Max,
You should keep looking further, as the short correct answer was
given, head or height holds power potenital , not the mass of water,
any extra pipe = friction, pressure or flow lowering power rubber.
Idealy a nozzle straight out the bottom of a tank, pond, lake etc into
the turbine would be best, an expensive drilling mining operation
than most would afford to do.
A filled pipe trades gravity and flow for pressure which is then
converted back to motion by the nozzle and then into torque via the
wheel.
Another asspect that few tap but has more potential is the flow speed
of the water for its momentum plus gravity engergy to act. A fairly
large pipe or tough is funneled down to use. Clean shot down hill is best
for this too.
hobot
