Mekong left starving

Mekong left starving

In this Dec 1 photo, the colour of the Mekong River's stretch in Nakhon Phanom becomes ocean-like blue. (Bangkok Post file photo)
In this Dec 1 photo, the colour of the Mekong River's stretch in Nakhon Phanom becomes ocean-like blue. (Bangkok Post file photo)

Known for its signature reddish-brown waters, the Mekong River recently turned a bright blue in some parts. Its crystal-clear water may be beautiful to look at, but this change is a symptom of a sick and starving river. For ecologists and observers, it will be too naive not to point the finger at the usual suspects -- dams.

The Mekong is usually reddish-brown because it is rich in sediments. Each year, around 160 million tonnes of sediment flow from upstream in China to Vietnam's "rice bowl" in the Mekong Delta.

According to WorldFish, sediments absorb and transport nutrients, such as phosphorus and nitrogen, as well as organic particles through the river and to the floodplains. Influencing the respiration, nutrition, reproduction and migration of the fish stock, and fertilising the soil in the floodplains, this nutrient-rich river is a major reason why agriculture and fisheries in the region are so abundant.

However, locals in Chiang Rai, Nakhon Phanom and Ubon Ratchathani provinces noticed that the river turned mostly ocean blue over the past week. Ecologists say this is the result of either a loss or reduction in sediments, resulting in the "hungry water" phenomenon.

Apart from the damage it will cause to agriculture and the fishing industry, the now ocean-blue river is naturally hungry for nutrients and will start absorbing sediments attached to its banks, resulting in serious coastal erosion in the long term. As for the Mekong Delta, people have been witnessing the hungry water syndrome for a few years.

So where has all the sediment gone?

Riverbed mining, land use and climate change can be blamed for sediment reduction, but the most recent change in the river is most likely a result of sediment being trapped by hydropower projects upstream. This coincides with the commencement of operations in October of the Xayaburi dam in Laos, the first of the 11 projects planned for the lower Mekong.

Scientific studies led by the inter-governmental Mekong River Commission (MRC) indicate that existing and planned dams in the Mekong Basin are expected to cumulatively trap sediment loads of up to 67% next year and 97% in 2040.

This will affect ecosystems and damage agriculture and fishing, unless these projects have effective measures to prevent sediment from being trapping. But will their measures work?

While little is known about the dams in China, the Xayaburi project developer has released "limited" information on its operation for the MRC study. And even with such limited information, the findings are alarming.

The study has concluded that measures taken to allow the flushing and flowing of sediments downstream will be largely ineffective because up to 80% of the sediments "will be trapped for the first several years to decades from the operation of just this one dam".

The Xayaburi dam is believed to be a benchmark for future projects, and its ineffective measure proves that there is still no good practice available for others to adopt. More dams will mean a greater loss of sediments, not to mention ecological changes and impact on livelihoods.

Developers of hydropower projects and their financiers should not overlook these changes and become more responsible by putting their plans on hold until there is more information on effective impact mitigation measures available.

The Mekong has started getting hungry, and soon it could be mankind's turn.


Bangkok Post editorial column

These editorials represent Bangkok Post thoughts about current issues and situations.

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