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  The Straits Times 25 Jul 05
Underground reservoir beneath reclaimed land
 By Alexis Hooi
Changi site found suitable for storing water to fill 35,000 swimming pools

SINGAPORE'S thirst for water drove a team of researchers underground looking for ways to set up reservoirs beneath the island's reclaimed land.

Three years on, their efforts are yielding promising results. They have found soil conditions in Changi East, near the airport, suitable for storing huge bodies of water up to 30m down. Their preliminary findings also indicate that the area can accommodate enough water to fill 35,000 swimming pools. This, they say, is more than twice the amount in Upper Peirce Reservoir.

To check out the possibility of creating an underground reservoir, the group, led by researchers from Nanyang Technology University (NTU) and Stanford University in the United States, have to pump water into the soil to boost existing reserves below ground, known as groundwater.

Groundwater occurs when rainwater seeps through sand and rock layers and collects in small pockets underground. The task is to extract this water without disrupting the land and its surroundings.

The effort is one of the latest in Singapore's bid to diversify its water supply. These include augmenting supplies from the island's catchment areas and Johor with Newater and desalinated water.

The project is also one of several that national water agency PUB is interested in. Said the director of its 3P network department, Mr Yap Kheng Guan: 'PUB is continually on the lookout for new water technologies, as this is an integral part of Singapore's water sustainability efforts.'

The study is funded mainly by the Agency for Science, Technology and Research and is part of the Singapore Stanford Partnership, a programme which trains postgraduates in environmental science and engineering. Stanford's co-director of the programme, Professor James Leckie, said the sandy quality of reclaimed land made it more suitable for storing and removing water than the clay-rich, alluvial soil found in most parts of Singapore.

Tapping Singapore's reclaimed land to store water would be advantageous, said Prof Leckie, 66. It would lessen the need to set aside huge tracts of land for reservoirs. In addition, the water collected would contain valuable minerals and electrolytes that would enhance its drinking quality. 'One of the issues with reclaimed water is that you make it too clean, you remove everything,' he said.

The idea of storing water underground is not a new one. There are many such large-scale projects which have been operating for decades in the US and Israel. Orange County in California, for example, diverts the water it reclaims back into its groundwater supplies through ponds and lakes.

Drawing water from the reclaimed land would be unique though, said Prof Leckie, as it is shallow. In other countries, water is taken from hundreds of metres down. The challenge would be to keep the groundwater at a level where the available space was fully filled, but not to the point that it overflows.

At the Changi test site, more than 20 professors and students take turns checking water movement and quality with the help of storage tanks, pumps and sampling tubes. Piezometers measuring changes in water pressure and a mini weather station which helps track rainfall are also used. The team aims to submit its findings to its sponsors by the end of the year so the researchers can test the concept 'on a much larger scale'.
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