Seems to me the issue is how hot the water is relative to their body temps.
If they cool themselves by panting or sweating (do birds even have sweat glands?) then it really depends on the air temperature/humidity relative to their body temperatures. If the air is close to their body temperature, they will get less of an evaporative cooling benefit from panting. The corollary is that they may need to pant more to lose the equivalent amount of heat. If, on the other hand, the air is cool relative to their body temperature, then they will lose more heat per unit water they lose by panting.
The point is, though, that I don't think they are cooled by drinking cool water - they're cooled by panting that water out, so it shouldn't matter much what temperature the water is when it goes in. I'm not a physicist, but this make sense to me.
I have heard of people who have accidentally killed their chickens by giving them cold water on a hot day, so I think of that as the greater danger. June is usually the hottest month here in Albuquerque, and we're halfway through it... so far my birds are OK, though I notice they do seek shade in the run. Good luck with whatever you come up with - I think a block of something frozen in the waterers should at least keep the temp down below what it would have been, so that's progress and can't hurt (since the temperature change will still be gradual over the course of the day).
If they cool themselves by panting or sweating (do birds even have sweat glands?) then it really depends on the air temperature/humidity relative to their body temperatures. If the air is close to their body temperature, they will get less of an evaporative cooling benefit from panting. The corollary is that they may need to pant more to lose the equivalent amount of heat. If, on the other hand, the air is cool relative to their body temperature, then they will lose more heat per unit water they lose by panting.
The point is, though, that I don't think they are cooled by drinking cool water - they're cooled by panting that water out, so it shouldn't matter much what temperature the water is when it goes in. I'm not a physicist, but this make sense to me.
I have heard of people who have accidentally killed their chickens by giving them cold water on a hot day, so I think of that as the greater danger. June is usually the hottest month here in Albuquerque, and we're halfway through it... so far my birds are OK, though I notice they do seek shade in the run. Good luck with whatever you come up with - I think a block of something frozen in the waterers should at least keep the temp down below what it would have been, so that's progress and can't hurt (since the temperature change will still be gradual over the course of the day).