Has this week’s rain helped the drought situation?
The weather has continued with an unsettled theme during the past week, with most places seeing further heavy downpours, but what impact, if any has this had on the drought situation?
I’ve had lots of people saying to me that surely the drought will end soon given the amount of rain that has fallen over the past few weeks. Unfortunately it won’t. For details on why it’s not enough to end the drought, have a look at an explanation in one of my previous blogs.
Today I thought that it would be interesting to examine the impact of the rain during the past week and see how this has influenced the water resources situation across England and Wales.
Each week, the Environment Agency produces a water situation report that highlights how much rain has fallen and how this has fed into the water systems. It’s very detailed and gives a good overview of the direction in which things are heading.
As you might expect given how unsettled the weather has been, the South West and South East Environment Agency regions have had around 80 to 90 per cent of their average April rainfall in the past week.
Looking at this month so far, up until 24 April, England and Wales as a whole has had 153 per cent of its April average rainfall with still a week to go. It’s been a very wet month and I have no doubt that once all the stats are finalised, a few locations could well have had their wettest April on record.
So what effect has this wet weather had on the water situation?
Soil moisture deficits
Soil moisture deficits are a measure of the difference between the amount of water actually in the soil and the amount of water that the soil can hold. In effect the greater the soil moisture deficit, the drier the soil and vice versa.
During the past week, the soil moisture deficits have responded to the wet weather well, with decreases for all parts of England and Wales. This means that the soil is becoming wetter and apart from the Midlands, South East and Anglian regions, the soils are close to full capacity.
The heavy rain during the past week has increased river flows tremendously, with increases at most sites across England and Wales. Normal or higher river flows are being measured at all but six locations. This is particularly good news for river environments as the low flows were resulting in poorer quality, less oxygenated water for plants and animals.
Reservoir levels have increased by up to 5 per cent at the majority of reservoirs during the past week, in response to heavy rain, with two thirds of reservoirs at normal or higher levels for the time of year.
This is one area that hasn’t shown improvement, with the majority of sites notably low or lower for this time of year. It is hard for rain to reach deep down into aquifers at this time of year because evaporation rates are higher and growing plants take up a lot of water through their roots.
So it’s clear that whilst the wet weather this week has helped the water situation at the surface, there is still a long way to go before the groundwater situation deep down will improve. Wet weather during the next few months may offer some help to groundwater levels, but it’s next winter’s rainfall that will prove crucial.
In the shorter term, the weather looks like staying very unsettled through the weekend and into next week – especially for England and Wales.
On Sunday a deepening area of low pressure will develop over the Bay of Biscay and head northwards towards us. Whilst there is some uncertainty in the detail, it could bring 25-50mm of rain across parts of England and Wales with a risk of localised flooding. It’ll also bring strong winds, with gusts of 50-60mph possible to coastal areas.