With neither natural aquifers nor lakes as well as little land to collect rainwater, Singapore's strategy has been to create estuarine reservoirs by damming the major rivers.
The newly completed Marina Reservoir and the upcoming Serangoon and Punggol Reservoirs are probably the last of these estuarine reservoirs.
Urban stormwater harvesting is best epitomised by Singapore's first reservoir in the city. Created by five rivers that run through the most densely-populated areas in Singapore, Marina Reservoir, Singapore's 15th reservoir and the first reservoir in the city, was formed by building a barrage across the Marina Channel.
With the largest and most urbanised catchment of 10,000 hectares (ha), that stretches from Ang Mo Kio to Kallang, Marina Reservoir can meet 10% of Singapore's current water needs.
The Punggol and Serangoon Reservoirs will further increase our total catchment area by 5,500 ha. These three reservoirs will increase our total water catchment area from half to two-thirds of Singapore by 2011.
Urbanised catchments are not new to Singapore as we have been collecting water from such unprotected catchments in denselypopulated areas since the 1980s, starting with Bedok Reservoir. It was a bold move then and even today, this is not the norm internationally. However, with today's advanced water technologies, all water can be treated to drinking standards – but at a cost.
This is why the public are constantly reminded to look at all waters as a precious resource, be it water in a tiny drain, canal, river or reservoir, as they are all part of our intricate water collection system. It is not a network for the public to dispose unwanted materials such as cups, paper bags, cigarette butts and various other forms of waste.
With all the major estuaries already dammed to create reservoirs, the next step is to move into tapping the minor catchments. PUB has pioneered a technology known as the Variable Salinity Plant to harness water from the remaining streams and rivulets near the shoreline. Due to their small sizes, it is not feasible to develop conventional reservoirs out of these streams.
With this new technology, PUB aims to increase the overall catchment area in Singapore to about 90%. Producing drinking water using the Variable Salinity Plant is more expensive than producing NEWater but cheaper than desalination.