Another boost to plausibility would be to fix the big lake - like how rivers tend not to diverge (there being only one way 'down' from any point on a watercourse) - a lake will have only one outflow (only one point on the shore would be lowest). If by chance two points were almost the same height, it would be temporary, only til one washed a bit deeper, and then that deeper one would capture more and more of the flow, once again leaving but one outflow. Lakes of course can have multiple inputs.

The 'look' is great.