Another problem of dams is the accumulation of heavy metals and other toxic sludge behind the dam itself (usually washes downstream in minimal quantities) and the deoxigenation of the watershed due to lack of flow.
On that note (interestingly and anecdotally) many of these dams are inundated with ash and sediment that should have flushed downstream from Mt St Helens!
The impact of these dams is just incomprehensible.
The impact of these dams is just incomprehensible.