The Mekong Rivers & Tonle Sap Great Lake

Longest river of Southeast Asia.

Rising in southern Qinghai province, China, it flows south through eastern Tibet and across the highlands of Yunnan province. It then forms part of the border between Myanmar (Burma) and Laos, as well as between Laos and Thailand. It runs through Laos and Cambodia before entering the South China Sea in a delta south of Ho Chi Minh City in Vietnam after a course of 2,700 miles (4,350 km). Vientiane, Laos, and Phnom Penh, Camb., stand on its banks.

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.
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.

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.
Temperatures in the lower Mekong basin are uniformly warm throughout the year. Daily highs at Phnom Penh average 89 °F (32 °C), and lows average 74 °F (23 °C). In the upper basin, temperatures are moderated somewhat by altitude and generally are lower and exhibit more seasonal variation than those found farther south.

People

A substantial majority of the people who live along the Mekong River are engaged in agriculture, and rice is the major crop. The heaviest population concentrations are in the delta and on the Khorat Plateau. The small urban population has been growing rapidly, chiefly through migration to the capital cities. The peoples of the basin are diverse. Most residents of the uppermost Mekong Valley are Tibetan. South of the Tibetan Highlands, the peoples of the river basin fall into two broad cultural groupings. The hill peoples subsist mainly through shifting cultivation, and have traditionally formed small, kin-based social units, while the lowland peoples, who practice sedentary agriculture, have formed complex state societies. The hill peoples speak languages belonging to five different language families: Tibeto-Burman (including the Yi, Hani, and Lisu of Yunnan), Tai (including the Shan of Myanmar and the so-called Black Tai and Red Tai of Laos and Yunnan), Hmong-Mien (including the Hmong of Laos and Yunnan), Austronesian, and Mon-Khmer (including the diverse Montagnard peoples of Vietnam). The lowland peoples, however, form the majority of the population, and most belong to one of the dominant ethnic groups of the region’s nations. These include the Han Chinese of Yunnan, whose language is distantly related to the Tibeto-Burman languages, the Lao of Laos and the Thai of Thailand, both speaking languages in the Tai family, and the Vietnamese of Vietnam and the Khmer of Cambodia, Vietnam, and Thailand, both speaking Mon-Khmer languages. The Cham, a minority lowland people of Vietnam and Cambodia, speak an Austronesian language.

Mekong Delta

The Mekong Delta covers an area of 67,000 square km in the southernmost region of Vietnam and is often referred to as the rice bowl of Vietnam as it produces three harvests per year. The Mekong River begins its life in Tibet and travels 4,500 km..The Mekong Delta covers an area of 67,000 square km in the southernmost region of Vietnam and is often referred to as the rice bowl of Vietnam as it produces three harvests per year. The Mekong River begins its life in Tibet and travels 4,500 km through six countries before eventually splitting into nine tributaries (Cuu Long in Vietnamese) and flowing into the South China Sea. Because the plains are periodically flooded by the rising Mekong River, traditional transportation is by boat, along a vast network of canals. These canals are the very lifeblood of the Delta and her 15 million inhabitants. Everything from human cargo to tropical fruits with exotic names such as Dragon fruit and Longan (Dragon’s eye) can be found along this complex system of waterways. A cruise along these canals with their floating markets always proves to be a fascinating and rewarding experience for all visitors.

The Bassac Rivers

Bassac River (commonly called Tonle Bassac) is a distributary of the Mekong River. The river starts from Phnom Penh and flows south out to the Vietnamese border near Chau Doc. Bassac River is a popular entry and exit route for the locals between Cambodia and Vietnam and is used for transporting goods between the two countries.

Tonle Sap Lake

Cambodia's Tonle Sap, or Great Lake, is one of the unique geographical wonders of the world. It offers visitors insights into the centuries-old traditions of riparian life and the natural splendor of the country.
On the banks of the mighty Great Lake and the Tonle Sap and Mekong Rivers, Khmers have celebrated for over two hundred years the changing of the river's flow. During the rainy season the Tonle Sap River reversed direction, flooding the lake, increasing its size almost tenfold, making it the largest freshwater body in Southeast Asia.  In the flood season, water engulfs surrounding forests, regulating agricultural production by ensuring that the countryside is covered with fresh, fertile silt for rice cultivation.  The rivers and lakes of Cambodia are truly the lifeline for the largely agrarian and fishing society.  The ancient temples of Angkor depict in exquisite basrelief detail how the life along the lake affected all walks of Khmer life. For centuries the Great Lake has yielded many tons of fish per square mile and provided the major source of Khmer sustenance.  Moreover, for the astute birdwatcher, the aquatic habitat attracts thousands of birds and fish-eating waterfowl who flock to the wetland before the rains begin in June.