The largest reservoir in Central Thailand is Pasak Jolasid Dam. Is it 4.8 kms long and stretches across Lopburi and Saraburi Provinces. It has a storage capacity of up to 960 million cubic meters. The project was initiated by H.M. The King in the early 1990’s and was officially opened in 1999. Pasak Jolasid Dam is a source of water for households, factories and farms in the Pasak Valley. It has also helped greatly with water management in the Chao Phraya Valley which often suffered from flooding during the rainy season. The Pasak River is a major tributary of the Chao Phraya River, flowing eastwards through Phetchaboon, Lop Buri and Saraburi Provinces, and joining the Chao Phraya River in Ayutthaya Province. Before the building of the dam, this river was one of the main sources of flooding in Bangkok.