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Growing capital feels the thirst
  • | VNS | October 29, 2012 07:21 PM

Ongoing urban expansion and growth in the capital has necessitated the diversification of water sources from its long-term sole dependence on underground water.

 
 Workers at a water treatment facility run by the Hanoi Water Co Ltd.
A prospective alternative source could be the so-called "surface water" - water collected from a network of nearby rivers, as stated in a Prime Ministerial decision on water resources planning towards 2030 for the city.

According to forecasts by the municipal People's Committee, total water consumption per day would be about 1.2 to 1.5 million cubic metres in 2020, 1.9 to 2.3 million cubic metres in 2030 and 2.6 to 3.1 million cubic metres in 2050.

Hanoi is endowed with abundant surface water which has been extracted for use since the French occupation around a century ago. However, perpetual extraction of underground water to cater for growing demand had resulted in negative impacts including depletion and quality deterioration.

The situation would only become worse if underground water continued to be the major source, senior scientists warned.

Director of Vietnam's Environmental Science and Development Institute Le Trinh said that rapid urbanisation had increasingly disrupted the cycle of underground water.

"Normally, underground water is replenished by rainfall, but the urban area has been quickly filled with concrete buildings that in turn prevent a remarkable amount of rainfall from returning to underground aquifers. Instead, it goes into the sewers," he explained.

Trinh said if water was extracted at a faster rate than it was recharged, it would result in a lower level of underground water. Once it fell to a certain threshold, it would allow pollutants to enter the aquifers and the pollution would then be irreversible.

Some evidence of these incidents have been recorded.

According to a report led by Professor Tran Duc Ha of the University of Civil Engineering conducted in 2010, about 20 percent of the wells had degraded and needed replacing. Some aquifers in low-lying areas in the south-eastern part of the city had already been contaminated with nitrate.

Tong Ngoc Thanh, director of the Northern Water Resources Planning and Survey Union, confirmed this but said the level was under control and contaminated water could still be treated with technology.

But Trinh insisted that if underground water was extracted at a huge volume, the negative impacts would be all the more prominent.

"The long-term impacts would be land subsidence on a large scale as has been demonstrated in Bangkok," he said.

Hanoi has 20 factories and 15 stations that pump water from more than 280 wells, the majority of which are in the southern part of the Hong (Red) River. The current capacity of the whole water supply system is only 730 to 800 million cubic metres per day, well short of the forecast demand of 1.2-1.6 million cubic metres per day in 2020.

"That figure does not include the amount lost to leakage that could be as high as 30 percent of the total water being transported within the pipe system," Trinh said.

The scientist, who is also the chairman of the Vietnam Association for Environmental Impact Assessment, said that the need to find alternative sources of water therefore was imperative and a network of nearby rivers appeared to be a promising source.

He said the big rivers including the Hong and Da rivers had a relatively high volume of water which could provide a steady supply. What was more important was that the pollution in those rivers could be easily treated.

The Da River Water Plant is the first and only plant in Ha Noi so far to exploit water from a river. It is operating at a capacity of 300,000 cubic metres per day and is set to double that.

While it may take time to develop a fully-fledged system of plants that deal with surface water, we may tap into new sources of underground water, recently found at depths of 197 to 447 metres in the southern part of the city.

The Northern Water Resources Planning and Survey Union, in a ten-year project, has located a new Neogen aquifer which holds a huge volume of water of high purity. Its volume is estimated to be so big it may be possible to extract up to 1.64 million cubic metres per day.

"If there are economically viable measures to tap into this huge source, it will make a remarkable contribution to the city's total water supply," the union's chairman Thanh said.

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