Chao Phraya Dam is the first large-scale diversion dam in Thailand. It is built across the Chao Phraya River. Located at the bend of Bang Kra Bian River, Moo 4, Bang Luang Sub-district, Sub Phaya District, Chai Nat Province, Chao Phraya Dam regulates the flow of the Chao Phraya River as it passes into lower Central part of Thailand, distributing water to an area of 11,600 square kilometers in seventeen provinces as part of the Greater Chao Phraya Irrigation Project. It gives benefit to irrigation and agriculture in the Central Plain. On February 7, 1957, their Majesties King Bhumibol and Queen Sirikit performed the opening ceremony of Chao Phraya Dam.