The Chao Phraya Dam is a barrage dam in Sapphaya District, Chainat Province. It regulates the flow of the Chao Phraya River as it passes into lower central Thailand, distributing water to an area of 11,600 square kilometres (4,500 sq mi) in seventeen provinces as part of the Greater Chao Phraya Irrigation Project. The dam has sixteen 12.5-metre gates, and its construction took place from 1952 to 1957.