 Cheddar Reservoir is a near @-@ circular artificial reservoir operated by Bristol Water . Dating from the 1930s , it has a capacity of 135 million gallons ( 614 @,@ 000 cubic metres ) . The reservoir is supplied with water taken from the Cheddar Yeo , which rises in Gough 's Cave in Cheddar Gorge and is a tributary of the River Axe . The inlet grate for the 54 @-@ inch ( 1 @.@ 4 m ) water pipe that is used to transport the water can be seen next to the sensory garden in Cheddar Gorge . It has been designated as a Site of Special Scientific Interest ( SSSI ) due to its wintering waterfowl populations . 
