The greater Dublin area faces acute water shortages later in the century, with new studies indicating that levels in the Liffey could be half what they are at present.
The Irish Climate Analysis and Research Units (Icarus) at NUI Maynooth estimates that summer levels in the rivers Boyne and Rye Water will be between 40 per cent and 50 per cent lower than now because of global warming.
The Rye Water in Co Kildare is the main strategic tributary of the Liffey and is indicative of what water levels can be expected to be in the Liffey, which supplies 80 per cent of Dublin's drinking water needs.
Icarus is forecasting that the availability of drinking water could be reduced by 20 per cent as early as 2020, and by 50 per cent by the middle of the century unless new water sources are found.
According to Icarus forecasts, temperatures will rise here by 2 degrees Celsius by the end of the century, and summer rainfall levels will be reduced by 40 per cent.
Poor summer runoff is likely to increase the risk of drought.
Dr Conor Murphy from Icarus said planners would have to look not only at a new water supply for the Dublin region, but other options such as desalination, the development of groundwater sources and increased reservoir capacity.
The population of the greater Dublin area is forecast to reach 2.4 million by 2031, a million more than at present. "We're in the unfortunate position that the most severe impacts from climate changes in summer are coinciding with, first of all, where population is greatest, and where there is the greatest potential for future growth," said Dr Murphy.
"You are getting these two characteristics competing head-on. That's for a water system that is reaching the limits of its capacity already. We cannot suddenly start adapting to climate change in 30 years' time."
Dublin City Council is currently looking at two major new water supplies - desalination, and extraction from the Shannon at Lough Ree.
The council has forecast that the present demand of 550 million litres of water a day will increase to 880 million litres by 2031.
The hydrological models of the impact of river extraction from the Shannon will be delivered to the council's consultants next month, and will be available to the public in October.
The council's deputy city engineer, Tom Leahy, says the models will address the concerns of Shannon locals about the potential impact on water levels in the area.
The Shannon Protection Alliance (SPA) believes the extraction of 450 million litres of water from Lough Ree on a daily basis would have disastrous consequences.
Alliance PRO PJ Walsh says any decision to proceed with the Lough Ree option is a "done deal" and could come as early as next year.
"By presenting it as a 2016 project, they [the council] are making people less aware of it than they should be. They have stated repeatedly that the decision will be taken in 2008. This has to be stopped now."
