Bakun Dam is a 205-metre concrete-face rockfill dam on the Balui River in Sarawak, Malaysian Borneo, with an installed capacity of 2,400 MW and a reservoir of roughly 695 km² — an area comparable to Singapore. Completed in 2011 after more than three decades of delays, it is the tallest dam of its type in Southeast Asia, and it flooded rainforest and longhouse communities in a resettlement that remains the most contested element of the project.
Thirty-Five Years From Proposal to Power
Few large dams have had a longer or more interrupted history. The Balui site was identified as hydroelectric potential in the 1960s, and a formal proposal followed in the early 1980s. Prime Minister Mahathir Mohamad's government approved it in 1986 as part of a wider industrialisation drive, then shelved it in 1990 amid cost and environmental objections.
It was revived in 1993 and awarded to a private consortium, only to be suspended again in September 1997 when the Asian financial crisis collapsed the ringgit and made foreign-currency financing untenable. Construction restarted under state control in the early 2000s, with Sarawak Hidro taking the project forward and a China-led consortium involved in construction.
Reservoir impoundment began in October 2010, and the first turbine was commissioned in August 2011. Filling the reservoir took several months. Final costs are generally reported in the region of 7–8 billion Malaysian ringgit, well above early estimates — a familiar pattern for megaprojects of this scale, and one repeated at Three Gorges and elsewhere.
Engineering: Why a Rockfill Dam Rather Than Concrete
Bakun is a concrete-face rockfill dam, or CFRD — a design in which the bulk of the structure is compacted rock and gravel, with watertightness provided by a relatively thin reinforced concrete slab on the upstream face.
The choice suited the site. The Balui valley offered abundant rock that could be quarried locally, avoiding the enormous cement imports a concrete gravity dam would have required at a location deep in the interior with minimal road access. Rockfill embankments also tolerate foundation movement better than rigid concrete, and they can be built through a tropical wet season more readily than mass concrete, which generates problematic heat while curing.
Key parameters:
- Height: 205 m, making it the tallest CFRD in Southeast Asia and among the tallest of its type worldwide
- Crest length: approximately 750 m
- Installed capacity: 2,400 MW from eight 300 MW Francis turbines
- Reservoir area: around 695 km² at full supply level
- Reservoir volume: on the order of 43 billion cubic metres
- Catchment: roughly 14,750 km² of the upper Rajang basin
An underground powerhouse sits within the rock of the right bank, with the turbines fed through pressure shafts — a standard arrangement in steep-sided valleys where a surface powerhouse would be exposed to landslides.
The Balui, the Rajang and Sarawak's Drainage
The Balui is the upper course of the Rajang, Malaysia's longest river at roughly 565 km, which drains much of central Sarawak before reaching the South China Sea through a broad delta near Sibu.
The site's hydrology is exceptional. Central Borneo receives roughly 3,000–4,000 mm of rain a year with no true dry season, so the Balui delivers a large and relatively reliable flow — the fundamental reason the site was attractive despite its remoteness. Steep interior terrain supplies the head, and the river cuts through resistant sandstone and shale of the Rajang Group, giving a narrow gorge suitable for damming.
That same geology creates a problem. Steep slopes, heavy rainfall and extensive logging across the catchment produce high sediment loads, and the Rajang carries a substantial suspended load. Reservoirs trap sediment, gradually reducing storage upstream while starving the river downstream of the material that maintains its channel and delta. Downstream of the dam, flow is now regulated to turbine demand rather than rainfall, altering the seasonal flood pulse that shaped the Rajang's floodplain ecology. The wider river system is covered in the Borneo island geography guide.
In 2010, shortly after impoundment began, an enormous raft of logs and debris — much of it vegetation not cleared before flooding, plus timber washed from the catchment — blocked stretches of the Rajang for weeks, disrupting river transport in a region where boats are the main means of travel.
Ten Thousand People and the Sungai Asap Resettlement
The most consequential impact was human. The reservoir submerged around 700 km² of the Balui valley, including the villages of roughly 9,000–10,000 people, predominantly from the Kayan, Kenyah, Lahanan, Ukit and Penan communities.
From 1998 they were moved to a resettlement scheme at Sungai Asap, some distance from the flooded valley. The transition broke a long-standing way of life. In the Balui, families lived in longhouses with access to river fisheries, forest products and shifting cultivation on customary land. At Sungai Asap each family received a much smaller land allocation — commonly cited at around 3 acres — insufficient for the farming systems they had practised, and households were charged for their new houses, leaving many in debt.
Compensation disputes over native customary rights land ran through the Malaysian courts for years. Long-term studies of the resettled communities have documented reduced food security, dependence on wage labour and out-migration of younger residents. Bakun is now widely cited in the resettlement literature as a case where physical relocation was completed but livelihood restoration was not.
Ecologically, the flooded area was lowland and hill dipterocarp rainforest, among the most biodiverse forest types on Earth and habitat for hornbills, gibbons and clouded leopards. A rescue operation captured some animals during impoundment, but such efforts recover only a fraction of displaced wildlife. Decomposition of unclear vegetation beneath the reservoir also generates methane and carbon dioxide — a well-documented issue for tropical reservoirs, which are not the zero-emission sources they are sometimes presented as.
Power With Nowhere to Go
Bakun's central paradox is that Sarawak did not need 2,400 MW when it was built. The state's peak demand at the time of commissioning was a fraction of the capacity created.
The original solution was extraordinary: transmit the power some 650 km across Borneo and then roughly 670 km beneath the South China Sea to Peninsular Malaysia via high-voltage submarine cables. It would have been one of the longest such links ever attempted, and it was abandoned as too costly and technically fraught.
The fallback became industrial demand. Bakun anchors the Sarawak Corridor of Renewable Energy (SCORE), launched in 2008 to attract energy-intensive manufacturing — aluminium smelting, ferroalloys, polysilicon and manganese processing — to coastal Sarawak, particularly around Samalaju near Bintulu. The strategy is to export embedded electricity in the form of metal rather than move electrons. Results have been mixed: several announced smelters were delayed or cancelled, and Bakun ran below capacity for years. A link to Kalimantan in Indonesian Borneo and supply to Brunei have since been pursued.
Bakun in Sarawak's Wider Dam Programme
Bakun was never intended to stand alone. Sarawak's energy planning treats the interior rivers as a linked system, and the dams built since follow directly from it.
Murum Dam, on a tributary of the Balui upstream of Bakun, was completed in 2014 with a capacity of 944 MW and displaced several hundred Penan families — a community that had been among the last in Sarawak to live semi-nomadically. Baleh Dam, a 1,285 MW project on another Rajang tributary, has been under construction since 2019. Together with the older 108 MW Batang Ai scheme from 1985, these give Sarawak a hydroelectric fleet far larger than a state of roughly 2.5 million people requires for domestic use.
More ambitious proposals met resistance. A plan circulating around 2008 envisaged a dozen or more additional dams across the state, including one at Baram that would have flooded an estimated 400 km² and displaced upwards of 20,000 people. Sustained protest by affected communities, including road blockades maintained for years, led the state government to shelve the Baram scheme in 2016 and return the land — a rare reversal, and one made possible in part by the documented outcomes at Sungai Asap.
That is Bakun's most durable legacy within Malaysia: it demonstrated both that Sarawak could build at this scale and what the social cost looked like in practice, and the second lesson shaped what came after as much as the first.
Bakun Compared With the Aswan High Dam
Aswan makes a revealing comparison — a similarly transformative dam in a completely different environment.
The physical contrasts start with purpose. Aswan, completed in 1970, was built primarily to control the Nile's annual flood and store water for irrigation; power was a secondary benefit, and its 2,100 MW capacity is slightly below Bakun's 2,400 MW despite Lake Nasser being vastly larger at around 5,250 km² — more than seven times Bakun's reservoir. The reason is head: Aswan's dam is only about 111 m high against Bakun's 205 m, and hydroelectric output depends on the height water falls through as much as on volume.
Their sediment problems run in opposite directions. Aswan traps silt that once fertilised Egyptian fields annually, forcing dependence on chemical fertiliser and leaving the Nile Delta eroding. Bakun traps sediment produced largely by logging in its own catchment — a human-accelerated load rather than a natural one being withheld.
The displacement comparison is stark in scale but similar in character. Aswan displaced well over 100,000 Nubians in Egypt and Sudan, an order of magnitude more than Bakun's roughly 10,000, and Nubian communities likewise report that resettlement severed them from a river-based way of life. Evaporation, meanwhile, costs Lake Nasser billions of cubic metres a year in the desert — a loss essentially absent in Borneo's humid climate, where Bakun's problem is the opposite: too much organic matter and rainfall, not too little water.
Bakun stands as a case study in what large dams actually deliver and at what cost: substantial low-carbon capacity built ahead of demand, in a catchment whose sediment problems it did not cause, at the expense of communities whose relocation is still being litigated. The wider setting is covered in the Malaysia country guide.
