"George" wrote in message
news:J5M4e.15943$Vx1.13708@attbi_s01...
Starting with autumn, let's see how the pond changed into the winter. The
water
at the surface started out in October at 42°F. The first frost and cold
wind
lowered the surface layer and it sank, while the warm water rose and
replaced it
and was chilled in turn. This circulation process continued until all the
water
reached 39.2°F, at this temperature water is at its heaviest. Normally,
any
cooling beyond 39.2°F does not sink, instead forms a thin layer at the
surface
because of the local geothermal gradient, ...........
============================
This has not been our experience. When our ponds are forming ice at the
surface (coldest place), the bottom can be anywhere from 39 to 42 degrees.
Nothing but a small surface pump (or air stone) runs to keep a hole in the
ice. There is no current to mix the water and disrupt natural
stratification or disturb the hibernating fish.
--
McKoi.... the frugal ponder...
~~~ }((((o ~~~ }{{{{o ~~~ }(((((o