The author of A Long Walk To Water provides at least two clues that the water Nya drinks in chapter 3 may not be safe. What are these clues?

We discover that it's not just people, but also animals, that drink from the water. This practically guarantees that the water isn't completely safe to drink. All kinds of diseases can be transmitted this way, and it's little wonder that diarrhea is a such a major problem in this part of the world.
When Nya dips her empty container in the pond, we're told that the water is muddy and brown. Immediately, this puts us on our guard, and we ask ourselves the question: Would we ever consider drinking such muddy brown water? Surely not.
It takes two gourdfuls of this muddy, brown water to make Nya feel a little cooler inside. If the water had been clean and fresh, she wouldn't have needed to drink so much before feeling cooler.