Water supplies serving a quarter of a million people are already in drought or on the verge of drought as the prolonged dry spell continues.
Irish Water is warning the shortage is worse now than when restrictions were introduced during the summer drought of 2018.
The utility expects to announce a formal water conservation order or 'hosepipe ban' within the next fortnight if conditions do not improve.
After the driest spring on record in many parts of the country, and a similar start to the summer, Met Éireann has said no significant rainfall is expected any time soon.
Night-time restrictions are already in place on the Aran Islands and other parts of Galway, Tipperary and Westmeath, while there are major concerns over supplies in Donegal and parts of Wicklow.
However, the Greater Dublin Area is likely to be hit with a hosepipe ban first as the region's water usage has rocketed during lockdown.
Irish Water said the surge in Dublin's demand on Saturday was the equivalent of an extra 200,000 people.
A major worry is the anticipated added demand when businesses emerge from lockdown next week with deep cleaning required before opening and ongoing additional cleaning needed thereafter.
Conditions now are even more challenging than during the historic drought of 2018, when restrictions ran from July to the end of September.
The ground in most places is drier now with a soil moisture deficit of 80mm compared to 60mm in July 2018, which means it will take more rain to replenish the soil before any surplus can feed into rivers and lakes - the source of most of our drinking water.
"Raw water sources are falling quicker than in 2018," Irish Water confirmed.
Referring to its drought indicator, the utility said: "The current SPI (standardised precipitation index) would indicate that we are at lower levels than in 2018."
Domestic demand, which is two-thirds of national demand, is also higher than in 2018 with more people at home and doing gardening. Increased handwashing and cleaning are also likely contributors.
A hosepipe ban prohibits non-essential use of water, so hosing gardens, washing cars or other large items, and filling paddling pools or ornamental ponds is ruled out.
During the 2018 restrictions, Irish Water received dozens of weekly reports of people flouting the regulations and made calls to advise householders they were in breach. But while the law allows for the issuing of €125 fines, none were handed out and there were no enforcement proceedings.
The company said: "Irish Water was grateful to the public for their support. It was really encouraging to see the public's response to the order and the conservation measures that people were taking in their homes and businesses.
"Irish Water is confident of a similar level of support from the public in 2020."