text: Codnor Park Reservoir originally retained 33,000,000 gallons. It was constructed to provide water down the western arm of the Cromford Canal (opened 1794) via the canal flight to Codnor Works below Lock 4. British Waterways undertook significant works as part of a flood prevention scheme and in 1985 the water level was lowered by about 1.8 metres and a lock was removed.