 Cow Green Reservoir was built later, though the approval process was protracted due to the loss of habitat for the Teesdale violet plant.Balderhead, which was originally in the North Riding of Yorkshire, was approved for recreational activities by the Yorkshire Naturalists Union in the same year that it was opened, there being no objections on wildfowl grounds.Balderhead Reservoir was constructed upstream of two existing reservoirs, Blackton and Hury, and added to the storage capacity on the River Balder.