Drainage
The Pennines constitute the main watershed in Northern England, dividing the eastern and western parts of the country. The rivers Eden, Ribble, Irwell and Mersey all rise in the Pennines and flow westwards towards the Irish Sea. On the other side of the watershed, the rivers Tyne, Tees, Wear, Swale, Ure, Nidd, Calder, Wharfe, Aire, Don and Trent also rise in the region but flow eastwards to the North Sea.
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