The Western Headworks system, of which the Calgary Bow River Weir is a part, was originally constructed by the Canadian Pacific Railroad in 1908 to divert water from the Bow River for irrigated agriculture in the semi-arid region east of Calgary. The "Calgary Weir" represented the only barrier to boaters and fish passage in the 100 km section of the Bow River between the Bearspaw Dam and the Carseland Weir. The ogee-shaped weir included a submerged, concave-shaped bucket deflector which created rollers (bucket roller and ground roller) to dissipate energy and prevent downstream scour. These rollers have claimed over 20 lives; consequently, the weir was infamously labelled the "Drowning Machine" as a testament to the unforgiving danger it posed. The Calgary Bow River Weir Project's primary purpose was to eliminate the extreme drowning hazard and enable passage for non-motorized boats and fish while maintaining water diversions from the Bow River. To achieve this, eight pools and eleven rapids were constructed to change the hydraulic conditions downstream of the weir from the existing concentrated circulating flow pattern to an extended linear pattern. The project creates an amenity for canoeists, kayakers, bird watchers, floaters, and educators. Construction with the Bow River flowing through the project was challenging. Utilizing innovative construction materials and techniques (boulders and macro-fibre reinforced concrete) provided the aesthetic character that was required, greatly increased the pace of construction, and reduced the project cost. The project was constructed on schedule and under budget at a cost of $16.5 million.
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