>every lake is part of a watershed that involves some kind of steady flow

every "every" does have its exception, much to the consternation of some North Dakota farmers; see these links regarding Devil's Lake, ND (it's where I grew up), whose eponymous lake has increased in size from 75 acres to 75,000 acres in the last 65 years -- most of that in the last 5 years.

http://www.cbcnews.cbc.ca/cgi-bin/templates/view.cgi?/news/1999/10/25/redriver991025

http://www.voyager.net/tailwinds/west/nd/d59.html