Shanghai is Sinking

ByJoe McDonald

S H A N G H A I,  China, July 28, 2000 -- The only thing keeping the Huangpu Riverout of the Peace Hotel’s Art Deco lobby on Shanghai’s waterfrontthis summer is a concrete flood wall.

It’s not that the river has risen more than usual during therainy season. Instead, Shanghai is sinking.

The land under the skyscrapers and 13 million people of thisbustling metropolis is deflating like a giant air mattress, slowlysettling as its shallow water table collapses after decades ofoveruse.

Sinking Widespread

Sinking cities are common in chronically dry China, which isguzzling water from underground aquifers to supply a boomingeconomy and growing population.

Land under 46 cities is sinking, the government says. Areasaround Beijing, the capital, have sunk by up to 14 inches over thepast decade.

Although Chinese officials warn publicly about relying tooheavily on wells, drought in recent years has complicated theirefforts. As rivers dry up, cities and farms drill more wells. Morethan 100 cities in northern China are short of water, the officialXinhua News Agency has reported. Some reservoirs are dry.

Shanghai has switched to river water for most uses, slowing itsannual descent to less than two-fifths of an inch. But after yearsof rapid decline, even that threatens China’s business capital,which sprawls across flat land less than 10 feet above the Huangpu.

“If we didn’t control this, the ground would collapse” bythree feet every decade, said Liu Yi, a government geologist whotracks the sinking. “The damage would be unbelievable — floods andwrecked buildings.”

Drained Water

Shanghai, one of the world’s most densely populated cities,switched fairly easily to water from the Huangpu and Yangtzerivers. But it still suffers the legacy of long, severe bouts ofground subsidence.

The problem stems from Shanghai’s rapid 19th centurymetamorphosis into a foreign colonial base. Shallow aquifers thathad supported a Chinese trading port were quickly strainedsupplying factories and a populace that tripled by 1900 to morethan 1 million.

The sinking was first noticed in 1921, but Shanghai went onusing ground water for decades, according to Liu, the seniorgeologist for the Shanghai Institute of Geological Survey. Theproblem got so bad by the 1950s and 1960s that the ground wassinking by four inches a year.

The government took action in 1963, banning most wells andlimiting use of the rest. Still the decline continued, and Liu saidthat since the mid-1960s the city has settled 16 more inches.

Shanghai has avoided nightmare scenarios of flooding in urbanneighborhoods or among the office towers of its sleek new financialdistrict. But official projections say water levels could rise 19to 27 inches by 2050, threatening waterfront areas.

Downtown Flood Wall

Worst-hit is the old city center, where sections are at or belowthe Huangpu’s level. The district has some of Shanghai’s mostvaluable real estate and the Bund, the former British settlementwhose 1920s-era buildings make up the city’s signature skyline.

The Bund’s name comes from Hindi — a reminder of Britishcolonial rule in India — and means embankment. The Huangpu then waslow enough that its flat bank was used as a mule path to tow junksup the river.

That bank is now topped by a flood wall built in the early 1990sby city leaders worried that the summertime Huangpu would overflowonto Sun Yat-sen Road, the eight-lane riverfront boulevard.

They concealed the menace with Shanghainese flair, filling thewall with shops and topping it with a tourist promenade. Familiesstroll the wide walkway on summer evenings, unruffled that thewater on one side is higher than the ground on the other.

Even before its mid-August peak, the Huangpu already is levelwith the road, said Zhang Liugang, an official of the cityAnti-Flood Office. In 1997, he said, the rain-gorged river ran fivefeet higher than the road and came within 3½ feet of the top of theflood wall.

Reversing Nature’s Flow

The geologist Liu has spent 12 years tracking the city’sdecline. His staff of 100 and network of 27 monitoring stationswith sensors drilled 300 to 600 feet into the earth monitor theshifts.

“You can’t see it if you look around, but the problem isterrible. We can’t wait until it’s visible,” Liu said.

In a tactic that borders on science fiction, Shanghai is tryingto reverse the decline by recharging its aquifers, pumping in 5.2billion gallons of water a year.

The program, Liu said, has met with modest success, with land insome areas rising as much as 4½ inches.

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