A combination of the rainfall and geology leads to an estimated average daily runoff from springs and boreholes of some 330,000 m3 (72 million imperial gallons). Bristol Waterworks Company (now Bristol Water) recognised the value of this resource and between 1846 and 1853 created a series of tunnels, pipes, and aqueducts called the "Line of Works", which still carry approximately 18,200 m3 (4 million imperial gallons) of water a day to Barrow Gurney Reservoirs for filtration and then on to Bristol and the surrounding areas. This collection and conveyance of water from the Chewton Mendip and East and West Harptree areas is accomplished by the effect of gravity on the runoff. Water from the Mendips is also collected in Cheddar Reservoir, which was constructed in the 1930s and takes water from the springs in Cheddar Gorge.