LONDON: Half of all households in Britain could face water restrictions unless exceptionally heavy and prolonged rain falls by April, water companies and the environment agency have warned.

Environment secretary, Caroline Spelman, will hold a crisis meeting of companies, wildlife groups and other river users next week after the Centre for Hydrology and Ecology (CEH) stated that the average rainfall so far this winter has been the lowest since 1972, and the English Midlands and Anglian regions (eastern England) have had their second driest years in nearly a century.

Thames Water, which supplies water to 14m households and businesses in and around London, on Wednesday appealed to customers to use less. "Groundwater levels in parts of our region are lower than they were during the 1976 drought, following below average rainfall for 18 of the last 23 months. It's now not a case of whether we'll be having a drought this year, it's a case of when and how bad," it said in a statement.

"We haven't had a lot of rain, and we haven't got a lot in the ground. We cannot rule out the possibility of restrictions over the next few months," said a spokesman.

Already parts of south-east England, Anglia (eastern England) and the east Midlands of England are officially in drought, raising the possibility of drought orders and permits being brought in within a few weeks. These could restrict farmers from drawing river water and prevent people washing their cars, filling swimming pools and watering playing fields.

"The current regional drought now extends across three winter periods with a range of impacts embracing water resources, agriculture and the aquatic environment. In the absence of an unusually wet late winter and early spring, it is now virtually inevitable that a significant degree of drought stress will be experienced in 2012. The magnitude of that stress, and its spatial extent, will be heavily influenced by rainfall over the next eight to ten weeks," said Terry Marsh, at the Centre for Hydrology and Ecology.

CEH data shows exceptionally low levels of ground water are being recorded in Lincolnshire and in Kent (east and south east England), the Thames Basin, Dorset in the south west and north Wales. But a dramatic split has emerged between south and east and north and west Britain, with Scotland receiving the heaviest rainfall since records began 100 years ago. Flood alerts were common in Scotland in January while river flows in many rivers in central and southern England have been notably depressed since the early autumn.

"A remarkably sustained exaggeration in the NW-SE rainfall gradient across the UK continued in January," said the CEH. "Much of central, eastern and southern England was again relatively dry and the development of the current regional drought now extends across three winter periods with a range of impacts embracing water resources, agriculture and the aquatic environment."

The light rainfall this winter comes on top of the two dry years in south east England. Last year was the driest in south-east England in 90 years, with only the summer recording normal levels of rainfall. One more dry winter could force then drier areas of the country will have to start looking at more drastic measures like desalination plants or transporting water from wetter areas in the north or west of the UK.

According to the UK Meteorological Office, there is only a 15 per cent chance of the of the next three months being abnormally wet.

By arrangement with the Guardian