Pa Sak River

The Pa Sak River (Thai: แม่น้ำป่าสัก, RTGS: Maenam Pa Sak, IPA: [mɛ̂ːnáːm pàː sàk], Pronunciation) 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. It then passes through the eastern part of Lopburi Province and Saraburi Province, until it joins the Lopburi River northeast of Ayutthaya Island, before it runs into the Chao Phraya River southeast of Ayutthaya near Phet Fortress. It has a length of 513 km (319 mi) and drains a watershed of 16,291 km² (6,290 sq mi). The annual discharge is 2.4 km³ (0.58 cu mi).

Pa Sak River (แม่น้ำป่าสัก)
The Pa Sak River flowing east of Ayuttaya's old city
Location
Country	Thailand
Physical characteristics
Source
• location	Phetchabun Mountains
Mouth
• location	Chao Phraya River at Ayutthaya Island
Length	513 km (319 mi)
Basin size	16,291 km2 (6,290 sq mi)
Discharge
• average	2.4 km3 (0.58 cu mi)/yr

The Chao Phraya River drainage basin showing the Pa Sak River

The valley of the Pa Sak through the Phetchabun mountains is a dominant feature of Phetchabun Province. Water levels vary seasonally. To address drought problems in the lower Pa Sak valley, in 1994 the construction of the Pa Sak Cholasit Dam (เขื่อนป่าสักชลสิทธิ์) in Lopburi Province was built. The 4,860-meter (15,940 ft) wide and 36.5-meter (120 ft) high dam retains 0.785 km³ (0.188 cu mi) of water. The dam also supplies about 6.7 MW of electricity.