'The expiry of the 1961 Water Agreement will have no impact on our water supply and water tariffs,' Dr Yaacob Ibrahim told Parliament during the debate on his ministry's budget.
Singapore has developed enough local sources to replace water imported under the 1961 agreement, which allows the drawing of up to 86 million gallons daily from Johor's Skudai and Tebrau rivers.
Singapore's three local sources of water are its reservoirs, desalination and Newater.
By the end of this year, when the Punggol and Serangoon Reservoirs are ready, the city state's water catchment will increase to two-thirds of its total land area. It has also ramped up production of Newater and desalinated water, which together now meet 40 per cent of total demand.
A second water agreement with Malaysia, signed in 1962 and which allows Singapore to draw up to 250 million gallons daily from the Johor River, will expire in 2061. Singapore aims to be self-sufficient in water by then.
In his reply to questions posed by MPs Lim Wee Kiak (Sembawang GRC) and Ho Geok Choo (West Coast GRC), Dr Yaacob gave a sense of how Singapore intends to reach water self-sufficiency.
It will open a second desalination plant in Tuas by 2013, which will add 70 million gallons of water a day to its supply.
It will also build a sixth Newater plant by 2030. Such plants use membrane technology to reclaim water from used water sources.
'By 2060,' Dr Yaacob said, 'we plan to increase our desalination and Newater capacities to be able to meet up to 30 per cent and 50 per cent of our water needs respectively.'
'We will continue to introduce Newater into our reservoirs, especially during dry spells such as the one we experienced in February last year,' he added.
When the first water agreement expires on Aug 31, Singapore will hand over the water treatment plant it now runs in Johor to Malaysia, free of charge and in good working order.
That was agreed to as part of a landmark land swop deal the two countries signed last September.
Dr Yaacob said that having a robust water supply is only half the story.
'We must continue our efforts in water conservation,' he said.
Households have cut down their daily domestic water consumption from 165 litres per capita in 2003 to 154 litres today.
The long-term target is to bring it down further to 147 litres by 2020, and 140 litres by 2030.
Some 70 per cent of public-sector buildings have been certified as water-efficient buildings. In the private sector, 86 premises have submitted plans to achieve water savings of up to 10 per cent.