Concrete is my area of expertise and I went with liner. For the system that
you describe, two ponds with a stream between, you will end up with one or
more cracks in the stream due to expansion and contraction caused by
temperature changes, and the two ponds being larger and anchored deeper in
the ground will not readily move, thereby causing the stream to crack.
Concrete is an excellent material for a pond if it is properly done, but if
not properly reinforced, placed on adequate soil foundation, or have trees
with invasive root systems, it is not very forgiving. Liner is nearly idiot
proof. Concrete also leaches calcium hydroxide into the pond if not
thoroughly cured, causing the pH to want to climb to near 13.
--
RichToyBox
http://www.geocities.com/richtoybox/pondintro.html


"Garry M. Silvey" wrote in message
...
I've ruled out preformed liners and am now looking at Cement VS Flexible
liner. Any suggestions? I have lots of cement working experience, so that
is
not an issue. I am looking at building a 2 pond with creek in middle
system,
a small pond above a larger pond. Larger pond will probably be 8 X 10 or
12.