25 May 2012

What impact has this week’s sunshine and heat had on our water resources?

Whilst many of us may be pleased that the warmth and sunshine has arrived, it’s important not to forget that southern and eastern parts of England are still officially in drought, with hosepipe bans in place in certain areas.

The wettest April on record may have meant a welcome top up of our water resources, but this doesn’t mean that they are completely back to where they should be – especially in terms of groundwater levels.

Two weeks ago the Environment Agency announced that south west England, the Midlands and parts of Yorkshire were no longer in drought. However they also stressed that should an extended dry spell of weather happen again, the drought area could once more expand.

So has this week’s dryness, warmth and sunshine had any notable impact on our water resources?

Each week, the Environment Agency produces a water situation report that takes a detailed look at all aspects of water resources across England and Wales.

The latest report notes that this week has been the driest since the end of March, which shows just how wet it has been during the last six weeks. Up until the 22 May England and Wales as a whole has had 83 per cent of the average May rainfall.

Soil moisture deficits

Soil moisture deficits have increased across all parts of England and Wales this week, which means that the amount of water in the soil has fallen. Despite some drying of the soils, they are still wetter than would normally be expected at this time of year.

However, spring and summer are times of the year when evaporation rates are high due to the hours of daylight being greater and temperatures higher. Also, with plants growing, roots take up a lot of water from the soils. So if the dry and warm weather continues the amount of water in the ground could once again fall quite quickly.

River flows

There was a remarkable increase in river flows during April with some rivers going from exceptionally low to notably high in the space of a few weeks.

Following the dry weather this week, river flows have decreased at all measuring sites, but are still normal or above everywhere except the River Kennet which has fallen back below normal.

Normal flows mean that the river environment is no longer stressed, with plenty of flowing water to support the life that lives within and around them.

Reservoir levels

Reservoir stocks have seen little or no change from last week. Most of the reservoirs across England and Wales are normal or higher for the time of year, although there are a small number that are below normal in the Midlands and south east England.

Groundwater levels

The groundwater situation is a little more varied, with eleven sites below normal or lower for this time of year. Whilst some water has managed to percolate down to the water table, it hasn’t managed to compensate for the general lack of rainfall during the last 18 months.

Groundwater levels are particularly sensitive in south east England and East Anglia because here, 50 per cent of the public water supply comes from groundwater sources.

The crucial factor for improving the groundwater situation will be getting average or above average rainfall during the coming winter – the time of year when the main recharge takes place.

So given the latest information available, it appears that this week’s dry, sunny and warm weather hasn’t had too great an impact on water resources. However, if the dry spell continues for another week, which it could well do in some places, it will be interesting to see what next week’s water report has to say.

Don’t forget you can get the latest five day weather forecast on the Channel 4 Weather website or you can contact me on Twitter – @liamdutton

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