Not every flooding event can be prevented, says PUB chief, as climate change impacts rainfall

SINGAPORE – With climate change expected to cause more erratic rainfall patterns, Singapore’s approach to dealing with flash floods has been expanded, said national water agency PUB chief executive Ong Tze-Ch’in.

The Government will continue to invest in drainage infrastructure, but on top of that, PUB recognises the need to build up societal resilience against flash flooding, he added.

“We have come to the realisation that we cannot possibly prevent every flooding event,” said Mr Ong, 50, in an interview with The Straits Times on Nov 28, as the country enters the rainy north-east monsoon season – the wettest period of the year.

According to Singapore’s third national climate change study, the growing amount of planet-warming gases in the atmosphere is expected to bring heavier, more intense and frequent storms.

In January, monsoon surges – weather events that happen during the wet phase of the north-east monsoon – dumped large amounts of rain over the country in a short period of time.

The first surge episode in early January led to a nearly three-hour flood in Jalan Seaview in Mountbatten, caused by the confluence of high tides and prolonged rain. Most flash floods here do not last for more than an hour.

“I think there is still a sense maybe that flash floods should not even happen in Singapore. But with climate change, from time to time, we can expect flash floods to happen,” he said, in his first media interview since he took over the reins of the agency in late 2023.

“We want to get to the stage where (a flash flood) is not such a shock as and when it happens,” he added. But a lot more work is needed to build the resilience of the populace, and the first thing is to adjust the public’s mindsets about flash floods here, Mr Ong noted.

Mr Ong was formerly the deputy secretary of resilience at the Ministry of Sustainability and the Environment, overseeing water and food policies between 2021 and 2023. In that role, he also covered communications, partnerships and engagement at the ministry.

That experience, he said, taught him that climate action requires inputs from all of society.

Mr Ong noted that investment in improving Singapore’s drainage system remains a key pillar of flood prevention. It was announced in February that

$150 million will be spent on drainage upgrading works

 in the 2025 financial year.

But with land constraints, there is a limit to how much more drainage can be built or expanded here, he added.

PUB has also undertaken the construction of more specialised flood-proofing infrastructure, Mr Ong said, citing the

recently completed Syed Alwi Pumping Station,

which features an underground tank in the low-lying Jalan Besar area.

It diverts storm water from Rochor Canal into an underground tank to prevent the area’s drains and canals from overflowing during a deluge.

Still, despite governmental efforts, residents, businesses and commuters in flood-prone areas also increasingly have to keep an eye on weather forecasts and flood alerts, and take steps to be out of the water’s reach, Mr Ong said.

Currently, PUB uses a few channels to update the public on potential flash flooding, including social media platform Telegram and vehicle on-board units.

But Mr Ong said the national water agency will continue to invest in new ideas to provide more accurate and far-reaching early warnings to the public.

For example, PUB announced in mid-November as part of its annual flood awareness campaign that it is working on tapping mobile phone signals to better predict places that may get intense rainfall.

This project, done with StarHub and water management solutions provider Hydroinformatics Institute, is targeted for completion by the end of 2025, with potential for islandwide implementation.

When it rains, rainfall can

interfere with cellular signals sent between telecommunication towers

. These interferences can be tapped to estimate rainfall intensity. With how ubiquitous mobile phones are, this data can augment the information from rain gauges located islandwide, said Mr Ong.

PUB also said in November that it will work to integrate

flood alerts

into

Google Maps and gradually

install 650 more water level sensors

islandwide by 2028.

PUB also started an annual flood awareness campaign in November 2024, as the country entered the rainy season. In its second run now, the focus is on educating the public about precautions they can take to avoid being caught in flood waters.

Asked what such action could look like, Mr Ong said: “If you’re a landed (property) owner, you put out barriers. If I’m a commuter, I adjust my plans. I don’t walk out into the heavy rain and risk being caught in a flood. If I’m a driver, I avoid the flooded area that I’m notified about, or I choose not to drive right now. To me, that’s resilience.”

Protecting Singapore’s coastlines from rising sea levels caused by climate change is also a relatively new area for PUB, with the agency designated in 2020 as the nation’s coastal protection agency.

Under Mr Ong’s tenure, PUB has done more public outreach on sea level rise and floods – from a series of community dialogues where participants could suggest coastal protection measures, to meetings where residents brainstormed ideas to better prepare for floods.

“The coast belongs to so many people. There are residents, there are companies, there are fishing enthusiasts, there are nature groups. And everybody would want some say into how they reimagine our coasts,” he acknowledged.

For example, taking in the feedback of Changi residents and nature groups, PUB

proposed to construct a raised platform

– such as a bund – farther inland of Changi Beach Park to ensure continued access to the beach and preserve the seagrass-rich shores.

Climate change could also put pressure on PUB’s primary role in the country – safeguarding Singapore’s water supply, Mr Ong said.

Of Singapore’s four main sources of water, two are exposed to the elements, making them vulnerable to fluctuations in rainfall. They include imported water from Malaysia – up to 250 million gallons a day from the Johor River – and Singapore’s 17 reservoirs.

The agreement for Singapore to import raw water from Malaysia expires in 2061. There is also limited space in the country to build new reservoirs.

Two other sources of water, NEWater and desalination, are more climate-resilient and are expected to provide a larger share of the local water supply in the coming decades, said Mr Ong. NEWater is produced by recycling and purifying used water and is currently mainly used for industrial processes and air-conditioning cooling purposes.

The country’s water demand is now about 440 million gallons a day. By 2065, this could nearly double, with the non-domestic and industrial sector accounting for about 60 per cent of water consumption.

“NEWater is essentially dependent on its input, the amount of used water that is generated by households and companies. As water demand goes up, the potential for more NEWater also goes up,” explained Mr Ong. “Where we can, we will maximise this source as much as we can,” he added.

Desalination – the process of producing drinking water from the ocean – is more expensive and energy-consuming, and its use will not be ramped up unless necessary, said Mr Ong.

Homes still have some way to go to reduce water use to meet the national target of 130 litres per person a day by 2030, as charted out in the Singapore Green Plan. In 2024, household water consumption crept up slightly, with each resident

using 142 litres of water a day

, up from 141 litres in 2023.

PUB’s chief highlighted three trends that are making it trickier to shave off the 10 to 12 litres – hotter weather, working from home and smaller household sizes.

“The same population split into smaller households would see greater water use. Once you have a household, there is a certain fixed water usage,” he explained.

The trend of flexible work arrangements post-pandemic diverts water use to homes, and with rising temperatures, residents would drink more and take more showers to beat the heat.

Mr Ong added: “These three trends are pushing up against our target... We continue to push towards the 130-litre target as best as we can.”

Singapore had a water price hike recently, when the price per cubic metre rose by 50 cents in total across 2024 and 2025.

When asked if water price is set to increase further amid climate change pressures on the resource, Mr Ong said: “Have you ever seen water price come down?”

“From PUB’s perspective, it’s important for us to recover the cost of producing water. We do need to (also) collect enough revenue so that we can continue to invest in future water infrastructure that we need,” he added.

With rising water demand, more infrastructure is needed, and that will come at additional costs. Mr Ong said: “We do take a long-term perspective to this... and that will mean water price increases from time to time.”