BANGKOK — Forest clearance has begun to make way for a new irrigation dam deep in the heart of the Cardamom Mountains, in Cambodia’s western province of Pursat, Mongabay has learned.

The dam, which officials say will safeguard against floods and secure water for agriculture, looks set to clear more than 7,300 hectares (18,000 acres) of protected forest within Kravanh National Park, according to an overlay of official project maps with satellite imagery of rainforest cover.

Mongabay first reported on the existence of the dam project in March. More recently, sources familiar with the area provided us with geolocated photos showing that ground broke on the project in February, with development continuing over the following months. Mongabay spoke with several residents in affected communities who confirmed that forest clearance and construction were taking place.

Satellite imagery appears to show a roughly 10-kilometer (6-mile) road being carved through the forest to the dam site between February and March 2025, followed by some 60 hectares (150 acres) of forest clearance taking place within the project area through at least Aug. 12.

Of the 7,300 hectares to be cleared, nearly 4,000 hectares (10,000 acres) will be inundated with water as part of the Irrigation Dam 2 project, as it’s formally known, with the rest of the area also being cleared, documents indicate.

Eng Rasmey, chief of the Pursat Provincial Department of Environment, told Mongabay that the forest clearance was happening under the onus of the dam project, which is overseen by the Ministry of Water Resources and Meteorology. He did not respond to questions about the environmental impact of the dam.

Despite being one of the best-preserved forest landscapes still standing in Cambodia, the Cardamoms’ lush rainforests face increasing threats, largely in the form of hydropower projects, with five new dams and their accompanying reservoirs currently being built atop some 15,000 hectares (37,000 acres) of forest.

The Cardamoms are also one of Cambodia’s last biodiversity hotspots, with a camera-trap survey from 2022 to 2023 identifying 108 species, including the critically endangered Sunda pangolin (Manis javanica) as well as the Asian elephant (Elephas maximus), dhole (Cuon alpinus), long-tailed macaque (Macaca fascicularis), pileated gibbon (Hylobates pileatus) and green peafowl (Pavo muticus) — all of which are listed as threatened on the IUCN Red List. Cambodia as a whole has one of the highest rates of deforestation in Southeast Asia.

Not even the dam site’s overlapping with part of the Samkos REDD+ project, a carbon-offsetting initiative, could prevent the project from moving ahead.

The Samkos REDD+ project, which aims to generate carbon credits from the preservation of forests across the Cardamoms, is yet to undergo validation and verification, meaning it still needs to be assessed by third-party auditors before it can sell carbon credits. But even before the REDD+ project begins in earnest, some 1,800 hectares (4,500 acres) of forest it aims to conserve are set to be lost to the dam’s reservoir. The Samkos REDD+ project has already seen other tracts of forest vanish at the hands of illegal loggers linked to the Stung Meteuk hydropower project, also in Pursat province.

Wildlife Alliance, an NGO that runs the Samkos REDD+ project jointly with Cambodia’s Ministry of Environment, told Mongabay it was aware of the forest clearance at the new dam site.

“The construction of the water reservoir project in Stung Arai, Pursat province is expected to cause deforestation of approximately 0.6% of the Samkos REDD+ Project Area,” the group said in a written statement, referring to the irrigation dam now under construction. It added that forest rangers from the group’s Cardamom Forest Protection Program were “closely monitoring the dam’s construction, and all deforestation will be fully accounted for during the project’s upcoming validation and verification.”

But while the Samkos REDD+ project is yet to generate any money that might otherwise convince the Cambodian government to avoid further deforestation, a 2020 World Bank report estimated that forests in the Pursat River Basin provide ecosystem services, including water and sediment flow regulation, worth some $99 million.

The loss and degradation of forests in the basin, the report said, “would tend to increase peak river flows and erosion, which would lower water availability in the dry season (when water is particularly valuable for irrigation), increase flood risk and increase siltation of reservoirs, thus reducing their useful life.” It added that sustainable forest and watershed management would be crucial for agricultural outputs, the continued operations of hydropower dams, as well as the carbon market and ecotourism potential.

Some hydropower projects in Cambodia have been known to provide cover for illegal logging. While the northern section of the new dam site has been picked clean of valuable timber, the southern half sits deeper in the dense jungles of the Cardamoms.

No company appears to have been announced as attached to the dam project. Provincial government officials contacted by Mongabay would only confirm it was being overseen by the Ministry of Water Resources and Meteorology. Representatives of the Ministry of Environment did not respond to requests for comment.

Communities set to lose forest and access to water

Irrigation Dam 2 is being built in Rokat commune, Phnom Kravanh district, Pursat province, and is the first of three new irrigation dams slated for construction within the Cardamoms known to have broken ground.

The dam is being built on the Arai River, a key tributary of the Pursat River, which in turn empties into Tonle Sap Lake. Tonle Sap is Southeast Asia’s largest freshwater lake, but upstream dam construction is weakening the annual flood pulse that swells its surface from roughly 250,000 hectares in the dry season to up to 1.6 million hectares (618,000 to 4 million acres) every wet season, contributing to a decline in the lake’s fisheries.

Some 70 freshwater fish species rely on the Pursat River system for spawning and migration, but research from the Mekong River Commission has shown how the proliferation of irrigation dams and other barriers across the river’s catchment area has restricted the access of fish to and from Tonle Sap Lake.

Irrigation Dam 2 looks set to exacerbate these conditions, restricting the flow of the Arai River and cutting off riverine communities who live between the site of the dam and Tonle Sap Lake.

“I feel deeply saddened by the loss of the land — there is so much forest, and the forest resources are abundant,” Phanha, a resident of Rokat commune who requested a pseudonym due to fears of retaliation from authorities, said by phone. “It would be better if they protected it and developed it for tourism instead.”

Pursat Governor Khoy Rida said at an event promoting rainforest conservation in May that the dam would have the capacity to store nearly 900 million cubic meters (32 billion cubic feet) of water for use by farmers downstream via the existing Damnak Ampil irrigation system, which ensures year-round water supply for 24,629 hectares (60,860 acres) of rice fields.

Phanha and others who live upstream, however, say they’ll lose out from the project as water is rerouted to other areas.

“[The government] are concerned there won’t be enough water by 2030, so they are building this dam,” Phanha said. “When downstream communities need water, it will be released from the dam for them, but for us, who live upstream, we’ll have nothing to support our rice cultivation — we rely only on small creeks.”

The Arai River is the largest natural source of water for more than 40 families in Rokat commune, who use it for everything from cooking, bathing and drinking to irrigating crops and sustaining livestock.

Rattan, various mushrooms and flowers which vary by season can all be found in the forest and sold commercially, along with vines, plants and herbs that locals use for cooking and traditional medicines. Ratha, another local farmer, said the flowers alone earn him between $250 and $500 each season. But villagers say that since construction on Irrigation Dam 2 began, they’ve been denied access to the forest, causing some members of their community move to the capital, Phnom Penh, in search of construction work.

“Water from the new dam will not benefit our community,” Ratha said by phone. “The downstream people will get water, while we here will lose the forest. Everyone in Rokat and Somraong communes will not get water from this dam.”

Communities’ concerns ignored

Cambodia has invested heavily in water management infrastructure in recent years, including in Pursat province.

It’s unclear, however, if an environmental impact assessment, or EIA, was finalized and approved by the Ministry of Environment ahead of forest being cleared for Irrigation Dam 2. Article 668 of Cambodia’s Code on Environment and Natural Resources prohibits construction on any project from beginning without the Ministry of Environment issuing “an approval letter and certificate on the full environmental impact assessment report, initial environmental impact assessment report, or environmental protection agreement.”

A March 3 letter from Environment Minister Eang Sophalleth to Water Resources Minister Thor Chetta, seen by Mongabay, directs the dam developer to “proceed with the necessary procedures” for carrying out an EIA, apparently signaling it hadn’t been done even as the project broke ground. The ministries did not respond to requests for comment on this matter.

CG Sustainable Co. Ltd., the consultancy identified in the letter as responsible for conducting the EIA, apparently read but did not respond to queries sent by Mongabay via messaging app Telegram.

Chapter 6 of the environmental code also dictates that developers guarantee and record public participation ahead of construction beginning, but both Phanha and Ratha told Mongabay their community hadn’t been formally consulted. Instead, their knowledge of the dam came from seeing the construction begin and from casual conversations with local officials, but they noted that, as a whole, the community was afraid to voice its grievances for fear of retribution.

“No one dares to protest,” Phanha said. “If [the government] asked us to choose between a dam and a tourism area, we have to say that we are happy with the dam — we cannot say we’re unhappy because they are powerful people. Some villagers say building the dam could provide many benefits to the agricultural economy, but it would also destroy a lot of forest.”

Banner image: It’s unclear whether an environmental impact assessment was conducted in accordance with Cambodian law before ground broke on Irrigation Dam 2, but the government-led project will clear protected rainforests and dam a key tributary of the Pursat River. Image supplied by source.