In this task, you are given a question and a context passage. You have to answer the question based on the given passage.

What water source flows into the River Ribble?, Context: To the east of the county are upland areas leading to the Pennines. North of the Ribble is Beacon Fell Country Park and the Forest of Bowland, another AONB. Much of the lowland in this area is devoted to dairy farming and cheesemaking, whereas the higher ground is more suitable for sheep, and the highest ground is uncultivated moorland. The valleys of the River Ribble and its tributary the Calder form a large gap to the west of the Pennines, overlooked by Pendle Hill. Most of the larger Lancashire towns are in these valleys South of the Ribble are the West Pennine Moors and the Forest of Rossendale where former cotton mill towns are in deep valleys. The Lancashire Coalfield, largely in modern-day Greater Manchester, extended into Merseyside and to Ormskirk, Chorley, Burnley and Colne in Lancashire.
Calder