I recall that Pelton Wheels are very efficient and seeing some in industrial use with a snail-like cast iron inlet manifold and multiple jets with exhausted water discharged axially. I think that the mine at Laxey on the IOM had a few Mac Adam Fourneyron turbines to work compressors etc towards the end of its life. Any ideas about power outputs and head of water required? Wilkpedia gives the basic formulae, but somebody must have produced a nomograph or spreadsheet at some point.
http://en.wikipedia.org/wiki/Pelton_wheel I live in an area with deep valleys around Stroud with plenty of small steams and rivers. We are always trying to fend off the wind turbine brigade from erecting any more of those horrors. What could be simpler than set up a few of these little beauties instead. Water would be returned to the river and could be used lower down. The Frome had a number of water mills on its route in the old days.
By the way, does anybody know whether hydraulic rams were ever use for pumping in mines - there are lots of them round here but they work to a relatively low head. Hydraulic rams have only two moving parts, a spring or weight loaded waste valve (the clack valve) and a delivery check valve making them cheap to build, easy to maintain, and very reliable. In addition, there is a drive pipe supplying water from an elevated source, and a delivery pipe, taking a portion of the water that comes through the drive pipe to an elevation higher than the source.