled to death by the intense rainfall.
In an effort to mitigate downstream floods that were already severe, Banqiao was ordered not to fully open its sluice gates early in the storm. Then communication lines were knocked out, leaving operators guessing as to how the situation outside was unfolding.
By the time the gates were fully opened, it was too late. Water was rising faster than it could escape. The hydrologist who had warned that the region's dam-building binge was dangerous had also recommended 12 sluice gates be included on Banqiao. In the end, only five had been installed, and even those were partially blocked by accumulated silt when the storm hit.
When the dam collapsed it sent a 50-kilometre-an-hour tidal wave crashing toward the valley below that would take out 62 other dams like dominoes. In minutes, entire villages with thousands of people were wiped off the map.
In a 2010 CCTV documentary, one survivor recalled that moment saying, "I didn't know where I was – just floating around in the water, screams and cries ringing in my ears. Suddenly, all the voices died down, leaving me in deadly silence." During the six hours the Banqiao Reservoir took to empty, an estimated 26,000 people were killed, many of whom were sleeping. The downed communication lines had thwarted any chance of a large-scale evacuation. Some managed to cling to life by holding on to trees or standing on rooftops, but many of those who survived the initial onslaught would soon wish they hadn't.
The storm that toppled Banqiao blindsided the dam's designers, who had only built it to withstand a one-in-1,000-year flood. For whatever design flaws the structure had, it might have survived if it weren't for the 1975 flood that was designated a one-in-2,000 year event. Today however, such designations are quickly becoming misnomers. What were once considered freak weather occurrences are transitioning to routine events. At a 2012 press conference on coping with urban flood disasters, Wu Zhenghua, a researcher with the Beijing Meteorological Bureau, warned that climate change would bring more frequent heavy precipitation to China.
One of the most dangerous implications is that areas already prone to flooding are likely to see more extreme storm events that local infrastructure isn't prepared for. These are precisely the areas in Central and Southwest China that are making major dam pushes.
If the big storm does hit, a complete communication breakdown like the one that hit Banqiao is very unlikely, thanks to improved technology. But there's still potential for dangerous communication issues. Katy Yan, China program co-ordinator of International Rivers, an international conservation group, warns that multiple companies sometimes operate different dams on the same river.
"Lack of communication and co-ordination between these companies and between different water and energy userscan often lead to problems, especially during a major drought period," she says. But perhaps the greatest danger of a dam break isn't the initial disaster itself, but the aftermath.
When the Banqiao reservoir had emptied and the waters had settled on the morning after the collapse, the horror was only beginning. Because dikes had gone unmaintained for years and flood diversion zones had been re-purposed, the water had nowhere to drain. Roads were washed out hampering rescue efforts. Survivors were left to wait on rooftops or huddled together on small patches of dry land. They stripped tree branches of leaves and wrangled floating livestock carcasses to eat. Food was airdropped, but much fell in the water and was lost or eaten after it had rotted. Disease spread quickly while people battled hunger and the summer heat.
For every person that had been swept to their death in the initial tsunami, it's estimated at least five died from the famine and plague that followed. The cascade of dams that had been built on the Huai River and its tributaries to reduce flood risks ultimately made the flooding deadlier and the rescue effort more difficult. The Probe International report warns that this development model is being used again today in China's southwest and it could have equally disastrous consequences.
"If one dam fails, the full force of its ensuing tsunami will be transmitted to the next dam downstream, and so on, potentially creating a deadly domino effect of collapsing dams," the report says. "A cascade of catastrophic dam failures would almost certainly cause an unprecedented number of casualties and deaths in major downstream population centres, such as Chengdu, and along these major river valleys."
If such a collapse were to occur today, it could be made more devastating by the chemical industry that's taken hold along rivers. Li Zechun from the Chinese Academy of Engineering Sciences was present for the aftermath of the Banqiao disaster. In 2005, he told People's Daily that "Once the chemical plants are flooded, the contamination to the environment is immeasurable."