I have long contended that the human mind has great difficulty in dealing with the mass of data which surrounds us. Particularly if you are of a curious nature.The only way we can cope is to make generalisations and, as it were, file them for future use. This carries with it the seeds of its own destruction. First, there is the problem of new knowledge making the generalisations invalid. I think it was Einstein who said "when the facts change, I change my position. What do you do ,Sir." Second, there is the problem of dynamism, in the sense of constant change.
In the Lower Lakes debate it is the largely the second dilemma that comes in to play. Few people seem to get their mind around the massive variability of our rainfall and thus river flows. We see people generalising about whether the Lakes were fresh or salty. The fact is they were both at different times, and often a "bit of both".