The part of the Mekong River Basin in Viet Nam has a total area of about 71,000 km2, or 8 per cent of the basin area, and 20 per cent of the country’s territory. The part is of rivers, as follows: In the North, Nam Rom and Nam Nua rivers have a total area of 1,650 km2. The former rises from north Dien Bien district and flows through Dien Bien – Pa Thom City before discharging into Lao territory. The later has an origin in Muong Nha, flows south-north direction before emptying into Lao side. High slopes and waterfalls are common features of these rivers.
In the Midle of Viet Nam, rivers and streams in west Huong Hoa district (Quang Tri province) flow west, discharge into Xe Bang Hieng River (Lao side) before emptying into the Mekong River. These rivers and streams have a total basin area of about 738 km2, of which the largest is Xe Pon River with its basin area in Viet Nam of 310 km2. The Xe Pon is winding complicatedly. It flows est – west, along Viet-Lao border.
Sekong River rises from Truong Son Mountains (Aso area) in A Luoi district of Thua – Thien – Hue province, where it is called A Sap river. The total basin area of Sekong is about 29,750 km2 in which the part in Viet Nam is 750 km2 (some tributaries of A Sap rise from Kon Tum province).
In the Central Highlands, rivers have their total basin area of about 29,700 km2. The area is upstream of Cambodia while in the South of Viet Nam, the Mekong Delta (Cuu Long) is last downstream of the Mekong River Basin. Rivers in these two areas are described in more details as following.
In the Central Highlands, Sesan and Srepok are two major branches on the left side of the Mekong River. The total catchment area in Viet Nam of these branches covers 5 provinces of Gia Lai, Kon Tum, Dak Lak, Dak Nong, and Lam Dong.
Sesan originating in the north-east mountains of Gia Lai and Kon Tum provinces, the Sesan River drains a total land area in Viet Nam about 11,450 km2 and flows approximately 252 km with river density of 0.38 km/km2. From the North of Kon Tum, the Sesan flows north – south, continuing to Ialyhydropower scheme, and turns west – south before reaching Vietnam – Cambodia border. The Sesan has an average elevation of 737 m above sea level and an average slope of 14.4 per cent.
Srepok originating in Lam Dong and Dak Lak provinces, the Srepok River drains a total land area in Viet Nam about 12,030 km2 with a river length of 291 km and river density of 0.55 km/km2. The Srepok River has two major branches, namely Krong Kno and Krong Ana. The former rising in a mountain with over 2000 m high, flows approximately 156 km and drains a land area of 3920 km2, and has an average river slope of 6.8 per cent and river density of 0.86 km/km2. The latter flows 215 km and drains a land area of 3960 km2.
According to national population statistics of the country in 2010, over 5.2 million people live in the Central Highlands with an average population density at about 95 people/km2. The figures indicate that the overall population has increased by about 14.8 per cent, and it is significantly higher compared to the country’s rate of 10.3 per cent. About 52 per cent of the region’s population has working age (1.257 million) and about 88 per cent of the population do farming and forestry. There are over 40 different ethnic groups living in the region such as Kinh, Ba Na, Gia Rai, Xo Dang, etc, of which the Kinh comprises about 58 per cent.
The Central Highlands is one of 7 economic zones of Viet Nam. In 2009, the region’s GDP is 33,800 billion VND. Given the natural resources, production of hydropower, agriculture, forestry, and services are major sectors of the region’s economy. Some hydropower stations have been completed and in operation, a few of the others are planned.
The Mekong Delta begins near Phnom Penh and ends up as a huge fertile flat plain in southern Viet Nam where the largest tributary, the Bassac River, branches away from Mekong River. The Mekong (Tien River) and Bassac (Hau River) split into a number of smaller distributaries, forming an area known as the “Nine Dragons” or “Cửu Long”.
The Mekong Delta in Viet Nam (VNMD) covers an area of some 40,000 km2, or 12 per cent of the country’s land area. It lies with the Vietnamese-Cambodian border in the north-west, the Vam Co River in the northeastern, the East Sea in the south-east and Thailand Bay in the south-west. The VNMD covers 13 provinces and city, namely: Long An, Tien Giang, Dong Thap, Vinh Long, Tra Vinh, Hau Giang, Soc Trang, Ben Tre, An Giang, Kien Giang, Bac Lieu, Ca Mau and Can Tho City.
The annual hydrological regime of the Cửu Long River determined by a major influence – climate. The regime is divided into two distinct seasons. While the flood season occurs from June to December contributing about 90% of annual flow volume, the dry season within 6 months between January and May. Driest flows occur annually in March and April.
The VNMD is very important in Vietnam’s economy. In 2010, rice production of the region reached 21.6 million tons and rice export of about 5 million tons, or 90 per cent of the country. With a sea-shore of over 700 km, the aquaculture land occupies approximately 70 per cent and aquaculture production about 54 per cent of the country. The estimated GDP of VNMD in 2010 achieved almost 161,043 billion VND. The major sectors in the region include agriculture, fishery, and processing industry.
According to national population statistics of the country in 2010, the population estimate of VNMD was over 17 million with a population density of 426 people/km2. About 4 million people live in urban areas. The working age population was about 10.129 million.
Concerning water resources in VNMD, Vietnamese people are very interested in flood, drought, salinity intrusion, bank erosion, climate change and sea level rise, etc.