Predicted water loss and sediment reduction from hydropower development

Vientiane, Lao PDR, 26th Mar 2018

Vientiane, Lao PDR, 27 March 2018 – Hydropower development on the Mekong River is predicted to intensify water loss and result in an acute reduction in sediment flows, according to findings from a Mekong River Commission (MRC) study released recently through two short technical notes.

The findings suggest that although water resource development brings economic benefits to the region and its people, if not properly planned, it could have serious consequences on the condition of the river, especially its downstream reaches in the Mekong Delta.

“The potential challenge before us now is nothing simple. Addressing this challenge requires more resources and most importantly stronger regional cooperation and well-coordinated planning and management,” said Mr. Pham Tuan Phan, MRC Chief Executive Officer.

One of the reports indicates that annual water loss from hydropower development is predicted to increase from 30 million m3 (MCM) in 2007 to 130 MCM in 2020, and 830 MCM by 2040. In addition to water loss, the Study on the Sustainable Development and Management of the Mekong River – or Council Study – also indicates that existing and proposed dams will have significant cumulative impacts on sediment loads entering the Mekong Delta.

The river itself serves as a circulatory system for the nutrients and building blocks of riverine life; the water is the lifeblood that carries the fine sediment, which in turn conveys the nutrients on which all life on the river depends. Remarkably, as the second report shows, sediment loads reaching the Delta in 2040 will fall to just 3% of 2007 levels.

The extent of expected sediment loss may be expected to have damaging consequences on the productivity of the river, its geomorphology, and persistence of the Delta landform itself.

To address the magnitude of potential sediment starvation on the Mekong River system, mitigation strategies for all dams should be developed to improve the amount of sediment reaching the Delta. One such mitigation measure consists of passing sediment through dams to reduce the consequences of downstream sediment starvation.

“But any mitigation measures are only likely to be effective if they are implemented in a coordinated way for all dams along the river,” said CEO Pham.

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