Seen at The Festival of the Tree

...if you would be happy all your life, plant a garden - Chinese proverb

Wednesday, 10 February 2010

ABC of Weather: Drought

The definition of drought differs across the world: here in the UK an absolute drought is defined as a period of at least 15 consecutive days where there's no more than 0.2 mm of rainfall over that time. In other areas (such as Libya or Mongolia in China) this would be considered quite rainy! There an absence of rain over 2 years is needed before it's considered abnormal, rather than our two weeks.

Living through the legendary drought of 1976 has made me particularly aware of this weather extreme. I'd just started studying geography A Level at the time which was following a new syllabus with lots more practical work. I chose a couple of weather related projects to count towards my exams because I found it such a fascinating topic.

My first project looked at soil infiltration rates (a posh term for how quickly water soaks into soil) on different types of soils in our garden before and after rain. My other one was keeping a weather diary. How much rain actually fell during the soil infiltration project? ...None. How many weeks of exactly the same hot, sunny weather did I record in my diary? ...Six. That's 42 different ways I had to find to explain what was happening i.e. high pressure from continental Europe blocking our usual rainy weather from the Atlantic. Luckily the seventh week was rather different, otherwise I reckon I would have gone bonkers!

As a gardener I'm also interested in physiological drought, where there's sufficient water but it's temporarily unavailable. We've seen this happen more frequently than usual this winter owing to its severity: the soil's water's been frozen and everything in the garden subsequently droops, particularly my Violas. They soon recover if the temperature increases sufficiently during the day. At other times, particularly in summer the same thing happens when the rate of water leaving a plant via evapotranspiration exceeds the water it can take in via its roots. This often happens on a hot, windy day. This time, the plant wilts in the daytime, but recovers overnight, when evapotranspiration ceases. Vigilance is especially needed with anything newly planted out as their roots have not had the time to establish and seek out water lower down in the soil.

Today, gardening on a limestone enriched clay soil sounds like I shouldn't have many problems with drought and I suppose it does mean I don't have to water as often during the summer as say someone gardening on sand. However, it seems we only need to have just a few days of sunshine for my soil to turn to what seems like concrete and for rather alarming cracks to appear. I react by frantically raiding the compost bins and pouring as much organic matter into the cracks as I can in a vain attempt to close them, so that my plants are kept happy. It might not be much of a solution, but at least I feel I'm doing something positive and I am getting some organic matter into the depths of my soil in addition to my autumn round of mulching everything.

How's the weather with you today? It's very cold, but sunny here. 1pm: Now it's snowing!

For more Delicious D's, Do visit the ABC Wednesday blog.

Image courtesy of prozac1 via freedigitalphotos.net.

18 comments:

  1. I must say I learn a great deqal from your posts. I wasn't familiar with the different definituions of drought, e.g.

    On behalf of the ABC Wednesday team, thank you!

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  2. It's sunny and cold, when it isn't trying to snow. But the garden is very wet, hence the title of my latest post, Bog Standard.

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  3. Interesting and informative post! I, too, always learn something!! Hope you have a great week!

    Sylvia

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  4. Hot, dry and concrete! And they tell it won't rain till April.

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  5. Wet, wet, wet...again. But we have been through drought conditions here, the worst classification for the US, extreme drought, two years running. Last year that condition was reversed and now we have flooding, going on year two. After planting all those xerics too. We shall see what survives, for they shall inherit the earth, here.

    Frances

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  6. I had no idea there were different types of drought.
    Even though we have had an amazing amount of rain here in Northern California the pundents are saying that we are still in a drought. It sure doesn't feel like it to me.

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  7. Beautiful ... although there is still water running under the garden from the mountains.

    Another interesting post - VP, thank you.

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  8. Excellent post, as always. This is a fascinating theme you've chosen, much for me to learn.

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  9. The weather here's utterly poisonous, vile, odious, execrable, hateful and loathsome. Not enough sun to bump up Wendy's (my greenhouse's) temperature, not quite cold enough for appreciable snow, nor yet warm enough for it to fall as ordinary rain.

    The wind is a bitchy north-easterly and today's high is forecast to be 3 degrees centigrade.

    All the snowdrops have gone into suspended animation; the ground is claggy and pasty, after weeks of deeper frost and my fingers and toes haven't felt properly warm since Christmas.

    Well, you did ask!

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  10. I particularly remember the drought here of '88. Everyone's lawn turned brown, and my father was gloomy because the crops were shriveling in the fields. This year we had the opposite problem--some farmers still have corn in their fields! No problem with drought right now as we have a half a foot of snow on the ground, and I can't even get out of my driveway.

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  11. Ahh, the summer of '76. I was 6, so having to go to stand pipes for water was an excitement rather than a drag. Today in Cheshire is sunny but very cold.

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  12. The summer of 76 seemed to last for ever, remember the grass verges turning yellow, it was like being abroad without the travel.

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  13. Blizzards! That's what we have at the moment. 1976 seems a dim and distant memory though I was very glad to see the rain when it came.

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  14. Darn - I got it wrong this week :) I started my first proper job in August '76 - remember that summer vividly. Bright and blue here today mainly but a few flakes of the white stuff late morning.

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  15. Ditto what Frances said! Stepping outside water squishes up...today not so much, it's frozen...but the big melt will come and that clay soil will be sticky and then dry as a bone! I love gardening!!! gail

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  16. Thanks to you I will think twice the next time I use the word drought! Informative!

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  17. Do you know, I've never thought about physiological drought, but now you've mentioned it it makes so much sense, and explains why my pansies are wilting! D'uh ... ! Silly me!

    I'm with you on the cracked clay soil. I have a boggy area all the way up the shady side of my garden during winter (when it's not frozen!) but come summer the grass will die because it's too dry. AND we've just paid huge amounts of money to landscapers to rectify the problem and it's still there!

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  18. Hi everyone - I'm so glad you're finding this series interesting. I'm having so much fun doing it!

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