Water companies in the south of England are considering emergency measures to preserve supplies after the second driest winter in 100 years.
Hosepipe bans are in force in parts of the south-east
Folkestone and Dover Water has asked the Environment Minister for the right to make customers install water meters.
Southern Water has asked for a drought order to cut water flow to rivers while Thames Water may impose a hosepipe ban.
The government said it backed water meters but was against bringing them in on a compulsory basis across the UK.
Southern Water, which has already imposed a hosepipe ban in Sussex, said its Weir Wood reservoir was less than half full.
The company said if the drought order was granted it would be able to reduce the amount of water it released into the River Medway.
The watchdog Watervoice has said it supports Folkestone and Dover Water's call for water meters.
Spokesman Andrew Marsh said: "Ultimately meters are the fairest system of charging.
"You pay for what you use and the system under which most water customers pay their bills - the old rateable value system - is archaic and loaded with unfairness.
"However, if you have a large family you will end up paying more and we would be concerned that there should be some sort of financial help."
Thames Water is starting to use its contingency reserve under north London - the company said it had not had to tap into its contingency reserve since 1997.
External affairs director Richard Aylard told BBC Radio 4's Today programme any hosepipe ban would be the first for the company in 15 years.
He said: "It depends on how much rainfall we get and it depends on how much water we can draw from elsewhere, but I would think that certainly there's a realistic possibility of a hosepipe ban by early August."
He said reservoirs were about 90% full, "but we have to balance very carefully the rate at which we draw down from those reservoirs because we can no longer take much water from the river or from our other bore holes, which are now very low".
The current shortage had occurred because of eight months of almost "unprecedentedly dry" weather, Mr Aylard said.
Environment minister Elliot Morley said: "We do support water metering.
"But in terms of national compulsory metering, while there are arguments in relation to resource management and also social equity, the matter of water shortage is not the same across the country.
"In the north east of England where you have the Kielder Reservoir, you have no shortage at all of water.
"That's not the case with London, the south and south east where there is increasing pressure on water resources and you do have to draw a distinction in relation to priorities."