LONDON -- Huge swaths of Britain remain stuck in drought after two abnormally dry winters despite the country's having suffered its wettest April on record last month, with little letup in the often torrential downpours enduring into May.
The rains in some areas have been so heavy that the Met Office, the United Kingdom's weather service, was issuing extreme weather warnings on a regular basis from mid-April onward. The Environment Agency has been warning of rivers about to burst their banks or of flash floods because the parched soils after an abnormally warm and dry March could not absorb the sudden supply of water.
"April was the wettest month in the U.K. since records began in 1910. There were quite a lot of weather warnings in place during the month," a Met Office spokeswoman said.
At 121.8 millimeters (4.8 inches) of rain, the United Kingdom saw a nearly doubled amount of the usual amount of rainfall in April. March, by contrast, was the fifth-driest on record, with about one-third the usual amount of rain.
Many drought orders -- restricting the use of water by households and businesses as well as farmers -- were not lifted after last spring, which was also exceptionally hot and dry. But the orders were extended and expanded earlier this year after the dry and mild winter.
And despite the recent heavy rains, those drought orders remain in force in the southeast, southwest, east and center of England as well as Wales -- the same areas where most of the rain fell. This prompted some to observe wryly that this must be the wettest drought on record.
"We still have a drought in some areas. The recent rains have made a difference in some river levels, and soils are also wetter. But groundwater is still very low in many areas," said a spokeswoman for the Environment Agency, an arm of government. "We need a sustained period of rain right through the summer to get us back up to decent levels."
Pouring water on a dry sponge
She added, "Heavy rain on parched ground is like pouring water on an old, dry sponge. Much of it will bounce off. The sponge needs to be wet in order to hold the water. Farmers are in a much better position than they were thanks to the rains. River levels have risen, soil moisture has increased and their water reserves have been replenished. But aquifers take much longer to fill."
The Met Office says the warm, dry March and cold, wet April are due to the vagaries of the jet stream -- a narrow band of fast-flowing wind blowing from west to east in the high atmosphere that has a tendency to move around and change track, taking the weather with it.
After predicting a "barbecue summer" in April 2009 only to find July and August a complete washout, the Met Office no longer makes long-term weather forecasts, contenting itself with a much less tricky month-ahead view. Thus the agency declines to say when the current wet spell may finally end.
But experts say it will take torrential rain for the next four to five months to return crucial groundwater levels -- on which much of the densely populated south of the country depends -- to normal.
"There has been a suggestion -- not ours, but we agree with the figures -- that we would have to get double the normal summer rainfall right through to the autumn in order to really deal with the accumulated groundwater deficit," hydrogeologist Andrew McKenzie of the British Geological Survey told ClimateWire.
"That would not only be very unpleasant, but improbable. The odd month of above-average is quite likely, but for it to be sustained for months at double the average would be highly improbable.
"Over the last two winters, the amount of rainfall we have had has been down 20 to 30 percent on what we would normally have. Most of the recharge of groundwater happens over the winter. We lost three to four months of groundwater recharge in total over that two-year period," McKenzie explained.
"We have now had the wettest April ever, and you might think that would go halfway to recharging the groundwater. But we also had a very dry March, and the soils had already switched to summer, dry mode and had to switch back," he added.
The long hangover of droughts
A very wet May, he estimates, would still reduce 25 to 30 percent of the groundwater deficit built up by two years of drought. And it is not just the groundwater levels that are a problem. Many reservoirs are also heavily depleted.
At Bewl Water reservoir, some 50 miles south of London and the largest expanse of water in southeast England, measuring 13 miles in circumference, levels have recovered to 60 percent of capacity thanks in large part to operator Southern Water pumping in river water after the rains. It had fallen to one-third of capacity in December -- the lowest level in a quarter of a century.
Even so, water levels are still 90 percent below the average for this time of year, compared with the past decade. They are also 80 percent below the average May minimum since 2000.
The reservoir is a key water supplier in the heavily populated southeast of the country.
"We're moving in the right direction, and the rain is a big help. But our sources have to recover from one of the driest periods of weather on record. To help them do this, we will be continuing with our water restrictions on hose pipes and sprinklers in Kent and Sussex," said water manager Meyrick Gough of Southern Water.
According to the Environment Agency, groundwater levels remain "exceptionally" low in 11 aquifers.
Dozens of rivers across southern and central England are deemed to be at either "notably" or "exceptionally" high levels -- with risk of flood in some cases if the rains do not end. Yet, in much of the same regions, groundwater levels are marked as "notably" or "exceptionally" low.