Topographic map of Thailand demonstrating primarily the Chao Phraya River System in the central plains and branches of the Mekong River System flowing west to east
The two principal
river systems of
Thailand are the Chao Phraya and the Mekong. Together, these rivers support the irrigation for Thailand's agricultural economy. In addition to these two large systems, there are a number of other river systems and individual rivers which drain the lands within Thailand's borders into the
Gulf of Thailand and the
Andaman Sea. The Mekong is the only river system in Thailand which drains into the
South China Sea.
Chao Phraya River System
thumb|right|Chao Phraya River System
Chao Phraya River in Bangkok
The Chao Phraya River System is the main river system of Thailand, as its basin defines much of the region of central Thailand. The
Chao Phraya River begins at the confluence of the
Ping and
Nan river at
Nakhon Sawan (also called Pak Nam Pho) in the
Nakhon Sawan province. It then flows from north to south for 372
km from the
central plains through
Bangkok to the
Gulf of Thailand. In
Chainat, the river splits into the main river course and the
Tha Chin river, which then flows parallel to the main river and exits to Gulf of Thailand at about 35 km west of Bangkok in Samut Sakhon. In the low alluvial plain which begins below the Chainat dam, many small canals (
khlong) split off from the main river. The khlong are used for the irrigation of the region's rice paddies.
Tributaries
The principal tributaries of the Chao Phraya River are the
Pa Sak River, the
Sakae Krang River, the
Nan River (along with its principal confluent the
Yom River), the
Ping River (with its principal confluent the
Wang River), and the
Tha Chin River..
Each of these tributaries (and the Chao Phraya itself) is further tributed by additional minor tributaries often referred to as
khwae. All of the tributaries, including the lesser khwae, form an extensive tree-like pattern, with branches flowing through nearly every province in central and northern
Thailand.
None of the tributaries of the Chao Phraya extend beyond the nation's borders.
[Google Earth] The Nan and the Yom River flow nearly parallel from
Phitsanulok to Chumsaeng in the north of Nakhon Sawan province. The
Wang River enters the Ping River near Sam Ngao district in
Tak province.
Drainage
The expanse of the Chao Phraya River and its tributaries, i.e. the
Chao Phraya river system, together with the land upon which falling rain drains into these bodies of water, form the
Chao Phraya watershed.The Chao Phraya watershed is the largest watershed in Thailand, covering approximately 35% of the nation's land, and draining an area of 157,924
km².
Lesser Gulf River Systems
There are numerous rivers which flow into the
Gulf of Thailand, including a number of west coast gulf rivers, east coast gulf rivers, and rivers which drain into the gulf on the east coast of the
Malay Peninsula. The following river systems, in addition to the Chao Phraya, are the most significant gulf systems in Thailand:
Bang Pakong
The
Bang Pakong River is a
river in eastern
Thailand. The river originates at the confluence of the
Nakhon Nayok River and the
Prachinburi River at
Pak Nam Yotaka in
Amphoe Ban Sang,
Prachinburi Province. It empties into the
Gulf of Thailand in the northeastern tip of the
Bay of Bangkok. The Bang Pakong's principal tributaries are the
Nakhon Nayok River and the
Prachin Buri River. The watershed of the Bang Pakong is about 17,000 km².
Phetchaburi
The
Phetchaburi River is a river in western
Thailand. It originates in
Kaeng Krachan National Park,
Kaeng Krachan district and flows through
Tha Yang,
Ban Lat,
Mueang Phetchaburi and mouths into the
Bay of Bangkok in
Ban Laem district. It is 210 km long, most of which is within the
Phetchaburi Province. It is the backbone of this province.
Mae Klong
The
Mae Klong River is a river in western
Thailand. The river begins at the confluence of the
Khwae Noi or Kwai Sai Yoke and the
Khwae Yai River or Kwai Si Sawasdi in
Kanchanaburi, pass
Ratchaburi Province and empties into the
Gulf of Thailand in
Samut Songkhram.
Pran Buri
The
Pran Buri River is a river in the
Prachuap Khiri Khan Province,
Thailand, on the
Kra Isthmus of the
Malay Peninsula. The Pran Buri river originates in southern part of the
Kaeng Krachan National Park, and after 130 km mouths into the
Gulf of Thailand. The only town at the river course is Pranburi, the center of the
Pran Buri district. The watershed of the Pran Buri River has an area of about 2000 km².
Khlong Kui
The
Khlong Kui River drains into the
Gulf of Thailand from the
Malay Peninsula in Thailand. It flows through Ban Pong Kasang and Ban Thung Faek,
Kui Buri district,
Prachuap Khiri Khan Province.
Tapi and Phum Duang
The
Tapi River with its main tributary
Phum Duang drain the area of
Surat Thani Province. The total watershed of the river system is about 11,500 km².
Pattani
The
Pattani River is the longest of all Thai rivers on the Malay Peninsula with a total length of 214 km.
Mekong River System
Mekong River System
The
Mekong River, one of the world’s major
rivers, drains into the
South China Sea. It is the 11th-longest river in the world, and the 12th-largest by volume (discharging 475 km³ of water annually). Its estimated length is 4880 km, and it drains an area of 810,000 km². From the
Tibetan Plateau it runs through
China's
Yunnan province,
Myanmar,
Thailand,
Laos,
Cambodia and
Vietnam. All except China and Myanmar belong to the
Mekong River Commission. The extreme seasonal variations in flow and the presence of
rapids and
waterfalls have made
navigation extremely difficult. Approximately half the river's length is in China, where it is known as the
Meigong in Chinese (). The river next forms the border between Myanmar and Laos for 200 km, at the end of which it meets the
tributary Ruak River at the
Golden Triangle. This point also marks the division between the
Upper and
Lower Mekong. The river then divides Laos and Thailand, before a stretch passing through Laos alone. It is known as
Maè Nam Khong (Mother of all rivers) in both
Lao and
Thai (แม่น้ำโขง). The river again marks the Lao-Thai border in the stretch which passes
Vientiane, followed by a short stretch through Laos alone. In Cambodia, the river is called the
Mékôngk or
Tonle Thom (great river). Just above
Phnom Penh is the confluence with the
Tonle Sap, the main Cambodian tributary. Below Phnom Penh, it divides into the
Bassac and the Mekong proper, which both flow into the
Mekong Delta in Vietnam. In
Vietnamese, the river as a whole is known as
Mê Kông. In Vietnam, the river divides into two major branches, the
Tiền Giang (Front River) and
Hậu Giang (Back River). These in turn enter the South China Sea through nine estuaries.
Thai Tributaries
The following are the principal
tributaries of Mekong River which flow through Thailand (tributaries entirely outside the Thai border not shown).
Drainage
The Mekong drains a considerable portion of northeast Thailand. In terms of Thai land area drained, it is second only to the Chao Phraya system.
Salawin River System
Salawin River System
The
Salawin River rises in
Tibet (Tibetan [རྒྱལ་མོ་རྔུལ་ཆུ།]http://tibetanecology.org/Seven_River_Map.htm) after which it flows through
Yunnan, where it is known as the
Nujiang river (), although either name can be used for the whole river. The river is 2815 km long. It then leaves
China and meanders through
Myanmar (where it is known as the
Thanlwin) and
Thailand (where it is known as the
Salawin, Thai: สาละวิน) on its way to emptying in the
Andaman Sea by
Mawlamyaing (Moulmien).
Thai Tributaries
The principal tributaries of the Salawin which flow through Thailand are the
Moei River and the
Pai River.
Other Andaman Sea Rivers
In addition to the Salween River, there are a number of rivers which drain into the Andaman Sea from the west coast of the
Malay Peninsula. None of them are significantly extensive, however, to be considered
river systems.
