UK drought prospects revisited
It’s being reported that the environment secretary has called for a drought summit next week in the face of drought fears during the coming months, so how have we got to the point where we are now?
Back in December, I reported on how there were increasing concerns that unless rainfall through this winter was significant, drought conditions across southern and eastern parts of England looked increasingly likely during 2012.
At that point, some central and eastern parts of England had had their driest first ten months of the year on record.
However, the lack of rainfall wasn’t a problem everywhere. Wales along with northern and western parts of England actually experienced wetter conditions, with rainfall generally above average.
The reason for this huge contrast in rainfall between north western and south eastern parts of the UK has been frequent occurrences of blocking weather patterns, where the jet stream alters position.
The jet stream is a fast moving ribbon of air high up in the atmosphere that determines where our rain-bearing weather systems go.
Normally in the UK, the jet stream snakes across us throughout the year, bringing spells of wet and windy weather, with drier and brighter interludes.
However, during the past 18 months there have been notable spells where the jet stream has been pushed to the north west of the UK, steering the bulk of any rainfall to these areas and away from the south east of the UK.
The impact of this has been extremely low reservoir levels in the Midlands, South East and Anglian regions, with some water companies having to apply for drought permits to use river water to top up reservoirs.
What’s the current situation?
During the period 1st December 2011 to 23rd January 2012, Met Office rainfall figures show that central, southern and eastern parts of England – the areas most sensitive to rainfall in the coming months – have typically had around 85% of their average rainfall.
But whilst this rainfall has helped the situation slightly, the Environment Agency says that this still falls well short of the levels required to ensure a full recovery of water resources.
Their latest weekly water situation report explains that although reservoir levels have risen in response to the rain that has fallen in the past two months, some are still below normal for the time of year.
Ground water levels are also not doing so well, with over three quarters of indicator sites in England and Wales below normal for the time of year and a third exceptionally low.
What’s the forecast for rain looking like?
In the shorter term forecast for the next few weeks, it looks like the weather across the UK will be fairly changeable, with wetter and windier spells, interspersed with drier and bright ones.
There does tend to be a trend to the greatest amounts of rain falling towards the north and west of the UK, but this would normally be expected.
The Met Office also provide longer term forecasts for contingency planners, which look at trends in temperature and precipitation and the likelihood of them being above or below average.
Importantly, however, it is worth stressing that such forecasts are a developing area of science and at the moment can only be used as an approximate guide.
The latest Met Office three month outlook for February – April this year says that drier than average conditions are very slightly favoured, giving only a 15% chance the rainfall amounts will fall into the wettest of its five categories.
In effect, there isn’t a particularly strong precipitation signal either side of average – which is why these forecasts need to be used with care.
There’s certainly no doubt that the amount of rainfall during the next few months will be crucial in determining the level of drought that some parts of the UK may experience this year.
If you’re a farmer or someone who relies heavily on water supplies and are concerned about the implications of a drought, I’d be interested to hear your story. The easiest way to contact me is via Twitter – @liamdutton