3. Lake Powell, Utah-Arizona
Another manmade reservoir on the Colorado River — but not the last in the countdown — Lake Powell is saddled with a high number of boating accidents. Officials in Arizona have named factors like falling water levels, since the same number of boaters in a smaller area of lake will have a higher chance of crashing. And because these Arizona lakes are both created by dams and regulated by international agreements, there’s no way to avoid lowering the water level if it’s needed.
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