Where did the Aztecs get their water?

The Aztec capital Tenochtitlan was surrounded by a gigantic lake. It is reasonable to assume that this is where they got their water from. Tenochtitlan was replaced by Mexico City when the Europeans conquered the land and the lake was drained to make room for the new city.

Actually they didn't get it from the lake. The built aqueducts that retrieve water from the mountains. I learnt it at school...