We have already seen 1 great water body lose to human hubris : L̶a̶k̶e̶ ̶B̶a̶i̶k̶a̶l̶ (edit: Aral Sea).
Aral Sea volume (1960) - 1000 cubicKm
Lake Erie volume - 500 cubicKm
So yeah, If L̶a̶k̶e̶ ̶B̶a̶i̶k̶a̶l̶ (edit:Aral Sea) can go down, so can the great lakes.