Bhumibol Dam

The Bhumibol Dam (formerly known as the Yanhi Dam) is a concrete arch dam on the Ping River, a tributary of the Chao Phraya River, in Sam Ngao District of Tak Province, Thailand. It is about 480 km north of Bangkok and was built for the purposes of water storage, hydroelectric power production, flood control, fisheries and saltwater intrusion management. The dam was named after King Bhumibol Adulyadej and it was Thailand's first multi-purpose project. It is the highest dam in Thailand at 154 m tall.

Background
The dam was originally called Yanhee Dam in 1951 when the government of prime minister Field Marshal Plaek Pibulsongkram initiated the project. It was renamed Bhumibol Dam in 1957. The dam, among others in the Chao Phraya basin, was constructed beginning in the 1950s to exploit the agricultural and hydroelectric potential of the basin. Construction on the dam began in 1958 and was finished in 1964 at a cost of 3.5 billion baht. The reservoir was completely filled in 1970. The first two generators were commissioned in 1964. In 1972, the Sirikit Dam was completed on the Nan River, one of two major tributaries of the Chao Phraya including the Ping. The Bhumibol and Sirikit Dams control 22 percent of the Chao Phraya's annual runoff combined. Both dams also help provide for the irrigation of 1200000 ha in the wet season and 480000 ha in the dry season.

In 1991, the Lower Mae Ping Dam (17.24194°N, 99.01611°W) was constructed 5 km downstream to create a lower reservoir for the one pumped-storage turbine that was installed. When constructed, the Bhumibol Dam contributed 73.66 percent of Thailand's power generation and in 2003 that number was 2 percent.

During the 2011 Thailand floods, rainfall for March 2011 over the area of northern Thailand was an extraordinary 344 percent above normal. Bhumibol Dam in particular got 242.8 mm of rain, 224.7 mm above the mean of 25.2 mm and since 1 January had accumulated 245.9 mm, 216 mm or 186 percent above normal.

Design
The dam is an arch-gravity type and is 154 m tall, 486 m long and 8 m wide at its crest. It withholds a reservoir of 13462000000 m3 of which 9762000000 m3 is active or "useful" storage. The dam's catchment area is 26400 km2 while its surface area is 300 km2. The Lower Mae Ping Dam is 8 m high, 300 m long and has a storage capacity of 5000000 m3. In off-peak hours, the one pump-turbine returns water back into the Bhumibol (upper) reservoir and when demand is high, the pump serves as a generator for power production.

Power station
The power plant contains eight turbines for an installed capacity of 779.2 MW. Six are 76.3 MW Francis-type, one is a 115 MW Pelton turbine and one is a 175 MW Francis pump-turbine.

The dam's power house underwent upgrades and renovations in the 1990s.