What An Inch Of Rain Means

WE have all been battered by rain this winter, but this is nothing new as this except from a 1920 newspaper shows.


Our television screens have been jammed with flood scenes and experts talking about rising floodwater, giant pumps and how much rain is expected from the next storm to hit us.


But all this speculation is nothing new as the 94-year-old article shows.


It, too, mused about just what a downpour might translate in to and came up with this scenario about what a wet day really means when an inch of rain falls.


It urged us to picture a canal four hundred miles long, stretching all the way from London to Edinburgh.


It would be 24 feet deep and so wide that fifty vessels of 5,000 tons and more could steam abreast along its whole length….adding that every drop of water in this imposing waterway could be supplied by one-inch of rainfall over the United Kingdom.


The article, which was written long before modern meteorological equipment was available for evaluation, still correctly pointed out that people talk lightly about “an inch of rain” which is the familiar result of a wet day.


Yet Stye in Cumberland had 197 inches of rain fall in 1897-1898 while a bludgeoning 20 inches of rain fell in Darjeeling in a single day.


Still, all this pales when stacked up against Cherrapongu in Assam, India, where the rainfall for 1861 reached an unbelievable 905 inches.


The article points out that by comparison “a mere inch of rain seems but a summer shower”, yet, if spread over the country, it represents something stupendous.


The article adds: “It means, for example, that if we allow our 400 mile long canal to empty its water into the Thames at the rate of three million gallons a minute then a whole year must elapse before the last gallon is drained from its bed.”


Almost prophetically, the article goes on to choose, of all places, Somerset – famous for the 2014 flood devastation wrecked on the Levels – for its next observation.


It says: “Let us in fancy level the whole county of Somerset and convert it into a reservoir with stout embankments six feet high.


“Now let us drain into our vast reservoir all the water represented by an inch downfall over the British Isles. We shall then find that our reservoir or lake, of over 1,600 square miles, is full to the brim.


“If we convert the more familiar county of Middlesex, with its 178,000, acres, into a gigantic reservoir, we shall find that our inch of rain will fill it to a depth of 36 feet.


“Similarly, if we girdle the County of London (roughly 117 square miles) with strong embankments, and let our inch of rain flow into it, Greater London would be under water so deep that, if Cleopatra’s needle were dropped into it upright, it would be lost to sight eight yards below the surface.


“Our inch of rain would fill a reservoir covering the site of the City of London – a little over a square mile — to such depth that, if you were to drop 3,560ft-high Mount Snowdon into it, pile Scafell at 3,210 ft on its summit, put Skiddaw at 3,045 ft on top of Scafell then the topmost peak of these three lofty mountains would only be visible for a height of about 100 yards. The contents of our reservoir would be 1,723,042 million gallons.


“Let us fancy, essay the task of emptying our City reservoir and transporting its contents. For this purpose we will requisition every locomotive in the United Kingdom. We shall see that, if each engine makes a couple of journeys dragging its maximum weight, a whole year must elapse before the last wagon tank is on its way from the drained City.


“Every horse in the British Isles, each drawing a ton of water would have to make ten journeys daily for twelve months before our gigantic reservoir is empty. While the entire population of the world would each require the strength of a score of giants to raise the weight from the ground, for the average individual the load would weigh 4¾ tons.


“So vast is the quantity of water represented by the fall of an inch of rain over the United Kingdom that it would allow a distribution of 160 tons to every man, woman and child living on the earth today. The equivalent of 35,840 gallons which, spread over a year, would furnish a daily allowance of ninety-eight gallons.”


Time marches on and it is interesting to note that, 35 years after this article was written, a record was set at Martinstown in Dorset on July 18th, 1955, for the most rain in 24 hours. Eleven inches of rain fell in just 15 hours.


The highest rainfall recorded in Weymouth over 24 hours was also on this date with seven inches.


Bet you’ll never consider an inch of rain in the same way again!



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