Hmmm. I'm not claiming to defy physics although I see how it came across that way. That was not my intention.

If you read the literature you can see why I was phrasing it like that so perhaps I too was misled.

http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/eng...

The potential energy harvest from a hydro setup must be 90% of available energy.

In practice half is lost due to the reasons outlined in the low tech magazine article I linked to. So the electricity production is lower than if we had the turbine hooked up to a motor. The other possibility is that small scale hydro is of a lower efficiency and that this explains the paradox. That is: the literature is talking of a large scale operation that can achieve 90% efficiency but smaller schemes incur losses that explain why converting a small hydro setup back to providing mechanical energy can double the output.