The Derwent Reservoir is a reservoir on the River Derwent, on the border between County Durham and Northumberland, in England. It is west of Consett. It is 3.5 miles (5.6 km) long) and covers an area of 4 km2 and has a maximum depth of 100 ft (30m) and when full, holds 11,000 million gallons (50,000,000m³).