The River Douglas is a 35-mile (56 km) waterway flowing through Lancashire and Greater Manchester in North West England, originating from the slopes of Winter Hill and eventually joining the River Ribble as a tributary. Also historically known as the River Asland or Astland, the Douglas drains a varied catchment that includes upland moorland, agricultural lowlands, and urban areas. Its major tributaries include the River Tawd and the River Yarrow. The upper reaches descend rapidly from the high ground, dropping below the 430-foot contour before flowing into Lower Rivington Reservoir near Horwich, where compensation water released from the dam maintains flow downstream. The river then winds in a generally southwesterly direction through communities including Adlington, Worthington, and Appley Bridge before reaching its lower stretches near Gathurst and Bispham. The Leeds and Liverpool Canal crosses the Douglas via a Grade II listed aqueduct designed by John Rennie in the 1790s, a notable landmark along the river corridor.