Not only is CAP’s infrastructure amazing, it’s also unique. Some of the unique features you may not have heard about – or seen — are overchutes and underchutes. 

Patrick Kernan, senior civil engineer, said that more than 250 underchutes and overchutes were constructed across the 336-mile canal with a singular purpose: transport stormwater from one side of the canal to the other. 

“The CAP canal bisects the state, crossing a lot of washes that transport stormwater from higher elevations to lower elevations,” said Kernan.  “Overchutes and underchutes help ensure that natural flow is continued.”

Overchutes were constructed in “cut” sections of the canal, where the canal is at or below ground level. Underchutes were constructed in “fill” sections of the canal, where the canal sits above the natural ground level. In both cases, storm water is directed toward them by collective embankments so it can flow over or under the CAP canal.

And, although all overchutes and underchutes have the same purpose, their design and size vary.

For example, the underchute in Reach 9 of the Hayden Rhodes Aqueduct is four pipes that each have a diameter of 84 inches. The overchute near Skunk Creek in the northern part of the Valley is a concrete flume that resembles a large bridge.

Kernan said the Bureau of Reclamation used hydrologic and hydraulic methods to look at the amount of water needing to be conveyed across and under the canal prior to construction to determine the size, number and location of the overchutes and underchutes.

CAP recently started an aqueduct hydrology improvement project. The team uses modern technology and looks at current storm data. It then examines the height of collective embankments and capacity of underchutes and overchutes to ensure they are adequate to move the flow.

Another way CAP is ensuring reliable water deliveries.