Tag Archives: weather

Storing Beijing’s Storm Water Before It Does Harm

Firefighters pull a submerged car near Guangqumen Bridge in Beijing, July 21, 2012.  (Xinhua/Li Fangyu)

Following the heavy rains that recently inundated Beijing with such loss of life, the capital is to build 20 underground flood pools to relieve future storm flooding. They will be put under places known to susceptible to flash floods, low-lying roadways in particular.

A conventional surface flood pool is the land around a reservoir that is intended to be flooded in the event of extreme rains as the reservoir rises and backs up. The excess water is then run off by being released through the reservoir’s dam in subsequent days. Underground storm water storage works in much the same way, temporarily holding storm water until a city’s drainage system can handle it.

Flood pools are not only a common form of flood management, but, smartly managed, are also a potentially profitable source of municipal water supplies, irrigation, recreation facilities and fish or wildlife habitats, Beijing’s flood pools won’t bring such broad public goods as far as we can tell. They will have to be fitted in between all the other subterranean construction beneath a long-established city: sewer and water pipes, subway lines, building foundations and the like.

Modern underground storm water storage systems are often modular, so can be constructed as shape and space allows. Alternatively they can be built from large diameter pipes and threaded around obstructions. Their capacity is typically equivalent to a swimming pool and are easiest to retrofit to places like roads and parking lots that can be dug up and the systems installed under them.

Urban flooding is a worsening problem in China (and elsewhere) as global warming, urbanization and industrialization pose a growing triple threat to cities’ natural defences, defenses urban planners have anyway been concreting over with reckless abandon.  It is, though, reasonable to ask why there hasn’t previously been more provision to deal with flash floods in the capital.

Hong Kong, for one, has underground storm water storage in several of its towns already and is planning to build more, notably in Happy Valley on Hong Kong Island which is to get an award winning, state of the art flood pool at a cost of HK$1 billion ($130 million). Hong Kong had the advantage of being able to build the lower -tech tanks it already has into its new towns from the outset, a luxury that Beijing doesn’t enjoy.

Urban planners are only now realizing that they have to make cities greener so they are less encouraging to extreme weather. All the newly constructed impervious surfaces such as roads, parking lots and rooftops, create run-offs that existing urban drainage, often old and inadequate, can’t handle. can’t handle.  Not only is ground storage for rainwater scarce and run-offs from hard surfaces absent, ancient streams that could carry rainwater to rivers and ponds that could help it find its way to acquirers below have been filled in. As Beijing’s are expensively learning– the economic cost of the recent floods  is estimated to be at least 2.3 billion yuan ($360 million), before the cost of installing the new storage tanks–they need to create the modern urban equivalent of something nature has provided naturally.

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China’s Fast And Furious Rising Seas

High billows strike on the seashore of a park in Weihai, east China's Shandong Province, June 26, 2011. Strong winds and heavy rains are forecast to hit China's eastern coast as tropical storm Meari is moving northwest from the southern Yellow Sea waters, according to a statement issued by the nation's meteorological authority Sunday. (Xinhua/Yu Qibo)
The annual report from the State Oceanic Administration on China’s rising sea levels brings no surprises and no cheer in equal measure. Sea levels continue to rise faster than the global average. By the middle of this century, they are forecast to be 145mm-200mm higher. That doesn’t sound much but is sufficient to flood 87,000 square kilometers (34,000 square miles) of lowlands, or about 10% of coastal provinces’ land area. More than 1,300 seaside townships, 2,000 kilometers of rail lines and 22,000 kilometers of roads are at risk of being underwater. The Bohai Sea and the adjacent southwestern side of the Yellow Sea. and the waters around Hainan are rising fastest.

As we’ve noted before, urbanization, industrialization and overuse of groundwater is exacerbating the problem. Large cities are sinking because the water table below is sinking. too. All in all, coastal regions are left more vulnerable to the ravages of wind and rain. Typhoons affected more than 500 million people in southern China last year and caused more than 3.3. billion yuan ($520 million) of damage. In addition, river deltas such as the Yangtze’s and the Pearl’s will become more vulnerable to surges, salt tides and the salination of farmland and coastal forests.

Short of dealing with climate change, there are few hard defences against rising sea levels. Soft natural defences and restricting development in the most vulnerable areas is, as the SOE recommends, the most prudent course.

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Flood And Drought Co-Exist In China

Despite heavy seasonal rains causing floods and havoc across southern China, the north and parts of the center of the country still face severe drought. Officials have warned that crops are at risk on the North China Plain between the Yellow and Huai rivers. More than 4 million people across eight provinces are short of drinking water. The lack of rain extends to the Korean peninsula across the Yellow Sea. The Associated Press reports that North Korea is facing its most extreme drought since records were first kept more than a century ago, threatening already tenuous food supplies.

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Rains Bring Scant Relief To Drought In Southwest China

A villager takes water at an almost dried out reservoir in Haila Township of Weining County, southwest China's Guizhou Province, May 20, 2012. Southeast regions of Guizhou are hit by rainstorm and flood while northwest of the porvince are still stranded in drought, which has lingered in the areas for about half a year. A total of 29,763 people and 1,600 hectares farmland in Haila Township have been affected by the drought, according to the local government. (Xinhua/Yang Wenbin)

Nearly 5.5 million people are still suffering from lingering drought in Yunnan and Sichuan despite the recent rains bringing some relief. Authorities say that only 290,000 fewer people and 220,000 fewer livestock in the two provinces are short of water because of the break in the weather. More than 400,000 hectares of crops have been affected, according to the Office of State Flood Control and Drought Relief Headquarters. Rainfall in the two provinces has been at 10% of normal levels, threatening tobacco, corn and rice crops.

Separately, disaster relief authorities in Guizhou say that more than 5.5 million people have been affected by drought, rainstorms and hailstorms that have caused direct economic losses of 1.8 billion yuan ($283 million) so far this year. The picture above of an almost dried out reservoir in Weining County in Guizhou is dated May 20.

Meanwhile, three people died when torrential rain hit Chongqing, and more than 5,000 people had to be relocated after a heavy rainstorm hit parts of Hunan. In Nanning, capital of Guangxi, nearly 900 people were evacuated after a road next to which a school had been drilling for drinking water subsided, causing one building to collapse and six more to tilt.

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Persistent Drought Starts To Threaten China’s Crops

Dried-up bed of the Xinba reservoir in Shilin County, Yunnan Province, March 22, 2012.

The persistent drought that has hit 13 provinces in southwest and central China is starting to have an adverse impact on farming, China’s drought-relief officials have indicated for the first time. The fear is that the spring planting on 4 million hectares of crop land is threatened by the shortage of water. Reservoirs, such as the one in the picture above, in Shilin County, Yunnan, have dried up, worsening China’s structural water shortages. Approaching 8 million people and 4.6 million head of livestock are short of drinking water, officials say, with the latest number suggesting the impact of the lack of rain is spreading with the drought now in its third year in some parts. Yunnan, Sichuan, Hebei, Shanxi and Gansu are worse affected. A widespread emergency relief effort is underway.

Footnote: The main cash crops in Yunnan, where the drought is most intense, are rice, maize and wheat. The province is also known for its tobacco and tea.

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Shanghai Becomes More Like Venice, In A Bad Way

So serious has the depletion of China’s groundwater become as a result of industrialization and urbanization that the country’s large cities are sinking, as, potentially, are the high-speed rail corridors between them. So concerning is that to authorities that the State Council has made areas with high-speed rail links a priority in a new land subsidence research project it has approved to be completed by 2015. In the order of these things, that is a crash deadline.

The survey is one of four projects that the Ministry of Land and Resources said this week that the State Council had ratified to combat the effects of China’s growing water shortage. Others include yet more controls on pumping underground water, and the setting up of monitoring networks in the worst affected areas–the Yangtze river delta, the North China Plain and the Fen and Hua river basins. The network is to be in place by 2020.

It didn’t take any technology to see the 8 meter crack that opened up earlier this month in a road near the Shanghai World Financial Center. (There are some pictures here.) That is despite authorities taking preventive measures since 2005 to combat ground subsidence caused by falling water tables. Municipal officials say the city is still sinking by seven millimeters a year. That is a better state of affairs than in the past, however. Shanghai used to be sinking by several centimeters a year.

A third of China’s water reserves lie in underground aquifers. They supply 70% of the country’s drinking water and 40% of its farm irrigation needs. They are being stretched to their limits, particularly across the grain belt of the North China Plain as evermore wells are sunk to draw water for city dwellers and industry. Underground water pollution is a separate concern, but as serious.

Shanghai is one of more than 50 large cities with a similar Venice-like problem of subsidence because the water table below it is sinking. Beijing, Tianjin, Hangzhou and Xian are among others. As the number of 50 cities has been quoted since at least 2006, we suspect it may undercount the problem today. In a paper the China Geological Survey published that year the direct economic cost of subsidence was put at 1 billion yuan ($160 million) a year. It will likely top that now.

Tianjin, which like Shanghai has been sinking since the 1920s although it wasn’t until the 1960s that it was understood why, shows why widespread limits on groundwater pumping are so urgent, and also how difficult it is to control subsidence. The city introduced restrictions as long ago as 1985. Its sinking has slowed from 80 millimeters a year then but is still dropping 20 millimeters a year now. Coastal cities share another characteristic with Venice. Floods are becoming more frequent and severe. The lower cities sink the more susceptible they are to them.

We have noted before the potential explosive social costs of a water crisis getting beyond the government’s control. It will take a comprehensive program of water conservation, better water resource management and better husbandry of the ecosystem. And there are plans on all those fronts. But if they fail, it will be more than a high-speed train or two that comes off the rails.

 

 

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Shrivelling Poyang Lake

Poyang Lake, China's largest freshwater lake, is now one-twentieth of its former size.

When this Bystander last checked on Poyang Lake, China’s largest freshwater lake, in September it was recovering from the severe spring drought that had shrunk it to 400 sq. kms, barely a third of its average size over the past decade. That replenishment has not only stopped. It has been dramatically reversed, as the picture above, published earlier this week by state media and reportedly taken on Tuesday, and the one below, taken in November, show. Jiangxi’s provincial hydrographic bureau says the lake’s surface area is now less than 188 sq. kms, about 5% of its former size. At full capacity, it is as large as 4,500 sq. kms, or  more than six times the size of Singapore.

The lake is fed by five rivers in Jiangxi and empties into the Yangtze. Its water level has fallen so far that fishing is possible for barely three months of the year. The lake used to provide a livelihood for a fleet of 10,00 fishing boats, as well as being home to a rare finless porpoise. It also supports hundreds of thousands of migratory birds including the Siberian crane in winter, that, like the fishermen, depend on a lake full of fish to survive. The lake’s nature reserve authority is planning to stock the lake again to help both groups, though last year’s restocking failed as so many of the fry perished for lack of water. In November, the birds had to have food brought in.

Lack of rain this year is being blamed for Poyang’s shrivelling, but it is far from the only lake in China to be drying up. Nor is drought the sole reason.

A dead fish lies on the exposed riverbed of the Poyang Lake in Duchang, east China's Jiangxi Province, Nov. 4, 2011.

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