Doubtless there were reasons ...

Doubtless there were reasons for choosing that location. As has already been stated, the primary rationale for using that same location is to be able to examine whether there have been changes in the lake conditions. Contrary to previous comments, sampling from the drainage point will only tell you the discharge conditions, which is not necessarily (in fact not likely) representative of the lake conditions - for what I hope are obvious reasons. You need to start with a hypothesis and then establish a sampling program or strategy to evaluate that hypothesis. What are you hoping to determine?