Sustainable Development and Environmental Awareness 1 MEKONG RIVER BASIN PHYSICAL, DEMOGRAPHIC, AND ECOLOGICAL CHARACTERISTICS1 Truly one of the world’s great rivers, SOME PHYSICAL AND the Mekong River begins its life as DEMOGRAPHIC DATA melting snow at 5,500 metres elevation in the pure, rarefied atmosphere of the In numerical terms, the Mekong Tanggulashan Mountains, on the River is the longest river in Southeast northeast edge of the Tibetan Plateau. Asia, and the eighth longest in the From there to the river delta on the world. The average annual discharge of 9 3 south coasts of Vietnam and Cambodia, 475 x 10 m places it as the twelfth in where it enters the South China Sea, its volume, and its total catchment area of 2 st meandering journey takes these waters 795,000 km ranks as 21 worldwide. almost 5,000 km through six countries Table 1 lists some additional data – China’s Yunnan Province, along the regarding Mekong River Basin (MRB) northeast border of Myanmar with demographics, catchment areas, and northwest Lao PDR, through northern contributions to overall flow. Lao PDR and along its western border More significant than these with northeast Thailand, then down the statistics, however, is the fact that 80% backbone of Cambodia to the southern of the 60 million people who live within tip of Vietnam and Cambodia – the Lower Mekong Basin (LMB) depend accumulating immense volumes of directly on the river and its associated water, sediment, and nutrients along natural resources for their existence the way. and livelihood. The countries through The river is known by many names, which the river flows have primarily reflecting its meaning to the peoples it agrarian economies, and their fishers and farmers rely on the annual cycles of the Mekong’s flow. According to the The Mekong River Asian Development Bank (ADB), approximately 300 million people in “The Mekong Basin has arguably the most diverse biotic and cultural Southeast Asia depend on products landscape in the world today.” from the MRB for sustenance. (Asian Development Bank) A BRIEF JOURNEY DOWN THE nourishes and challenges: Mother of All MEKONG RIVER Waters; Nine Dragons River; River of Rocks; The Great River. In Yunnan The topography through which the Province it is called the Lancangjiang. Mekong River flows varies considerably. In its early reaches it drains the 1 Information in this lesson is taken in part from ADB (2000) and MRC (1997). Last Revised 10/17/2001 2 Sustainable Development and Environmental Awareness Table 1 MRB riparian country populations and catchment areas COUNTRY POPULATION POPULATION % OF MRB (MILLIONS) WITHIN MRB (MILLIONS) AREA FLOW Yunnan, China n/a 10 22 16 Myanmar 44 2 3 2 Lao PDR 5 5 25 35 Cambodia 11 10 19 18 Vietnam 79 ~20 8 11 Thailand 62 ~25 23 18 Northern Highlands in Yunnan Province, impressive phenomena of the MRB Lao PDR, Myanmar, and Thailand, where occurs in the Tonle Sap (or Great Lake), the river and its tributaries flow the largest body of freshwater in through deep valleys eroded by natural Southeast Asia. Fed by floodwaters of and anthropogenic actions. In its phase the Mekong River in the rainy season, as the Lancangjiang River in Yunnan the Tonle Sap grows at least seven-fold Province, the Manwan dam – the only from its minimum dry season area of dam, so far, on the mainstream river – approximately 2,500 sq. km to 16,000 detains the natural flow. Several more sq. km. Its depth increases from 1 large dams are planned in the steep metre or less to as much as 10 metres. canyons of this upstream stretch. In The Mekong River also contributes northern Lao PDR and northeastern fresh silt, replenishes nutrients, and Thailand the river transects the flatlands provides abundant habitat for fish and of the Sakon and Korat Plateaux with other aquatic organisms in flooded their saline soils, before draining the forest areas around the Tonle Sap. In mountain regions of eastern Lao PDR. return, the Tonle Sap helps to regulate These Eastern Highlands also have floods in the LMB by storing water deeply etched valleys that have during the rainy season and releasing it attracted the attention of dam builders. when the rains abate. Upstream of the border between At Phnom Penh, the Bassac River Lao PDR and Cambodia, the Mekong forks off the main stem of the Mekong expands to a width of 10 km and drops River at Chaktomuk Junction, 30 metres at Khone Falls, known locally immediately downstream of the point as ‘Leepee’ or ‘Spirit Trap’. Above and where the Tonle Sap River flows below Leepee, the river separates into northwest to feed and drain the Great many ribbons surrounding Si Pan Don Lake. The Bassac River eventually (Four Thousand Islands), the richest reconnects with the main stem of the fishing area in Lao PDR. Several Mekong in the northern reaches of the proposals have been made over the Mekong Delta. The Southern Uplands, years to dynamite Leepee to permit consisting of the Cardamom and navigation upstream. Elephant Ranges, drain into the Great Lake, and the Tonle Sap and Bassac As the river passes into southern Rivers. Lao PDR and then Cambodia and Vietnam, it flows into the Lowlands In its final stretch, the Mekong River Floodplain, where one of the most fans into approximately 50,000 sq. km Last Revised 10/17/2001 Sustainable Development and Environmental Awareness 3 of channels in the Delta, known as ‘Cuu far too many – are endangered or face Long’ in Vietnamese (or ‘The Nine- extinction because of habitat loss and Tailed Dragon’ for the nine principal excessive hunting, fishing or collection. channels of the river), where much of its remaining silt load is deposited, Cambodia supporting intensive agriculture and fisheries. In the northern part of the Relative to its size, Cambodia has Delta, the river passes through one of the highest proportions of approximately 10,000 sq. km of the natural forest and wetlands habitats in Plain of Reeds. Here, efforts have been the world, and one of the least made to adjust acid-sulphate soils to disturbed coastlines in Asia. More than make them more suitable for crops. 45 habitat types have been Closer to the mouth of the Delta, characterised in the country. The saltwater intrusion, largely as a result of natural cycles of the Mekong River and irrigation schemes, is causing the weather have provided a vast range salinification of soils, which also poses of natural products. Of 2,300 species of challenges to agriculture. plants that have been described in Cambodia, 40% have traditional uses as The Mekong Delta occupies food and medicine. The country is approximately 12% of Vietnam, contains believed to have over 130 mammals and almost 40% of the cultivated area of the more than 500 bird species, many of country, and is home to about 20% of its which are significant to international population. Two-thirds of the Delta is conservation. At least 300 species of under cultivation, providing more than freshwater fish have been identified, of half of the food consumed in Vietnam, which 215 frequent the Tonle Sap. As including rice; over 50% of the fish; 60% in each of the riparian countries, of the fruit; and about 300,000 tonnes wildlife capture and trade threaten of aquaculture products, primarily overall biodiversity and the existence of shrimp, much of which is exported. The many species. average discharge rate in the Mekong Delta is 15,000 m3/sec. Lao PDR Along its journey from Tibetan Because of its mountainous mountains to the South China Sea, the geography, Lao PDR has wide variations Mekong is joined by more than 130 in climate, soils, forested and open substantial tributary rivers, each of areas, which have endowed the country which contributes its water flow and with an extraordinarily rich diversity of sediment load to the ‘Mother of All ecological niches. Forested areas are Rivers’. believed to be inhabited by approximately 10,000 known species of A BRIEF OVERVIEW OF mammals, reptiles, amphibians, birds, BIODIVERSITY IN THE MRB fish, butterflies and plants. Undoubtedly many-fold more are still As reflected in the quote at the ‘undiscovered’. According to the beginning of this lesson, the MRB is International Union for the home to one of the richest and most Conservation of Nature and Natural diverse biota in the world. New species Resources (IUCN), Lao PDR is second to of plants, land animals, and fish Cambodia in species density, and fourth continue to be found, even as some – Last Revised 10/17/2001 4 Sustainable Development and Environmental Awareness after Thailand, Myanmar, and Vietnam species, about 40% are endemic; in endemic species (i.e., those found approximately 5,000 plants have only in a particular region or country). existing economic value. About 25 species of mammals and birds Loss of a species is irreversible, in Lao PDR, including the kouprey, Javan diminishes ecosystem and genetic rhinoceros, Siamese crocodile, and biodiversity, and may harm future Eastern Sarus crane, are rated as economic prospects. endangered. Thailand FISHERIES IN THE MRB No figures were available specific to Approximately 1,300 fish species the MRB portion of Thailand, but the have been identified in the MRB, of country overall has been a cornucopia which 50% are endemic to the region, of now rapidly diminishing plant and and 120 are of commercial importance animal life. Countrywide, Thailand is in local markets. There are about 125 said to contain 10,000-13,000 vascular species of catfish, but large specimens plants and 86,000 animal species, of of the Giant catfish are now extremely which 5,000 are vertebrates.