More on the bad drought story I wrote about yesterday, an AP piece with heart-rending stories about drought in Kansas. Standardized precipitation index data showing that, since December, conditions in the area in question have been “near normal”:
It’s not like there hasn’t been drought in the United States, just not in Kansas in any significant measure, where the story originated.
(From the NOAA SPI page)
There are some extra facets to consider. The type of drought the article is meaning is really an agricultural one, not meteorological (which is what the SPI is measuring). “Drought” means different things to different people. Going into the ag drought concept are factors above and beyond the depth of rainfall – how sunny it’s been (evaporative demand); groundwater levels (this is not rainfed ag we’re talking about). A further level of complexity which you should be happy with is variability – there will be less available water if it comes in a shorter overall period than if the same amount fell more slowly.
While I’m not defending the journalism, we should look for the pudding’s proof in the eating, not the recipe.
Daniel –
Fair enough. Though the Palmer index, which captures evaporation with its strange magic black box formula, shows much the same thing in Kansas:
http://lwf.ncdc.noaa.gov/oa/climate/research/prelim/drought/palmer.html
Yeah, after I left the comment I looked for it (and for a map to tell me where Kansas was). Palmer says “same as average”, while SPI says “a little wetter”.
I’m embarassed to admit I was doing the same thing trying to figure out which climate divisions were in Kansas.
A further data point: the last six months (ending at the end of Sept.) were unusually warm in southwestern Kansas, a bit outside of one standard deviation. March, April, May and June had daytime highs that averaged way above normal in Ashland. July was cooler than normal.
This actually raises a really interesting underlying point about the problems associated with the drought measures we use. I like SPI because you can slice it up timewise however you want. But you’re right in that it only does precip and ignores temperature (though it’s highly correlated with SPI at around nine months in duration). Palmer is useful because everybody’s familiar with it, and because it ostensibly captures the temperature component. But it’s such a black box! What we really need are actual soil moisture measurements, which they’re talking about funding as part of the new National Integrated Drought Information System.
A black box indeed. And certainly soil moisture measurements are an obvious improvement. But I would stress again for North America: ag isn’t rainfed here. River and g/w extraction go to irrigation. These both extend the spatial and temporal extent on which the farmer depends. Spatial, because river flow accumulates water downslope (g/w similarly). Temporal, because aquifers are being depleted.
Daniel –
Thanks for the comments. I admit I’m on thin ice here. I don’t know Kansas ag at all, so I don’t know how much is rainfall dependent and how much based on groundwater pumping and irrigation. This suggests groundwater depletion from the Ogalla aquifer in southwestern Kansas is huge, which suggests both a near-term drought buffer and a long-term disaster in the making.
This says the majority of Kansas ag is rainfed, not irrigated. But I’d bet there’s an east-west gradient to the thing, with western Kansas far more dependant on irrigation, because of…
This shows western Kansas on the John Wesley Powell 20 inch per year bubble – a bad place to do agriculture without irrigation.
But the bottom line for me in all of this is that we should properly think of drought as an extreme case, not the dry side of the normal precipitation distribution. As a policy matter, stumbling along in this country taking wet years for granted and then shreiking “drought” when it gets dry, we’re not doing it right. I don’t know enough about Kansas to be sure this is such a case, but it’s a pattern repeated over and over again in the land “beyond the 100th meridian” that Powell tried to warn us about.
Yes, a good back and forth. I shall dig up some numbers on relative roles of irrigation and rainfed water supply, and if I can, also distinguish between river and g/w extraction. I’ll try Kansas first. (I agree with the W-E gradient. I didn’t realise Kansas broke 1000 mm/yr.)
As for crying bloody drought when things start to become unfavourable, sure, suck it up, so to speak.