by Bryce CowellDams serve three primary purposes that are vital to us humans: water supply, agricultural irrigation, and electricity. However, not all dams are created equal. Some no longer serve their original purpose and their environmental impacts are well-documented. So do we really need all of these dams? And which ones are appropriate for Hayduke, Seldom, Doc and Abbzug to take out?The Patagonia-sponsored documentary film DamNation attempts to answer these questions from both sides of the debate. Slated to be released in early 2013, this film is the cornerstone of a campaign to restore US waterways to their former untamed glory while taking into consideration the socioeconomic consequences.Each dam in this country needs to be objectively analyzed on a case-by-case basis to determine if removal is beneficial to the majority. And of course, there are potent political and financial goliaths that are going to try to prevent that from happening, even if the costs outweigh the benefits.One such controversial dam, the O'Shaughnessy Dam (pictured above) is located within Yosemite National Park. This fall, San Franciscans will vote on whether to keep the damn thing in place or restore Hetch Hetchy, which John Muir referred to as "one of nature's rarest and most precious mountain temples," and devise a modern water plan.**So the question is, which dams do you think should be removed or improved?