Chao Phraya

Geography

The Chao Phraya begins at the confluence of the Ping and Nan rivers at Nakhon Sawan, Nakhon Sawan province. It flows south for 372 kilometres (231 mi) from the central plains to Bangkok and the Gulf of Thailand. In Chai Nat, the river splits into the main course and the Tha 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 in Samut Sakhon.

In the low alluvial plain which begins below the Chao Phraya Dam, there are many small canals (khlong) that split off from the main river. The khlongs are used for the irrigation of the region's rice paddies.

The 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.

History

On the basins of Chao Phraya River rose the earliest civilizations in Southeast Asia, most notably the ancient kingdom of Mon-Tai and the civilization of Dvaravati from the 7th century to the 11th century. The river played a crucial role in the Lavo kingdom that 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 Ayodhya Kingdom, which was later incorporated into the Ayutthaya Kingdom in the 14th century, which was the precursor of modern Thailand. The river became significant after the establishment of Rattanakosin (Bangkok) in 1782 on its east bank, its location ensuring protection from Burmese invasions coming from the west.

Ecology

The lowland areas of the Chao Phraya watershed in central Thailand have been designated as the Chao Phraya freshwater swamp forests, a tropical and subtropical moist broadleaf forests ecoregion, 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.

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 augmented by minor tributaries 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. The Nan and the Yom River flow nearly parallel from Phitsanulok to Chumsaeng in the north of Nakhon Sawan Province.