On or around Fri, 5 May 2006 09:16:57 +0100, "Colin Hammond"
enlightened us thusly:

I am surprised no one has mentioned those pumps that extract energy from the
flow of the river and go donk donk donk. I know nothing about them except I
often hear them while walking in the country.

they have, several of 'em.

mind, for the application involved, you might have to use a waterwheel and
pump. More moving parts, but less head required, just flow. Partly depends
if it's in a place that can be vandalised.
--
Austin Shackles. www.ddol-las.net my opinions are just that
"Any man's death diminishes me, because I am involved in Mankind; and
therefore never send to know for whom the bell tolls, it tolls for thee"
John Donne (1571? - 1631) Devotions, XVII