How Singapore’s Marina Barrage keeps fresh water in and the sea out
by Grace Chua
SINGAPORE — On a sunny Saturday afternoon here, children scamper about on a broad green lawn, families lay mats down for picnics, and a man maneuvers a kite in the sky.
This is no ordinary lawn; it’s three floors up on the roof of a pump house next to Singapore’s first urban reservoir, Marina Bay.
“It’s an easy place to fly kites,” says Erich Chew, 45, whose day job is running a small IT business, but whose passion is aerial photography by kite (“Compared to a drone, there are more surprises”).
“It’s quite high,” he says, “and at this level the wind is usually quite good.”
Next to the pump house, a dam known as Marina Barrage stretches across the mouth of a wide channel. On one side of the dam is salt water, leading out to sea. On the other side is the fresh-water reservoir, a shimmering blue backdrop to some of the most expensive real estate in Singapore — tall office towers, a conference center, hotel and shopping complex and the popular Gardens by the Bay botanic garden, all built after the dam went up in 2008.
For a single piece of infrastructure, Marina Barrage does a remarkable number of things. It holds back the ocean, offering low-lying areas flood protection during storms and a hedge against sea-level rise. It stores fresh water from a massive catchment zone, helping the city-state wean itself off water imports from Malaysia. And on a crowded island of 6 million people, the lawn and the reservoir itself have created some much needed recreational space. It’s a popular place to run, bike, sail boats, and take wedding photos.
Today, other cities have their eye on the barrage’s multipurpose functionality. In a May report on protecting Manhattan from storm surges, New York City’s Economic Development Corporation cited Marina Barrage as an example of flood protection that accomplishes other goals as well. Although New York is considering a levee rather than a dam, the report said, “the Singapore example is worth noting” because it “provides space for a mix of uses and not just coastal protection.”
Marina Barrage is only the latest step in the evolution of Singapore’s water management.
Like many tropical cities, Singapore had a long history of floods. In December 1978, the island was buffeted by some 512 millimetres (20 inches) of monsoon rain in a single day. Cars stalled in chest-high waters, pigs and chickens drowned or escaped, and a thousand people had to be evacuated from their homes. Seven people died.
Singapore’s young government — independence came only in 1965 — was left casting about for a flood-control solution. Damming the broad mouth of the Singapore River, the major artery winding through the island’s southern half, seemed like a potential fix.
It would take years of work to make it possible. At the time, boats still plied the river and went out to the coast, so closing up the river mouth wasn’t realistic. Plus, the Singapore River and other major rivers had to be cleaned up. Upstream areas were still pretty rural, with villages, farms, boat repair yards and street hawkers along the riverbanks discarding oil and food scraps into the water. The rivers were filthy with pig-farm effluent, food waste and sewage; damming it all in then would only have created a giant cesspool.
The cleanup began. Some 4,000 squatters living near the rivers were resettled into public housing. The pig and duck farms were shut down; a growing economy meant farmers could find alternative jobs. Boats and repair yards were moved to port terminals elsewhere on the island. And about 5,000 street hawkers were coaxed to base themselves in centralized markets.
The river cleanup laid the groundwork for the dam to eventually be built, says Dr. Cecilia Tortajada, a water policy expert at the Lee Kuan Yew School of Public Policy at the National University of Singapore.
“It meant the sacrifices of people who had to leave their homes and resettle,” Tortajada says. They “may not have understood the reason for the decision at that point in time.” It also meant writing and enforcing anti-pollution laws, she adds.
But even by the late 1980s, it was not yet clear that the proposed reservoir could be a viable water source. The technology needed to treat water from an urban catchment to achieve safe drinking-water standards was not yet cost-efficient, says Koh Boon Aik, senior project director at Singapore’s water agency, known as PUB. “But by 2003,” he says, “we knew.”
By then, the agency was using membranes to reclaim wastewater and treat it to become ultra-pure, to lessen the city’s reliance on outside sources of fresh water. Finding new sources of water was also a necessity: Between 1980 and 2000, the city’s population doubled to 5 million people.
Work on the barrage started in 2005 and finished three years later. It cost $226 million Singapore dollars to construct, or roughly $135 million U. S. at the time. It’s an impressive structure, but building it was nothing compared with the effort required to clean up the waterways. “Constructing the barrage was just the cherry on top,” Tortajada says.
As the reservoir was slowly desalted and flushed, its brackish water turned fresh. Its ecology slowly shifted — saltwater fish and crabs swam out with the pumped-out water, while freshwater species began to appear, studies by local biologists revealed. Today, the reservoir harbors fish such as tilapia, while the surrounding greenery has lured smooth-coated otters, a native species here.
The city reservoir will never be clear as a rural lake, says biologist Peter Ng of the National University of Singapore. “The habitat is sediment-rich most of the time,” Ng says. “It is open so it is exposed to the hot sun, and the banks are concretized in most parts and not very good for plant growth.”
One thing it has been good for is flood control. Singapore has weathered big storms recently without the calamitous results seen in 1978, although it’s hard to isolate Marina Barrage’s impacts from other concurrent drainage projects. Thanks to the dam and other improvements, the amount of flood-prone land in all of Singapore now amounts to just 40 hectares (or about 100 acres.) That’s a far cry from the 3,178 hectares vulnerable to flooding in 1970.
When heavy rain swells the water level in the reservoir, fresh water is released into the sea. If it’s low tide, gates can be opened and water flows out; at high tide, the barrage’s seven huge pumps can flush out 40 cubic meters of water per second. “We will never prevent floods totally,” says Tan Nguan Sen, PUB’s head of sustainability. “But we can always minimize the occurrence of floods.”
Linking recreation and conservation
Other challenges remain, says PUB’s Koh. As the land around Marina Bay continues being developed, silt from construction sites is washed into the reservoir when it rains. Meanwhile, environmental chemists have found contaminants such as pesticides and nonylphenol in the reservoir’s sediments and deeper waters, apparently from runoff or leaking sewer lines.
While current water-treatment methods can remove these, the water agency is set on monitoring water quality, using stations that float in the reservoir and transmit water-quality data to headquarters wirelessly.
Litter is another problem — a side effect of opening the area to recreational use.
The Marina Barrage and its pump house were not originally planned as a recreational space, Koh admits, but their recreational value became clear as urban plans were drawn up in the 1990s for the growing financial district in the downtown Marina area.
Today, an average weekend sees dozens of joggers and cyclists around Marina Bay. Tourists visit the nearby Gardens by the Bay, with its iconic funnel-shaped “supertrees,” connected to the Barrage by footpaths. The annual National Day Parade, held to commemorate Singapore’s independence, has been held next to Marina Bay several times. Road races are held here, along with sailing lessons, and other activities in and around the reservoir.
Now, allowing people to play in and around reservoirs is a deliberate public-engagement strategy: The water agency hopes that these recreational pursuits will help people to literally see the value of conserving water.
And any open space is valuable in a dense, land-scarce city. “It’s important that this is multi-purpose,” says Tortajada, “because projects like this cost a lot.”
So what can other countries or cities learn from Singapore’ experience?
The PUB’s Tan says having public agencies work together to clean up pollution, enforce legislation and draw up city plans was key to developing an urban flood-control barrier and reservoir. “A lot of countries want to follow us,” Tan says. “But we always tell them: The thing is to clean up the catchment. The engineering part can always be solved.”
Tortajada says long-term planning was vital, along with continued operations and monitoring once such a project is in place.
“Singapore was not born rich and does not have plentiful resources,” Tortajada says. “But it has planned to get the resources it needs to grow.”