* Oppose As with most of these many hydro- related merges of late, their effect would seem to be to treat a general article (not just electricity generation, not just natural water head) as if it were a narrowly specific article (their hydroelectricity aspects only) and then merge it into a far larger and broader article. That's not a good move. Low-head hydro has a huge history for watermills etc. that had nothing to do with electricity for centuries. run-of-the-river has also (IMHO, admittedly) implications of being "zero head" hydro, based on large flow rates but almost no head (i.e. possibly a dam or weir as a barrier, but no constructed leat to provide a fall equivalent to the wheel diameter). 
 : Clearly there's some confusion here, but I don't feel that it's fixable by merging what we already have. I think a better route might be to write from scratch a "table of contents" section, possibly on a project talk page, not as wikilinks at all. This would list "new" articles that cover the broad scope of water power, in a way that gives a broad, balanced and appropriately detailed encyclopedic view of the entire topic. Then, and only then, we convert these article titles to wikilinks (or redlinks) and start wondering how we re-organise the content chunks we have available and ready-authored into being encyclopedic articles. 
 : Personally I avoid broad-scope articles like hydroelectricity (also steam locomotive, diesel engine etc.). WP works well on narrow-scope, but has an obvious problem in maintaining editorial structure and readability when we get to the broad scope. Everyone has their own favourite para they want to see included and the result is a list of factoids, not an article. "Editorial control by merge" doesn't seem to work to solve this, we need to take a stand further back and start structures or ToCs from scratch more often. After all, the content (and the work that represents) is still re-usable within them.