^ while Dupage does not lie within the GL basin (most of Chicagoland doesn't), the vast majority of Dupage people now drink lake michigan water.
Light blue is lake michigan water, the oranges are various groundwater sources.
Source:
https://drinkingwater123.metroplanni...n-introduction
Chicagoland in general is a gray area with the two great basins of the interior laying so flat and close together, and with the reversing of the Chicago river eventually connecting them.