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  • From: Thomas Allen <thallen@nwlink.com>
  • To: permaculture <permaculture@lists.ibiblio.org>
  • Subject: Re: [permaculture] Rain Measurements
  • Date: Mon, 6 Oct 2008 17:58:59 -0700

The table below if from a report I did on water quality in a municipal storm water detention pond in a suburb of Seattle. Rainfall for water year 2006-07 was 51.76 inches. There is some effect of runoff from yards and streets but the figures aren't much different for the outlet of a sand filter downstream of the pond. I also monitor a bog wetland to see what effect the development is having on the bog. So far, the county has opted not to dump residential storm water into the bog. Not suprisingly, pH levels are much lower in the bog, on the order of 4 or less at times.

--Tom Allen


Table 3.3.1 Synopsis of water quality findings for location WQ2
Constituent

Minimum Value

Maximum Value

Average Value



pH

5.80

7.30

6.08

Temperature, deg. C

0.50

14.90

8.58

Conductivity, umohs/cm

25.60

45.60

35.84

Spec. Conduc., umohs/cm

44.10

63.40

52.91

Salinity, ppt

0

0

0

DO, mg/l

1.15

9.54

2.87

TSS, mg/l

1.00

13.00

3.00

TP, mg/l

0.01

0.05

0.04

Calcium, mg/l

2.80

5.00

2.80

Nitrate + Nitrite, mg/l

0.02

0.47

0.02

TKN, mg/l

0.15

0.79

0.64

Ammonia N, mg/l

0.01

0.12

0.11

Alkalinity, mg/l

12.00

18.00

12.00

Chloride, mg/l

1.00

7.00

2.50

Sulfate, mg/l

1.20

3.70

3.70

Magnesium, mg/l

1.40

2.40

1.40

Potassium, mg/l

0.35

0.77

0.42

Sodium, mg/l

1.50

2.40

1.70




On Oct 5, 2008, at 8:34 AM, Toby Hemenway wrote:

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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