All water you collect outside should be treated as potentially contaminated and should be treated. Although it may look clear, harmful organisms could be lurking unseen. Drinking even a few sips of such water could make you extremely ill.
For that reason, and with so many effective and easy ways to treat water, you should never drink untreated water unless it’s a true emergency. Even then, you should be able to do some sort of treatment, even if it’s just taking off your shirt and using it as a filter. That’s still better than doing nothing at all!