Minister Mentor Lee Kuan Yew said with Singapore's diversified water strategy, there would be sustainable supply of water by 2061 when its water agreements with Malaysia ends.
Singapore could be self-sufficient in water, he added.
He was speaking on Tuesday at the ground breaking ceremony to dam the Marina Channel, making it the country's 15th reservoir.
When completed in 2007, this new reservoir in the city will store one-tenth of Singapore's current water demand, and enlarge the country's water catchment from half to two-thirds of the island.
MM Lee said: "With the PUB's diversified water of the four National Taps, there will be sustainable supply of water for all uses by 2061 when our Water Agreements with Malaysia ends. Singapore can be self-sufficient in water. The government will provide the infrastructure. It is up to Singaporeans to maintain the clean and green environment we live in."
Mr Lee noted that the marina lake can allow canoeing, skiing, and water taxis.
But before that, navigational safety procedures and pollution control measures will be needed.
MM Lee said: "Any litter thrown carelessly into the canals in areas even as far as Ang Mo Kio and Alexandra will finally end up in the Marina. That very thought should make us want to protect its cleanliness and to prevent all drains, canals and rivers that flow into it from being polluted."
The $226 million barrage will also control floods.
Low-lying areas in the city, Chinatown, Boat Quay, Jalan Besar and Geylang, will not have flooding unless there's exceptional rain coinciding with very high tides.
The flood-prone areas in Singapore will be cut from more than 3,000 hectares in the 1970s to just 100 hectares by the end of 2007.
Mr Lee also issued another challenge for PUB.
He suggested that it should think of extracting water from Jurong West although PUB had told him years ago that it was not possible because of industrial pollution in the water there.
Mr Lee believes it will be possible one day with new membrane technology as extracting water from the Jurong West sector will help increase Singapore's water supply.
And he hopes this can be achieved in the next 20 years.
Mr Lee said that from the 1930s till the 1980s, the Singapore River was an open sewer that smelt worse year by year.
So in 1977 he challenged the Environment Ministry to make fishing possible in the rivers in ten years.
He said: "The stench in the City was dreadful at low tide. In 1977, a blind clerk in Lee and Lee told my wife that he knew when his bus was approaching the Singapore River on his way to work."
"HDB helped more than 26,000 families resettled from squalid squatter huts into flats. Every remaining brick or concrete building left in the catchment of these rivers was connected to sewers. People stopped throwing rubbish into the rivers. 5,000 street hawkers were relocated into purpose-built food centres. 2,800 riverine industries were moved into industrial estates. A multitude of pig farmers, vegetable wholesale and lighter operators were relocated, the most pollutive industries closed down."
At the same time, anti-pollution measures were strictly enforced and soon marine life revived in the rivers and the marina.
MM Lee said: "We now have an effective system of refuse collection and disposal. People must help to keep our drains and canals clean so that we can collect clean rainwater. Sullage water is connected separately by sewers on to reclamation plants. We are building a Deep Tunnel Sewerage System to free up land and make the treatment of waste water more effective lowering the cost of recycling." - CNA
Finally... A dream came true