[permaculture] Rain Measurements

Toby Hemenway toby at patternliteracy.com
Sun Oct 5 11:34:21 EDT 2008


Paul, hurray! You actually did the experiment! Enough hearsay, let's get 
some data.

7 ppm is a respectable brew, though. Enough to kick the water from pH7 
to 5.7, or about 20-30 times more acidic (log scale, right?). And 7 ppm 
is the effective dose for some herbicides, vitamins, and a lot of other 
stuff--a thousand times more than what's needed for hormones or dioxins. 
It means that in a 120,000 gallon tank there'd be about 8 pounds of 
stuff suspended in it, if my math is right. A fair amount.

Mollison does exaggerate a bit (as usual) when he calls rainwater a 
soup, but it adds up. That forest in New Hampshire I mentioned earlier, 
that's getting 8kg calcium per hectare from rain: figure a meter of rain 
a year over a hectare, that's 10,000 cubic meters, or 10 million kgs of 
water with at least 8kg, or 0.8ppm calcium suspended in it (surely a lot 
more, since the 8kg is just what's taken up by the forest), but it's 
enough to supply sufficient calcium to feed a forest. So even a thin 
soup makes a difference.

I'd be curious to see what pondwater, municipal water, wellwater, and 
other less than pristine waters have for TDS.

Thanks for the numbers!

Toby
http://patternliteracy.com



Paul Cross wrote:
> It is raining tonight in the mountains of north central New Mexico USA. 
> With so much talk of water on the list lately, I thought I'd measure 
> mine. Coming off the roof of the greenhouse and running down the dirty 
> gutters the water has
>
> 7 parts per million total dissolved solids
> 5.7 ph
> 14 millimhos electrical conductivity
>
> Makes me want to measure some distilled water for comparison.
>
> I hear a lot of talk about rainwater containing a lot of "stuff" in it. 
> Every time I have measured it at my house, it doesn't appear to have 
> much in it.
>
> Paul
>
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