Thinking about hydroelectric

 

It struck me at Greenside Mine that the pipe feeding the Glenridding Hydro has exactly the same drop as the water in the river because the hydro is next to the river at the bottom. So why not just put the turbine in the river? My first thought was about energy. The amount of white water and sound suggests a lot of dissipation in the stream and there will probably be less of that in the pipe. The question is whether water in the pipe will reach the bottom faster than water in the stream that set off at the same time, as it should end up with more kinetic energy if less of the gravitational potential energy is dissipated. On a more practical level, the flow in the stream is very variable and the turbine could be left without water if placed in the stream. There is also the way it would be pelted with stones and other debris is spate.