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Last Updated: Monday, 13 March 2006, 18:29 GMT
Why water levels have run so low
Reservoir storage in England and Wales
Thames Water has become the latest water company in the South East to ban hosepipes. So why are some areas experiencing such low rainfall levels?

For some parts of the UK, the past winter has been one of the driest since the winter of 1963/64.

In the Southern region, levels are down to 54% of capacity. After normal winter rains, levels would generally be much higher.

The lack of rain for the South East this winter has been related to a large blocking ridge of high pressure across Northern Europe.

The high has acted to block weather systems from moving across the UK after crossing the Atlantic.

And while the seasonal forecast for the next three months is predicting above normal rainfall for the north-west of Europe, this should only be taken as a guide and not a certainty.

The months between October and April are traditionally when rainfall tops up reservoirs, rivers and groundwater, replenishing supplies before the summer.

Imperfect storm

Atlantic storms are one such source of valuable rainfall, and these moisture-rich weather systems usually cross the UK during autumn and early winter.

This winter, such storms have passed to the north or the south of the country, and as a result the associated rainfall did not fall where it was needed most.

Good rainfall totals in October 2005 helped to increase water resources across the country, including the South East, but there was below-average rainfall in subsequent months and water levels fell again.

England and Wales rainfall

While rainfall in February and March have improved and increased reservoir levels a little, that will do little to avert the prospect of water shortages this coming summer.

And while the reservoirs of some companies have not been too badly affected, many have suffered from low water levels in their aquifers.

Aquifers - also known as ground reservoirs - are underground layers of rock that collect water.

Many water companies rely on aquifers for significant amounts of their water supply.

Kent and Sussex are the counties most at risk from drought in summer 2006, and here it would take a prolonged spell of above-average rainfall between now and April to avert water shortages.

According to the Met Office, there are equal chances of dry, normal or wet weather for the south of England over the next few months.

On that basis, everyone must seriously consider the likelihood of continued dry weather through the spring.



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