It delivers enormous quantities of water by gravity across the mid-Wales countryside, through north Herefordshire, south Shropshire and into the West Midlands through eleven major river valleys. The aqueduct is 73 miles (117 km) long, down which the water travels at less than two miles per hour (3 km/h), taking one and a half days to get to Birmingham.
Construction
View over the aqueduct as it crosses the River Severn
Work on the first 13 miles (21 km) of the route from the Elan Valley was started in June 1896 by Birmingham Corporation Water Department. The aqueduct was built in sections by outside contractors, using three types of construction depending on the nature of the terrain it had to cross. "Cut and cover" was essentially a brick lined channel which was manually dug as a trench, then roofed over and concealed underground. Where the route of the aqueduct encountered high ground above the gradient needed to maintain the downward slope, a certain amount of tunnelling was required; at one point the tunnel is 100 metres below ground, ensuring the aqueduct was at only 220 metres above sea level. This totalled around 12 miles (19 km), with the longest single length being just over 4 miles (6.4 km). The third construction type was the use of either bridged aqueducts or inverted syphons to cross valleys and rivers where the ground level dropped too steeply for the required hydraulic gradient to be maintained. The pipeline was continued at the other side of the valley at the same height as the delivery pipe. With the inverted syphon technique, the water naturally fills the lower section of pipe due to the head of water and flow continues downstream.
The initial scheme opened in 1906 with two 42 in-diameter (1,100 mm) pipes. Two more pipes of 63 in (1,600 mm) diameter were added between 1919 and 1961.
Engineer
The engineer for the Elan aqueduct scheme was James Mansergh.
Some crossings over canals and railways have been replaced by buried pipes.[27][26] The line of the buried aqueduct through woodland is marked by a 20 metres (66 ft) "exclusion zone" from which trees are removed.[27]
