River Weaver, river rising on the boundary between the counties of Shropshire and Cheshire, England, and then flowing 45 miles (72 km) north to reach the Irish Sea estuary of the River Mersey to the west of Runcorn. In its upper reaches it passes through dairy farming country, but major industrial development is found near its confluence with the Mersey. The Trent and Mersey Canal runs parallel to the River Weaver for some way; towns situated along the river are Nantwich, Winsford, and Northwich. Winsford has been used to accommodate overspill population from Liverpool.