Often described as the backbone of England, the Pennine Hills form a more-or-less continuous range in most of Northern England. The range stretches northwards from the Peak District at the southern end, through the South Pennines, the Yorkshire Dales and North Pennines to the Tyne Gap, which separates the range from the Cheviot Hills across the Anglo-Scottish border (some definitions include the Cheviot Hills). South of the Aire Gap is a western spur into east Lancashire, comprising the Rossendale Fells, West Pennine Moors and the Bowland Fells in North Lancashire. The Howgill Fells and Orton Fells in Cumbria are sometimes considered to be Pennine spurs to the west of the range. The Pennines are an important water catchment area with numerous reservoirs in the head streams of the river valleys.