For overwintering, yes, if they're going to hibernate in it. But not for breeding; they go for extremely shallow water, and the tadpoles only need enough depth to live safely, with plenty of cover. They won't overwinter in it. There used to be a frog pond on the moors above where I lived in Cornwall, and I regularly found spawn in rain puddles less than an inch deep. The water wasn't more than a foot or so deep anywhere.