Nakhonnayok river basin is the sub-basin of Bangpakong river basin. The area of this basin is around 2,000 square kilometers covering Muang , Banna , Pakplee and Ongkharak district in Nakhonnayok province. The basin has Nakhonnayok river mainstream which has an origin in the Khao Yai national park. Mostly runoff flows into the ocean and always causing flooding. However, in the dry season is always a shortage of water and partially as acid soil cannot be cultivated.