We are considering installing a closed loop geothermal system using the Muskoka River as the heat source.  Our concern is that we are right adjacent to a waterfall.  In the spring, a lot of debris comes over and the current is fairly strong.  We have one installer that is willing to install, while 2 others do not recommend.  Has anyone else encountered this situation.  Due to the waterfall, this area of the river does not always freeze in winter.  We are currently spending over $5k per year on propane and would like to switch over to a greener alternative.  Since we are located on the rocky Canadian Shield, I don't know if a ground loop is an option.

What kind of Debris? You mean wood? Small stones? How deep is the water at the bottom of the falls? I can't imagine the waterfall is forcing boulders, cars and big trees over it. I wouldn't think anything be large enough to be washed over the falls that would sink to the bottom of the pond to damage the closed loop lines at the bottom. Smaller stuff might be, but over time it would just bury it the lines protecting it for future damage. That's my thoughts anyway. 
  

Logs and parts of docks that get washed out over the winter. The water can rise 8 - 10 feet and after spring flood there are usually a dozen or so 8 - 10 foot logs washed up along the shoreline. Our home is well above the flood line.  We are going to validate the depth, but we are right beside a hydroelectric power plant.  I think the depth is 10 - 20 feet (varies).