Chao Phraya River

TheChao Phraya Riveris the major river inThailand,with its lowalluvial plainforming the centre of the country. It flows throughBangkokand then into theGulf of Thailand.
On many old European maps, the river is named theMae Nam(แม่น้ำ), the Thai word for "river" (literally, "motherly water"). IrishsurveyorandcartographerJames McCarthy,F.R.G.S., who served as Director-General of the Siamese Government Surveys prior to establishment of theRoyal Thai Survey Department, wrote in his account, "Mae Namis a generic term,maesignifying "mother" andNam"water," and the epithet Chao P'ia signifies that it is the chief river in the kingdom of Siam."
Herbert Warington Smyth, who served as Director of the Department of Mines in Siam from 1891 to 1896,refers to it in his book first published in 1898 as "the Mae Nam Chao Phraya".
In the English-language media in Thailand, the name Chao Phraya River is often translated asriver of kings.
On the basins of Chao Phraya River rose the earliest civilizations in the south east Asia, most notably the ancient Mon kingdom and the civilization ofDvaravatifrom the 7th century to the 11th century. The river played a crucial role in theLavo kingdomthat existed on its left bank in the Upper Chao Phraya valley, and then maintained its role in the kingdoms that succeeded the Lavo kingdom. It formed the basis of the Ayodhaya kingdom, which was later incorporated into theAyutthaya Kingdomin the 14th century, which itself was the precursor of modern Thailand (known formerly as Siam). The river became very significant after the establishment of Rattanakosin (Bangkok) in 1782 on its east bank, the location of Bangkok on the east bank of Chao Phraya River ensuring protection for Siam from the Burmese invasions coming from the west.
The Chao Phraya begins at theconfluenceof thePingandNanrivers atNakhon Sawan(also called Pak Nam Pho) inNakhon Sawan province. After this, it flows south for 372 kilometres (231 mi) from thecentral plainstoBangkokand theGulf of Thailand. InChai Nat, the river then splits into the main course and theTha Chin River, which then flows parallel to the main river and exits in the Gulf of Thailand about 35 kilometres (22 mi) west of Bangkok inSamut Sakhon.
In the lowalluvial plainwhich begins below theChao Phraya Dam, there are many small canals (khlong) which split off from the main river. Thekhlongsare used for the irrigation of the region's rice paddies.
The rough coordinates of the river are 13 N, 100 E. This area has a wet monsoon climate, with over 1,400 millimetres (55 in) of rainfall per year. Temperatures range from 24 to 33 °C (75 to 91 °F) in Bangkok.
The lower Chao Phraya underwent several human-made modifications during theAyutthayaperiod. Several shortcut canals were constructed to bypass large loops in the river, shortening the trip from the capital city to the sea. The course of the river has since changed to follow many of these canals.
Provinces along the Chao Phraya include, from north to south,Nakhon Sawan Province,Uthai Thani Province,Chai Nat Province,Sing Buri Province,Ang Thong Province,Ayutthaya Province,Pathum Thani Province,Nonthaburi Province,Bangkok, andSamut Prakan Province. These cities are among the most historically significant and densely populated settlements of Thailand due to their access to the waterway.
Major bridges cross the Chao Phraya in Bangkok: theRama VIrailroad bridge;Phra Pin-klaonear theGrand Palace;Rama VIII, a single tower asymmetrical cable-stayed bridge;Rama IX, a semi-symmetric cable-stayed bridge; andMega Bridge, on the Industrial Ring Road.
In Bangkok, the Chao Phraya is a major transportation artery for a network of river buses, cross-river ferries, and water taxis ("longtails"). More than 15 boat lines operate on the rivers and canals of the city, includingcommuter lines.
The principal tributaries of the Chao Phraya River are thePa Sak River, theSakae Krang River, theNan River(along with its principal confluent theYom River), thePing River(with its principal confluent, theWang River), and theTha Chin River.Each of these tributaries (and the Chao Phraya itself) is augmented by minor tributaries referred to askhwae. All of the tributaries, including the lesser khwae, form an extensive tree-like pattern, with branches flowing through nearly every province in central and northernThailand.None of the tributaries of the Chao Phraya extend beyond the nation's borders.The Nan and the Yom River flow nearly parallel fromPhitsanulokto Chumsaeng in the north of Nakhon Sawan Province. TheWang Riverenters the Ping River near Sam Ngao district inTak Province.
When measured from the most commonly accepted source, which is the confluence of the Ping and Nan River in Nakhon Sawan, the river measures 372 km (231 mi). However, when measured from the longest source, which is the origin point of the Nan River in theLuang Prabang Range, the river measures 1,112 km (691 mi).
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 Phrayawatershed.
The Chao Phraya watershed is the largest watershed in Thailand, covering approximately 35 percent of the nation's land, and draining an area of 157,924 square kilometres (60,975 sq mi).
The watershed is divided into the following basins:
To the west, the central plain of Thailand is drained by theMae Klongand the east by theBang Pakong River. They are not part of the Chao Praya system.
The landscape of the river basins is a very wide, flat, well-watered plain continuously refreshed with soil and sediment brought down by the rivers. The lower central plain from the delta north toAng Thong Provinceis a flat, low area with an average of two metres above sea level. Further north and into the plains of the Ping and the Nan the elevation is over 20 m. Then the mountains that are the natural boundary of the Chao Praya watershed form adivide, which has, to some degree, historically isolated Thailand from other Southeast Asian civilisations. In northern Thailand the divide roughly corresponds to a long section of the political border of the country today. Southern portions of the divide's boundary correspond less to the nation's political border, because isolation in this area was prevented by the ease of transportation along the lowlands surrounding the Gulf of Thailand, allowing a unified Thai civilisation to extend beyond the watershed without issue. The slightly higher northern plains have been farmed for centuries and saw a major change from the 13th century during theSukhothai Kingdomin the 13th and 14th centuries and theAyutthaya Kingdomthat succeeded it when rice growing intensified with the introduction offloating rice, a much faster-growing strain of rice fromBengal. The southern swamps meanwhile changed radically from the 18th century when KingBuddha Yodfa Chulalokemoved the capital of Siam to Bangkok, and a process of canalisation and cultivation began, especially as Thailand began to export rice from 1855.
TheTha Chin Riveris the major distributary of the Chao Phraya River. The expanse of the Chao Phraya andTha ChinRivers and their distributaries, starting at the point at which the distributaries diverge, together with the land amid the triangle formed by the outermost and innermost distributary, form the Chao Phrayadelta. The many distributaries of the Chao Phraya delta are interconnected by canals that serve both for irrigation and for transportation.
The lowland areas of the Chao Phraya watershed in central Thailand have been designated as theChao Phraya freshwater swamp forests, atropical and subtropical moist broadleaf forestsecoregion,an area about 400 km (249 mi) north to south and 180 km (112 mi) wide.
The original swamp forests have almost entirely been removed as the plain has been converted to rice paddies, other agriculture, and urban areas like Bangkok. Much of the wildlife that once inhabited these plains has disappeared, including a large number of fish in the river systems, birds such as vultures, theOriental darter(Anhinga melanogaster),white-eyed river martin(Pseudochelidon sirintarae), thesarus crane(Grus antigone)and animals such astigers,Asian elephants,Javan rhinoceroses, and the much-huntedSchomburgk's deer.Today we can only guess at the original habitat and wildlife by comparing it with neighbouring countries. It is believed that the area would have consisted of freshwater swamps inland and saltymangroveson the coast and the river estuaries. The swamp would have been covered inPhragmitesmarsh grasses. Today there is a small area of this remaining inKhao Sam Roi Yot National Park, a relic of the original landscape.
As so much has been cleared or altered the potential for creating large protected areas to preserve original habitat no longer exists. However much wildlife does remain in the rice fields and steps may be taken to preserve these as urban and industrial development on the plains is ongoing and theIndustrial Estate Authority of Thailandhas very little control or planning over this. Particular threats come from the conversion of rice paddies to large-scale production of prawns by pumping in seawater, and the use of pesticides to eliminate the introduced snail,Pomacea canaliculata, which damages rice plants.
There are populations of threatened birds, including colonies of breeding water birds such as the world's largest populations of the near-threatenedAsian openbill(Anastomus oscitans), and other birds such as the winteringblack kite(Milvus migrans). Endemic mammals that remain are thelimestone rat(Niviventer hinpoon),Neill's long-tailed giant rat(Leopoldamys neilli), and the near-endemicThailand roundleaf bat(Hipposideros halophyllus).
The Chao Phraya basin is home to about half a dozen endemicdragonfliesanddamselflies. The conservation status of most of these in unclear (they are rated asdata deficientby theIUCN), butCryptophaea saukraiscritically endangeredandCaliphaea angkaisendangered.
There are few areas of wetland protected as national parks, but these are mostly very small.
The Chao Phrayabasinis home to around 280 species of fish, including about 30endemics.By far the most diverse family isCyprinidaewith 108 species.The mainstream of the Chao Phraya River has about 190 native fish species.In general, the aquatic fauna of Chao Phraya andMae Klongshow clear similarities, and they are sometimes combined in a singleecoregionwith 328 fish species.Despite their similarities, there are also differences between the aquatic fauna of Chao Phraya and Mae Klong; the latter (but not the former) is home to a fewtaxaotherwise only known in majorBurmeserivers: theIrrawaddy,Salween, andTenasserim.The aquatic fauna in Chao Phraya–Mae Klong also show clear similarities with that of the middleMekong(the lower Mekong fauna more closely resembles that of the easternMalay Peninsula).It is believed that the upper Mekong was connected to Chao Phraya (rather than present-day lower Mekong) until theQuaternary, which explains the similarities in their river faunas. This included theNan Riverbasin, a tributary of the Chao Phraya, which is home to a number of taxa (for example,Ambastaia nigrolineataandSectoria) otherwise only known from Mekong.Of the fish species known from the Chao Phraya–Mae Klong, only about 50 are absent from the Mekong.
There has been extensive habitat destruction (pollution,dams, anddrainageforirrigation) in the Chao Phraya basin andoverfishingalso presents a problem.Withinmainland Southeast Asia, the only freshwater region with similar high levels of threat is the lower Mekong.It has been estimated that only around 30 native fish species still are able to reproduce in the mainstream of the Chao Phraya River.
The catfishPlatytropius siamensisis endemic to Chao Phraya andBang Pakong, but has not been recorded since the 1970s and is consideredextinct.Recent records of the near-endemic cyprinidBalantiocheilos ambusticaudaare also lacking and it is possibly extinct.Three of thelargest freshwater fishin the world are native to the river, but these are all seriously threatened: the critically endangeredgiant barb(wild populations have beenextirpatedfrom Chao Phraya, but remain elsewhere),critically endangeredgiant pangasius,and endangeredgiant freshwater stingray.The critically endangeredred-tailed black shark, a small colourful cyprinid that is endemic to Chao Phraya, is commonly seen in the aquarium trade where it is bred in large numbers, but the only remaining wild population is at a single location that covers less than 10 km(4 sq mi).The endangereddwarf loach, another species bred in large numbers for the aquarium trade, has been extirpated from most of its range in Chao Phraya.The critically endangeredSiamese tigerfishhas been entirely exirpated from Chao Phraya and Mae Klong, but small populations remain in the Mekong basin.
Many other species that either are prominent in the aquarium trade or importantfood fishare native to the Chao Phraya basin, such as theclimbing perch,blue panchax,Asian bumblebee catfish,giant snakehead,striped snakehead,walking catfish,banded loach, severalYasuhikotakialoaches,tinfoil barb,Siamese algae eater,silver barb,pearl danio,rainbow shark,Hampala barb,black sharkminnow,Leptobarbus rubripinna,long pectoral-fin minnow,bonylip barb,Jullien's golden carp,blackline rasbora,scissortail rasbora,Tor tambroides,finescale tigerfish,marble goby,Chinese algae eater,giant featherback,clown featherback,giant gourami, severalTrichopodusgouramis,iridescent shark, severalPangasius,Belodontichthystruncatus, severalPhalacronotussheatfish, severalWallagocatfish,largescale archerfish,smallscale archerfish, andwrestling halfbeak.
The Thai Pollution Control Department (PCD) reports that thewater qualityof major rivers flowing into the upperGulf of Thailandhas seriously deteriorated, and the lower Chao Phraya contains bacteria andnutrient pollutionfromphosphates,phosphorus, andnitrogen. Nutrient pollution causesalgaeto grow faster than ecosystems can handle, harming water quality, food resources for aquatic animals, and marine habitats. It also decreases the oxygen that fish need to survive. PCD rated water quality at the mouth of Chao Phraya at Bangkok'sBang Khun Thian Districtas "very poor", worse than in 2014, and their findings indicated large amounts of wastewater were discharged into the river from households, industry, and agriculture.In addition, 4,000 metric tons of plastic flows down the river into the Gulf of Thailand every year. To counter this, Thailand's Department of Marine and Coastal Resources (DMCR) signed an agreement withThe Ocean Cleanuporganization to deploy an Interceptor Original, one of the organization's solar-powered, automated systems, in the river. Since 19 February 2024, an interceptor of the latest third generation has been deployed for testing purposes.
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