Mekong Encyclopedia > Places > Asia > Southeast Asia Physical Geography Mekong Mekong (māˈkŏng, mēˈ–) [ key ], Chinese Lancang, one of the great rivers of SE Asia, c.2,600 mi (4,180 km) long. From its marshy source (definitively identified in 1994) on the Rup-sa Pass in the highlands of Tibet, it rises as the Za Qu (Dza Chu) and flows generally S through Yunnan prov. in deep gorges and over rapids. Leaving Yunnan, the Mekong forms the Myanmar-Laos border, then curves E and S through NW Laos before marking part of the Laos-Thailand border. From SW Laos the river descends onto the Cambodian plain, where it receives water from Tônlé Sap during the dry season by way of the Tônlé Sap River; during the rainy season, however, the floodwaters of the Mekong reverse the direction of the Tônlé Sap River and flow into Tônlé Sap, a lake that is a natural reservoir.

The Mekong River finally flows into the South China Sea through many distributaries in the vast Mekong delta (c.75,000 sq mi/194,250 sq km), which occupies SE Cambodia and S Vietnam. The delta, crisscrossed by many channels and canals, is one of the greatest rice-growing areas of Asia. It is a densely populated region; Vinh Long, Can Tho, and Long Xuyen are the chief towns there. Ho Chi Minh City (Saigon) is located just east of the delta. The Mekong delta was the scene of heavy fighting in the Vietnam War . The Mekong River is navigable for large vessels c.340 mi (550 km) upstream; Phnom Penh is a major port. North of the Cambodian border, the Mekong was navigable in short sections, but dams and other developments have increased the reach of river traffic in the 21st cent. At Khone Falls, a series of rapids (6 mi/9.7 km long) in S Laos, the Mekong drops 72 ft (22 m).

The falls are the site of a hydroelectric power station, part of the Mekong Scheme, a project undertaken by the United Nations in the early 1960s to develop the potentials of the lower Mekong basin. The project sought to improve navigation, provide irrigation facilities, and produce hydroelectricity. The Mekong River Commission, whose members consist of Cambodia, Thailand, Laos, and Vietnam, have agreed to pursue sustainable hydropower and irrigation projects and to explore the establishment of fisheries and the construction of a trans-Indochinese roadway system. Laos in particular is undertaking an extensive hydroelectric development of the river and its tributaries. China is developing the upper Mekong, constructing a series of dams to provide hydroelectric power and a navigable waterway; the first, at Manwan, was completed in 1993. In 2010 a report to the commission recommended that no dams that span the full breadth of the river channel be built on the lower Mekong for 10 years because of projected losses to fisheries and other environmental damage that could worsen poverty despite the revenues from producing hydroelectricity. The Columbia Electronic Encyclopedia, 6th ed.

Copyright © 2012, Columbia University Press. All rights reserved. Mekong Valley | Article about Mekong Valley by The Free Dictionary Mekong Valley | Article about Mekong Valley by The Free Dictionary Related to Mekong Valley: Mekong River Mekong (mā`kŏng, mē`–), Chinese Lancang, one of the great rivers of SE Asia, c.2,600 mi (4,180 km) long. From its marshy source (definitively identified in 1994) on the Rup-sa Pass in the highlands of Tibet, it rises as the Za Qu (Dza Chu) and flows generally S through Yunnan prov. in deep gorges and over rapids. Leaving Yunnan, the Mekong forms the Myanmar-Laos border, then curves E and S through NW Laos before marking part of the Laos-Thailand border. From SW Laos the river descends onto the Cambodian plain, where it receives water from Tônlé Sap Tônlé Sap [great lake], lake, central Cambodia; largest lake of SE Asia.

It occupies the depression of the Cambodian plain and is fed by many streams; the Tônlé Sap River, c. ..... Click the link for more information. during the dry season by way of the Tônlé Sap River; during the rainy season, however, the floodwaters of the Mekong reverse the direction of the Tônlé Sap River and flow into Tônlé Sap, a lake that is a natural reservoir. The Mekong River finally flows into the South China Sea through many distributaries in the vast Mekong delta (c.75,000 sq mi/194,250 sq km), which occupies SE Cambodia and S Vietnam. The delta, crisscrossed by many channels and canals, is one of the greatest rice-growing areas of Asia. It is a densely populated region; Vinh Long, Can Tho, and Long Xuyen are the chief towns there. Ho Chi Minh City Ho Chi Minh City, formerly Saigon, city (1997 pop. 5,250,000), on the right bank of the Saigon River, a tributary of the Dong Nai, Vietnam.

Ho Chi Minh City is the largest city, the greatest port, and the commercial and industrial center of Vietnam. ..... Click the link for more information. (Saigon) is located just east of the delta. The Mekong delta was the scene of heavy fighting in the Vietnam War Vietnam War, conflict in Southeast Asia, primarily fought in South Vietnam between government forces aided by the United States and guerrilla forces aided by North Vietnam. The war began soon after the Geneva Conference provisionally divided (1954) Vietnam at 17° N lat. ..... Click the link for more information. . The Mekong River is navigable for large vessels c.340 mi (550 km) upstream; Phnom Penh Phnom Penh or Phnum Penh , city (1994 est. pop. 527,000), capital of Cambodia, SW Cambodia, at the confluence of the Mekong and Tônlé Sap rivers. Phnom Penh was founded in the 14th cent. and was made the Khmer capital after the abandonment (1434) of Angkor. ..... Click the link for more information. is a major port.

North of the Cambodian border, the Mekong was navigable in short sections, but dams and other developments have increased the reach of river traffic in the 21st cent. At Khone Falls, a series of rapids (6 mi/9.7 km long) in S Laos, the Mekong drops 72 ft (22 m). The falls are the site of a hydroelectric power station, part of the Mekong Scheme, a project undertaken by the United Nations in the early 1960s to develop the potentials of the lower Mekong basin. The project sought to improve navigation, provide irrigation facilities, and produce hydroelectricity. The Mekong River Commission, whose members consist of Cambodia, Thailand, Laos, and Vietnam, have agreed to pursue sustainable hydropower and irrigation projects and to explore the establishment of fisheries and the construction of a trans-Indochinese roadway system. Laos in particular is undertaking an extensive hydroelectric development of the river and its tributaries. China is developing the upper Mekong, constructing a series of dams to provide hydroelectric power and a navigable waterway; the first, at Manwan, was completed in 1993.

In 2010 a report to the commission recommended that no dams that span the full breadth of the river channel be built on the lower Mekong for 10 years because of projected losses to fisheries and other environmental damage that could worsen poverty despite the revenues from producing hydroelectricity. Mekong a river in China, Laos, Campuchia (Cambodia) and Vietnam that partially forms the border between Laos and Burma and Thailand; the largest river in Indochina. Length, approximately 4,500 km; basin area, 810,000 sq km. The Mekong originates in the Tangkula Mountains in the Tibetan highlands. The upper course of the river is called the Dzi Chu; the middle course (in China), the Lantsan Chiang. The river flows into the South China Sea, forming a delta. The Mekong’s main tributaries are, on the right, the Mun and Tonle Sap; on the left, the Wu, Theun, and Sen. In its upper and middle courses, the Mekong flows mainly through deep gorges, and its channel has many rapids.

One of the world’s largest waterfalls, Khone Falls (elevation to 21 m), is situated where the river flows into the plain. The rapids end near the city of Kratie in Campuchia. Below the city of Phnom Penh, the Mekong Delta begins (area, approximately 70,000 sq km); the river divides into two large streams linked by numerous channels. Approximately 75 percent of the Mekong’s total flow passes through the main left stream, the Bassac. The delta projects into the sea in the shape of an arc with a coastline approximately 600 km in length; as a result of the river’s abundant regular flow, the delta’s size increases by 80–100 m a year. The delta is marshy and in many places is covered with mangrove thickets. The Mekong is fed primarily by rain, and in the upper course also by snow and partly by glaciers. High water occurs in summer and fall. In the river’s middle course, maximum water level is usually recorded in August (in the lower reaches, in October); the lowest flow occurs in April.

The fluctuation in water level reaches 10–15 m in the mountains, and up to 10 m on the plain and in the delta. The mean annual flow rate in the middle course, at Vientiane, is 4,600 cu m per sec; the maximum annual flow rate is approximately 21,000 cu m per sec. In the lower course, at Kratie, the mean annual flow rate is 14,800 cu m per sec, with a maximum annual flow rate of 33,000 cu m per sec (some years it reaches 67,000 cu m per sec). The Mekong freezes only in the upper course for 1–2 months. It carries an average of 1.5 cu km of drift a year. Tonle Sap, a lake that is connected with the river by the Tonle Sap tributary, exerts a great regulatory influence on the river’s flow.

In the humid season (June-November) the lake fills up with water from the Mekong; in the dry season (November-June), the water level of the river falls lower than that of the lake, which results in an intensive overflow of lake water into the Mekong channel, uncovering vast areas of farmland fertilized with productive silt. The lower Mekong is used for irrigation. Its extensive flooding is conducive to rice growing. The Mekong’s huge hydraulic power resources (estimated at approximately 75 million kilo-watts) are not much used. The rivers and lakes in the Mekong basin are rich in fish, primarily of the carp family; there are many waterfowl, and crocodiles are still common. The river is navigable year round for 700 km, and for 1,600 km (to Vientiane) during high water. Ocean vessels can reach Phnom Penh (350 km). The cities of Luang Prabang, Vientiane (Laos), and Phnom Penh (Campuchia) are on the Mekong. A. P.

M Mekong facts, information, pictures | Encyclopedia.com articles about Mekong The Columbia Encyclopedia, 6th ed. Copyright The Columbia University Press Mekong (mā´kŏng, mē´–), Chinese Lancang, one of the great rivers of SE Asia, c.2,600 mi (4,180 km) long. From its marshy source (definitively identified in 1994) on the Rup-sa Pass in the highlands of Tibet, it rises as the Za Qu (Dza Chu) and flows generally S through Yunnan prov. in deep gorges and over rapids. Leaving Yunnan, the Mekong forms the Myanmar-Laos border, then curves E and S through NW Laos before marking part of the Laos-Thailand border. From SW Laos the river descends onto the Cambodian plain, where it receives water from Tônlé Sap during the dry season by way of the Tônlé Sap River; during the rainy season, however, the floodwaters of the Mekong reverse the direction of the Tônlé Sap River and flow into Tônlé Sap, a lake that is a natural reservoir.

The Mekong River finally flows into the South China Sea through many distributaries in the vast Mekong delta (c.75,000 sq mi/194,250 sq km), which occupies SE Cambodia and S Vietnam. The delta, crisscrossed by many channels and canals, is one of the greatest rice-growing areas of Asia. It is a densely populated region; Vinh Long, Can Tho, and Long Xuyen are the chief towns there. Ho Chi Minh City (Saigon) is located just east of the delta. The Mekong delta was the scene of heavy fighting in the Vietnam War . The Mekong River is navigable for large vessels c.340 mi (550 km) upstream; Phnom Penh is a major port. North of the Cambodian border, the Mekong was navigable in short sections, but dams and other developments have increased the reach of river traffic in the 21st cent. At Khone Falls, a series of rapids (6 mi/9.7 km long) in S Laos, the Mekong drops 72 ft (22 m).

The falls are the site of a hydroelectric power station, part of the Mekong Scheme, a project undertaken by the United Nations in the early 1960s to develop the potentials of the lower Mekong basin. The project sought to improve navigation, provide irrigation facilities, and produce hydroelectricity. The Mekong River Commission, whose members consist of Cambodia, Thailand, Laos, and Vietnam, have agreed to pursue sustainable hydropower and irrigation projects and to explore the establishment of fisheries and the construction of a trans-Indochinese roadway system. Laos in particular is undertaking an extensive hydroelectric development of the river and its tributaries. China is developing the upper Mekong, constructing a series of dams to provide hydroelectric power and a navigable waterway; the first, at Manwan, was completed in 1993. In 2010 a report to the commission recommended that no dams that span the full breadth of the river channel be built on the lower Mekong for 10 years because of projected losses to fisheries and other environmental damage that could worsen poverty despite the revenues from producing hydroelectricity. Cite this article Pick a style below, and copy the text for your bibliography.

MLA Mekong River | river, Southeast Asia | Britannica.com river, Southeast Asia Alternative Titles: Lan-ts’ang Chiang, Lancang Jiang, Mae Nam Khong, Mékôngk River, Mènam Khong, Song Cuu Long, Sông Tiên Giang Related Topics Khone Falls Mekong River, Cambodian Mékôngk, Laotian Mènam Khong, Thai Mae Nam Khong, Vietnamese Sông Tiên Giang, Chinese (Pinyin) Lancang Jiang or (Wade-Giles) Lan-ts’ang Chiang, river that is the longest river in Southeast Asia , the 7th longest in Asia , and the 12th longest in the world. It has a length of about 2,700 miles (4,350 km). Rising in southeastern Qinghai province, China , it flows through the eastern part of the Tibet Autonomous Region and Yunnan province, after which it forms part of the international border between Myanmar (Burma) and Laos , as well as between Laos and Thailand . The river then flows through Laos, Cambodia , and Vietnam before draining into the South China Sea south of Ho Chi Minh City (formerly Saigon).

Vientiane (Viangchan), the capital of Laos, and Phnom Penh , the capital of Cambodia, both stand on its banks. About three-fourths of the drainage area of the Mekong lies within the four countries the river traverses on its lower course—Laos, Thailand, Cambodia, and Vietnam. The Irrawaddy and Mekong river basins and their drainage networks. Encyclopædia Britannica, Inc. Overview of the Mekong River and its declining fish population. Contunico © ZDF Enterprises GmbH, Mainz Physical features The Mekong River drains more than 313,000 square miles (810,000 square km) of land, stretching from the Plateau of Tibet to the South China Sea . Among Asian rivers, only the Yangtze and Ganges have larger minimum flows. Mekong River delta, southern Vietnam. M. Gifford/De Wys Inc. The contrast between the physical conditions that prevail above and below the Mekong’s descent from the Yunnan highlands divide it into two major parts.

The upper Mekong flows 1,215 miles (1,955 km) through a long, narrow valley comprising roughly one-fourth of the total area, cutting through the mountains and plateaus of southwestern China. The lower Mekong, below the point where it forms the border between Myanmar and Laos, is a stream 1,485 miles (2,390 km) in length draining the Khorat Plateau of northeastern Thailand, the western slopes of the Annamese Cordillera in Laos and Vietnam, and most of Cambodia, before reaching the sea through the distributary channels of its delta in southern Vietnam. Similar Topics Godavari River In its upper reaches, the Mekong rises in the Tibetan Plateau between the Salween and Yangtze rivers; the streambed has cut deeply into the rugged landscape through which it flows. Along its course between Myanmar and Laos, the Mekong drains about 8,000 square miles (21,000 square km) of territory in Myanmar, comprising rough and relatively inaccessible terrain.

In its more gentle lower stretches, where for a considerable distance it constitutes the boundary between Laos and Thailand, the Mekong inspires both conflict and cooperation among Cambodia, Laos, Thailand, and Vietnam. Physiography The sources of the Mekong, including its principal headstream, the Za Qu River, rise at an elevation of more than 16,000 feet (4,900 metres) on the north slope of the Tanggula Mountains in Qinghai province. They flow southeast through the Qamdo (Chamdo) region of Tibet, where the Za Qu joins other headstreams to form the main stream, called the Lancang in Chinese. It descends south across the highlands of Yunnan, through which it carves a deep valley, to a point south of Jinghong , where it briefly marks the border between Myanmar and China. The river then bends southwest; over a reach of more than 125 miles (200 km) it forms the Myanmarese-Laotian border.

Although two great roads cross it—the caravan route from the southeast to Lhasa and the road from Kunming to Myanmar—much of the river valley in the highlands of Tibet and Yunnan is remote and sparsely populated. Below Myanmar, the river basin may be divided into six major sections on the basis of landforms, vegetation, and soils: the northern highlands, Khorat Plateau, eastern highlands, southern lowlands, southern highlands, and delta . Most of the vegetation in the lower basin is of the tropical broad-leaved variety, although the occurrence of individual species varies with latitude and topography . Britannica Stories Scientists Ponder Menopause in Killer Whales The northern highlands have highly folded ranges that reach elevations of about 9,000 feet (2,700 metres) above sea level, many with steep slopes. As far south as Vientiane, these dissected uplands (i.e., cut by erosion into hills and valleys) are covered with dense deciduous forest that has deteriorated as a result of frequent cutting and burning for shifting cultivation.

The Mekong’s important tributaries in this region include the Tha , the Ou , and the Ngum rivers, all draining northern Laos. All About Asia To the south of the east-west course of the river below Vientiane lies the Khorat Plateau , which embraces almost all of the Thai portion of the basin as well as the lower parts of the Mekong’s Laotian tributaries. This is an area of gently rolling hills set amid relatively flat alluvial plains. Soils and deciduous vegetation on the hills are thin, and much of the original forest has been replaced by grassland as a result of grazing and repeated burning. The Songkhram River drains the northern part of the plateau and enters the Mekong above Tha Uthen in Thailand. The Mun River —one of the Mekong’s most important tributaries—drains the majority of the plateau and joins the Mekong at Ban Dan, Thailand. The eastern highlands form part of the Annamese Cordillera, from which streams drain west into the Mekong.

Throughout most of the distance between Ky Son (Muong Sen) in northern Vietnam and Ban Hèt in southern Laos, the watershed forms the border between Vietnam to the east and Laos to the west. There is greater relief in the northern than the southern parts of the watershed, but the highlands in general are characterized by rapid streams that flow through narrow valleys before entering the lowlands bordering the Mekong. The Mekong’s most important tributaries in this region are the Kading, the Bangfai, the Banghiang, and the Kong—which, with its affluent the San, drains a large area of southern Laos, central Vietnam, and eastern Cambodia. Forest degradation , which has resulted from lumbering, shifting cultivation, and grazing, is widespread in this region. The southern lowlands border both sides of the Mekong below Pakxé (Pakse) in Laos. The Mekong enters Cambodia with a sudden plunge at Khone Falls. Between the falls and Krâchéh there are rapids interspersed with alluvial plains. Below Kâmpóng Cham the river’s gradient becomes gentle, and it flows through wide stretches of alluvium in its floodplain.

Near Phnom Penh a junction occurs between the Mekong and the Sab River, which connects it to the Tonle Sap , sometimes called the Great Lake . The direction of flow of the Sab River varies according to the season. During the peak flood season, when the level of the Mekong is high, waters flow through the Sab River to the lake, which then expands from a little more than 1,000 square miles (2,600 square km) to a maximum of about 4,000 square miles (10,400 square km). In the dry season when the floods subside, the Sab reverses its flow to drain southeastward into the Mekong. The Tonle Sap is a highly productive fishing ground. Connect with Britannica Facebook Twitter YouTube Instagram Pinterest The Dâmrei (Elephant) and Krâvanh (Cardamom) mountains in southwestern Cambodia constitute the southern highlands. Several streams flow from these uplands into the Tonle Sap. The river divides into two branches below Phnom Penh: the Mekong proper and the Bassac (Basak). Below this point the delta spreads out to the sea.

It has a total area of about 25,000 square miles (65,000 square km) and can be divided into three major sections. The upper section, above Chau Doc (Chau Phu), has strong natural levees (embankments built on either side of the river by accumulated deposits of silt) behind which are low, wide depressions. The middle section has some areas that are well drained, others that are poorly drained and swampy. Along the lower section, formed by the river mouths and by the area to the southwest, sediment carried down from the upper river is in the process of being deposited, and the flooding is less extreme than in the upper sections of the delta. The area north of the Ca Mau Peninsula is forested and swampy. Climate and hydrology The Mekong’s flow comes chiefly from rainfall in its lower basin, which fluctuates seasonally with the monsoon winds. In April the flow is ordinarily at its lowest. In May or June—as the rain-bearing southerly monsoon winds arrive—the flow begins to increase, with an especially rapid increase in the eastern and northern highlands.

The Mekong’s highest water levels occur as early as August or September in the upper reaches and as late as October in the southern reaches. The northeasterly monsoon wind, beginning ordinarily in November in the southern areas, brings dry weather until May. During the long dry period, rice cultivation is impossible without irrigation, and the river’s waters are vital to agricultural production. Britannica Lists & Quizzes Mekong River | Article about Mekong River by The Free Dictionary Mekong River | Article about Mekong River by The Free Dictionary Also found in: Dictionary , Thesaurus , Wikipedia . Mekong (mā`kŏng, mē`–), Chinese Lancang, one of the great rivers of SE Asia, c.2,600 mi (4,180 km) long. From its marshy source (definitively identified in 1994) on the Rup-sa Pass in the highlands of Tibet, it rises as the Za Qu (Dza Chu) and flows generally S through Yunnan prov. in deep gorges and over rapids.

Leaving Yunnan, the Mekong forms the Myanmar-Laos border, then curves E and S through NW Laos before marking part of the Laos-Thailand border. From SW Laos the river descends onto the Cambodian plain, where it receives water from Tônlé Sap Tônlé Sap [great lake], lake, central Cambodia; largest lake of SE Asia. It occupies the depression of the Cambodian plain and is fed by many streams; the Tônlé Sap River, c. ..... Click the link for more information. during the dry season by way of the Tônlé Sap River; during the rainy season, however, the floodwaters of the Mekong reverse the direction of the Tônlé Sap River and flow into Tônlé Sap, a lake that is a natural reservoir. The Mekong River finally flows into the South China Sea through many distributaries in the vast Mekong delta (c.75,000 sq mi/194,250 sq km), which occupies SE Cambodia and S Vietnam. The delta, crisscrossed by many channels and canals, is one of the greatest rice-growing areas of Asia.

It is a densely populated region; Vinh Long, Can Tho, and Long Xuyen are the chief towns there. Ho Chi Minh City Ho Chi Minh City, formerly Saigon, city (1997 pop. 5,250,000), on the right bank of the Saigon River, a tributary of the Dong Nai, Vietnam. Ho Chi Minh City is the largest city, the greatest port, and the commercial and industrial center of Vietnam. ..... Click the link for more information. (Saigon) is located just east of the delta. The Mekong delta was the scene of heavy fighting in the Vietnam War Vietnam War, conflict in Southeast Asia, primarily fought in South Vietnam between government forces aided by the United States and guerrilla forces aided by North Vietnam. The war began soon after the Geneva Conference provisionally divided (1954) Vietnam at 17° N lat. ..... Click the link for more information. . The Mekong River is navigable for large vessels c.340 mi (550 km) upstream; Phnom Penh Phnom Penh or Phnum Penh , city (1994 est. pop.

527,000), capital of Cambodia, SW Cambodia, at the confluence of the Mekong and Tônlé Sap rivers. Phnom Penh was founded in the 14th cent. and was made the Khmer capital after the abandonment (1434) of Angkor. ..... Click the link for more information. is a major port. North of the Cambodian border, the Mekong was navigable in short sections, but dams and other developments have increased the reach of river traffic in the 21st cent. At Khone Falls, a series of rapids (6 mi/9.7 km long) in S Laos, the Mekong drops 72 ft (22 m). The falls are the site of a hydroelectric power station, part of the Mekong Scheme, a project undertaken by the United Nations in the early 1960s to develop the potentials of the lower Mekong basin. The project sought to improve navigation, provide irrigation facilities, and produce hydroelectricity.

The Mekong River Commission, whose members consist of Cambodia, Thailand, Laos, and Vietnam, have agreed to pursue sustainable hydropower and irrigation projects and to explore the establishment of fisheries and the construction of a trans-Indochinese roadway system. Laos in particular is undertaking an extensive hydroelectric development of the river and its tributaries. China is developing the upper Mekong, constructing a series of dams to provide hydroelectric power and a navigable waterway; the first, at Manwan, was completed in 1993. In 2010 a report to the commission recommended that no dams that span the full breadth of the river channel be built on the lower Mekong for 10 years because of projected losses to fisheries and other environmental damage that could worsen poverty despite the revenues from producing hydroelectricity. Mekong a river in China, Laos, Campuchia (Cambodia) and Vietnam that partially forms the border between Laos and Burma and Thailand; the largest river in Indochina. Length, approximately 4,500 km; basin area, 810,000 sq km. The Mekong originates in the Tangkula Mountains in the Tibetan highlands.

The upper course of the river is called the Dzi Chu; the middle course (in China), the Lantsan Chiang. The river flows into the South China Sea, forming a delta. The Mekong’s main tributaries are, on the right, the Mun and Tonle Sap; on the left, the Wu, Theun, and Sen. In its upper and middle courses, the Mekong flows mainly through deep gorges, and its channel has many rapids. One of the world’s largest waterfalls, Khone Falls (elevation to 21 m), is situated where the river flows into the plain. The rapids end near the city of Kratie in Campuchia. Below the city of Phnom Penh, the Mekong Delta begins (area, approximately 70,000 sq km); the river divides into two large streams linked by numerous channels. Approximately 75 percent of the Mekong’s total flow passes through the main left stream, the Bassac.

The delta projects into the sea in the shape of an arc with a coastline approximately 600 km in length; as a result of the river’s abundant regular flow, the delta’s size increases by 80–100 m a year. The delta is marshy and in many places is covered with mangrove thickets. The Mekong is fed primarily by rain, and in the upper course also by snow and partly by glaciers. High water occurs in summer and fall. In the river’s middle course, maximum water level is usually recorded in August (in the lower reaches, in October); the lowest flow occurs in April. The fluctuation in water level reaches 10–15 m in the mountains, and up to 10 m on the plain and in the delta. The mean annual flow rate in the middle course, at Vientiane, is 4,600 cu m per sec; the maximum annual flow rate is approximately 21,000 cu m per sec.

In the lower course, at Kratie, the mean annual flow rate is 14,800 cu m per sec, with a maximum annual flow rate of 33,000 cu m per sec (some years it reaches 67,000 cu m per sec). The Mekong freezes only in the upper course for 1–2 months. It carries an average of 1.5 cu km of drift a year. Tonle Sap, a lake that is connected with the river by the Tonle Sap tributary, exerts a great regulatory influence on the river’s flow. In the humid season (June-November) the lake fills up with water from the Mekong; in the dry season (November-June), the water level of the river falls lower than that of the lake, which results in an intensive overflow of lake water into the Mekong channel, uncovering vast areas of farmland fertilized with productive silt. The lower Mekong is used for irrigation. Its extensive flooding is conducive to rice growing. The Mekong’s huge hydraulic power resources (estimated at approximately 75 million kilo-watts) are not much used.

The rivers and lakes in the Mekong basin are rich in fish, primarily of the carp family; there are many waterfowl, and crocodiles are still common. The river is navigable year round for 700 km, and for 1,600 km (to Vientiane) during high water. Ocean vessels can reach Phnom Penh (350 km). The cities of Luang Prabang, Vientiane (Laos), and Phnom Penh (Campuchia) are on the Mekong. A. P. M "Journey to the Source of the Mekong: For Decades, the Source of the Mighty Mekong Has Caused Debate among Geographers the World over. Last Year, John Pilkington Followed the Great River from Its Sprawling Delta in Vietnam to China's Qinghai Province, North of Tibet, in Order to Try to Set the Record Straight" by Pilkington, John - Geographical, Vol. 76, Issue 7, July 2004 | Online Research Library: Questia Read preview Article excerpt The Mekong has lured me for years.

At 4,200 kilometres it's the world's 12th-longest river, whose very name suggests mystery. Its lower reaches fascinated early French explorers, notably Francis Garnier, who spent two years from 1866 trying to forge a trading route along the Mekong from French Southeast Asia into China. Thwarted by sandbanks, cataracts and politics, he barely reached the Chinese border before turning his attention eastwards to the Red River. Even today, the Mekong's dramatic gorges in Tibet and Yunnan are rarely visited, so they offer long stretches of exhilarating exploring. The Chinese call the river Lancang Jiang, 'Turbulent Flood'; the Tibetans Za Qu, 'Water on the Rocks'. Who could resist the call of such tempting names? As a geographer, I was spellbound by the late 1990s race to find the source of the Mekong.

This began when another distinguished Frenchman, the Tibet specialist Michel Peissel, claimed in Geographical (April 1995) to have found it the previous year on a pass called Rupsa La, at an altitude of 4,975 metres on the Qinghai plateau north of Tibet. Experts in China, Japan and the USA questioned Peissel's claim, and after some spirited debate, four separate expeditions in 1999 established a cluster of new 'sources' 90 kilometres northeast of Peissel's. In October of that year, the Chinese Academy of Sciences declared the true source to be Lasagongma, a stream that issued front a glacier at 5,224 metres on the north face of a prominent peak called Guosongmucha. Among other things, the academy is China's official surveying and mapping authority, so I thought this would be the end of the matter. But, in 2002, the leader of one of the academy's expeditions, Dr Liu Shaochuang, published his own appraisal, which placed the source at 5,200 metres on nearby Jifu Shan.

But I wasn't convinced, so I decided to find out for myself. Before leaving for Vietnam, I visited the Map Room at the RGS-IBG. There I found a once-top-secret 1:1,000,000 Soviet map dated 1971 that clearly showed the two competing tributaries. So it was that in January 2003, I set off, like Gamier, from the old French customs house in Ho Chi Minh City (Saigon) and headed for the southern tip of Vietnam, where the Mekong divides into a dozen delta channels before spilling into the South China Sea. Over the next four months I walked, hitchhiked and commandeered boats through Cambodia, Laos, Thailand and Myanmar. The river here is a broad highway, a vast fishing ground and a prolific irrigator of crops. The legendary quarter-ton giant Mekong catfish has been fished virtually to extinction, but other freshwater species form the staple diet of some 30 million people. And the fertile silt brought downriver with the rains has made the Mekong's floodplain the ricebasket of Southeast Asia.

Punctuated only by the Khone Falls in southern Laos, which had sounded the death knell for Garnier's dream, the lower 1,500 kilometres are navigable by surprisingly large vessels, a fact not lost on the tourist-cruise industry. In the Lao capital, Vientiane, I persuaded a sleepy Chinese consul to grant me a 90-day visa. Few foreigners seem aware that the Mekong is a spectacular and legal way of entering China. Chinese cargo boats ply upstream daily from the Thai port of Chiang Saen, and after some tortuous negotiations I secured a passage. The three-day voyage took me through the heart of the so-called Golden Triangle, where poppies are grown for opium production. For the next 1,000 kilometres I was in China's vast and enigmatic Yunnan province, home to the parallel gorges of the Yangtze, Mekong and Salween. Long stretches of the river here proved completely inaccessible, and I could understand why Garnier's expedition gave up. I made wide detours, hitchhiking through communities of extraordinary minorities such as the Lisu, Hani and Dai.

Returning to the Mekong above the town of Weixi, I broke my journey in a tiny Lisu village called Yezhi. … Subscribe to Questia and enjoy: Full access to this article and over 10 million more from academic journals, magazines, and newspapers Over 83,000 books Access to powerful writing and research tools Article details

Question: Which river with a vast delta to the South china Sea rises as the Za Qu in Tibet?
Answer: Mekong