It has been an extraordinary year of weather so far, there’s no doubt about it. After 3 very dry months here in Dorchester, our rivers like the Stour, the Avon and Piddle were showing record low flows at the end of March heading on for one in fifty year events.
A couple of days ago, returning to Dorset from Sussex I was amazed to see the Test, Avon and Stour had all burst their banks and the Stour in particular was flooding into fields into which it rarely ventures even in the middle of the “wet” season. It was a spectacular site to see hundreds of acres of floodplain under water between Canford and Wimborne, though I would imagine the farmers whose crops had just disappeared under water would have other words to describe it.
So far here in Dorchester we’ve had a stonking 178mm of rain in April, with more to come this evening. That compares with 116mm in the 3 previous months, and last April we had – 8.75mm!It’s a long time since we’ve had such a wet month – if I have time to go back through the records I’ll provide an update but it may well be a record wet April down here.
Has it helped the drought? Probably not that much, particularly here because we rely on groundwater from aquifers deep underground for our water and these take many months to recharge, from water filtering through soil and rock. At this time of year most of the water from rainfall is either taken up by vegetation or evaporates and little if any reaches the aquifers. This means the hydrological year is split into two phases – a period when rainwater reaches the aquifer – October to April, and the warmer, growing months May – September when it doesn’t.
It reminded me of the value of semi-natural grasslands which are so much better for recharging aquifers because their soils hold the rainfall allowing it to trickle through into the underlying rock. In arable fields and improved grasslands, especially where the soil is compacted, rain flashes off the surface and is quickly lost (along with soil) into ditches, streams and rivers.
Perhaps the water companies will be able to make use of the extra water available from our rivers and reduce pressure temporarily on the aquifers. And at least those rivers where low flows were causing major problems for wildlife through low oxygen levels will be much healthier. Farmers with their own reservoirs will be able to pump the excess out to fill them, for use later on in dry periods.
In the longer term, as climate change increasingly bites, it seems likely that the dry phase will lengthen and the recharge time will be shorter. Unlikely as it seems in this wettest of months, the long term prospects are that we will all have to live with less water and use it more wisely. More intense rain is another consequence of climate change and we will also have to change the way our landscapes are managed, to capture every last drop of precious rain when it does come.
This could be good news for semi-natural grasslands and other valuable habitats as it will hopefully mean the surviving fragments are increasingly valued, and new habitats are created for their functional value.
Don’t forget today is your last chance to vote for us in Mark Avery’s Poll of wildlife charities – so far we have a fantastic 83 votes and we’re in an amazing 6th place – let’s see if we can get past 100 votes. Thanks to everyone who’s already voted.
Director of Conservation