Marina Reservoir to be ready by year-end

But another dry spell may delay this as rain is needed to dilute salt content
Amresh Gunasingham, Straits Times 20 Apr 10;

The 10,000ha Marina catchment is the island's largest and most densely built catchment. It is about one-sixth the size of Singapore. -- ST FILE PHOTO

THE Marina Reservoir, which when completed will be able to supply up to 10 per cent of Singapore's water needs, is expected to be ready by the end of the year.

But another dry spell like the one just past could push its ready date to next year, as the reservoir depends, to a large extent, on rainwater to dilute its salt content, the PUB said.

Over the last 15 months, the reservoir's concentration of salt water has come down from around 35,000mg

per litre - which is typical of seawater - to around 2,000mg per litre today, PUB's director, water supply (plants) department Tan Yok Gin told The Straits Times.

This will have to be brought down further to around 100mg per litre before the reservoir can be considered suitable enough to be of drinking water standard, he added.

The timeframe for when this will happen, however, will be determined to a large extent by the amount of rain that falls over the rest of the year.

'The desalting process depends on rain bringing water to displace the seawater,' said Mr Tan.

Currently, the water in the reservoir, which is part of the iconic $226 million Marina Barrage built to boost Singapore's water supply while also alleviating flooding in low-lying parts of the island, is made up of a mixture of salt water and fresh water.

Since its completion in October 2008, the national water agency has used two methods to turn the catchment into a freshwater source: opening the nine tidal gates located at the barrage to allow sea water to flush the reservoir; and depending on rain to dilute the catchment's salt content.

But a repeat of the dry spell seen in February - the driest month ever recorded in Singapore's history with just 6.3mm of rainfall - will mean its conversion to a freshwater catchment is delayed.

Mr Tan also told The Straits Times that a 13.32km network of underground pipes is also being constructed, and it will be completed later this year, to pump fresh water from Marina Reservoir to the Upper Peirce Reservoir, which has a larger storage capacity.

'Once the water quality meets our target, it will be pumped to Upper Peirce for storage,' said Mr Tan.

Water will also be channelled for treatment at Chestnut Avenue Waterworks, near Bukit Panjang, before being returned to the reservoir.

With a catchment area of 10,000ha, or one-sixth the size of Singapore, the Marina catchment is the island's largest and most densely built catchment.

Together with two other new reservoirs - Serangoon and Punggol - scheduled for completion in the next few years, the Marina Reservoir will increase Singapore's water catchment from half to two-third's of the country's land area.