Yes, this photo was taken in winter. Either the shade in this exhibit naturally preserves the snow longer than elsewhere in the zoo, or they stockpile it.
I don't think it is decently sized actually, but it's tough to compare it to somewhere like Hannover, where the landscape and texture of the exhibit is so much richer.
@FunkyGibbon Again il prefix that its sometimes really hard to judge perspective based off of one photo. Comparing it to Hanover seems a bit unfair though 95% of western zoos dont reach that standard anyways. I would say this looks bigger than Maryland or Denver zoos exhibits for example.