Lake Boundry Detection with Mathematica

My friend discussed a problem he faced in finding seasonal fluctuations in water level and thus its consequences in varying lake areas and its perimeter. Given the satellite imagery of a lake, I wondered if Mathematica could solve this efficiently. I have uploaded the mathematica notebook related to it which you can find here The notebook is self-explanatory, and I have written textual arguments alongside it if someone wants to recreate it. I have tried to do it with more than one method and also put up some examples in it. Some of the pre-build functions in Mathematica do a fairly good job at it, and it is very quick to implement, but it is not super accurate. __