IMHO, the main parameter seems to be how many time is needed to fill&#x2F;empty the dam and to apply a reasonable ratio to ensure the dam is working 95% of the time.<p>From Wikipedia on Hoover Dam: &quot;Filling of Lake Mead began February 1, 1935, ... ... In the latter half of 1936, water levels in Lake Mead were high enough to permit power generation ...&quot;<p>To empty Hoover Dam once every 60&#x2F;80 years doesn&#x27;t sound absurd to me.