Oh, I would say there's negative environmental effects of hydroelectricity, including the destruction of habitat.
Dams also have a life span, which is measured in decades (or less). Once the silt has built up, the dam doesn't really work in generating power any more.
> hasn't the hoover dam been up since the the '30s?
There are tens of thousands of dams in the US alone, and most if not all are not built to the proportions of the Hoover Dam. If you would like to use the Hoover Dam - one of the largest dams in the world, holding back one of the largest man made reservoirs in the world as my counterexample, be my guest.
My point wasn't that the dam will fail (although they do) - far from it: my point is that the dam, once put in, is really hard to take out and the dam itself holds back all the debris that usually flows out the river. That debris builds up, until - uh oh - you don't have enough water in your reservoir anymore to generate power.
That, and plugging up an entire watershed is pretty much akin to destroying the ecosystem that depends on the water flowing free to the ocean. Entire species of fish die off; the natural environment of other plants and animals is hopelessly changed, etc.
Some parts of the US only have 5% of rivers flow without a dam. Hydroelectricity is not sustainable now, and is far from inexhaustible.
So, back to the Hoover Dam - who's idea was it, to build a reservoir for water, in the middle of the desert? Did anyone think, "wonder if the water will all evaporate?" Because that's what's happening,
You seem to believe I am a staunch proponent of hydroelectric, but I am just asking you to give examples that most dams have a life span of "decades or less".
Your own link, says "Nowadays, from what structural engineers tell me, the typical design life is more like 100 years".
Swedish dams, some which are 100 years old already, are getting upgraded. This example, on a 50 year old dam, is supposedly prolonging the lifetime by 100 years.
"Although large concrete gravity dams have a theoretical design life of 80-100 years, the actual lifespan of a dam is determined by the rate at which its reservoir fills with sediment. In severely eroding catchments, millions of cubic metres of sediment can be transported annually. The average lifespan of a large dam in China is 45 years. "
http://mightyclutha.blogspot.com/2010/02/decommissioning-rox...
"Many scientists predict that within two decades, rising demand for Colorado River water and falling supply will drop the surface of the reservoir to its lowest level, known as “dead pool.” Because the lowest exit from the dam (the river outlet works) is 237 feet above the original riverbed, at dead pool Lake Powell will still hold 2 million acre-feet of water, one-thirteenth of capacity. "
https://orionmagazine.org/article/calamity-on-the-colorado/
And on, and on, and on. The takeaway is, the silt and sediment that collects on one side of the dam drastically shortens the usable lifespan of the dam, no matter how long the structure itself will be structurally be sound. That's a total engineering fall.
Dams also have a life span, which is measured in decades (or less). Once the silt has built up, the dam doesn't really work in generating power any more.