T about six o'clock in the evening on Monday 28, September 2009, Ru Chom watched helplessly as a wall of water surged through her riverside village, uprooting her house and washing away livestock, trees and wild animals.

"The money that I had earned I spent on the previous house. I hadn't even finished it yet and now it is upside down. Now I have nothing and no business," she said, pointing to the remnants of her former home.

Typhoon Ketsana had struck, bringing a torrent of water with it and while the nation's eyes were fixated on the tragic floods in Kampong Thom province, further north in Ratanakkiri province another catastrophe was quietly unfolding.

Two hours earlier at the Yali Falls Dam, 900 kilometres east in neighbouring Vietnam, desperate officials had opened the floodgates of smaller regulation dams, fearing the dam walls would collapse under intense pressure from the floods.

The dams simply hadn't been built to withstand the pressure of torrential downpours on the scale of Ketsana, and shortly after the gates were opened Ratanakkiri provincial Governor Pav Hamphan received a phone call, warning him of the impending flood.

"They had to open their flood gates into Cambodian land when the water became too much; if they hadn't the dam would have collapsed," he said in a telephone interview.

Just 10 hours later Andoung Meas village had disappeared, submerged under a 13-metre swell of the Sesan river's water level.

Village representative Ting Ramon was in Banlung, the provincial capital, when he heard the news and rushed back to his village. "When I came to the village I just sat on the boat and measured the rising water level by diping a long stick, and I could see the water go up very high. Compared to the normal water level in the rainy season, it was 8 meters higher," he said. "There are 21 houses in my village and 13 of them floated away."

By morning the floods waters were surging towards the neighbouring province of Stung Treng, the site of another proposed dam that has ethnic minority villagers fearing that last year's flood will become an all-too-common occurrence.

They already complain that since the Yali Falls Dam was first sealed closed in 1996, floods have become a routine occurrence along the Sesan river, inundating nearby villages two to three times a year.

But the complaints of small, isolated minority villages situated on the periphery of Cambodia's rural outskirts barely stir a ripple downstream where the decision-making about major infrastructure projects takes place.

Meach Mien, project coordinator of the 3S Rivers Protection Network (3SPN), is deeply concerned about the upstream impacts of the planned 400-megawatt Lower Sesan 2 dam due to be completed in 2014.

The dam, which will inundate 30,000 hectares of forest and displace an estimated 4,785 people is, is being built by Electricite du Vietnam (EVN) through the company Power Engineering Consulting Joint-Stock Company 1 (PCC1) and is intended to provide enough power to generate significant international sales.

But 3SPN is worried it will do so at the expense of local livelihoods for riverside villages on the banks of the Sesan in Ratanakkiri who already complain that existing dams have decimated their fish stocks and made river water undrinkable.

He wants these concerns heard and knows that local ethnic minority villagers simply don't have the capacity and avenues of communication to gain exposure without outside assistance. "We help them share information because we get the information from our communities: for example, changes in the water level or any other changes that they have noted," he said.

Using soft advocacy, the support of local and international partners and their access to local government, his organisation is trying to develop communication networks to promote local concerns that in the past have fallen on deaf ears.

Ting Ramon is part of that information network and his feelings about the new dam mimic those of all the villages that have been mobilised by the community networks 3SPN has developed.

"Building a big dam like this always affects the people around it. It makes life more difficult for people and doesn't have pity for people living on the river. It seems like they are killing us off," he said. "I feel that the government is building this dam to develop the country, but they just make life difficult for people along the river."

It's not just at the local level that concerns are being raised about hydropower development projects that are pursued with scant regard for the consequences they create elsewhere.

Carl Middleton, Mekong programme coordinator for the US-based International Rivers, said the combined impact of a plethora of dams slated for construction on the Mekong and its tributaries such as the Sesan is incalculable and deeply concerning.

"The health of Mekong ecosystem is linked to the fact that it's a flood pulse, the fact that there's a lower level in the dry season and then a very high level in the rainy season, and it's that characteristic that makes the river one of the most productive," he says.

"It's the most productive in the world for fisheries, and it also has an exceptional biodiversity as well, so the cumulative impacts of building so many projects on the tributaries combined with mainstream dams could be pretty grave."

Those cumulative impacts are not just confined to sporadic floods, fish stock depletion and water quality degradation. With the Mekong river basin in the midst of a severe drought that has brought river flows to a complete halt in some areas, the impact of upstream dams in China was a hot topic at a summit of the Mekong River commission in April this year.

Converging in the luxury seaside resort town of Hua Hun in Thailand, the prime ministers of Cambodia, Thailand, Laos and Vietnam - as well as delegates from China and Myanmar - discussed the future of the river. And though China, who has four major dam projects on the Mekong already, agreed to share dry season water flow data with downstream companies for the first time, it continued to deny Chinese dams were having any impact on the river's water level.

A map produced by the Mekong River Commission in February 2008 showed 14 existing dams on the Mekong and its tributaries, with another 11 under construction and a staggering 57 planned by six countries along the river and its tributaries.

That includes seven more in Laos and two in Cambodia, mostly using Build-Operate-Transfer schemes in which a private company builds and operates the dams for a set period of time, before handing them over to the national government.

Meach Mein is convinced that such schemes are particularly counterproductive because the host country reaps no economic benefit until they inherit the ageing dam 30 or 40 years later. "By then the materials are already old and the dam collects increasing amounts of sediment. It means we get a garbage dam," he said.

His colleague at 3SPN, advocacy adviser Paul Humphrey, said the Cambodian government should seriously consider the efficiency of "old, dirty" hydropower dams against alternative sources of generating power such as micro-dams, solar and bio-gas.

Micro-dams produce electricity for local consumption by blocking off only a small section of the river, allowing fish migration to continue while causing comparitively small impacts to water quality and sediment accumulation. They also avoid large transmission losses associated with transporting power long distances to neighbouring countries for sale.

"Cambodia has a real opportunity that they can embrace all these new, renewable energy sources which, given that there's more research coming out everyday and there have been vast improvements in this technology, are really viable alternatives," Humprey says.

If Prime Minister Hun Sen's recent visit to the province is any indication, Cambodia will not be investigating such alternatives.

At the opening of a new national road in March, Hun Sen lauded the fact that because of new hydropower dams slated for construction on the Srepok and Sesan rivers, Vietnam would soon be buying power from Cambodia - a reversal of the current situation.

At the same time, Provincial Governor Pav Hamphan failed to deliver a letter of protest he'd promised to deliver to the prime minister about the dam, sighting the fact that he had already received too many protests from different interest groups that week.

Perhaps one point of optimism for the communities living along the Sesan is that, after seeing a copy of the environmental impact assessment (EIA) for the Lower Sesan 2 project, Hun Sen deemed that more information was required, suggesting a new EIA may be on the way.

But even if a new assessment is produced, Meach Mien has little faith that such a report will prompt any real change, believing the assessments are conducted largely as show exercises to appease the requirements of the developmental bureaucracy.

He remains frustrated that the Cambodian government continues to support major internationally financed dam projects justified by invariably misleading, inaccurate and impotent EIA reports.

"It seems like they conduct them just to suit their needs. For instance, they only study around the area where the dam sits and where the community will be directly impacted; it's not a full EIA," he said.

Meach Mien does not understand why indirect impacts to upstream villages - affected by changes to river flow, destruction of fish stocks, increased susceptibility to floods and reductions in water quality - are not incorporated into these assessments.

One of the men tasked with conducted the EIA, completed in 2008, was Sopha Nara, an environmental engineer with Key Consultants Cambodia, who were sub-contracted to produce the EIA by the company building the dam.

He said that those indirectly affected by the impacts of the dams were consulted, including villagers in Ratanakkiri but that it simply was not practical to survey villagers a long way from the project site.

"So far from the project site we don't do it; we do it around 40 kilometres from the dam site but we can't do it 100 or 200 kilometres, it is very far," he said, laughing.

The joke is lost on Ting Ramon, whose village was not included in Key Consultants' report. In fact, in the 10-page public consultation section of the 178-page report, only one village from Ratanakkiri and five from Stung Treng province were consulted.

Sopha Nara insists that where it was not practical to consult villagers, accurate predications were made in the Lower Sesan 2 Dam EIA and compensation provisions afforded accordingly to those both directly and indirectly affected.

But Tep Bunnarith, director of the Culture and Environment Preservation Association, which advocates on behalf of affected villagers in the proposed flood region in Stung Treng province, said not even those directly affected have received any guarantee of compensation. "I have not known of any plan by the authorities to compensate or resettle villagers," he said.

For Ting Ramon and his fellow villagers, compensation offers are neither here nor there. They want to remain on the lands they have cultivated for generations and don't see where authorities plan to relocate him.

"Since I was a child and I could see the river, nothing changed. In the dry season, the water was crystal clear like a mirror and was much fresher and we could fish. Since the time that they built the dam, the river changed," he said.

"Where can I move to? I don't have any other land. When we move to the place that has no water, no floods, it belongs to private companies, so I stay here. I'll stay here forever. When I die, I'll die here."