East Anglia is bracing itself for the worst drought in living memory as the continued lack of rainfall threatens to dry up precious supplies of domestic and agricultural water.

Anglian Water has warned that if current weather trends continue, the region could be heading for its most severe shortages since 1921, raising the prospect of its first hose pipe ban for 20 years.

The prolonged period of below-average rainfall now stretches back almost 18 months, with eight out of the last 12 months seeing significantly less precipitation than the previous year.

In the west of the region it has drained rivers and reservoirs to well below capacity, while in the east the extended drought is even threatening groundwater boreholes which are usually more resilient to seasonal changes.

And while farmers are already working on ways to preserve dwindling supplies vital for irrigation, householders have been told they must take urgent action now to save water for the peak demands of the spring and summer.

Anglian Water (AW) spokesman Ciaran Nelson said: “The rainfall figures show that the only year in the last 100 when it was lower than this was in 1921. So we are looking at something which could potentially be the worst in living memory.

“We cannot predict the weather, but we can plan for its worst impacts. We are already thinking about what we might have to do in the summer. It has been 20 years since we last issued a hose pipe ban in the AW region. We would love for it not to happen, but we are planning for a worst-case scenario just in case.

“What I would say is that we have already managed to get through one dry year without having to do it. That is the kind of resilience we have had to build into the network for long periods of dry weather.

“This is not about scare-mongering, it is about letting people know that the things they do now can genuinely make a difference on what the summer looks like.”

Jim Bacon, a forecaster with Norwich-based Weatherquest, said the groundwater shortages stemmed from a period of exceptionally dry weather in the critical period leading up to the winter.

“Looking at 2011 overall, then the rainfall in East Anglia and Norfolk in general is running at 65-75pc of the long-term average,” he said. “You would normally expect the autumn and winter months to contribute, but for the autumn we were running at a staggering 30-50pc of average. That is the crucial part of the year when the water soaks into the aquifer and evaporation rates are at their lowest. We have already lost half a winter’s worth of rain, and instead of making up the losses we’ve actually added to the deficit.

“It would have to be a hugely wet spring to bring things back to average and for it to be anything other than a concern, certainly for farmers and growers. It is a continuing problem and the answers are more to do with managing limited resources than worrying about how much rain we are going to get.”

The Environment Agency sets limits on abstraction licences in order to preserve the ecological health of rivers. But in November, the EA granted Anglian Water a temporary drought permit to refill its reservoirs by extracting extra water from the Nene in Northamptonshire, even though the river’s threshold had been reached. Any environmental impact will be closely monitored.

Most of Norfolk and Suffolk’s water comes from groundwater abstraction, while the western counties are more dependent on rivers flowing into reservoirs, which are most vulnerable to drops in rainfall.

Mr Nelson said reservoir levels on average are about 74pc full, but there can be large variations across neighbouring catchments.

“It is fair to say that our concerns are slightly worse in the west of the region, but that is not to exclude areas like Norfolk and Suffolk from being in the danger zone,” he said.

“The boreholes are more resistant to seasonal changes. If we had seen things return to average towards the end of last year we wouldn’t be so concerned. But the winter recharge period has started later and is taking longer than usual which means we cannot be confident that borehole sources will be at the levels where we need them to be in the spring, when we need to call on those resources.”