The Howden Reservoir is a Y-shaped reservoir, the uppermost of the three in the Upper Derwent Valley, England. The western half of the reservoir lies in Derbyshire and the eastern half is in Sheffield, South Yorkshire; the county border runs through the middle of the reservoir, following the original path of the River Derwent. The longest arm is around 1+1/4 mi in length. The reservoir is bounded at the southern end by Howden Dam; below this, the Derwent flows immediately into Derwent Reservoir and subsequently the Ladybower Reservoir. Other tributaries include the River Westend, Howden Clough and Linch Clough. Work commenced on the dam's construction on 16 July 1901 and completed in July 1912. The chief engineer was Edward Sandeman. He was also in charge of building nearby Derwent dam and was awarded the Telford Medal in 1918 for his work "Derwent Valley Waterworks". The works involved constructing a temporary village at Birchinlee, or "Tin Town", for the workers, a temporary railway line from the main line at Bamford, construction of a link aqueduct to the Derwent Dam. The dam is of solid masonry construction, and 117 ft tall, 1080 ft long, and impounds 1,900,000 impgal of water, from a catchment area of 5155 acre. The workers who died during the construction of the dam were buried in St John the Baptist's Church, Bamford. To the east of the reservoir stands Featherbed Moss, one of the highest tops in the area at 545 m, and one of several tops of that name in the area. This is not to be confused with the more well-known Featherbed Moss on the Pennine Way between Kinder Scout and Bleaklow.