Science
China's three gorges dam (Source: Allen Watkin/Wikimedia Commons)
Rains have been lashing China like never before in decades. It’s pouring across the country with little to no respite for citizens as forecasts read more rain in the future. The locals keep making references to the previous two years of great inundation in China – 1998 and 1954.
However, the rain and flood season of 2020 is not over yet. Already close to 200 people are missing or dead since June, and close to 24 million people have been affected across as many as 24 provincial regions.
China’s Ministry of Water Resources has said that the water levels have risen in 433 rivers with 33 of them registering “historical highs” (as of 13 July).
Especially nerve-wracking is the rise of water levels in the historic Yangtze River. At over 6,000 kilometres long, Yangtze is the longest river in Asia and third longest in the world. It traverses largely through a mountainous course, demarcating provinces by creating natural boundaries. It originates in Tibet and flows out through major metropolises like Wuhan and into the East China Sea.
Even as rains rose and fell and floods continued to submerge farmlands and homes, the local authorities were left dialling the emergency level response up and down – from level IV to III to II and back down to III.
The levels have been varying both centrally and in individual provinces led by local authorities. China has a four-tier system for emergencies, with level one representing the most severe kind. For weather, they have four colours – blue, yellow, orange, and red in the increasing order of severity.
On 18 July, China issued a red alert for flooding in Yangtze River's Nanjing section. That is when the controversial engineering marvel “three gorges dam” was compelled to face a second round of flood, this one much larger than before.
China’s Three Gorges Dam
The three gorges dam is all about scale and magnitude. It’s the largest dam and power station in the world. The money spent on it, 95.5 billion yuan (over Rs 1 trillion), puts it on any list of the most expensive projects in the world.
It stands on the ever-mighty Yangtze River, around which live 500 million people – considerably higher than even the population of the United States of America. In fact, so massive is the three gorges dam that there is a view grounded in science that it changed Earth’s rotation.
The idea of this dam is said to have been conceived by the father of modern China and its first president Sun Yat-sen in 1918. But it only got a push along during the reign of Mao Zedong in 1953 when he asked for feasibility studies to be conducted at various sites. (Fun fact: the famous and prolific American dam builder John Savage even did an assessment in the 1944.)
The idea of the three gorges dam sharply divided opinion. The proponents argued that it would control extreme flooding, help in power generation, and enhance economic activity. The opponents said over a million people would be displaced (more than 1.2 million were displaced eventually), the risk of dam collapse was far too high, and the many magnificent art and artifacts hidden in caves and other sites along the ancient Yangtze would be destroyed.
This debate stalled major construction until Premier Li Peng in the 1990s took matters in his hands and got the National People’s Congress to ratify the decision. Even then, nearly a third of voters either abstained or voted against dam construction.
A decade after its construction, the 2020 China floods are testing the dam big time.
Beijing is not one for open admissions, but it revealed recently that the dam saw "displacement, seepage, and deformation" with a second round of flood gushing at a fierce 61,000 cubic metres per second. On 18 July, the waters had reached a peak flood level of 164.18 metres, surpassing the previous high and going over the flood limit level. Three lower floodgates were opened to release the water that day.
The three gorges reservoir is capable of holding a maximum water level of 175 metres.
Fear and anxiety arose over the structural integrity of the dam with the rising waters and stubborn rain. It got officials issuing clarifications and a defence.
On 20 July, the China Three Gorges Corporation said that the second flood had “smoothly passed” the dam as the reservoir inflow had decreased.
An Asia Times report quoted some state officials and experts who assured that the dam was safe with claims like it could withstand a flood with even twice the mass flow rate, that nothing could topple the dam in the next 500 years (there you go, another estimate), and possible compromise in any one section of the dam wouldn’t affect any other.
Chinese newspaper Global Times pushed back by claiming that the three gorges dam is stable despite the “deformation smear”. It reported the chief engineer of the dam’s operator, Zhang Shuguang, as saying there is a monitoring system with 12,000 devices in and around the dam where alarms would go off in case of an abnormality.
“People's conscience is more easily distorted than a dam,” concluded the report.
At the time of deliberation in 1993 on the idea of building the three gorges dam, controlling floods of “cataclysmic” proportions was one of the selling points. They had pegged the interval between such extreme floods at a millennium. However, the dam’s ability and strength have come into question in just a decade after completion, and not the first time this decade either.
As a result of the rain and floods, China's Guang-Xi region's 55-year-old dam has already collapsed, reports WION, adding that there are as many as “94,000 dying dams” in the country.
Unfortunately, Yangtze is bracing for more rain in the coming days, congregated in the river basin itself, starting 24 July. The forecast in some parts, according to the National Meteorological Center, is for severe weather like thunderstorms and gale. China is on blue alert for rainstorms. The dam may have to withstand more.
The last catastrophic dam failure in China occurred in August 1975. It was caused by Typhoon Nina. The resulting casualties numbered over 150,000. The Banqiao Dam, too, had been designed to withstand the flood of a millennium, but excessive flooding in 1975 took it out. Over 10 million people were affected. Banqiao was rebuilt in 1993.
Rain and flood have caused loss of life and property across Asia. India has been at the receiving end too. Unusually strong rains have been observed in several parts, especially the north and north east. According to the World Meteorological Organization, these parts have recorded 15 centimetres more rain than normal in mid-July. Assam, where pictures and videos of inundation are sinking hearts, witnessed 20 per cent above average rainfall.