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长江水深的真实历史数据
[版面:史海钩沉][首篇作者:whoami2012] , 2019年11月09日13:30:07 ,233次阅读,10次回复
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发信人: whoami2012 (nosce te ipsum or temet nosce), 信区: History
标  题: 长江水深的真实历史数据
发信站: BBS 未名空间站 (Sat Nov  9 13:30:07 2019, 美东)

Yangtze River
RIVER, CHINA
WRITTEN BY: Aleksandr Pavlovich Muranov Charles E. Greer
See Article History
Alternative Titles: Ch’ang Chiang, Chang Jiang, Da Jiang
Yangtze River, Chinese (Pinyin) Chang Jiang or (Wade-Giles romanization) Ch
’ang Chiang, longest river in both China and Asia and third longest river
in the world, with a length of 3,915 miles (6,300 kilometres). Its basin,
extending for some 2,000 miles (3,200 km) from west to east and for more
than 600 miles (1,000 km) from north to south, drains an area of 698,265
square miles (1,808,500 square km). From its source on the Plateau of Tibet
to its mouth on the East China Sea, the river traverses or serves as the
border between 10 provinces or regions. More than three-fourths of the river
’s course runs through mountains. The Yangtze has eight principal
tributaries. On its left bank, from source to mouth, these are the Yalung,
Min, Jialing, and Han rivers; those on the right bank include the Wu, Yuan,
Xiang, and Gan rivers.

The name Yangtze—derived from the name of the ancient fiefdom of Yang—has
been applied to the river mainly by those in the West. Chang Jiang (“Long
River”) is the name used in China, although it also is called Da Jiang (“
Great River”) or, simply, Jiang (“[The] River”). The Yangtze is the most
important river of China. It is the country’s principal waterway, and its
basin is China’s great granary and contains nearly one-third of the
national population.

Physical Features
The upper course
The upper course of the Yangtze flows across the Plateau of Tibet and
descends through deep valleys in the mountains east of the plateau, emerging
onto the Yunnan-Guizhou (Yungui) Plateau. Summers there are warm, and the
winters are cold. The source of the Yangtze is the Ulan Moron (Wulanmulun)
River, which originates in glacial meltwaters on the slopes of the Tanggula
Mountains in southern Qinghai province on the border with the Tibet
Autonomous Region. From the confluence of this stream with several others,
the river flows generally easterly through a shallow, spacious valley, the
bottom of which is studded with lakes and small reservoirs. This part of its
course lies in the higher regions of the Tibetan highlands.

First bend of the Yangtze River, Yunnan province, China.
First bend of the Yangtze River, Yunnan province, China.
Bruno Morandi—age fotostock/Imagestate
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The river’s character changes sharply upon reaching the eastern limits of
the highlands. There the river—which in this stretch is called the Jinsha—
descends from a high elevation, winding its way south of the high Bayan Har
Mountains and forming a narrow valley up to 2 miles (3 km) in depth.
Individual mountain peaks exceed elevations of 16,000 feet (4,900 metres)
above sea level and are crowned with glaciers and perpetual snow. The steep,
rocky slopes are cut with gorges and deep valleys. For several hundred
miles the Yangtze flows in a southeasterly direction, before turning south
to flow downward in rushing rapids. For a considerable distance the river
flows through passes that are so steep that no room is left even for a
narrow path. Villages, which are rarely found, are located high above the
river. In this region the Yangtze runs close and parallel to both the Mekong
and Salween rivers; all three rivers are within 15 to 30 miles (25 to 50 km
) of one another and continue to flow in mutual proximity for a distance of
more than 250 miles (400 km).

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North of latitude 26° N these great rivers diverge, and the Yangtze turns
east to pass through a winding valley with steep slopes. The river receives
the waters of many tributaries, among which the Yalong River is the largest
and contributes the most water. The Yangtze then widens to between 1,000 and
1,300 feet (300 and 400 metres), reaching depths often exceeding 30 feet (9
metres). In narrower gorges the water width decreases by almost half, but
the depth increases sharply.


Near the end of the upstream part of its course, the Yangtze descends to an
elevation of 1,000 feet above sea level. Thus, over the first 1,600 miles (2
,600 km) of its length, the river has fallen more than 17,000 feet (5,200
metres), or an average of more than 10 feet per mile (2 metres per km) of
its course. In the mountains, however, there is a substantial stretch where
the fall of the river is considerably greater.

The middle course
The middle course of the Yangtze stretches for about 630 miles (1,010 km)
between the cities of Yibin in Sichuan province and Yichang in Hubei
province. The climate is characterized by hot summers and relatively mild
winters, as the high mountains to the west protect the region from the cold
north and west winds. Annual precipitation measures between 40 and 60 inches
(1,000 to 1,500 mm), a large part of it occurring in summer; the growing
season lasts for more than six months. In most of this segment, the river
crosses hilly Sichuan province, where the lower mountains and plateaus
connect the highlands of southwestern China with the Qin (Tsinling)
Mountains lying between the Yangtze and Huang He (Yellow River) basins.
Located in this area is Chongqing, a major industrial centre and river port.
The river’s width there is from about 1,000 to 1,600 feet (300 to 500
metres), and the depth in places exceeds 30 feet. The current is swift; the
banks often are high and steep. The river falls some 820 feet (250 metres)
in Sichuan, more than a foot per mile (0.2 metre per km) of flow.

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As the Yangtze flows through eastern Sichuan and into western Hubei, it
traverses for a distance of 125 miles (200 km) the famous Three Gorges
region before debouching onto the plains to the east. The gorges have steep,
sheer slopes composed mainly of thick limestone rocks. Prior to the
completion of the Three Gorges Dam in 2006, they rose some 1,300 to 2,000
feet (400 to 600 metres) above the river, although with the creation of the
reservoir behind the dam their height has been diminished fairly
significantly. Nonetheless, they still present the appearance of fantastic
towers, pillars, or spears. Qutang, the first gorge—about 5 miles (8 km)
long—is the shortest; prior to its inundation, the river there was
considered the most dangerous for navigation, being extremely narrow with
many rapids and eddies. Wu, the second gorge, stretches for about 30 miles (
50 km); it is a narrow, steep corridor with almost vertical walls of heights
up to 1,600 or even 2,000 feet above the river. The last gorge, Xiling, is
located upstream of Yichang and extends for a distance of 21 miles; in
places limestone cliffs rise directly out of the water, although with the
rise of the reservoir to much lower heights than before. The gorges are
rocky, and the walls are speckled with cracks, niches, and indentations.
Even before the river was inundated, its depth in the gorges was
considerable, increasing to between 500 and 600 feet (150 and 180 metres)
and giving the Yangtze the greatest depths of any river in the world.

Xiling Gorge, in the Three Gorges section of the Yangtze River (Chang Jiang)
, as it appeared before completion of the Three Gorges Dam, Hubei province,
China.
Xiling Gorge, in the Three Gorges section of the Yangtze River (Chang Jiang)
, as it appeared before completion of the Three Gorges Dam, Hubei province,
China.
© Wolfgang Kaehler

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The lower course
The lower part of the Yangtze basin is centred on the extensive lowland
plains of east-central China. The region experiences a temperate climate
with warm springs, hot summers, cool autumns, and relatively cold winters
for the latitude. Monsoons (seasonally changing winds) dominate the weather
of the region, and in the summer and autumn typhoons occur periodically. As
the Yangtze exits from the Three Gorges Dam, near Yichang, it enters a
complex system of lakes, marshes, and multiple river channels developed on
the plains of Hunan and Hubei provinces. This vast region, lying at
elevations below 165 feet (50 metres), has served as a natural flood-
regulation basin in recent geologic history. Three main tributaries (the
Yuan, Xiang, and Han rivers) and many smaller ones join the Yangtze in this
region, which also is where the current slows as the river reaches the plain
. Water levels fluctuate considerably between the flood and low-flow seasons
. In addition, the presence of a number of large lakes, including Dongting
Lake and Lakes Hong and Liangzi, also causes considerable fluctuations in
water volume. The total area of the lakes, at average water levels, is some
6,600 square miles (17,100 square km). The lakes are of national economic
significance, mainly as fisheries.

At the edge of the Lake Liangzi plain the Yangtze widens markedly, the
course of its stream wandering in the form of a large loop. The width of the
river is up to 2,600 feet (800 metres), the depth is more than 100 feet (30
metres), and the water current flows at a rate of about 3.5 feet (1 metre)
per second. The banks are built up for protection from floods. In the
southern part of the plain lies Dongting Lake, which once was the largest
freshwater lake in China but now has been reduced in area by silting and
land reclamation; it shares four tributaries and two canals with the Yangtze
, whose flow it serves to regulate. The surrounding area, agricultural and
studded with lakes, is China’s most important rice-producing region.

At the centre of the lakes region is the large metropolis of Wuhan. Situated
on the Yangtze near the mouth of the Han River, it was formed in 1950 by
the merger of the cities of Hanyang and Hankou on the left bank and Wuchang
on the right bank and has become one of China’s most important
metallurgical-industry centres and river ports. Farther east the Yangtze
flows into a narrowing, picturesque valley and then passes onto the plain of
Jiangxi province, which contains Lake Poyang, China’s largest natural
freshwater lake. The lake, with an average area of about 1,385 square miles
(3,585 square km), receives the Kan River tributary and, in turn, is linked
to the Yangtze by a wide tributary. The river then turns to the northeast,
passes through a widening valley, and flows out onto the southern North
China Plain. The width of the river increases at this point to between 3,000
and 6,000 feet (900 and 1,800 metres), and the depth in places approaches
100 feet. In this region there are a number of large cities, including
Anqing, Wuhu, and Nanjing. The Grand Canal (Da Yunhe), which, with a length
of nearly 1,100 miles (1,800 km), is one of the longest canals in the world;
it crosses the Yangtze in the vicinity of the city of Zhenjiang.



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SIMILAR TOPICS
Ganges River
Indus River
Euphrates River
Yellow River
Brahmaputra River
Jordan River
Mekong River
Godavari River
Narmada River
Krishna River

The Yangtze delta
The Yangtze delta, which begins beyond Zhenjiang, consists of a large number
of branches, tributaries, lakes, ancient riverbeds, and marshes that are
connected with the main channel. During major floods the delta area is
completely submerged. Lake Tai, with an area of about 930 square miles (2,
410 square km), is notable as the largest of the many lakes in the delta.
The width of the Yangtze in the delta, as far as the city of Jiangyin,
ranges from less than 1 mile to almost 2 miles (1.6 to 3.2 km); farther
downstream the channel gradually widens and becomes a large estuary, the
width of which exceeds 50 miles (80 km) near the mouth of the river. Major
cities in the delta include Wuxi, Suzhou, and, at the river’s mouth,
Shanghai.

Before emptying into the sea, the Yangtze divides into two arms that drain
independently into the East China Sea. The left branch has a width of about
3 to 6 miles (5 to 10 km), the right branch of 6 to 15 miles (10 to 25 km).
Between the branches is situated Chongming Island, which was formed over the
centuries by the deposit of alluvium at the mouth of the Yangtze. The depth
of the river in places approaches 100 to 130 feet (30 to 40 metres) but
decreases to only several feet near the sea at the mouth of the river
because of the presence of sandbars.

The section of river from the mouth to 250 miles (400 km) upstream is
subject to the influence of tides. The maximum range of the tides near the
mouth is 13 to 15 feet (4 to 5 metres). The Yangtze delta is rich in mud and
silt and is dominated by fluvial and tidal processes.


The present-day bed of the Yangtze in this area is somewhat above the
elevation of the plain. Thus, to protect the surrounding region from
floodwaters, the banks of the main and other rivers are built up; the total
length of banks on the Yangtze on which levees have been constructed is
about 1,700 miles (2,740 km). Dams also have been built for flood protection
on the shores of several lakes; the Qingjiang Reservoir, for example, built
for this purpose near Dongting Lake, has a design capacity of 194 million
cubic feet (5.5 million cubic metres). The delta is protected from the sea
by two gigantic parallel banks that are faced with stone in most parts.

Geology
In its upper reaches the Yangtze River drains across the Plateau of Tibet,
which is still uplifting as the Indian and Eurasian tectonic plates collide.
The bedrock comprises an assemblage of marine sedimentary, igneous, and
metamorphic rocks. Within intermontane basins, thick deposits of sediments
of Cenozoic age—i.e., less than about 65 million years old—overlie the
bedrock. The Yangtze descends abruptly from the Tibetan Plateau to flow
across deeply eroded mountain plateaus consisting of Paleozoic and Mesozoic
rocks roughly 350 to 150 million years old. In its lower reaches, the
Yangtze River flows across basin fills of Cenozoic material that is about 65
to 25 million years old. These are the result of fluvial sedimentation as
the Yangtze has migrated across its lower basin throughout its Cenozoic
history.


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Hydrology
The Yangtze basin is comparatively well irrigated; the average yearly
rainfall amounts to about 43 inches (1,100 mm). Most of the precipitation is
brought by the monsoon winds and falls primarily as rain in the summer
months. In the mountainous part of the basin the precipitation is mainly
snow. Floods, which result from the monsoon rains in the middle and lower
parts of the basin, usually begin in March or April and can occur at any
time during the next eight months. In May the water level decreases somewhat
but then sharply increases again, continuing to rise until August, when it
reaches its highest level. After that the water level gradually falls to the
premonsoon levels, the decrease continuing through the autumn and most of
the winter until February, when the lowest annual level is reached.

The annual range of water-level fluctuations is considerable—an average of
about 65 feet (20 metres)—with 26 to 35 feet (8 to 11 metres) during years
of low water. Downstream from the Three Gorges Dam the impact of the water-
level variation is lessened by the dam itself and by the regulating effect
of the lakes. In the delta tides exert the greatest influence on the water
level. Near the city of Wusong the daily tidal range is 15 feet (4.5 metres)
, and the yearly range is 20 feet (6 metres).

A breakdown of the water volume delivered to the mouth of the Yangtze shows
that the highland part of the basin contributes 10 percent of the flow,
while the remainder of the water in the river is contributed by the middle
and downstream parts of the basin, with runoff from the basins of Dongting
Lake and Lake Poyang being responsible for about two-fifths of the volume.


The Yangtze carries a tremendous volume of water. In the upstream areas the
average flow exceeds 70,000 cubic feet (1,980 cubic metres) per second,
which is more than the discharge rate of the second longest river in China,
the Huang He, at its mouth. After the inflow from the first large tributary
—the Yalong River—the volume in the Yangtze increases sharply, approaching
an average of 194,000 cubic feet (5,500 cubic metres) per second. Farther
downstream the Yangtze admits many tributaries, and the volume gradually
increases. Prior to the completion of the Three Gorges Dam, it reached 529,
000 cubic feet (15,000 cubic metres) per second at the end of the Three
Gorges area, 847,000 cubic feet (24,000 cubic metres) per second at Wuhan,
and some 1,100,000 cubic feet (31,100 cubic metres) per second at its mouth;
the total volume entering the sea annually was roughly 235 cubic miles (979
cubic km), ranking it third in volume of flow behind the Amazon and Congo
rivers. Those numbers have decreased somewhat since the completion of the
dam in 2006. The suspended sediment load at the mouth of the Yangtze is some
478 million tons per year, one of the highest sediment loads of any river
in the world.

During the seasonal rains the Yangtze widely floods the lower areas, and the
maximum volume of water entering the sea can be more than double the
average flow. Likewise, the flow decreases during the dry season, sometimes
to about one-fourth the average flow. In spite of the fact that the
discharge volume of the Yangtze vastly exceeds that of the Huang He, the
Yangtze is significantly less silty than the Huang He. This is because much
of the Huang He’s course is over the Loess Plateau with its easily erodible
loess (wind-deposited soil), whereas the Yangtze flows over little loess,
and its floodplains are more vegetated and less erodible. In the mountainous
part of the basin, particularly in the Plateau of Tibet, the waters of the
Yangtze contain little silt.


Downstream, however, the waters become muddy and acquire a coffee colour. It
is estimated that the Yangtze annually carries between 280 million and 300
million tons of alluvium to its mouth, depositing an estimated 150 million
to 200 million tons on the river bottom in addition. Thus, the total amount
of suspended material carried or deposited is between 430 million and 500
million tons per year, one of the highest sediment loads of any river in the
world. As a result of the depositing of alluvium at the river’s mouth, the
delta extends into the sea an average of one mile every hundred years.

During the period of monsoon rains, the Yangtze and its tributaries formerly
spilled over, creating extensive floods. If the floods in the main channel
coincided with flooding in one or more of the major tributaries, powerful,
destructive flood waves could result, an occurrence that happened repeatedly
in the history of China. One of the major objectives of the Three Gorges
project was to control such flooding by the river.

When flooding occurs, it frequently results from the deposit of silt in the
bed of the Yangtze. Upon leaving the mountains and entering the plain, the
current in the Yangtze sharply decreases, and thus the flow cannot continue
to carry the entire amount of silt. As a result, a significant portion is
deposited in the bed, causing the bottom to rise. A similar situation occurs
in many of the Yangtze’s tributaries. Flooding thus presents a great
danger to the inhabitants of the adjacent plains.

Human adaptation to and utilization of the plains of the Yangtze valley have
evolved in the context of such floods. Among the legends and myths handed
down from the earliest historical times are accounts of floods that
submerged vast areas. These are said to have turned the plains into inland
seas, with water remaining in the lowest places for many years at a time.
Catastrophic floods have occurred throughout recorded history. During the
period from 206 BCE to 1960 CE, China experienced more than 1,030 major
floods. Especially extensive flooding has occurred on the Yangtze more than
50 times and on the tributary Han River more than 30 times. On the average,
the Yangtze basin has been the scene of catastrophic flooding every 50 to 55
years.

Widespread flooding also may take place at shorter intervals. This has been
the case since the mid-19th century, as the Yangtze basin has flooded in
1870, 1896, 1931, 1949, and 1954. Of these, the 1931 and 1954 floods were
national disasters. The 1931 flood resulted from heavy, continuous monsoon
rains that covered most of the middle and lower parts of the basin. During
May and June, six huge flood waves swept down the river, destroying the
protecting dams and levees in two dozen places and flooding more than 35,000
square miles (90,000 square km) of land; 40 million people were rendered
homeless or otherwise suffered. Many population centres, including Nanjing
and the Wuhan conurbation, were underwater. In Wuhan the water remained for
more than four months, the depth exceeding 6 feet (1.8 metres) and in places
more than 20 feet (6 metres). In the summer of 1954 another powerful flood
occurred, again the result of continued monsoon rains. The water level
sharply increased and at times exceeded the 1931 flood levels by almost 5
feet (1.5 metres). Effective flood-control measures developed since the
1930s, however, averted many of the potential consequences of the flood.

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People
The Yangtze basin contains a significant portion of China’s population, but
distribution is uneven. The highland area of the river’s upper reaches is
among the most sparsely settled regions in China, while the Yangtze delta
has the country’s highest population density. Outside the delta the
greatest concentrations of people are in the plains that adjoin the banks of
the river and its tributaries in the middle and lower basins, especially in
the vicinity of the cities of Chengdu, Chongqing, Wuhan, and Nanjing. These
cities are among the largest in China, and Shanghai is the country’s most
populous.

In the highlands of the upper basin, the population consists mainly of
ethnic Tibetans engaged in traditional animal husbandry and the cultivation
of such hardy grains as barley and rye. The population of the Yunnan-Guizhou
Plateau is a mixture of Chinese (Han) agriculturalists and numerous ethnic
minorities who combine some farming with herding and hunting. The population
of the middle and lower basins becomes progressively more Chinese, although
, especially in the middle basin, many other national minorities are
represented.

Economy
The economy of much of the Yangtze basin is focused largely on agricultural
production, although inland cities such as Wuhan and Chongqing and the
coastal region centred on Shanghai are among China’s most important
industrial centres. The lower basin and the delta are among the most
economically developed areas in the country. Mineral resources include
reserves of iron ore near Wuhan and Nanjing and such deposits as coal,
copper, phosphorus, gold, oil, and natural gas in Sichuan province.


Agriculture
The Yangtze basin contributes nearly half of China’s crop production,
including more than two-thirds of the total volume of rice. Among the other
crops grown are cotton, wheat, barley, corn (maize), beans, and hemp. Of
note is eastern Sichuan province, which its people call the “Land of Plenty
.” The soil there is extremely fertile, and the climatic conditions are
highly favourable to agriculture. The mild climate also facilitates
sericulture, the production of raw silk by raising silkworms. Cultivation is
most intensive, however, in the lower basin and delta, where the natural
conditions are exceptionally favourable: the growing period ranges from 8 to
11 months, and in some areas two or three crops can be harvested annually.

The extensive territory under cultivation in the Yangtze basin—especially
for rice—requires man-made irrigation facilities. Even in the areas of
highest precipitation, severe droughts are experienced, resulting in crop
losses. This is explained by the extremely irregular distribution of
precipitation over the course of the year, with 60 to 80 percent falling in
the summer. Rainless periods sometimes last for six to eight weeks.
Irrigation has existed in the Yangtze basin since ancient times, but many
modern irrigation projects have been undertaken, the largest being the Three
Gorges project.


Fisheries
The Yangtze River and its associated tributaries and lakes abound with fish.
The fishing trade is widely developed and is a major livelihood for much of
the population of the region. Hundreds of species are found in Chinese
rivers, the majority of which inhabit the Yangtze and its tributaries. Some
30 species are of economic significance, especially carp, bream, Chinese
perch, gapers (a species of large burrowing clam), and lamprey; the most
valuable economically are white and black amur (large members of the carp
family), flatfish, and spotted flatfish. Sturgeon also are important, the
gorges being a favourite spawning area. Farther downstream great amounts of
roe can be found, and these are collected and distributed throughout the
country for artificial cultivation. The artificial cultivation of fish for
trade involves mainly white and black amur, flatfish, and carp.

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Navigation
The Yangtze is the principal navigable waterway of China. Along the river
for 1,700 miles (2,700 km) there is intensive cargo and passenger traffic.
The river serves as a continuation of the sea routes, binding the inland and
coastal ports together with other major cities into a transportation
network in which Nanjing, Wuhan, and Chongqing play the leading roles.
Motorized junks, other powered vessels, and a small number of sail craft are
widely used for transporting cargo. Because of the ship locks at the Three
Gorges Dam, large ships of up to 10,000 tons can travel as far upriver as
Chongqing. Water routes in the Yangtze basin total about 35,000 miles (56,
300 km). The Yangtze is joined to navigable stretches of the Huang He and
the Huai, Wei, and Hai rivers by the Grand Canal, which is further connected
with the seaports of Hangzhou and Tianjin.

Of the several projects undertaken since the 1950s to improve navigation
through the gorges region, none has matched the massive Three Gorges Dam
project. Large projects have been undertaken to strengthen and enlarge the
levee system. In addition, bridges have been built across the Yangtze at
Wuhan, Chongqing, Nanjing, and other cities, improving north-south transport
links and reducing dependence on ferries.

Hydroelectric power
The resources for the production of energy from the Yangtze are enormous,
although they have not been developed to a large extent. The total potential
power is estimated to be more than 200 million kilowatts, representing
about two-fifths of the total energy potential of all the rivers of China.
Until the Three Gorges Dam project got under way, the most ambitious project
completed was the Gezhouba hydroelectric dam above Yichang, which was the
first structure to block the flow of the Yangtze. Gezhouba was superseded by
the massive Three Gorges Dam project. At the time of the Three Gorges Dam’
s completion in 2006, it was the largest dam structure in the world. It
blocks the Yangtze to create a reservoir that submerged large areas of the
Qutang, Wu, and Xiling gorges for some 375 miles (600 km) upstream. The
hydroelectric component of the project, which became fully operational in
2012, has the capacity to generate approximately 22,500 megawatts of
hydroelectric power. Many tributaries of the Yangtze that have significant
fall and volume—such as the Yalong, Min, and Jialing rivers—and other
rivers that are tributaries of Dongting Lake and Lake Poyang also have
considerable potential.


Human impact on the environment
Environmental degradation in the Yangtze basin has accelerated with
increased economic development since 1950. Pollution levels have risen in
the rivers and lakes, soil erosion in the middle and upper basins caused by
overgrazing and the overcutting of trees has increased silt loads, and land
reclamation has reduced surface areas of lakes and wetlands. However,
nothing has had a greater impact than the Three Gorges project. One of the
greatest objections critics of the project have made is that it floods an
area that is one of the most scenically beautiful in China. Another concern
has been that the changes made to the Yangtze’s regime could adversely
affect several endangered animal species inhabiting the basin, including the
Chinese alligator, the finless porpoise, and the Chinese sturgeon. In
addition, numerous towns and cities have been inundated by the reservoir,
forcing the relocation of some one million people. It is also argued that
the buildup of sediment will cause reservoir levels to rise too high to
contain floods and that the area—which is highly active seismically and
frequently is prone to landslides—could be at increased risk for
catastrophic dam failure. Furthermore, it is feared that the waters
downstream from the dam, now largely free of their silt burden, will tend to
erode surrounding banks rather than build them up and may cause much land
degradation.

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History
The Yangtze River basin is one of the longest-inhabited regions in China.
Although much of China’s political history has centred around North China
and the Huang He basin, the Yangtze region always was of great economic
importance to successive dynasties for its agricultural potential. The Grand
Canal was built in order to transport grain from the Yangtze basin to the
great northern capital cities; it is possible that the southernmost portion
of the canal was in use as early as the 4th century BCE, and much of it was
constructed in the 7th century CE.

Over the course of time the Yangtze has served as both a political and a
cultural boundary. The river now demarcates the provinces constituting South
China. The Yangtze also was the focus of many of the imperialist incursions
into China in the 19th century and the first half of the 20th, with
Shanghai at the river’s mouth becoming the main foreign commercial base.
Since 1950 the river and its basin have been the focus of much of China’s
economic modernization.

Aleksandr Pavlovich Muranov
Charles E. Greer
The Editors of Encyclopaedia Britannica
--
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发信人: whoami2012 (nosce te ipsum or temet nosce), 信区: History
标  题: Re: 长江水深的真实历史数据
发信站: BBS 未名空间站 (Sat Nov  9 13:31:19 2019, 美东)

North of latitude 26° N these great rivers diverge, and the Yangtze turns
east to pass through a winding valley with steep slopes. The river receives
the waters of many tributaries, among which the Yalong River is the largest
and contributes the most water. The Yangtze then widens to between 1,000 and
1,300 feet (300 and 400 metres), reaching depths often exceeding 30 feet (9
metres). In narrower gorges the water width decreases by almost half, but
the depth increases sharply.
--
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发信人: whoami2012 (nosce te ipsum or temet nosce), 信区: History
标  题: Re: 长江水深的真实历史数据
发信站: BBS 未名空间站 (Sat Nov  9 13:31:50 2019, 美东)

Located in this area is Chongqing, a major industrial centre and river port.
The river’s width there is from about 1,000 to 1,600 feet (300 to 500
metres), and the depth in places exceeds 30 feet. The current is swift; the
banks often are high and steep. The river falls some 820 feet (250 metres)
in Sichuan, more than a foot per mile (0.2 metre per km) of flow.
--
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标  题: Re: 长江水深的真实历史数据
发信站: BBS 未名空间站 (Sat Nov  9 13:32:32 2019, 美东)

Qutang, the first gorge—about 5 miles (8 km) long—is the shortest; prior
to its inundation, the river there was considered the most dangerous for
navigation, being extremely narrow with many rapids and eddies. Wu, the
second gorge, stretches for about 30 miles (50 km); it is a narrow, steep
corridor with almost vertical walls of heights up to 1,600 or even 2,000
feet above the river. The last gorge, Xiling, is located upstream of Yichang
and extends for a distance of 21 miles; in places limestone cliffs rise
directly out of the water, although with the rise of the reservoir to much
lower heights than before. The gorges are rocky, and the walls are speckled
with cracks, niches, and indentations. Even before the river was inundated,
its depth in the gorges was considerable, increasing to between 500 and 600
feet (150 and 180 metres) and giving the Yangtze the greatest depths of any
river in the world.
--
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标  题: Re: 长江水深的真实历史数据
发信站: BBS 未名空间站 (Sat Nov  9 13:33:13 2019, 美东)

At the edge of the Lake Liangzi plain the Yangtze widens markedly, the
course of its stream wandering in the form of a large loop. The width of the
river is up to 2,600 feet (800 metres), the depth is more than 100 feet (30
metres), and the water current flows at a rate of about 3.5 feet (1 metre)
per second.
--
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标  题: Re: 长江水深的真实历史数据
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At the centre of the lakes region is the large metropolis of Wuhan. Situated
on the Yangtze near the mouth of the Han River, it was formed in 1950 by
the merger of the cities of Hanyang and Hankou on the left bank and Wuchang
on the right bank and has become one of China’s most important
metallurgical-industry centres and river ports. Farther east the Yangtze
flows into a narrowing, picturesque valley and then passes onto the plain of
Jiangxi province, which contains Lake Poyang, China’s largest natural
freshwater lake. The lake, with an average area of about 1,385 square miles
(3,585 square km), receives the Kan River tributary and, in turn, is linked
to the Yangtze by a wide tributary. The river then turns to the northeast,
passes through a widening valley, and flows out onto the southern North
China Plain. The width of the river increases at this point to between 3,000
and 6,000 feet (900 and 1,800 metres), and the depth in places approaches
100 feet. In this region there are a number of large cities, including
Anqing, Wuhu, and Nanjing.
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标  题: Re: 长江水深的真实历史数据
发信站: BBS 未名空间站 (Sat Nov  9 13:34:32 2019, 美东)

Before emptying into the sea, the Yangtze divides into two arms that drain
independently into the East China Sea. The left branch has a width of about
3 to 6 miles (5 to 10 km), the right branch of 6 to 15 miles (10 to 25 km).
Between the branches is situated Chongming Island, which was formed over the
centuries by the deposit of alluvium at the mouth of the Yangtze. The depth
of the river in places approaches 100 to 130 feet (30 to 40 metres) but
decreases to only several feet near the sea at the mouth of the river
because of the presence of sandbars.
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标  题: Re: 长江水深的真实历史数据
发信站: BBS 未名空间站 (Sat Nov  9 13:37:33 2019, 美东)

The annual range of water-level fluctuations is considerable—an average of
about 65 feet (20 metres)—with 26 to 35 feet (8 to 11 metres) during years
of low water. Downstream from the Three Gorges Dam the impact of the water-
level variation is lessened by the dam itself and by the regulating effect
of the lakes. In the delta tides exert the greatest influence on the water
level. Near the city of Wusong the daily tidal range is 15 feet (4.5 metres)
, and the yearly range is 20 feet (6 metres).
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标  题: Re: 长江水深的真实历史数据
发信站: BBS 未名空间站 (Sat Nov  9 13:40:22 2019, 美东)

从长江第一桥到中国“新名片”——中国桥梁的“成长”故事
2017-10-03 10:57:29 来源: 新华社
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  新华社武汉10月3日电 题:从长江第一桥到中国“新名片”——中国桥梁的“
成长”故事

  新华社记者熊金超、皮曙初、李劲峰

  再过12天,武汉长江大桥将迎来通车60周年。矗立在滚滚江水中的万里长江第
一桥,开启中国现代桥梁建设的华章。

  60年前,建设万里长江第一桥,需举全国之力;60年后,一座座大桥跨越江河
湖海、深山峡谷,不断刷新世界之最,成为中国亮丽的“新名片”。

(新华全媒头条·图文互动)(1)从长江第一桥到中国“新名片”——中国桥梁的“
成长”故事

  武汉长江大桥建设时期,技术人员在大桥施工现场做记录(资料照片)。再过12天
,武汉长江大桥将迎来通车60周年。矗立在滚滚江水中的万里长江第一桥,开启中国现
代桥梁建设的华章。 60年前,建设万里长江第一桥,需举全国之力;60年后,一座座
大桥跨越江河湖海、深山峡谷,不断刷新世界之最,成为中国亮丽的“新名片”。新华
社发

  扎实奋斗:填满两毫米缝隙背后的责任追求

  9月17日,河北怀来县。作为2022年冬奥会的交通干线,京张高铁土木特大
桥完成上万吨桥体的高空转体,精准对接,引发声声赞叹。

  桥墩上印制的二维码,包含桥墩各类施工信息。京张高铁五标项目部总工程师高光
品说,扫一下二维码,谁打的混凝土、谁打的钢筋,一目了然,“要对大桥质量终身负
责”。

  61年前的初秋,在武汉长江大桥建设工地上,工人们正忙着铲下已装好的铆钉。

  担任武汉长江大桥施工组织设计小组组长的赵煜澄老人回忆,1955年,在新中
国一穷二白的条件下,武汉长江大桥动工建设。大桥钢梁拼装两个月后,发现固定桥梁
杆件的上万颗铆钉,与孔眼间有2毫米缝隙,出现松动,“拼装马上停工,直到新铆钉
填满缝隙,先期铆钉全部弃用”。

  一个个二维码,一颗颗长铆钉,虽然相隔60多年,但凸显同样的扎实、严谨的责
任追求。

  相对于摩天大楼、大型机场等建筑主要承受自身重量荷载,架在峡谷、江河、大海
上的大型桥梁,不仅要承受自身重量,还得经受起大量汽车甚至高速列车通过带来的巨
大冲击。

  中铁大桥勘测设计院院长张敏说,桥墩要防洪水、抗地震、防船撞,桥身还需面对
来自各个方向的压、弯、扭、拉等形式受力,“夸张点说,就像揉面、拉面过程中的面
条,一不小心就断裂”。

(新华全媒头条·图文互动)(2)从长江第一桥到中国“新名片”——中国桥梁的“
成长”故事

  建设中的武汉长江大桥在进行钢梁架设(资料照片)。再过12天,武汉长江大桥将
迎来通车60周年。矗立在滚滚江水中的万里长江第一桥,开启中国现代桥梁建设的华章
。60年前,建设万里长江第一桥,需举全国之力;60年后,一座座大桥跨越江河湖海、
深山峡谷,不断刷新世界之最,成为中国亮丽的“新名片”。新华社发

  桥梁技术含量高、施工挑战大,重重风险伴生而来。上世纪40年代,美国新建的
塔科马海峡大桥,通车4个月后就因风振断裂。

  第一次带队修建长江大桥时的一次经历,让中交二航局沪通大桥项目经理杨志德记
忆犹新。彼时,江阴长江公路大桥两百多米高主塔塔冠浇筑进入尾声。混凝土泵突然出
现故障,前期浇筑的混凝土凝固,与后浇混凝土间产生缝隙。

  按常规,这类缝隙可按施工缝处理,但可能影响桥塔受力。杨志德毫不犹豫组织上
百名员工,凿除300多立方米已浇筑的混凝土,重新浇筑。耽误的半个月工期,经他
与员工一起24小时轮班连续作业最终追回,如期完工。

  现在,桥梁设计施工规范与标准日趋严格,建桥企业质量管理体系日趋完善,加上
各类质量监控、后期养护技术与设备投入使用,让建在山谷、江河、海峡间的各类大型
、特大型“中国桥”,犹如一座座坚固的钢躯,保障频次越来越高的汽车、火车安全通
行。

  60年间,武汉长江大桥经历近百次大小船舶撞击,依旧坚固如初。今年4月,武
汉长江大桥养护“体检报告”显示:目前全桥无变位下沉,桥墩可承受6万吨压力、可
抗8级以下地震和强力冲撞,2.4万多吨钢梁和8个桥墩无裂纹、无弯曲变形,百万
颗铆钉未发现松动。

  自力更生:屡屡惊艳世界的创新力量

  伶仃洋海域,一桥飞架三地的港珠澳大桥,正紧锣密鼓地开展收尾施工,年底具备
通车能力。

  世界上最长的跨海大桥,世界上最长的钢结构桥梁……站在这座超级工程前,中国
交建总工程师林鸣放言:拿下港珠澳大桥,世界上几乎没有中国人不能造的桥。

  环境的恶劣、功能的多样、经济的考量、美观的需要,让中国桥梁建设的每次突破
,都带来工艺与经验的积累、技术与装备的创新。

  中铁大桥局原副总工程师、85岁老人刘长元说,民国时期,国内外桥梁专家对长
江大桥先后开展4次勘探、设计,均因资金、技术问题无功而返,“桥墩建设难题首当
其冲”。

  当时,深水中建造桥墩主要采取“气压沉箱法”:先将一个大沉箱沉入江底,充入
高压空气排出江水,供工人下到江底直接施工。1934年由茅以升主持兴建的钱塘江
大桥就是使用这种工艺。但这种工艺,安全极限是水下35米,长江武汉段汛期水深超
过40米,一年中能施工的时间仅三个月。

  刘长元回忆,支援武汉长江大桥建设的苏联专家提出“管柱钻孔法”,先打混凝土
管柱到江底,再在江底钻孔浇筑混凝土建桥墩,实现水上施工。但这种工艺,世界上没
有实践先例。

  冒着失败的风险,大桥工程师们先行试验。从苏联引进的打桩机力量不够,国内技
术人员在长江岸边维修车间的简陋环境中,重新设计图纸,制造出世界上最大的震动打
桩机,确保“管柱钻孔法”试验成功,运用在长江大桥建设上。

  中铁大桥局董事长刘自明介绍,武汉长江大桥当年摸索的建桥技术,早已被更先进
、更经济的工艺所取代,“但万里长江第一桥,为我国桥梁建设者们播下了自主创新的
自信种子”。

  不断增强的综合国力、幅员辽阔的建桥需求,为中国桥梁建设创新提供了强大保障
与广阔舞台。中国桥梁正向世界展示中国制造中的创新力度与速度:

  在工艺上——从只能建造类似武汉长江大桥的钢桁梁结构,到现在世界排名前十的
斜拉桥、悬索桥、拱桥中,中国桥梁占席均超过“半壁江山”,建设工艺创新不断惊艳
世界。

  在材料上——武汉长江大桥所用桥梁钢全部从国外进口,芜湖长江大桥上首次使用
国产Q370(一平方毫米能承受37公斤的拉力)桥梁钢,在建沪通长江大桥使用的
国产桥梁钢强度达到Q500。

  在装备上——实现国产化的大型桩工机械、施工船舶、运架梁设备等先进建桥装备
,使大型桥梁建设从武汉长江大桥时需举全国之力,变为现在一家企业就能像“搭积木
”一样同时建造上十座大桥。

  勇担重任:“梦想之桥”折射的基因传承

  南亚孟加拉国帕德玛河下游,全长近10公里的在建公铁两用桥梁帕德玛大桥,桥
墩与桥身正在同步施工。

  中铁大桥局帕德玛大桥项目部经理刘建华说,这座桥通车后,将结束孟加拉国西南
部地区与首都达卡靠轮渡过河的历史,被当地群众称为“梦想之桥”。

  从武汉长江大桥到帕德玛大桥,经历“建成学会”“发奋追赶”“超越引领”三个
阶段的“中国桥”,不同时代承载着不同的历史使命。

  1957年10月15日,武汉长江大桥通车,举国欢庆。赵煜澄回忆,作为新中
国成立后的首批国家项目,各地群众争相前来支援,为大桥搬上一块砖都觉得特别光荣
,“修建长江大桥的热情,背后是全国人民建设新中国的强烈愿景”。

  武汉长江大桥、南京长江大桥的先后通车,仍难缩小中国桥梁与世界先进水平的巨
大差距。

  1982年,参与过武汉长江大桥建设的李赢沧,受邀参访日本本州四国联络桥。
施工现场上千米跨度的大桥,起重3000吨的吊船,让他内心震撼不已。“国内最大
吊船才35吨,我们什么时候能赶上日本?”忆往昔,李赢沧老人一语哽咽。

  与国外同行存在的巨大差距,让国内桥梁建设者们发奋追赶。改革开放,国内经济
发展一日千里,让建设大桥、连通南北的社会需求与日俱增,使桥梁建设者们习惯于风
餐露宿、加班加点。

  在中交二航局,仅由杨志德领衔建造的长江大桥就达17座。这位年过六旬的安徽
汉子,在建桥工地上两次头部受伤,但都没离开过工地,“大桥都是交通干线的控制性
咽喉,工期一天也拖不得呀”。

  芜湖长江大桥、苏通长江大桥、贵州坝陵河大桥、杭州湾跨海大桥……一座座打通
天堑阻隔的中国桥梁,使中国高速公路、铁路纵横成网,为经济社会发展提供有力支撑。

  目前我国公路桥梁总数已超过80万座,铁路桥梁超过20万座。中铁大桥局一家
企业修建的桥梁长度,累计起来相当于北京往返上海的距离。

  中国桥梁究竟实力几何,需要在海外市场上与国际桥梁企业同台竞技来检验。中铁
大桥局海外分公司原副总经理周一桥说,本世纪初,大桥局首个海外中标的孟加拉国帕
克西大桥,设计使用美国标准,施工所需钢筋和水泥等材料须按美国标准采购;施工试
验结果认证,须按美国标准执行。

  如今,按中国标准建设的“中国桥”已遍布亚洲、非洲、欧洲等大洲。位于印尼的
泗马大桥完全采用中国标准规范设计、施工,首次实现桥梁领域的中国标准走出国门。

  “中国桥梁企业近年来大量拓展海外业务,参与国际竞争,不仅代表着中国企业‘
出海’探路,更能让世界共享中国桥梁建设发展成果。”中交二航局董事长王世峰说。


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whoami2012
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发信人: whoami2012 (nosce te ipsum or temet nosce), 信区: History
标  题: Re: 长江水深的真实历史数据
发信站: BBS 未名空间站 (Sat Nov  9 13:40:37 2019, 美东)

  中铁大桥局原副总工程师、85岁老人刘长元说,民国时期,国内外桥梁专家对长
江大桥先后开展4次勘探、设计,均因资金、技术问题无功而返,“桥墩建设难题首当
其冲”。

  当时,深水中建造桥墩主要采取“气压沉箱法”:先将一个大沉箱沉入江底,充入
高压空气排出江水,供工人下到江底直接施工。1934年由茅以升主持兴建的钱塘江
大桥就是使用这种工艺。但这种工艺,安全极限是水下35米,长江武汉段汛期水深超
过40米,一年中能施工的时间仅三个月。
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whoami2012
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我的博客
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发信人: whoami2012 (nosce te ipsum or temet nosce), 信区: History
标  题: Re: 长江水深的真实历史数据
发信站: BBS 未名空间站 (Sat Nov  9 13:43:42 2019, 美东)

南京长江大桥建设者之一万方:自力更生建起南京长江大桥
南京长江大桥地质复杂,从7号墩到5号墩采用钢沉井基础,水深达40米至50米,第一次
采用钢沉井,为解决定位后的清基问题,需潜水工下探解决,当时的潜水设备只能达到
水深30米以内,但潜水工在5、6、7号墩的潜水清基深度已达50米,这是一个了不起的
超越。
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