River in the Sky

Engineers building the Brooks Aqueduct had to carry water across a valley while also crossing CPR tracks that were too high to pass beneath the aqueduct as planned. Lowering the railway would have been too expensive, so they used an inverted siphon to take the water under the tracks and back up into the aqueduct on the other side. The siphon was a large pipe that narrowed from 12 feet 8½ inches where it met the aqueduct to 9 feet 9 inches under the tracks, increasing the water's speed before widening again and slowing the flow back to its earlier rate. The Brooks Aqueduct formed one part of the irrigation system that brought Bow River water to farmers in the Eastern Irrigation Section, with water entering from an earthen canal, passing through a 150 foot long sloped and graded intake designed to reduce frictional losses, and leaving through a 30 foot outlet structure with a 21 inch high baffle wall to prevent side whirls that could erode the canal banks. The siphon's operation reflected Bernoulli's principle and Venturi's effect: as flowing water entered the narrower pipe, pressure dropped and speed increased while the energy per unit mass remained the same.

Alberta · Canada