2.2. Characteristics of Chao Phraya River Basins and Thai Rice
The CPRB was the largest river basin in Thailand, the most fertile region of the country with the largest
irrigated area with a catchment area of 162,800 square kilometer or approximately 35% of the country’s areas.
It can be divided into eight sub-basins including the Ping, Wang, Yom, Nan, Chao Phraya, Sakae Krang,
Pasak, and Tha Chin Rivers. The CPRB in the northern region of the country or known as the upper CPRB
consists of Ping, Wang, Yom, and Nan Rivers. These tributaries flow from the upper basin to meet at Nakhon
Sawan Province form the “Chao Phraya River” in the central region or known as the lower CPRB. After that
the Sakae Krang and the Pasak joins the Chao Phraya Rivers, then the Tha Chin River branches at the main
stream before entering the Gulf of Thailand at Bangkok and Samut Prakarn Provinces [3].
Thailand was the largest exporter and leading rice suppliers in the world, as well as chicken and shrimp
products, processed foods such as canned tuna, and pineapples or 13.3% of a total number of Thailand’s
export revenue in 2008 [2]. Hence, rice was a main crop of agricultural cultivation in the lower CPRB because