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VIETNAM: Saltwater Intrusion Adds to Water Woes
By Tran Dinh Thanh Lam
MEKONG DELTA, Vietnam, Jun 13, 2009 (IPS) - When they got out of bed one morning in April this year, the residents of Vi
Thanh City here in southern Vietnam’s Mekong Delta were surprised to find that
their water had become salty.
During the night, seawater had intruded into the Xa No canal, the main
source of water for the city of 200,000 people.
"Never in my life have I seen the water at Vi Thanh become that salty," said
76 year-old Nguyen Duc Bon, who was born in the city. "Our running water
has become so salty that we could not use it for cooking or for washing."
For daily use, inhabitants now have to buy fresh water supplied from the
nearby regional centre of Can Tho at high prices.
A dam is being built to prevent the penetration of saltwater, but it will not be
finished until 2011.
The area’s farmers also worry that their 37,000 hectares of paddies and
aquaculture could be totally destroyed by the seawater intrusion.
Many factors are being blamed for the change in water quality - hydropower
construction upstream on the Mekong River, global warming, and, ironically,
the network of small dams build by local farmers themselves to protect their
crops and aquaculture products.
There are two seasons in the Mekong Delta, the dry season, usually taking
place from May to November; and the rainy season, from December to April.
During the dry season, the water level of the Mekong is very low, enabling
the intrusion of saltwater.
During the rainy season, the Mekong overflows, flooding the delta but also
washing out the areas recently invaded by seawater.
To fight these floods, local farmers have built a network of dams to protect
their crops and aquaculture products - a method that in previous years was
acclaimed as an innovation because it helped farmers continue producing
even in the rainy season. Now, however, these dams have turned out to be
one of the causes of saline intrusion.
"Because of these closed dams, the overwhelming quantity of flooding water
is not retained [in the soil] and thus runs out into the sea," said Le Van Banh,
president of the Mekong Delta Institute of Rice. "When the dry season comes,
the small quantity of underground water that remains is not enough to stem
the invading seawater."
With global warming, April and May have become the hottest months of the
dry season -at a time when the Mekong’s level of water is at its lowest.
This has resulted in further seawater intrusion into the dried-out regions of
the Delta.
According to experts, seawater intruded up to 70 kilometres into some parts
of the Delta during the 2009 dry season - the farthest distance in the last 20
years. More than 20,000 hectares of crops throughout the Delta have been
immersed in saltwater.
"The areas covered by sea water extend year by year," Vu Anh Phap, of the
Institute for the Development of the Mekong Delta, told Radio France
International in an interview. "The salinity is also increasing."
Phap said that due to intensive irrigation in the Mekong region in the past
few years, especially by farmers in upstream countries like Laos and
Cambodia, the water level downstream has gone lower and lower and allowed
greater penetration of seawater.
Increasing dam construction projects upstream is also widely viewed as
another major cause of the water shortages downstream.
"These dams have reduced the water flow of the Mekong significantly," said
Ky Quang Vinh, head of the Centre for Natural Resources and Environment in
Can Tho.
"Water shortage has already occurred this year and will be more critical in the
coming years," added Vinh. "Even in time of floods, the water flow of the
Mekong in downstream has also been reduced."
In October, he said, it fell from 40,000 cubic metres a second to 28,000 cubic
metres a second.
The shortage of water in the Mekong emerged as a matter of significant
public concern in Vietnam in late May after the newspaper ‘Tuoi Tre’ cited a
United Nations report saying that dams built by China on the upper reaches
of the Mekong could have significant implications for Vietnam.
The report stated: "China’s extremely ambitious plan to build a massive
cascade of eight dams on the upper half of the Mekong River, as it tumbles
through the high gorges of Yunnan Province, may pose the single greatest
threat to the river." It went on to say the impacts of the proposed dam
development could include "changes in river flow volume and timing, water
quality, deterioration and loss of biodiversity."
These dam developments include the recently completed Xiaowan dam, which
at 292 metres is the world’s tallest and has a reservoir storage capacity equal
to all the other Southeast Asia reservoirs combined.
It is part of China’s long-term plan to direct water for irrigation and
hydropower to dry areas of the country.
"Dams are already big at heights of 15 metres, and 292 metres is
unbelievable," Vinh told ‘Tuoi Tre’.
"[Chinese] dam construction now joins hands with climate change to worsen
droughts, salinity intrusion, landslides and land erosion," Ngo Dinh Tuan,
chair of the scientific council of the South-east Asia Institute of Water
Resource and Environment, told ‘Tuoi Tre’.
"The Vietnamese government must create a national strategy for protecting
the river downstream, not only for the Mekong but the Red River [in
Vietnam’s north], as China has started to build dams on it as well," Tuan
added.
The U.N. report also found increasingly low water levels at several river basins
such as Tonle Sap in Cambodia, Nam Khan in Laos and Sekong-Sesan in
Cambodia and Vietnam.
(END)
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