Lake Michigan (and thus Huron) is up since then.

Which I don't intend as a comprehensive explanation, maybe just a wedge towards pointing out that estimating the amount of human managed/available surface water is not something that is easy to do by intuition.

edited to fix lake spelling.

There are a lot of intermediate parts of the water cycle in between human's using it and it ending up back in the locations that humans use as sources of fresh water, and the water we use will end up living there. For example, some of it will end up in the oceans, as outflow from water treatment facilities flows into rivers and then into oceans. Some of it will end up in ground water, as the river water seeps into the ground along the way. Some of it will evaporate due to the inefficiencies of irrigation. Etc.

they say it kept raining on the desert areas they were trying to film mad max 4 in..