[at-l] Filtering water.

[stephensadams at hotmail.com (Steve Adams)]

Sly,

Reference your post, dated 5-9-03, where you advise, “I find it hard to 
believe that "most" of the water along the trail is contaminated.  Afterall, 
much of it is naturally filtered springs and since it's a ridge trail many, 
if not most, of the sources are above agriculture and industrial use.”

You raise an interesting point; if most water sources are higher in altitude 
than the contaminants, how do they become polluted?

There are at least two major reasons I find your point interesting; I’ve 
wondered about this myself, and; I don’t know the answer, either.

Presumably, when water evaporates and rises it is “purified,” or at least 
decontaminated for purposes of human consumption, by the sun.  I suppose 
with “Acid Rain,” precipitation captures the elements suspended in the air 
in which droplets form, and through which the droplets pass.  Presumably, 
the components of giardia, etc., aren’t suspended in air and, thus, wouldn’t 
be introduced into groundwater through this process.

The water table does not necessarily follow the earth’s contours.  I have 
seen depictions of rises in the water table.  This means subterranean water 
can flow uphill.

I visited an intermittent waterfall which originated from within a mountain. 
   The waterway would be without water, then suddenly water would flow with 
a dramatic volume, then stop.  There would be a pause, then the process 
repeated.  (There was no on-off switch visible.)

This was a siphon.  Water was obstructed within the mountain, impeding its 
flow.  Water collected within the mountain, during the “dry” phase of the 
waterfall at the exit, until a sufficient amount accumulated.  The weight of 
accumulating water pushed water before it up within the air shaft in the 
mountain until it spilled over the obstruction.  The water would then gush 
downward, creating a vacuum within the closed system, emptying all the water 
that had accumulated.  There would be no more water, flowing from the 
waterfall, until sufficient water accumulated again.

I lost touch with a hydrologist whom I once knew; I bet he’d know.

Your point remains interesting; how do contaminants enter all that water?

Steve

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