Pasak river flows through the middle from north to south. In the past Pasak river is the main transportation for Phetchabun people. The Pasak River is a river in central Thailand. The river originates in the Phetchabun Mountains, Dan Sai District, Loei Province, and passes through Phetchabun Province as the backbone of the Province. The valley of the Pasak through the Phetchabun Mountains is the main part of Phetchabun Province. As the watershed of the river is rather narrow, the amount of water in the river varies seasonally. To address drought problems in the lower Pasak valley, in 1994 the construction of the Pa Sak Cholasit Dam (เขื่อนป่าสักชลสิทธิ์) in Lopburi Province was started