The Shulchan Aruch OC 160:2 rules that water with which one has done "melachah," is disqualified from netilat yadayim. Does this include water which has flowed downstream from a hydroelectric plant?
1Now that I think about it, returning to "mechubar" status (e.g. entering a river after leaving the plant) may "reset" the water... not sure– yitznewtonJan 3, 2012 at 19:43
That is true, and even without that I assume there would be a din of hamshacha. The question still stands if he catches the water as it comes out of the plant- has the water done halachic melacha. It would seem that it does, though this case is different enough that I would not answer definitively without a similar case ruling.– YDKJan 3, 2012 at 21:05
Indeed (as in your comment), in 160:5 it says that melachah disqualifies water only if it was drawn, "but not with water from a mikvah or a spring while they are still attached [to their source]." I'm not entirely familiar with how hydroelectric plants work, but doesn't the water continue flowing nonstop as it's turning the turbines or whatever? So that should allow it to be classified as still mechubar.
The one hydroelectric plant that I have seen (Hoover) was made by damming up the Colorado River creating Lake Mead. The lake (now a mikva not a river) as I have seen it is zochalin. Perhaps there are other scenarios.– YDKJan 3, 2012 at 21:52