Estuary reservoir will boost Singapore supplies
A 300m long tidal barrier is under construction in the estuary of Singapore's main river. When completed, the Marina Barrage will create a unique freshwater reservoir in downtown Singapore, as Yap Kheng Guan of PUB explains.Singapore comprises a main island and numerous smaller islands with a total land area of about 680km2. Annual rainfall averages about 2400mm, and rain falls almost all year round, but is most abundant during the November-January monsoon.
Being a small island nation, Singapore has limited natural resources, including land and water. Collection of rainwater is one of four sources of water contributing to Singapore's water supply. The other three sources are imported water, reclaimed water (or NEWater) and desalinated water.
PUB is the national water agency of Singapore constituted to optimise the use of Singapore's limited water resources. PUB's mission is to secure an adequate supply of water at an affordable cost for Singaporeans.
The Marina Barrage
The Marina Barrage is a tidal barrier that will be built across the 350m wide Marina Channel, which is located at the southern tip of Singapore. When the barrage is completed in 2007, it will keep seawater out of the 240ha Marina Basin.
Through natural flushing from monsoons over time, the saline water now in the Basin will be gradually displaced and turned into a body of freshwater, which will augment the local sources from water catchments.
Spanning an area of 10,000ha or one-sixth the size of Singapore, the Marina catchment is currently the largest water catchment among all the other reservoirs in Singapore. When the Marina Barrage is completed, Singapore's water catchment areas will increase from half to two-thirds of Singapore.
Stormwater within the Marina catchment is drained by five main rivers/canals into Marina Basin. They are Singapore River, Stamford Canal, Rochor Canal, Kallang River and Geylang River.
The Marina Barrage reflects PUB's proactive approach in expanding Singapore's sources of water supply by employing the latest water technologies. The project is a bold and innovative way of expanding Singapore's local catchments (and maximising rainwater collection) into a highly urbanised catchment. Urbanised catchments, such as the Marina catchment, are traditionally not suitable as water catchments due to their inherently higher levels of pollution which results from the presence of human activities.
Ten-year cleanup programme
The Marina Basin and its rivers, which are clean today, were once dirty and polluted. In 1977, Singapore embarked on a ten-year inter-Ministry effort to remove the filth and stench from the rivers and canals, and to bring back aquatic life:
- Residents of squalid squatter premises were resettled into public housing
- Street hawkers were relocated into purpose-built food centres
- Riverine industries were moved into industrial estates
- A multitude of pig farmers, vegetable wholesalers and lighter operators were rather relocated or, in some cases of extreme pollution, told to cease operation.
Once littered with squatter huts and polluted by riverine activities such as trading, transport, boat building and repairing, muddy river banks have become beautiful riverside walkways, sandy beaches and landscaped parks.
Not only have fish and aquatic life returned to the rivers, but people too have returned. Activities like fishing, jogging, walking, swimming, boating and water skiing are now common features of our river scenery.
With the Marina Basin kept clean and the advancement in water treatment technology in recent years, there is confidence in developing the Marina catchment, one of the most urbanised and densely populated parts of Singapore, into another water catchment to add to the source of water supply for Singapore.
The Marina Barrage project is a uniquely Singaporean 3-in-1 initiative. Beyond just a simple dam to create a reservoir to augment Singapore's water supply, it will also achieve two other objectives of acting as a tidal barrier for flood control and creating a new body of freshwater at constant level that will be a major lifestyle attraction of our city centre.
There are pockets of low-lying areas in the city such as Chinatown, Boat Quay, Jalan Besar and Geylang. These areas are below or slightly above high tides and are therefore prone to flooding whenever heavy rain coincides with high tides. The barrage will act as a tidal barrier to keep out high tides, with crest gates and pumps to release excess stormwater during heavy rains.
The crest gates that will be built across Marina Channel to keep out seawater will be non-obtrusive and easy to operate. When heavy rain coincides with low tide, the crest gates will be lowered to discharge excess stormwater to the sea.
However, when heavy rain coincides with high tide, it is not possible to do so, as sea water will flow into the reservoir and contaminate it. In this situation, the excess stormwater will be pumped out into the sea instead of operating the crest gates. Pumping of excess stormwater is carried out by six water pumps with a total capacity of 240m3/s and a seventh pump to act as a standby.
The Downtown at Marina Bay is envisioned to be a lively, vibrant and exciting waterfront destination. Marina Bay and the adjacent promenade areas have already been successfully used for activities such as the F1 Power Boat Grand Prix, outdoor concerts and dance parties, and arts and cultural events.
With the expected completion of the Marina Barrage at the mouth of Marina Channel in 2007 and the relocation of the commercial vessels in Marina Bay to the New Clifford Pier outside Marina Reservoir, the water body will be suitable for staging water-based events and performances, and international watersport competitions.
The stable body of water in the Marina Basin will enhance its value as a recreational resource for Singaporeans and tourists. Recreational activities such as power boating, pleasure boating, canoeing, kayaking, sailing, water skiing and wind surfing, can also take place, in addition to the water taxis and pleasure cruises that ply the area today.
PUB recognizes the value of the Marina Basin as an important body of water in the heart of our city. We are actively working with our 3P partners such as other public agencies, non-governmental organisations (such as Waterways Watch Society) and sports associations to make it a vibrant waterbody, which can be shared and enjoyed by all.
The success of this 3-in-1 project requires our 3P sectors' involvement to keep the basin clean and beautiful for enjoyment. The Marina catchment encompasses some of the most densely populated and urbanized areas in Singapore.
From anywhere within the catchment, a piece of litter thrown carelessly into the drains or waterways will eventually find its way to Marina Reservoir, thereby dirtying the very body of water meant for all Singaporeans to enjoy. It is therefore important that everyone plays a part in not littering and in keeping the waterways clean.
Also playing an important role in maintaining the cleanliness of Marina Reservoir are the construction sites in the Marina catchment. It is important for construction sites to implement effective earth control measures to ensure that the water discharged from these sites into the drains or waterways does not remain silty or muddy.
If allowed to enter Marina Reservoir, the silty or muddy water will dirty the water body and turn it brownish, rendering it aesthetically unpleasing for people to enjoy the pristine water and the vast varieties of water activities. PUB has embarked on an educational programme tailored for our 3P partners to bring across to them the importance of good erosion control measures and the negative impact of brown water being discharged into the waterways.
Workshops on earth control measures are being conducted for public agencies who are developers of major construction projects. PUB has also been working closely with our private sector partners and associations in conducting seminars and courses on earth-control measures for their members who are contractors.
This is a slightly edited version of the paper presented at the International Desalination Association World Congress in September 2005.