I know I have a weird, often unpopular with many people, take on certain things. I know the OP has said nothing about free range or organic, but I see this as an organic - free range thing. I don’t like the legal definition of free range. All you need to legally claim your chickens are free range is put a 2’ x 4’ (or even smaller) area outside a building with 10,000 chickens and give them a hole to get to it and that is technically “free range”. Don’t get me started on what is “certified organic”. I see both these labels as marketing gimmicks. Seeing either of these labels at the grocery store does not cause my little heart to go pitter-patter.
Don’t get me wrong. There are people that follow the spirit of free range and organic and not just the legal definitions. I like these people.
To me, the spirit of free range and organic is that the chickens are able to do some foraging. They can bathe in and eat dirt. They can eat all kinds of creepy crawlies. They can scratch in cow piles or horse manure and find all kinds of great treats. They can drink water wherever they find it, not just form sterile sources. They are exposed to nature and live in nature.
Here I see people that normally would be highly in favor of anything labelled free range and organic. But when they see something that the spirit entails, they freak out. “No, no. Don’t do that. They need sterile water. They need a sterile environment.” Chickens don’t need a sterile environment. They need a healthy environment.
It reminds me of a thread from a few years back. A lady was cleaning out an old chicken coop and found some insect eggs. From her description they were not harmful in any way. But the consensus on this forum was “Kill! Clean! Sanitize! Destroy!” I agree the old coop needed to be thoroughly cleaned, even though it had been years since it held chickens. But my thoughts were more about how much fun those chickens would have had chasing down that free protein than any potential risk to them. I told you I thought weird.
I obviously don’t know much about that specific water. The OP has said nothing that would indicate it’s polluted in any way. I’d feel better if she said there were animals, fish, reptiles, amphibians, and insects living in that river. A river void of life would scare me silly. But a river filled with life it’s a healthy environment. It will help those chickens, not hurt them.