bardenmatt wrote:
Definition: A pondless waterfall or "child-proof waterfall" is a
waterfall that cascades into a subterranean catch basin or cistern
rather than a pond. The collected water is then returned to the top of
the waterfall by means of a pump system.

Why Pondless?

In 1984 I built what I called a "childproof" waterfall using
reinforced concrete, because building codes state that because of the
liability factor, ponds can only be 18" deep or you are required to
conform to all of the same building codes and requirements of a
swimming pool (6 foot fence perimeter, special gates, door alarms,
etc.)." Since this waterfall was located in the front yard, it could
not be more than 18" and if it was, there was not enough space for a
large enough pond to prevent it from being sucked dry by the time the
water returned back to the pond by way of the waterfall. So I
installed an electronic water leveler system to insure the collection
basin would automatically be replenished with water as needed. My
term for this type of water feature is "child-proof" because it makes
it safe for children and eliminates the liability factor and passes
the building codes. Since the advent of utilizing rubber liners to
construct waterfalls and ponds in the early nineties, this type of
waterfall has been called a "pondless waterfall."

Rubber liner ponds and waterfalls are okay for short term use.
However, they are susceptible to attacks from rats, mice, ground
squirrels, gophers, chipmunks, tree roots, sharp objects, stretching
from heavy boulders etc. I go into great detail on the critical flaws
of pond liner construction in an article entitled Pondless
Waterfalls: Concrete vs. Liners. This article contains documentation
that leaves no doubt that pondless waterfalls are cheaper to build
using concrete and steel rather than using a pondless waterfall liner
kit. Not to mention that it is cheaper to operate and maintain.

Did you know that if you make the shape of your waterfall a Klein bottle it
doesn't need a pump?

David