Originally known as Yanhee Hydroelectric Project, Bhumibol Dam was first conceived in 1951 to provide irrigation water to farmlands in the downstream Chao Phraya River Valley and to counter Thailand’s electricity shortage. Construction commenced in 1952 and the first two turbines were commissioned in 1964. Six additional units were installed in later years to cope with the country’s rapid growth in electricity demand.

Bhumibol is a concrete arch gravity dam constructed across the Ping River, a tributary of the country’s main lifeblood, the Chao Phraya River. The dam is 154 meters high, 486 meters long and 6 meters wide at its crest, creating a storage of 13,462 million cubic meters. This is sufficient for flood mitigation and the provision of irrigation water for year round rice cultivation.

In an effort to maximize benefits, a lower barrage was constructed approximately 5.5 kilometers downstream of Bhumibol Dam in 1991, providing a lower pond suitable for the operation of a new reversible pump turbine. The concrete Lower Mae Ping Barrage is 8 meters high and 300 meters long and has a storage capacity of 5 million cubic meters.

The hydroelectric plant situated at the dam base has a total installed capacity of 743.8 MW from seven conventional generating units (Units 1-6 of 76.3 MW each and Unit 7 of 115 MW) and one reversible pump turbine unit of 171 MW. Bhumibol Unit 8 has a two-fold function, serving as a water pump during the off-peak hours to recapture water from the lower reservoir and pump it back up to the upper reservoir; and also operating as a generator to produce electricity during peak periods.

At the time of commissioning, Bhumibol Dam and its powerhouse operated as a baseload station and contributed 73.66% of the total Thai generating capacity. By 2003, the dam contributed only 2% of the nations electricity supply. Nonetheless, Bhumibol Dam remains an essential power generation asset during periods of peak electricity demand.