Wanderlust World Wanderlust World No. The River Mersey is a natural river formed by glacial and fluvial processes. It rises in the Pennines (Stockport, Greater Manchester) from the confluence of the River Goyt and River Tame, flows ~110 km (70 mi) west/northwest through Manchester, Warrington, Runcorn, and Widnes, and empties into the Irish Sea at Liverpool Bay. Its estuary was modified for shipping (dredging, training walls, Liverpool docks), but the river itself is entirely natural.