.

Asia – Eastern AsiaF Wang, University of Manitoba, Winnipeg, MB, CanadaJ Chen, Peking University, Beijing, P. R. China

ã 2009 Elsevier Inc. All rights reserved.

Introduction

Eastern Asia usually refers to China, Japan, andNorth and South Korea. It covers an area of about10.2� 106 km2, or 7% of the Earth’s total land area.As of 2008, the region is inhabited by more than1.56 billion of people, almost one fourth of the globalpopulation. China is the largest country in EasternAsia, accounting for 94% of its landmass and 86% ofthe population.With an average elevation of over 4000m asl, the

Qinghai-Tibetan Plateau in western China is the roofof the world and the birthplace for some of thelargest rivers in the world, including the Changjiang(Yangtze River) and the Huanghe (Yellow River)that flow entirely in China, and the Yarlung Zangbo-Brahmaputra, the Lancang-Mekong, and the Nujiang-Salween whose headwaters are located in China withriver mouths in Bangladesh, Vietnam, and Myanmar(Burma), respectively. The latter three rivers emptyinto the ocean from Southern Asia and are included inthe Monsoon Asia chapter. Also not included in thischapter is the Ertix River (Irtysh) which originatesin western China and flows northward joining theOb River before emptying into the Arctic Ocean.Hereafter, the rivers of Eastern Asia shall refer to allother rivers in China, Japan, and North and SouthKorea (Figure 1).

General Features

Table 1 summarizes the major rivers in Eastern Asiaand their hydrological and geochemical features. Allthese rivers empty into the Pacific Ocean. Among thecontinental rivers (in contrast to island rivers), theHeilongjiang-Amur flows through Russia, Mongolia,China, and North Korea, and empties into theOkhotsk Sea. The Yalu (Amnok) and the Tumen(Duman) Rivers originate from the ChangbaiMountains in northeastern China. The Yalu flowssouthwest into the Yellow Sea draining water fromChina and North Korea, and the Tumen flows north-east into the Sea of Japan draining water from China,North Korea, and Russia. A small percentage (�2%)of the Zhujiang (Pearl River) drainage basin is locatedin northeastern Vietnam. All other major continentalrivers are entirely located in continental China.Most continental rivers of China have their origins

in one of the three massive topographic ‘stairs’ in

306

China (Figure 1). Slopping down from west to east,the first and the highest topographic stair is theQinghai-Tibetan Plateau (>4000m asl) from wherethe Changjiang and theHuanghe originate. The second,intermediate stair is formed, from northeast tosouthwest, by the Greater Hinggan Mountains–InnerMongolian Plateau–Loess Plateau–Yunnan-GuizhouPlateau series (1000–2000m asl), and is the sourcewater of the Heilongjiang-Amur, the Liaohe, theHuaihe, and the Zhujiang. The third and the loweststair includes the Changbai Mountains–ShangdongPeninsula–Southeast Coast Mountains (�500m asl) inthe east. Examples of rivers originating from the thirdstair include the Yalu, the Tumen, theMinjiang, and theQiantangjiang.

Rivers in Eastern Asian islands (e.g., HainanIsland, Taiwan Island, and Japan Islands) and KoreanPeninsula are characterized by their relatively shortlengths and small drainage areas. However, due totheir steep elevation gradients, abundant precipita-tions, and frequent typhoons, these small island riv-ers, particularly those in Taiwan Island, can beassociated with very high runoff and TSS contents.

In addition to the oceanic rivers, there are also agreat number of inland rivers in China that dischargeto internal regions and evaporate in salt lakes, a pro-cess referred as endorheism. They drain a total area ofmore than 3� 106 km2, and are located mostly on theQinghai-Tibetan Plateau, and in arid and semiaridnorthwest China. Among the largest inland riversare the Tarim River with an active drainage basin of0.20� 106 km2, and the Ili River which has a drain-age basin of 0.057� 106 km2 with an annual waterdischarge of �12 km3.

Water Discharge

The Changjiang, the Heilongjiang-Amur, and theZhujiang are among the largest rivers in the world interms of water discharge. At Datong, the most down-stream main-channel hydrological station without tidalinfluence, the annual water discharge of the Changjiangaverages 900 km3 year�1 (range: 680–1360km3) dur-ing the period 1950–2006 (Table 1), ranking it thefourth largest river in the world (after the Amazon,Zaire, and Orinoco). The Heilongjiang-Amur has amean annual water discharge of 355 km3 year�1,

50º

40º

30º

20º

1308

1208

125º

1308

1308

1358

140 8

1458

358

408

458

358

408

8121 1228

110 8

110 8 8111

188

198

208

238

248

258

1908

1008

908

100 km

N

N

N500 km

1000 km

50 km

100 km

Continental China

Japan Islands

Cartography by Douglas Fast

Continental China River Names

Korean Peninsula Taiwan Island Hainan Island

7. Huanghe (Yellow)

8. Huaihe

9. Changjiang (Yangtze)

10. Qiantangjiang

11. Minjiang

1. Heilongjiang (Amur)

2. Songhuajiang

3. Tumen (Duman)

4. Yalu (Amnok)

5. Liaohe

6. Haihe

12. Zhujiang (Pearl)

13. Lancangjiang (Mekong)

14. Nujiang (Salween)

15. Yarlung Zangbo (Brahmaputra)

1 6. Tarim

1

2

3

4

5

6

7

8

9

10

11

1213

1415

16

Figure 1 A map showing major rivers in Eastern Asia.

Rivers and Streams _ Asia – Eastern Asia 307

Table 1 Major rivers in East Asia and their hydrological and geochemical features

River Length(km)

Drainagearea(106 km2)

Monitoringstation(% of thedrainagearea)

Dataperiod

Waterdischarge(km3

year�1)

Runoff(mmyear�1)

TDS(mg l�1)

TSS(mg l�1)

TDSflux(106

tonsyear�1)

TSSflux(106

tonsyear�1)

TDSyieldb

(tonskm�21

year�1)

TSSyield(tonskm�21

year�1)

Continental Riversa

Exorheic

Changjiang

(Yangtze)

6300 1.81 Datong (94.5%) 1950–2006 900 526 178b 458 160c 408 93.5c 239

Heilongjiang-

Amur

4440 1.92 1976–1990 355d 185 73d 146d 25.8d 52d 13.4d 27.1d

Jiamusie (27.6%) 1955–2006 64.9 123 150f 197 9.9f 12.8 18.7f 24.1

Zhujiang (Pearl) 2210 0.45 Gaoyao/Shijiao/Boluog (91.1%)

1954–2006 285 695 166h 264 47.5h 75.3 116h 184

Minjiang 541 0.06 Zhuqi (90.8%) 1951–2006 53.8 988 112 6.0 110

Huanghe (Yellow) 5460 0.75 Lijin (99.9%) 1950–2006 31.9 425 514i 23 900 16.5i 787 22.0i 1049Yalu (Amnok) 790 0.06 29 483 4.0

Huaihe 1000 0.19 Bengbu (63.1%) 1950–2006 26.9 224 346 9.3 77.6

Qiantangjiang 668 0.06 Lanxi (32.5%) 1977–2006 16.5 907 121 2.0 110

Tumen (Duman) 520 0.03 8 267 3.0Liaohe 1390 0.23 Liujianfang

(59.3%)

1987–2006 2.9 215 1565 4.6 33.7

Endorheic

Tarim 2179 0.20 Aral 1964–2006 2.2 5028 11Heihe (Black) 821 0.12 Zhengyixia 1963–2006 1.0 1500 1.5

Island Rivers

29 rivers in Taiwan Island 0.022j 1970–1999 41.2j 1870j 9320j 384j 17500j

Rivers in Hainan Island 0.034k 1957–1982 50.4k 1210k 108k 94.4k 5.44k 4.76k 160k 140k

15 major rivers in Japan 0.12l 1938–1992 114l 343l

aUnless otherwise specified, all the data were compiled from the following sources: The Ministry of Water Resources of the People’s Republic of China. River Sediment Bulletin, 2000–2006.bNot corrected for sea salts.cMean annual average for 1960–1990; Chen J, Wang F, Xia X, and Zhang L (2002) Major element chemistry of the Changjiang (Yangtze River). Chemical Geology 187: 231–255.dFraser AS, Meybeck M, and Ongley ED (1995) Water Quality of World River Basins. United Nations Environment Programme (UNEP) Library No 14. Nairobi: UNEP.eJiamusi is on the Songhuajiang, the major Chinese tributary of the Heilong-Amur River.fChen J, Xia X, Zhang L, and Li H (1999) Relationship between water quality changes in the Yangtze, Yellow and Songhua Rivers and the economic development in the river basins. Acta Scientiae Circumstantiae 19:

500–505 (In Chinese).gThe sum of Gaoyao on the Xijiang, Shijiao on the Beijiang, and Boluo on the Dongjiang.hChen J and He D (1999) Chemical characteristics and genesis of major ions in the Pearl River Basin. Acta Sci. Natur. Univ. Pekin. 35, 786–793 (In Chinese).iChen J, Wang F, Meybeck M, He D, Xia X, and Zhang L (2005) Spatial and temporal analysis of water chemistry records (1958–2000) in the Huanghe (Yellow River) basin. Global Biogeochemical Cycles 19, GB3016.

doi:10.1029/2004GB002325.jCompiled from Dadson SJ, Hovius N, Chen HG, Dade WB, Hsieh M-L, Willett SD, Hu J-C, Horng M-J, Chen M-C, Stark CP, Lague D, Lin J-C (2003) Links between erosion, runoff variability and seismicity in the

Taiwan orogen. Nature 426: 648–651.kChen, J., Xie, G., and Li, Y.-H. (1991) Denudation rate of Hainan Island and its comparison with Tainwan Island and Hawaiian Islands. Quaternary Sci. (4), 289–299 (In Chinese).lMLIT (Ministry of Land, Infrastructure and Transport, Japan). Major Rivers in Japan. http://www.mlit.go.jp/river/basic_info/english/table.html (visited on June 19, 2008).

TDS: total dissolved solids; TSS: total suspended solids.

308

Rivers

andStre

ams_A

sia

–Eastern

Asia

Rivers and Streams _ Asia – Eastern Asia 309

followed by the Zhujiang with 285 km3, similar tothat of the Mackenzie and the St. Lawrence Rivers inNorth America, but larger than the Magdalene Riverin South America.Water discharge of most rivers in Eastern Asia

varies greatly within a year. Most rivers (e.g., theChangjiang, the Minjiang, and the Huaihe) peak inthe flood season from May to September due to theinfluence of the East Asia monsoon. Rivers in north-ern China (e.g., the Heilongjiang-Amur, the Yalu, andthe Tumen), Korea, and northern Japan also experi-ence high flows during the spring freshet fromMarchto April following snow melting. Rivers in southeastcoastal areas (e.g., the Zhujiang, the Minjiang, andrivers in Hainan and Taiwan islands) are subject tothe influence of frequent typhoons, and may not seethe highest water discharge until later in September orOctober. The highest degree of seasonal variationsoccurs with small rivers in semiarid and arid areas(e.g., some tributaries of the Huanghe on the LoessPlateau), where the entire water discharge in a yearmay be due to a few storm events only.Water discharge also fluctuates from year to year.

While some of the fluctuations are caused by naturaland climatic processes, there is evidence that anthro-pogenic influence has been playing an increasingly

Year

1950 1960 1970 1980 1990 2000 2010

Wat

er d

isch

arge

(km

3 )

0

20

40

60

80

100

(A) (

a

b

c

d

1950 1960 1970

TS

S (

106

t/yr)

0

500

1000

1500

2000

(C)

a

b

Figure 2 Seaward discharge of water (A), total dissolved salts (TDS

Hydrological Station Lijin, the most downstream station without tidal

indicates the years when various large reservoirs started to store wat

capacity: 3.1 km3), (b) – Liujiaxia Reservoir (Oct. 1968; designed storadesigned storage capacity: 24.7 km3), and (d) – Xiaolangdi Reservoir

important role. Extensive and continuous hydrologicalmonitoring has been in place for 30–100 years formost rivers in continental China and Hainan andTaiwan Islands. These long-term databases make itpossible to detect some persistent changes in waterdischarge from natural fluctuations.

The most notable and alarming change is the dra-matic decrease in water discharge of the Huanghesince�1969. As shown in Figure 2a, the mean annualwater discharge of the Huanghe has decreased from49.1 km3 during 1950–1969 to 14.1 km3 in the 1990sand 13.3 km3 in the 2000s (2000–2006). Indeed,the lower reaches of the Huanghe have been experi-encing frequent dry-ups since the early 1970s. Themost severe dry-ups occurred in 1997, when StationLijin (the most downstream main-channel stationwithout tidal influence) remained dry for a total of226 days; the length of the river section dried upextended to near the City of Kaifeng, some 700 kminland from the river mouth. In addition to climaticreasons – the basin seems to have been experiencing adrought in recent years, the significant reduction inwater discharge is certainly accelerated by theincreasing water withdrawal for agricultural irriga-tion and cross-basin water diversion to NorthernChina, and by the evaporation loss from the surfaces

TD

S (

106

t/yr)

Year1950 1960 1970 1980 1990 2000 2010

0

10

20

30

40

50

B)

b

d

Year1980 1990 2000 2010

cd

; B), and total suspended solids (TSS; C) of the Huanghe at

influence. The dashed lines are linear regression lines. (a)–(d)

er: (a) – Sanmenxia Reservoir (Sept. 1960; designed storage

ge capacity: 5.7 km3), (c) – Longyangxia Reservoir (Oct. 1986;(Oct. 1999; designed storage capacity: 5.1 km3).

310 Rivers and Streams _ Asia – Eastern Asia

of extensive reservoirs in the basin. The sharpdecrease in water discharge around 1969 coincidedwith the operation of the Liujiaxia Reservoir (‘b’ inFigure 2; designed water storage capacity: 5.7 km3),the first large reservoir to be built in the upper reachesof the Huanghe, from where the majority of its wateris collected.No significant trend has been observed in the water

discharge of the Changjiang, the Zhujiang, and theSonghuajiang (the largest Chinese tributary of theHeilongjiang-Amur). The construction of reservoirsdoes not seem to have caused major changes in thewater discharge of the Changjiang (Figure 3(a)),likely buffered by its much larger water dischargeand above-normal precipitation in recent years.Despite their short lengths and small drainage

areas, the rivers originating from the third topo-graphic ‘stair’ in China are abundant in water runoff.The runoffs of the Minjiang and Qiantangjiang, forexample, are almost double that of the Changjiang. Inparticular, rivers from Taiwan and Hainan Islands typ-ically have an annual runoff of more than 1000mm.

Y1950 1960 1970

0

200

400

600

800

TS

S (

106 t/

yr)

(C)

a

Year

1950 1960 1970 1980 1990 2000 2010

Wat

er d

isch

arge

(km

3 )

400

800

1200

1600

(A)

a b

c

Figure 3 Seaward discharge of water (A), total dissolved salts (TDS

Hydrological Station Datong, the most downstream station without ti

indicates the years when various large reservoirs started to store wa

capacity: 21.0 km3), (b) – Gezhouba Reservoir (June 1981), and (c) –39.3 km3).

With a small drainage basin of 122km2, the ShuangRiver in Taiwan Island, for example, has a mean runoffof 4500mmyear�1 during the period 1970–1999, i.e.,about 12 times the world’s average runoff.

Total Suspended Sediment (TSS)

Eastern Asia is home to some of the most TSS-gener-ating rivers in the world. The Huanghe is the mostturbid large river in the world. The TSS concentrationaveraged 23.9 g l�1 (range: 4.8–48 g l�1) during theperiod 1950–2006 at the most-downstream stationLijin. In 6 out of the past 56 years, the annual averageTSS concentration at Lijin exceeded 40 g l�1, a crite-rion above which very dense (hyperpycnal) flowswould develop in the river mouth due to its higherdensity than seawater. Many smaller tributaries of theHuanghe have even higher TSS concentrations.

Until very recently the Huanghe was the largestriver in the world in terms of the TSS flux to the sea.Over its 0.15My history, the Huanghe is estimated tohave discharged a total of 7.0� 1012 tons of TSS, the

ear1980 1990 2000 2010

b

c

Year1950 1960 1970 1980 1990 2000 2010

TD

S (

106 t/

yr)

50

100

150

200

(B)

; B), and total suspended solids (TSS; C) of the Changjiang at

dal influence. The dashed lines are linear regression lines. (a)–(c)

ter: (a) – Danjiangkou Reservoir (July 1967; designed storage

Three Gorges Reservoir (June 2003; designed storage capacity:

Rivers and Streams _ Asia – Eastern Asia 311

majority of which was deposited in the lower reachesof the basin to create the North China Plain and thecontinental delta, but as much as 1.8� 1012 tons ofTSS made its way to the Bohai Sea of the PacificOcean. The TSS load of the river is so high that itsaccumulated deposition in the lower reaches hasraised the river bed up to 10m above the surroundingareas in the North China Plain, making the lowerreaches of the Huanghe essentially a ‘suspendedriver.’ This has become a major threat to its flood-plain which has been inundated regularly since histor-ical periods. The last major flooding event occurredin the 1930s, causing tens of thousands of casualties.However, the seaward TSS flux of the Huanghe has

dramatically decreased in the past decades (Figure 2(C)),especially since the 1970s, dropping from 1230� 106

tons year�1 during 1950–1969 to 390� 106 tons year�1

in the 1990s, and 154� 106 tons year�1 in recent years,with a 57-year mean annual seaward TSS flux of790 � 106 tons year�1 during 1950–2006. Note thatthe widely quoted number of 1600� 106 tons year�1

cannot be regarded as the seaward TSS flux of theHuanghe, as it was based on old data obtained at thestation Sanmenxia, some 1060km upstream inlandfrom the river mouth. The lowest ever TSS flux wasobserved during 2000–2001 with a mere average ofonly 22� 106 tons year�1, less than 2% of its pre-1969average. Such a sharp decrease in the TSS flux is notindicative of water becoming less turbid; rather, itis mainly caused by the sharp decrease in water dis-charge (Figure 2(A)) and by sediment trapping in reser-voirs (e.g., the Sanmenxia Reservoir). Similar to thetrend in water discharge, the dramatic decrease in TSSflux of the Huanghe also started at the same time whenthe LiujiaxiaReservoir started to regulate thewater. Thereduction in theTSS loadmay also be attributed, in part,to the extensive soil and water conservation programslaunched in the basin some decades ago to improve localagriculture and reduce soil erosion.The TSS flux of the Changjiang averaged 410� 106

tons year�1 (85–680� 106 tons year�1) at the stationDatong during the period 1950–2006, surpassedthat of the Huanghe since the 1990s. As shown inFigure 3(C), the TSS load of the Changjiang increasedfrom 400� 106 tons year�1 in the 1950s to around600� 106 tons year�1 in the later 1960s, then droppedback to �440� 106 tons year�1 during 1968–1980.Since the 1980s, a persistent and sharp decreasingtrend has been observed in the TSS load with an aver-age value of 150� 106 tons year�1 during 2000–2006.Different from the Huanghe, in the same period therewas no significant trend in the water discharge ofthe Changjiang (Figure 3(A)). Sediment retentionby large-scale reservoirs and reduced soil erosion byextensive soil and water conservation programs in the

basin were the most likely causes. For instance,the reduction in the TSS flux in the 1970s coincidedwith the operation of the Danjiangkou Reservoir (onthe Hanjiang, a major tributary of the Changjiang)since 1967. About 50� 106 tons year�1 of TSS wasestimated to have been stored in the reservoir duringthe first decade of its operation. The further decreasesince the 1980s is likely due to the Gezhouba Dam onthe main channel of the Changjiang which becameoperational in June 1981, and more recently, theconstruction of the Three Gorges Dam. The ThreeGorges Dam started to store water in June 2003, andin 2004 the TSS load at Datong dropped to 150� 106

tons year�1. In 2005, a total of 150� 106 tons of TSSwas estimated to have been stored already in theThree Gorges Dam. The seaward TSS of the Chang-jiang decreased to 85� 106 tons year�1 in 2006, thelowest in the past 57 years. Further reduction inthe downstream and seaward TSS load is expectedupon the completion of the Three Gorges Dam in 2009.

In addition to their high runoffs, the rivers inTaiwan Island have the highest TSS yields in theworld. With a total drainage area of 0.022� 106km2,the 29 major coastal rivers in Taiwan Island collec-tively supplied 380� 106 tons year�1 of TSS to theocean during the period 1970–1999. The mean TSSyield is about 17 500 tons km�2 year�1, more than16 times that of the Huanghe (at Lijin), and canonly be matched by a few mountainous rivers inNew Zealand. The Pei-Nan River in Taiwan Islandhas a 30-year average TSS yield of 55 400 tons km�2

year�1, which is about 250 times the world’s average.Many rivers in Taiwan Island are hyperpycnal (as forthe Huanghe), with TSS concentrations frequentlyexceeding 40 g l�1, particularly during typhoon-related floods. The extremely high TSS yields aredue to readily and rapid erosion of poorly consoli-dated sediments under the subtropical climate (meanannual precipitation of 2500mmyear�1) with highfrequency of typhoons and in a tectonically activeisland (frequent earthquakes with related landslides).

The rivers in Taiwan and Hainan Islands serve as aclassic example of how geology and precipitationaffect the TSS yield. Both islands are located in sub-tropical to tropical climate zones. They are of similarsize and in close proximity (Hainan Island is about 5�

latitude south and 10� longitude west of TaiwanIsland). However, the TSS yields of the rivers inHainan Island average only 140 tons km�2 year�1

(Table 1), less than 1% of that of the rivers in TaiwanIsland. Hainan Island was formed long before and isgeologically much more stable than Taiwan Island.The lithology of Hainan Island is dominated by lesserodible igneous rocks. In addition, the amount ofprecipitation and the annual runoff of the rivers are

312 Rivers and Streams _ Asia – Eastern Asia

also much smaller in Hainan Island when comparedto Taiwan Island.

Chemical Composition of TDS

Major solute chemistry of the rivers in China has beensurveyed very early and synthesized already in the1960s, although the data have only become availablein the Western literature since the 1980s. Long-termtrends in major solute compositions of large rivershave been studied since the late 1990s. Table 2 sum-marizes the major solute chemistry of selected riversin Eastern Asia.

Major Solute Composition of TDS

Much of the drainage basins of the Changjiang andthe Zhujiang are dominated by carbonate rocks andare located in humid climatic zones. The southeastbasin of the Changjiang and the south basin of theZhujiang are famous for the well developed karstformations (e.g., near Guilin). As a result, the majorsolute chemistry of both the Changjiang and theZhujiang is controlled primarily by the weatheringof carbonate rocks, with HCO3

� being the dominantanion and Ca2þ the dominant cation. As the Zhujiangbasin is subjected to more intensive weathering andleaching, the TDS concentration of the Zhujiangaveraged 189mg l�1, slightly lower than that ofthe Changjiang (206mg l�1); both are well above theworld spatial mean (WSM) value of 126mg l�1.The Changjiang indeed has the highest relative abun-dance of HCO3

� among the major rivers of the world.The Cl� and SO4

2� in the Zhujiang originate mainlyfrom the sea salt spray due to its close proximity to theocean,whereas those in theChangjiangbasin aremainlyderived from the weathering of evaporates in the upperreaches of the basin, as well as from acid deposition.Much higher TDS concentrations are found in the

Huanghe, with a basin-wide average of 450mg l�1,about 3.5 times the WSM value. In particular, theconcentrations of NaþþKþ, SO4

2�, and Cl� are10–20 times higher than in the other major rivers inthe world. With much of its basin underlain by loessand clastic rocks under arid and semiarid climaticconditions, the dissolved salts carried by the Huangheare predominantly controlled by evaporation andfractional crystallization, and chemical weathering.The evaporation and fractional crystallization arefurther promoted by intensive irrigation and reservoirconstructions.Among the four major rivers in Eastern China, the

Heilongjiang-Amur has the lowest TDS concentra-

tion, averaging 73mg l�1 for the drainage basin and150mg l�1 for the Chinese tributary the Songhua-jiang, due to its much lower weathering intensity,under a cold to temperate climate, of silicate andaluminosilicate rocks that dominate in this basin.

Within the same river system, significant variationsin the TDS composition and concentration occur spa-tially. For instance, the Zhujiang is composed of threetributaries, the Xijiang in the west, the Beijiang in thenorth, and the Dongjiang in the east, joining at San-shui just before entering the South China Sea of thePacific Ocean. The subbasin of each tributary isdominated by very different rocks: the Xijiang bylimestone, the Beijiang by red sandstone, and theDongjiang by granite and shales. Reflecting the chem-ical weatherability of these different rocks under ahumic subtropical climate, the TDS concentrationin the Xijiang is the highest (202mg l�1), followedby the Beijiang (121mg l�1) and the Dongjiang(66mg l�1). However, much larger spatial variationis found in the Huanghe basin. At Guochengyi on theZulihe, where evaporation and fractional crystalliza-tion dominates, the TDS concentration is as high as8500mg l�1, i.e., 60 times that at Yimenzhen of theWeihe where chemical weathering of granite domi-nates the process.

Long-Term Trend in Major Solute Concentrations

Since the major solute concentrations at most of thestations along the rivers in China have been moni-tored continuously or semicontinuously for morethan 30 years, it is possible to statistically detect thechanges in the major solute composition of the riverwater. Three distinctive trends have been reported:(i) acidification; (ii) salinization; and (iii) alkalinization.

Acidification in the Changjiang A significantincrease trend has been found in the concentrationsof SO4

2� and, to a lesser extent, Cl� in major tribu-taries in the Chongqing–Guiyang area and at alldownstream main-channel stations of the Changjiang.The rate of SO4

2� increase was the highest in thetributary Tuojiang with an average rate of 1.50mgl�1 year�1 at Lijiawan, just before it joins the Chang-jiang. Even at the most downstream main-channelstation Datong (some 1800 km downstream fromChongqing), the increase was still significant at arate of 0.22mg l�1 year�1 since 1960. The increas-ing trend is attributed to acid deposition in theChongqing–Guiyang area, one of the most severeacid deposition centers in the world. The mountain-ous Chongqing–Guiyang region has become one ofthe largest bases of the heavy industry in China sincethe later 1950s, fuelled by sulfur-rich coals. As a

Table 2 Major ions and dissolved SiO2 composition of some Eastern Asian rivers

River Station Data

period

Ca2þ

(mg l�1)

Mg2þ

(mg l�1)

NaþþKþ

(mg l�1)

HCO3�

(mg l�1)

SO42� (mg l�1) Cl� (mg l�1) SiO2

(mg l�1)

TDS Source

Continental rivers

Changjiang Datonga 1960–1984 30.1 6.3 5.0 113.2 11.9 4.2 7.0 171.3 1

191 stations in the

basinb1960–1990 34.1

(7.9–53.1)

7.6 (2.0–17.5) 8.2

(3.7–23.5)

134

(41.4–215)

11.7

(2.90–41.4)

2.9

(1.1–17.1)

6.2

(1.6–9.1)

206

(69.2–342)

1

Huanghe Lijinaa 1964–1998 51.2 25.2 65.2 197.7 101.5 65.4 508.0 2

100 stations

in the basinb1960–1998 51.0

(27.5–328.6)

18.7

(6.2–256.8)

48.2

(15.6–1150)

206

(115–297)

74.1

(16.2–2020)

30.7

(7.0–1205)

6.0

(3.3–9.1)

452

(221–5258)

2

Zhujiang Gaoyao/Shijiao/

Boluoa,c1959–1984 26.2 4.4 11.2 112.0 8.8 3.5 166.0 3

96 stations in the

basinb1959–1984 32.9

(6.1–57.8)

5.0 (1.8–16.4) 5.5

(2.2–17.0)

130

(35.9–225)

6.6

(2.2–31.7)

1.75

(0.51–6.95)

5.9

(3.8–11.5)

189

(57.0–330)

3

Songhuajiang Jiamusia 1960–1984 16.3 4.7 18.9 89.8 11.8 8.2 5.0 150.0 4

68 stations in the

basinb1960–1984 14.5

(7.6–43.7)

4.2 (2.1–11.0) 12.5

(6.6–46.4)

78.1

(40.8–250)

6.9

(2.5–19.7)

5.6

(2.6–16.6)

7.9

(4.1–20.8)

126

(65.9–430)

4

Island rivers

7 rivers in Hainan Island 1959–1988 6.65 1.51 13.46 54.1 7.68 3.63 15.6 79.6 5

aArithmetic mean (not discharge weighted) of the data during the data period.bMedian (5%–95% percentiles) of the data for all the stations in the Huanghe basin during the data period.cDischarge-averaged value of the three stations.

1. Chen J, Wang F, Xia X, and Zhang L (2002) Major element chemistry of the Changjiang (Yangtze River). Chemical Geology 187: 231–255.

2. Chen J, Wang F, Meybeck M, He D, Xia X, and Zhang L (2005) Spatial and temporal analysis of water chemistry records (1958–2000) in the Huanghe (Yellow River) basin.Global Biogeochemical Cycles

19: GB3016. doi:10.1029/2004GB002325.

3. Chen J and He D (1999) Chemical characteristics and genesis of major ions in the Pearl River Basin. Acta Sci. Natur. Univ. Pekin. 35: 786–793 (In Chinese).

4. Chen J, Xia X, Zhang L, and Li H (1999) Relationship between water quality changes in the Yangtze, Yellow and Songhua Rivers and the economic development in the river basins. Acta Scientiae

Circumstantiae 19: 500–505 (In Chinese).

5. Chen J, Xie G, and Li Y-H (1991) Denudation rate of Hainan Island and its comparison with Tainwan Island and Hawaiian Islands. Quaternary Sciences 4: 289–299 (In Chinese).

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result, acid rain has been reported in the region sincethe 1970s with rainwater frequently having a sulfateconcentration of more than 20mg l�1 and a pH lowerthan 4.1. A strong correlation has been foundbetween the SO4

2� in the Changjiang near Chongqingand the coal consumption in the Sichuan Province.Although no significant trend was observed in totalalkalinity and pH along the main channel of theChangjiang due to the abundance of buffering carbo-nates, the ratio of hardness to alkalinity did increasesignificantly in some large tributaries (e.g., the Tuo-jiang and the Wujiang), showing early signs of loca-lized acidification in the river basin.

Salinization in the Huanghe A more profoundincrease trend is observed in the Huanghe. Concen-trations of TDS and all the major ions except forHCO3

� at all main-channel stations except for theuppermost Lanzhou have been steadily increasingsince the mid1970s. The rate of TDS increase wasthe highest in the middle reaches (10.5mg l�1 year�1

at Toudaoguai) and remained high in the lower reaches(5.5mg l�1 year�1 at Stations Luokou and Lijin). Theincrease trend agreed well with the sharp decreasein the water discharge, suggesting primarily a concen-trating effect, although the impact of other processes(e.g., industrial discharges) cannot be ruled out.

Alkalinization in the Songhuajiang Among 24 long-term monitoring stations in the Songhuajiang basin,16 stations showed a distinctive trend of alkaliniza-tion since the 1960s, evidenced by an increase in theconcentration of NaþþKþ, HCO3

�, and TDS, and adecrease in the ratio of hardness to alkalinity. At a fewstations the pH value also increased slightly. Thealkalinization trend of the Songhuajiang can beattributed primarily to the pulp and paper industryand the practice of groundwater irrigation. Theproduction of pulp and paper in the Heilongjiangprovince, for example, increased fourfold from<10000 tons year�1 in 1961 to more than 40000 tonsyear�1 in 1984. As NaOH and Na2S are commonlyused in chemical pulping, an increasing amount ofNaþ may be directly or indirectly discharged into theriver. The degradation of high organic pulp and paperwastewater also produces CO2 and increases theHCO3

� concentration. Agricultural irrigation withNaþ-enriched groundwater in the region furtherincreases the Naþ concentration in the return waterdue to evaporation.

Seaward TDS Flux

Based on long-term monitoring data at the mostdownstream stations, the Changjiang, the Zhujiang,

the Heilongjiang-Amur, and the Huanghe transport atotal of 250� 106 tons year�1 TDS (not corrected forsea salts) to the ocean (Table 1), accounting for morethan 10% of the global total seaward TDS flux. TheTDS flux of the Changjiang alone amounts to160� 106 tons year�1, second only to the Amazon.The Zhujiang transports a total of 47.5 tons year�1

TDS, similar to that of the Yukon and Rhine. Theseaward TDS flux of the Heilongjiang-Amur is about25.8� 106 tons year�1, 38% of which is derived fromthe Songhuajiang. Despite of its high TSS flux, theHuanghe transported only 16.5� 106 tons year�1 ofTDS to the sea during the period 1950–2005.

Due to the increasing trend in the SO42� concentra-

tion of the Changjiang at Datong as a result of aciddeposition, the TDS flux by this river is likely toincrease further. The rate of increase is rather smallat present (0.25mg l�1 year�1), but with its massivewater discharge it results in an annual increase of0.23� 106 tons of SO4

2� to the ocean. In contrary,despite the increasing trend in the TDS concentra-tions, the seaward TDS flux by the Huanghe, asmeasured at Luokou and Lijin, has decreased bymore than 50% from over 20� 106 tons year�1 inthe 1960s to less than 10� 106 tons year�1 at present(Figure 1(b)), due to the significant decrease in waterdischarge.

Elemental Composition of TSS

Elemental composition of riverine TSS in Eastern Asiawas not included in many earlier studies on globalchemical composition of riverine TSS, due to the lackof relevant data. Such data have become availablesince the 1990s and are summarized in Table 3.

The TSS from Eastern Asian rivers shows a widevariation in elemental composition. The TSS from thenorthern rivers (e.g., the Heilongjiang, Tumen, andYalu) in the cold and temperate zones contains highercontents of K and Na, whereas that from the southernsubtropical zones is richer in Al, which is in generalagreement with the global picture and reflects themobility and fate of elements under different climates.

The Ca concentration in TSS varies significantlyamong the rivers. Despite the fact that limestone isthe dominant rock type in most southern rivers,especially in the upper and middle reaches of theChangjiang and the Zhujiang, the Ca concentrationsare only near the global average of 3.1%, due to thestrong leaching by weathering in humid subtropicalclimates. The highest Ca concentration (5.8%)almost double the global average, is found in TSSfrom the Huanghe, and is among the highest in theworld’s large rivers. This is resulted from the

Table 3 Elemental composition and flux of riverine TSS in Eastern Asia

River Si Al Ca Fe K Mg Na Ti Mn Zn V Cr Cu Ni Pb Co Cd

Concentrations (mg/kg)a

Changjiang 297 000 81 800 28 900 48 200 20 400 18 300 7050 5770 892 164 137 76.4 49.2 50.1 38.6 24.1 0.33

Heilongjiang 62 700 19 300 48 000 24 900 14 700 9590 6430 662 155 77.3 52.6 25.4 37.0 34.0 18.6 0.15

Zhujiang 246 000 111 000 13 100 60 900 18 400 10 100 3460 7570 1030 236 118 91.9 58.2 46.7 49.9 24.8 0.78

Minjiang 97 700 6470 50 200 16 200 5460 4900 5130 1072 291 106 55.9 45.0 37.9 76.3 21.4 0.62

Huanghe 304 000 72 500 58 100 35 600 18 400 17 700 10 600 3670 694 120 87.5 69.1 27.4 42.1 20.9 13.7 0.19

Huaihe 54 800 20 600 41 200 10 300 4740 814 80.0 88.3 84.8 23.1 44.1 23.1 23.8 0.27

Qiantangjiang 74 800 7280 33 000 19 200 11 700 5100 4630 938 239 98.1 59.1 41.6 44.1 38.8 23.2 0.47

Liaohe 68 000 30 100 31 600 21 600 21 200 9300 457 152 34.3 56.7 38.2 30.0 19.6 0.12

Yalu 72 500 23 200 58 700 28 700 16 500 9700 404 231 44.6 42.3 40.2 40.0 24.5 0.15

Tumen 72 100 20 100 69 600 25 600 20 000 8700 456 351 46.6 55.0 43.6 34.6 24.4 0.12

Global

Average

255 000 67 600 30 800 44 000 17 000 12 500 7430 4090 755.2 163.7 122.4 76.4 50.1 45.4 45.0 22.2 0.19

Seaward flux (103 tons year�1)b

Changjiang 123 000 33 900 11 200 19 900 8450 7570 2920 2390 369 67.8 56.8 31.6 20.4 20.7 16.0 9.992 0.14

Heilongjiang 3260 1000 2490 1290 765 498 334 34.4 8.06 4.02 2.73 1.32 1.92 1.77 0.969 0.01

Zhujiang 3100 1400 165 767 232 128 43.6 95.3 13.0 2.98 1.48 1.16 0.733 0.588 0.629 0.312 0.01

Minjiang 479 31.7 246 79.4 26.8 24.0 25.1 5.25 1.42 0.521 0.274 0.221 0.186 0.374 0.105

Huanghe 243 000 57 800 46 400 28 400 14 700 14 200 8470 2930 554 96.0 69.8 55.1 21.8 33.6 16.6 10.96 0.15

Huaihe 525 195 391 97.8 45.0 7.73 0.76 0.839 0.806 0.219 0.419 0.219 0.226

Qiantangjiang 150 14.6 66.1 38.4 23.4 10.2 9.26 1.88 0.477 0.196 0.118 0.083 0.088 0.078 0.046

Liaohe 333 147 155 106 104 45.6 2.24 0.742 0.168 0.278 0.187 0.147 0.096

Yalu 290 92.8 235 115 66.0 38.8 1.61 0.924 0.178 0.169 0.161 0.160 0.098

Tumen 216 60.3 209 76.8 60.0 26.1 1.37 1.05 0.140 0.165 0.131 0.104 0.073

Global Totalc 4460 000 1180 000 539 000 770 000 298 000 219 000 130 000 71 600 13 200 2860 2140 1340 877 794 788 388 3.33

aChen J and Wang F (1996) Chemical composition of river particulates in eastern China. GeoJournal 40: 31–37.bThe flux of each river is calculated from the concentration data in the first half of the table and the TSS flux data from Table 1.cThe global total flux is calculated from the global average concentration data and an estimate of 17 500 � 106 tons year�1 of global TSS flux.

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relatively weak weathering of the high Ca-containingloess (5–20%) in the middle reaches of the river. Theconcentrations of most trace elements (e.g., Cu, Pb,Zn, Cd, Cr) in TSS show a general trend in theincrease from north to south, coincident with thehigh density of nonferrous mineral deposits in south-ern China. An anthropogenic impact is also possiblebut can be masked by the generally high sedimentyields.Due to the very highTSS load andCa content, theTSS

from theHuanghe alone accounts for 6.5%of the globalTSS flux of particulate Ca. In total, the 10 EasternAsianrivers listed in Table 3 account for 5.2–11.1% of theglobal TSS flux of the elements studied.

Human Impacts

As is true around the world, the health of the riversystems in Eastern Asia has been increasinglyimpacted by human activities since the Anthropo-cene. The situation is most challenging in China dueto the regional imbalance of water resources, thelarge population base, and a rapid industrializingeconomy and society. Although southern Chinaenjoys a bountiful freshwater supply, northern andnorthwestern China has one of the lowest per capitawater resources in the world and faces severe watershortages. Large scales of damming and canal build-ing have taken place along many large, medium andsmall rivers to facilitate irrigation, flooding control,water diversion to other regions, and electricity gen-erating. Groundwater has been taken at an unsustain-able rate in many areas in northern China. The needfor such a development and its socioeconomic bene-fits are obvious, but in most cases their environmentalimpacts are not fully studied, understood, and miti-gated. In addition to being increasingly regulated bydams and reservoirs, most rivers have been increas-ingly contaminated and polluted by domestic andindustrial wastewaters, agricultural activities, solidwastes, and atmospherically transported chemicals.On top of all these is climate change which is likelyto alter the hydrology and quality of the rivers further.As a result, not only has the quality of most small,medium, or urban rivers been heavily degraded, manylarge river systems in the continent have also beensignificantly modified. As discussed earlier, the dra-matic decrease in water discharge of the Huanghe, theearly acidification signs in the Changjiang, and thealkalinization in the Songhuajiang can be all relatedto, if not primarily caused by, human activities.The Huanghe probably serves as the most alarming

example of human impacts on large river systems inChina and in the world. The Huanghe basin isregarded as the cradle of the Chinese culture, and

has been inhabited by people since at least 1Mya.At present more than 100 million people live in thebasin, with a mean population density of 130 peopleper square kilometer. Irrigated agriculture has beenthe major economic development in the basin formore than 2000 years. The amount of irrigationwater taken from the Huanghe has more than dou-bled in the past 50 years, from 12.5 km3 year�1 in the1950s to more than 30 km3 year�1 in the 1990s. Inaddition, the hydrology of the Huanghe has beengreatly regulated by thousands of dams and reser-voirs. The total storage capacity of the reservoirs inthe Huanghe basin was nearly 60 km3 in 1993,almost twice that of its annual water discharge atthe river mouth. Since 1972, water from the Huanghehas frequently been diverted to the City of Tianjinwhich is located outside of the Huanghe basin.Together with the decreased atmospheric precipita-tion, the increasing amount of water withdrawal andloss has resulted in a dramatic decrease in water, TDSand TSS discharge (Figure 2), one of the most severe inthe world’s history and only surpassed by the Colorado(USA/Mexico) and the Amu Darya (Turkmenistan/Uzbekistan). At present, the Huanghe only delivers12.3km3year�1 of water and 155� 106 tons year�1

of TSS at the downstream station Lijin, a reductionof more than 75% and 87%, respectively, from itscorresponding levels during 1950–1969.

The physical, ecological, and socioeconomicimpacts of the sharp decline in water, TDS and TSSdischarge of the Huanghe are expected to be pro-found and remain to be fully understood and appre-ciated. For instance, the reduced water discharge willfurther severe the water shortage problem in northernChina, as well as make the lower reaches of the rivermore prone to contamination. The frequent dry-upswill increase the precipitation of calcite cement on theriverbed which will harden the riverbed and continu-ously raise the riverbed level thus threatening morethe floodplain population, and increase water evapo-ration which will salinize soils and groundwater inthe surrounding areas. The reduced sediment dis-charge to the delta region will slow down the growthof the delta and make the shoreline prone to seawatererosion and invasion. Ecologically, many aquaticbiota in the lower Huanghe and coastal Bohai relyon the dissolved salts from the Huanghe as theirnutrients. A declined or stopped flux of those saltsand nutrients could result in dramatic changes in theecosystem structures in the area.

Unless drastic actions are taken, the decrease in thewater, TDS and TSS discharge of the Huanghe islikely to continue and probably become worse dueto climate variations, population increase, and eco-nomical development. If this were the case, the

Rivers and Streams _ Asia – Eastern Asia 317

Huanghe could become a new endorheic river cutofffrom the ocean, similar to the Colorado River, andwhat have been experienced in the lower Coloradoand the Gulf of California could be repeated in theHuanghe and the Bohai Bay.

Concluding Remarks

Two mega hydrological projects are currently ongo-ing in China which are likely to have major impactson the river systems in China and on regional andglobal biogeochemical cycles. The first one is theThree Gorges Project to dam the main-channelChangjiang in its middle reaches to control floodingand generate electricity. The construction started in1994 and the reservoir began filling in 2003. By itscompletion in 2009, the Three Gorges Reservoir willhave a designed water storage capacity of 40 km3.The second one is the South-to-North Water Diver-sion (SNWD) project which was initiated in 2003 tosolve the serious water shortage problem in northernChina. It is the largest water diversion project in theworld. Under the SNWD project, three massive cross-basin canal networks (Eastern, Central, and Westernlines) will be constructed to divert water from theChangjiang to the Huanghe and to northern China.The proposed capacity of the SNWD is 44.8 km3

year�1, which is about 5% of the annual water dis-charge of the Changjiang, and 140% of the annual

water discharge of the Huanghe. The project isexpected to be completed by 2050 and will connectthe drainage basins of the Changjiang, the Huanghe,the Huaihe, the Haihe and many other smaller riversystems and essentially create a single mega pseudo-basin. Long-term and high density monitoring, andrapid analysis and interpretation of the monitoringdata are needed now to understand and manage anydramatic beneficial and adverse effects of projects ofthis scale.

Further Reading

Chen J and Wang F (1996) Chemical Composition of River Parti-

culates in Eastern China. GeoJournal 40: 31–37.Chen J, Wang F, Xia X, and Zhang L (2002) Major Element

Chemistry of the Changjiang (Yangtze River). Chemical Geology187: 231–255.

Chen J, Wang F, Meybeck M, He D, Xia X, and Zhang L (2005)Spatial and Temporal Analysis of Water Chemistry Records

(1958–2000) in the Huanghe (Yellow River) basin. Global Bio-geochemical Cycles 19GB3016, doi:10.1029/2004GB002325.

Dadson SJ, Hovius N, and Chen HG (2003) Links between erosion,runoff variability and seismicity in the Taiwan orogen. Nature426: 648–651.

Meybeck M (2003) Global Analysis of River Systems: From Earth

system controls to Anthropocene syndromes. PhilosophicalTransactions Of the Royal Society of London B 358:

1935–1955.

Zhao S (1986) Physical Geography of China. New York: Wiley.