The fountains in Trafalgar Square could be switched off from next week as part of the hosepipe ban.
A Greater London Authority spokesman said:
"We are working with Thames Water on finding a sustainable supply of water that will allow the fountains to be used throughout a summer of celebrations in the capital"
"As we explore alternative options the fountains are currently being used for one hour a day at a low plume using an existing store of water that is expected to last for about a week. This is to enable the water cleansing systems to work."
Millions of homeowners have been banned from using hosepipes from today as drought grips parts of the country.
Deep underground, the drying-up boreholes of East Sussex show the extent of the UK's drought problem.
20 million people across the south and east of England will be hit by hosepipe bans that have come into effect since midnight.