Sometimes in life one must make choices.  Hydropower and dams used to produce it is absolutely vital to sustainable long term power production free from carbon emission.  Here we see a profound conflict.  Many folks support any cause that promises to return the world to mother nature.  Free flowing rivers.  Reduced carbon emission.  Forests that are not harvested.  etc.  Here we have a head on collision between back to nature free rivers and fighting climate change.  It is interesting how many warmers support dam removal or less than optimal power production while at the same time professing concern over climate change. 

Of course, if varying river flow is a significant concern, the way to eliminate it is to place a small secondary dam downstream of the primary which acts as a buffer storing high flow from the main dam and releasing it when the main dam is reducing less.  Below the secondary dam the flow would only exhibit seasonal variations.