Lower sediment levels major concern for Delta

VietNamNet Bridge – Viet Nam will spend US$6.3 million next year to examine the impacts of mainstream hydro-power on the downstream Mekong River.

Many fishermen in Tien Giang Province live on aqua-culture farming in the Mekong River. Their practice might be threatened by the lower supply of upstream sediments and nutrients, caused by the building of hydro-power plants on the downstream river.

As the country most affected by hydro-power dams upstream, this study could provide Viet Nam with sound scientific-based evidence of any negative impacts.

This would enable it to negotiate with project developers to revise the scale and design of each dam if necessary.

The study is expected to conclude in June, 2015. Funding will be provided by the Vietnamese Government and possibly from international sources.

The Viet Nam National Mekong Committee (VNMC) met development partners at a roundtable meeting on Cuu Long (Mekong) Delta Integrated Water Resources Management held in Ha Noi on Tuesday.

The committee's deputy director general Truong Hong Tien said that the study's terms of reference had been sent to other countries in the Lower Mekong Basin (LMB), Laos, Cambodia and Thailand for comment.

It has been submitted for approval to the Vietnamese Ministry of Natural Resources and Environment.

Tien said the study aimed to establish scientific-based data to assess the potential impacts of proposed mainstream hydropower projects on the LMB, including the Mekong Delta in Viet Nam.

This would include river flow, the movement of suspended sediments and nutrients (mud), water quality and biodiversity.

So far, 14 hydro-power dams are being developed on the Lancang River (the upper half of the Mekong River in China), of which four have been completed. In the Lower Mekong Basin, there are another 11 hydro-power dams. However, comprehensive studies on impacts of such dams have been quite limited.

A Strategic Environment Assessment of hydro-power on the mainstream Mekong held by the Mekong River Commission from 2009 to 2010 was among the few. One of the main findings was that decisions to develop the Mekong river were regional.

The assessment team recommended decisions on mainstream dams should be deferred for 10 years so that other options are studied, including partial in-channel diversions and other innovative systems that do not require full-width river dams.

Environmental Systems Engineer Tarek Ketelsen from the International Centre for Environmental Management, which commissioned the study, said there was an understanding among LMB countries that the issue would affect different countries in different ways.

"It was acknowledged that Laos and Cambodia would benefit from the mainstream projects while all the countries agreed that Viet Nam would be most affected," he said.

Ketelsen said that the impacts really came down to sediments and nutrients. Sediments were important to the stability of the coastline while the main agricultural practices, including rice production and fisheries, heavily relied on natural fertilisation that arrived every year.

He said that if blocked by dams, the lower supply of upstream sediments and nutrients would affect delta stability and productivity. It could lead to bank erosion and bridge collapses, disrupting the livelihoods of millions of people.

The study estimated that hydro-power projects on the mainstream Mekong would result in up to 75 per cent reduction in sediment inputs to the Mekong flood plain and delta, which Ketelsen warned would trigger a fundamental change to how the delta worked.

Marc Goichot, WWF's Greater Mekong Programme Co-ordinator, said the impacts of lower Mekong mainstream dams on sediment were intense, even far beyond those on fisheries and biodiversity.

During field observations conducted for over 2.5 years, the WWF team recorded evidence of increasing bank erosion on the coastline of the Cuu Long (Mekong) Delta.

While this can be associated with climate change, Goichot believed it was mainly caused by dams plus sand extraction.

Experts have noted that while the Mekong was a trans-boundary river, developing hydro-power dams was still very much done on a unilateral or bilateral government basis initiated by private developers, most of whom are from China, Thailand and even Viet Nam itself.

This appeared to be the opposite of international practices that the mechanisms of managing a trans-boundary river had to be agreed at the top level among governments first.

Ketelsen said the best approach was to establish a regulatory authority which had capacity in terms of institution and finance to enforce appropriate management of the river.

At the moment, the Mekong River Commission involves all four LMB countries. While initially established as a framework for mutual discussion on the Mekong River, it is still a voluntary agreement.

"This is the next step, but international lessons show that it will take a long time," he told Viet Nam News.

The Mekong River, which passes through six countries from China down to Viet Nam (China, Myanmar, Laos, Thailand, Cambodia and Viet Nam) is one of the few remaining international rivers undammed over much of its length.

Source: VNS

Vietnam, Mekong River, hydro-power, VNMC