SINGAPORE - What do a national prison service, a primary school, a multinational aero-engine firm and a community group have in common? They all won this year's Watermark Awards.

National water agency PUB whittled down the 35 applications they received to the Singapore Prison Service (SPS), Tampines North Primary School, Pratt & Whitney, and the Nee Soon South Clean and Green Committee.

The annual Watermark Award recognises individuals and organisations for their contributions to the conservation of Singapore's water resources.

One of the winners of this year's award, the prison service, changed the water fittings in all of its prison clusters and workshops, and this contributed to it using 12.8 per cent less water in 2016 than 2013.

The deputy commissioner of prisons and chief of staff at the service, Ms Shie Yong Lee, said she was proud and thankful for the award.

"It's an affirmation of not just the efforts of our staff, but also our inmates and our partners," said Ms Shie.

She noted: "Winning this award doesn't mean that the journey ends here. We will continue to support our water conservation and other environmental sustainability efforts."

This is the 10th year of the awards, and the ceremony will take place on March 31 at the Marina Barrage.