&gt;  hasn&#x27;t the hoover dam been up since the the &#x27;30s?<p>There are <i>tens of thousands</i> 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.<p>My point wasn&#x27;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 <i>out</i> and the dam itself holds back all the debris that usually flows out the river. That debris builds up, until - uh oh - you don&#x27;t have enough water in your reservoir anymore to generate power.<p>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.<p>Some parts of the US only have 5% of rivers flow without a dam. Hydroelectricity is not sustainable now, and is far from inexhaustible.<p>So, back to the Hoover Dam - who&#x27;s idea was it, to build a reservoir for water, in the middle of the desert? Did anyone think, &quot;wonder if the water will all evaporate?&quot; Because that&#x27;s what&#x27;s happening,<p><a href="http:&#x2F;&#x2F;www.latimes.com&#x2F;nation&#x2F;la-na-lake-mead-low-20150429-story.html" rel="nofollow">http:&#x2F;&#x2F;www.latimes.com&#x2F;nation&#x2F;la-na-lake-mead-low-20150429-s...</a><p><a href="http:&#x2F;&#x2F;www.straightdope.com&#x2F;columns&#x2F;read&#x2F;2666&#x2F;how-long-are-dams-like-hoover-dam-engineered-to-last" rel="nofollow">http:&#x2F;&#x2F;www.straightdope.com&#x2F;columns&#x2F;read&#x2F;2666&#x2F;how-long-are-d...</a><p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Hoover_Dam#Environmental_impact" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Hoover_Dam#Environmental_impac...</a><p><a href="https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=qou2KkLkYVg" rel="nofollow">https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=qou2KkLkYVg</a><p><a href="http:&#x2F;&#x2F;www.nytimes.com&#x2F;1989&#x2F;11&#x2F;25&#x2F;opinion&#x2F;too-many-dammed-rivers.html" rel="nofollow">http:&#x2F;&#x2F;www.nytimes.com&#x2F;1989&#x2F;11&#x2F;25&#x2F;opinion&#x2F;too-many-dammed-ri...</a><p><a href="https:&#x2F;&#x2F;www.youtube.com&#x2F;results?search_query=dam+disaster" rel="nofollow">https:&#x2F;&#x2F;www.youtube.com&#x2F;results?search_query=dam+disaster</a>