What helps me decide, is to think about the question I want to answer. Do you want to identify regions for remediation, for example? If so, maybe think about what the remediation size might look like (maybe the goal is to treat lakes within 1 square mile at a time). If you are thinking about pollution sources, then you might want to think about how best to represent lake connectivity (you can create a spatial weights matrix to represent custom relationships perhaps based on whether or not lakes are connected by small streams ?). If you just want to show where water quality is bad, with only 30 lakes, maybe you can just map the water quality for each. If you have at least 30 water quality samples at different locations within some lakes, you can run hot spot analysis on the samples within those lakes separately to see if there are hot spot pollution points with a lake.
I hope this helps!
Best wishes,
Lauren
