Siphons and Crossings


Siphons and Crossings

Many Boulder ditches use siphons to cross creeks, highways, railroads, and other ditches.

Over the years, many flumes and pipes have been replaced with siphons. A siphon is a pipe that is buried across and under an obstacle like a creek. As long as the proper gradient is maintained between the inlet and outlet of the siphon, unpressurized ditch water will flow through it.

Left: The fish-screen-roller on Lower Boulder Ditch is unique. The metal mesh roller allows water and debris to pass, but keeps grass carp confined to one section of the ditch, and out of the creek. During the summer the carp graze to keep the ditch clear of weeds. In the fall, the carp are herded together and netted, then transferred to a pond to over-winter. In the spring they are released back into the ditch.

Middle: An Overchute is a structure that carries a creek OVER (rather than under) a ditch channel. A good example is at the intersection of Four Mile Canyon Creek and the Boulder & White Rock Ditch. Here, a concrete tray carries the normally tiny flow of Four Mile Canyon Creek over the top of Boulder and White Rock Ditch.

Right: In 1953 Farmer's Ditch installed Boulder's biggest siphon under North Boulder Park, after a child drowned in the ditch in the Newlands neighborhood. This $28,000 project eliminated 3900 feet of leaky ditch. The siphon goes from Ninth & Maxwell underground to Ninth & Delwood. Clipping courtesy of Carnegie Branch Library for Local History, Boulder CO.



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