SINGAPORE - The Public Utilities Board (PUB) has begun supplying additional potable water to Johor after the Malaysian state's water regulatory body put up a call for assistance.

With the current dry weather severely affecting water levels in Johor's Sungai Layang dam, the Badan Kawalselia Air Johor (Bakaj) had requested that PUB provide an additional six million gallons per day for a month.

This is to supplement the water supply in areas serviced by the dam, and increases Singapore's supply of treated water to its closest neighbour to 22 million gallons daily.

PUB, in a press release on Monday (June 6), said it had agreed to help, and started injecting the additional supply from the Johor River Waterworks - which it operates in the state - last Saturday (June 4).

It stressed that the arrangement was temporary and subject to regular review.

Supplying the additional water will also not affect Singapore's water supply in the short-term.

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But PUB warned that the dry weather was cause for concern as it has affected water levels in the Linggiu Reservoir, which dipped to an all-time low of 33 per cent from 40 per cent in April.

The reservoir is operated by PUB and improves the yield of water from the Johor River, from which both Johor and Singapore draw water.

"PUB is monitoring the situation closely," it added.

Despite facing its own shortages, Johor's state minister in charge of public works pledged last month that it would continue to supply water to Singapore.

Under the 1962 Water Agreement, PUB is entitled to draw up to 250 million gallons of water from the Johor River daily. In return, Johor is entitled to a daily supply of treated water of up to 2 per cent - or five million gallons - of the raw water it supplies to Singapore.

Over the years, PUB has - at Johor's request - supplied about 16 million gallons of potable water per day to Johor. The last request by Bakaj from Aug 14, 2015, to Jan 8 this year saw PUB increasing its supply by an additional five to six million gallons - similar to the current arrangement.

"We remain committed to working with Bakaj and relevant agencies to ensure a reliable supply of water for both Singapore and Johor," PUB concluded.