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  • From: Toby Hemenway <toby@patternliteracy.com>
  • To: permaculture <permaculture@lists.ibiblio.org>
  • Subject: Re: [permaculture] Rain Measurements
  • Date: Sun, 05 Oct 2008 08:34:21 -0700

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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