Complex sentence: Parts of the lake have been dredged, other parts reshaped by landfill, and the surviving fragment of the lake now, with the rest of the city of Chicago, drains into the Des Plaines River and the Mississippi River basin.
Split into simpler sentences: Parts of the lake have been dredged, and other parts reshaped by landfill. Together with the rest of the city of Chicago, the remnant of the lake now drains into the Des Plaines River and the Mississippi River basin.