The Great Lakes aren't exactly the same as pristine aquifers suitable for drinking water...

https://www.usgs.gov/news/widespread-plastic-pollution-found..., https://www.safewater.org/fact-sheets-1/2017/1/23/the-great-... etc.

The Great Lakes sources their water from glaciers melting. Too little and too much of a thing it’s still worrying.

The great lakes watershed isn't within 1000 km of a glacier. It's a snowpack and rainfall watershed.

The great lakes were created by receding glaciers, but it's been more than 10,000 years since they were glacier fed.

Do you have a source for this? I thought they were sourced was almost all rainfall both directly into the lake and from the streams and rivers that surround them

Glaciers formed them, but probably have little to do with sustaining them https://en.wikipedia.org/wiki/Great_Lakes