Thursday, 21 June 2018

Drought History

Is there someone in your family tree who farmed on the Prairies? Did they settle in the period from the opening of the West by the railway in 1885 and the First World War. If so they were fortunate to have arrived during a period with a favourable climate—only minor droughts.
As you can see from the bar chart the period was preceded and followed (the dirty thirties) by multi-decadal droughts. We can only imagine how different development would have been without the favourable climate.
The bar chart is taken from the SaskAdapt webpage on drought. There is no source given for what is described as Annual Precipitation Variation From the Average. I'm sure there were no precipitation measurements for the first two-thirds of the period shown so suspect it's derived from an analysis of tree-ring data at
The second bar chart is from the same tree-ring dataset for the point nearest to Ottawa. Negative values are drier than average. Unfortunately the tree-ring data used isn't very close to Ottawa so I'm skeptical about how well it represents the city; the year 1870 that saw a major Ottawa Valley Fire although drier than average was not especially so according to the PDSI.

Drought is a serious problem for Canada's farmers. 60 per cent of our croplands and 80 per cent of our range lands are in dry-land areas. Wildfires flourish.

Drought can reduce hydro-electric output, hamper navigation and recreational opportunity.

These days while the extent of drought in Canada is well monitored the forecast reliability remain very limited and is no substitute for being prepared for the inevitable next drought event.

What do we know about droughts, devastating for a country where the population relied on the productivity of the land?

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