The Threat of a Dam Disaster in Luang Prabang

[reader]

From The Diplomat

Building a huge dam just upstream from a legendary UNESCO World Heritage site in an earthquake prone region poses serious risk to the local population and the town of Luang Prabang, warns a leading Thai earthquake specialist.

Dr. Punya Churasiri, formerly the earthquake expert at Chulalungkorn University’s geology department, has considerable field research experience in northern Laos. As construction on the dam moved forward, he told The Diplomat, “We worry about what could happen and the possibility of damage to the World Heritage site.”

The main developer and builder of the dam is the Thai construction giant CH Karnchang corporation. The dam site sits precariously close to an active earthquake faultline only 8.6 kilometers away. A sharp reminder of the danger was provided on July 7, when a 4.7 strong earthquake was registered in Luang Prabang district.

Many local people in the World Heritage city fear that the 1410 MW Luang Prabang dam could trigger another disaster after the Xepian Xenamnoi dam accident in 2018. Damage to the dam caused a massive flood that swept away villagers and villages alike, leaving 14,440 people homeless and 71 confirmed dead.

The dam site is 25 kilometers upriver from Luang Prabang, a cultural mecca and cornerstone of Lao history. The city harmoniously blends old architecture and culture with the surrounding nature, flanked by the confluence of the Mekong and Khan rivers, all part of the protective UNESCO World Heritage zone.

Among many issues UNESCO’s World Heritage Committee (WHC) will be considering at its annual session, which began on July 16 in China, will be the increasing impact of dams on World Heritage sites, most recently in the Selous Game Reserve in Tanzania and Luang Prabang in Laos. The potential for damage to the sites has prompted global outcry. In the draft decision the WHC recommended the government of Laos “to halt all construction activities until a full heritage impact assessment is carried out.”

Continues at

https://thediplomat.com/2021/07/the-threat-of-a-dam-disaster-in-luang-prabang/

[PeterRS]

This seems another case of bureaucratic madness. China already has 11 massive dams on its part of the Mekong river. According to a Bloomberg article in April last year, the effect of these dams is now being felt very seriously down stream in Laos and Cambodia. Although it refers primarily to China blocking water from flowing downstream, given the seemingly cavalier attitude of China to its neighbours, what if it suddenly let out a large amount of water which found its way to this new dam north of Luang Prabang? Could it withstand the increased pressure? What if this coincided with a period of massive flooding as seen recently in other countries, notably Germany? Luang Prabang is one of Asia's most beautiful old cities. It should be protected at all costs, not put a risk.

"China considers water management data to be a state secret, and, barring new evidence, it has always been difficult to reach defensible conclusions about China’s management water levels in the Mekong River. That is, until this month, when remarkable new data became public. It shines a dramatic light on how much water China’s upstream dams have blocked—even as downstream countries suffered through unprecedented drought.

"Every year, the Mekong River rises and falls in cycle with the rainy season, when a massive pulse of water driven by monsoon rains and Himalayan snow melt flows downstream. Yet along the Thai-Lao border between June and November of last year the mainstream of the Mekong ran dry, the river bed and shoals were exposed, and isolated pools of flopping fish were unable to reach their spawning grounds.

"That July, as the mainstream’s level fell so far that irrigation pumps could not reach it, the Thai government mobilized its army to conduct relief efforts. In the fall, Tonle Sap Lake will typically fill with monsoon waters rushing in from the mainstream for five months, providing Cambodians with up to 70 percent of their protein. Last year, the expansion of the lake, often described as the Mekong’s heartbeat, lasted just five weeks, and reports suggest it produced a fraction of the normal 500,000 tons of food.

"Observers, myself included, initially concluded that the abysmally low levels in the mainstream were due to low precipitation in the broad Mekong Basin. An El Niño weather pattern still today leaves most of the region suffering from its worst drought on record. In Vietnam’s Mekong Delta, millions of people are currently without access to freshwater. But a new study from the U.S-.based climate consultant Eyes on Earth provides us with a different reason: For six months in 2019, China’s dams blocked an unprecedented amount of water from entering the lower Mekong. The amount of water withheld was so large that, for the first time since modern records have been kept, there was no monsoon-driven rise in water levels just over the Chinese border in Chiang Saen, Thailand.

https://foreignpolicy.com/2020/04/22/science-shows-chinese-dams-devastating-mekong-river/

Note: Underlining is in the original article. Boldface is my addition.

[Guest]

The sudden release of water from Chinese dams should not cause a significant increase in pressure, as the amount they could release is constrained by river capacity on their own territory AND there should be a damping effect as it arrives in a full reservoir.    Also the dam should be built with a large safety margin.

I would think the biggest concern is the possibility of China withholding water from downstream countries to put political pressure on them whenever there is some disagreement.    Bear in mind that this Chinese regime seems to lay claim over sea stretching all the way down to the Philippines, which is a rather aggressive & optimistic.

There is also a risk that the Mekong delta would not be replenished with silt, but in the long term, global warming will finish that off anyway.

Incidentally, I believe Thailand has contracts to take most of the electricity from some hydro electric dams in Laos, which must contribute to the viability of these projects.  So Thailand should keep that in mind when complaining about any water shortage caused by Laos.

Of course, if every country is fair and does not divert water away from the Mekong, the construction of a reservoir should only mean a temporary reduction of flow, as once the reservoir is full, the flow should revert to normal.   I would not count on fair behaviour by all upstream countries.

[Guest]

By some coincidence, there are reports of flooding in more than one part of China currently, one clearly north well away from the Mekong and something to the south.      

Probably mostly outside the Mekong basin, but clearly periods of abnormal rainfall are a very good time to start filling an empty reservoir.    

There are reports of one collapsing in the north, but I'm not sure if this is from a reliable source.    This really shouldn't happen, as the maximum head of water is a known and these structures should be over engineered with a huge safety margin.