Water management - what's your strategy?

Most of you know that we live in the sub tropics and one of the reasons we chose this area to live in was the annual rainfall. It wasn't the only factor in our choice of property when we bought our home, but it was one of the important ones. We knew when we came here that we'd grow vegetables and keep chickens, so we knew we'd need plenty of water. Our average rainfall here is 1800mm/70inches