While I believe that even a small body of water like Winni has tides, at least theoretically, the 3" number sounds way too large. I've seen numbers like 1" - 2" for tides on Lake Michigan. I tried to research it a bit, to see if I could find a reasonably simple way to calculate an approximate tide for Winni but alas I've not yet found one. The 2 sites below start to give an idea a to how to do it but I've yet to have time to fully comprehend them. Perhaps if it's snowing tomorrow and I break out the Brandy early, I can do a little light reading
and post a result. It won't be as much fun as mcdude's snow day train thread but what can I do ...
http://www.rain.org/~mkummel/stumpers/06dec02a.html
http://www.jal.cc.il.us/~mikolajsawicki/Tides_new2.pdf
ps - is the study done by the UNH Maritime Club available online ?