DUBLINERS have been warned that a new water supply must be found or they will face rationing.
Dublin City Council said the restrictions will have to be imposed unless it gets approval for its proposal to extract water from the River Shannon.
Demand in the greater Dublin area, which takes in households in six local authority regions, has been outstripping supply.
Figures released for 2009 showed regional demand stood at 540 million litres a day, whereas production stood at 518 million litres.
City engineer Tom Leahy said the supply is on a "knife-edge" every day and taking water from the Shannon is the one option that recommends itself.
He said this plan stood "head and shoulders above the rest".
Mr Leahy pointed to the situation Dubliners found themselves in in 1996 and 1997 when there was "daily water rationing".
"It could be a return to that," he warned.
His comments echo those of Dublin city manager John Tierney, who said last month the capacity of the rivers in the Dublin region to supply water is limited. "We need a new source because demand for water is increasing and will continue to increase," he said.
"Demand is expected to increase to 800 million litres a day by 2031 and we are planning now to meet the expected demand," Mr Tierney added.
The council is seeking to extract about 350 million litres of water a day from the Shannon. The plan includes a proposal for an eco-park built around a reservoir at Garryhinch in Co Laois.
The reservoir could be filled when the Shannon is flooded and used to store water during dry periods, according to a council report.
Mr Leahy said the supply would also serve Tipperary, Laois, Offaly and Kildare, as well as Dublin.
In all, the local authority examined 10 "supply options", including desalination, using groundwater supplies in neighbouring counties and extracting from the River Barrow.
However, the recommended option was taking water from Lough Derg on the Shannon.
The estimated capital cost of the project is €470m, while the operational costs would be €8m a year, rising to €15m by 2040.
The Shannon Protection Alliance group was established to oppose the scheme, while politicians in the midlands, such as Mary O'Rourke, are also opposed to taking water from the river.
A planning application is expected to be lodged in 2012.
Due to the scale of the project, it is likely to be 2020 before it would be completed.