"Chris Barnes" wrote in message
...
George wrote:
Large ponds and lakes are a bit different because of the dilution
factor, and because there are usually inflow and outflow routes. If
they have inflow and outflow routes, then the pH can fluctuate during
times of heavy rainfall, but under normal conditions is relatively
stable. Having said that, large ponds and lakes in temperate zones tend
to stratify and then overturn with the changing seasons. Large ponds
and lakes in sub-tropical to tropical zones rarely overturn, and so
remain stratified for long periods of time, which causes a buildup of
gases in the lower levels, particularly of CO2 and H2S. Disturbing
those layers (say due to an earthquake or landslide/slip) can cause a
release of large quantities of built up gases all at once, which can
potentially be a dangerous situation for lifeforms living nearby. But
for the size of the pond you are talking about, I don't think that is
much of a problem. There may be some minor stratification, but if it is
in a temperate zone, it will overturn during the spring and fall, and
naturally get rid of those gases.


That begets another question then.

For my pond (~100'x45'x25'deep) I am planning on drilling a water well
(the well is for more than just the pond). Summers here in Texas
typically mean ponds go dry, or at least drop their levels (not THIS
year...), so the well is to help keep the pond full.

I have been toying with the idea of having the pipe filling the pond be
at the BOTTOM of the pond, rather than what is typical around here (a
fountain which sprays the top). Would doing this help/hurt the
stratification that occurs during the hot weather?

The main issues, as I see it, are what is the salinity (i.e., total
dissolved solids - TDS) of the well water you intend to use as well as the
pH, and how well oxygenated it is. Well water generally is not well
oxygenated since it is sequestured below ground and so doesn't get good gas
exchange, and is often quite saline, so if it were me, I'd run the water
over a waterfall or create a fountain that would agitate and add oxygen to
the water. Alternatively, you good build a 30 gallon oxygenator using a
plastic chemical drum, and pump air through the water before it is pumped
to the bottom of the pond. That remedy, however, might be more expensive
than to simply create a cascade of water into the pond. That would solve
the oxygen problem (if one exists).

As for TDS, your water well driller usually will attempt to tap an aquifer
that is low in TDS but that is not always possible. For drinking water
purposes, drillers have often had to rely on installing whole house reverse
osmosis units to get rid of the high TDS if there is not other alternative.
Just remember this; the EPA allowable levels of TDS in well water for
drinking water purposes cannot exceed 500 parts per million. If your water
is below that limit, you should be ok. When you have your well drilled,
ask the driller to test for TDS (in most states that is a requirement),
fecal coliform, and dissolved oxygen (DO) at a minimum. You may want to
ask your state department for natural resources what the testing
requirements are for new water wells in your state, and make sure your
driller follows their guidelines (drillers are notorious for cutting
corners, so arm yourself with the right information and watch him like a
hawk).

As for stratification, all you need to do to prevent that from occurring to
to make sure there is a constant flow of water that turns the water over.
Pumping the water into the bottom is one method. You could also install an
aerator that will pump a curtain of air (at least half way down) and let
the bubbles create an upflow of water, allowing the water to be constantly
over turned. Don't install either straight on the bottom, since that could
stir up bottom sediments and cause your pond water to become turgid
(cloudy). Another method I've seen that is related to the aerator method
is to create a sort of water feature out of it. You pump air into a pipe
(from the bottom) that is suspended in the water column. The pipe only
need go halfway down in the water. At the top, you create some kind of
scupture like a spitting fountain (works best if it is not too far above
the top of the water). I've seen people make a feaure that floats on the
surface but remembles a grist mill stone with a hole in the middle. The
aerated water then flows over the surface of ther "grist mill stone" and
flows back into the pond. The air will pull the water from the bottom to
the top and "spit it out" just like a riser pipe on an undergravel filter
in an aquarium, adding oxygen to the water and creating a vertical
cirulation of the water column. Just remember that pumping air ten feet
down is going to require a substantial air pump. A simply aquarium air
pump will not do. Here is a self-contained aerator that is said to work
well.

http://www.livingwateraeration.com/pa33.html

If you decide to install a water pipe from your water well near the bottom
of your pond, you could combine an aerator with it and kill two birds with
one stone. That would also prevent evaporation loss because you are adding
water to the pond as you are aerating it.

Good luck.

George