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  • From: rmhoward@omninet.net.au
  • To: permaculture <permaculture@lists.ibiblio.org>
  • Subject: Re: [permaculture] Sydney drinking water
  • Date: Mon, 22 Sep 2003 08:52:49 +0800

On 18 Sep 2003 at 8:31, Gilbert Grace wrote:
>
> "...I do not know if I would be prepared to drink rainwater falling on
> Sydney roofs, however. A look at airflow map for the Sydney region
> indicates that polluted air is pushed out to sea, depending on winds,
> and can then return and settle south-west of the metropolitan area.
> That puts it over the Campbelltown-Camden region, where the
> inhabitants get to sample three-day old city air. Whether this air is
> so polluted that it could contaminate rainwater, even to a small
> amount, is unknown. Clearly, what we need is the testing of rainwater
> in different regions of Sydney over the different months.Perhaps one
> of those first-flush diverters that channel the first rainwater wash
> over the roof into the stormwater drain would be a good idea.
>

In Perth there is a distinct daily sea breeze which occurs in summer. In the
morning,
summer easterlies take pollution out over the sea and this pollution is
bought back on
the sea breeze in the afternoon. Air studies in Perth in the 1980's
established that
there was a hlaf hour daily spike in pollution levels as the sea breeze came
in with
pollution levels rising to up to 10 times the average daily level.

In Sydney the situation is somewhat different since there is no distinct sea
breeze.
However, the Perth measurements do indicate that, when the winds turn due to
diurnal
effects( ie a sea breeze) or because of meteorological conditions i.e. a
change in the
weather, then the maximum period of pollution is at the time of the wind
change.

If the wind change is associated with rainfall then first flush diverters
will also work as
pollution revention agents. taking the most polluted water with them.
(Assuming where
talking about NOx, SO2 and similar water soluble pollutants and dust).

Bob howard




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