Which water will warm up first?

[Bowhunter57]

Would an above ground water impoundment, like a reservoir, warm up quicker than an in ground body of water...like a same sized lake/pond?

Last year, I started fishing in farm ponds, as that's where I was catching fish. It seemed as though the reservoirs were taking longer for the fish to become as active as they were in simular sized ponds/lakes. Kiser Lake is another example of the fish hitting earlier than the local reservoirs...of the same size.

What's your thoughts, experiences and opinions?

Thank you, Bowhunter57