That's was a quote Marcus I found it when doing some research on water after Flagg posted them very interesting items.
I found it here:
20 Interesting and Useful Water Facts
But as you asked about closed system I got back onto google
And found this for you:
http://www.uvm.edu/~cmehrten/courses...d%20System.pdf
A quick extract from the PDF:
Material flows between reservoirs or sinks along pathways, or fluxes.
Examples: Water vapor in the atmosphere condenses and falls as rain and breaks down rocks. Ocean water evaporates into the atmosphere. Volcanoes erupt and spew water vapor into the atmosphere