Robles Diversion Dam Robles Diversion Dam is located on the Ventura River about 1.5 miles downstream from the confluence of Matilija Creek and North Fork Matilija Creek. The dam has a height of 24 feet and a crest length of 598 feet. The structure is rockfilled with a timber cutoff wall and a rolled earth core. The dam diverts water into the headworks of the Robles-Casitas Canal. The dam's sluiceway has a capacity of 10,000 cubic feet per second and is controlled by four radial gates.
Water entering the diversion canal headworks at the dam is controlled by three radial gates.
The cutoff wall needed to be repaired twice after heavy storms, once in 1969 and once in 1979. The canal is about 4.5 miles long with a capacity of 500 cubic feet per second. The open canal has a width at the top of 27 feet, sloping to a bottom width of 7 feet. The Ventura River Project's conveyance system includes miles of pressure pipeline, five pumping plants, since much of the service area lies at a higher elevation than Casitas Reservoir, six steel tank balancing reservoirs for peak and emergency storage, and chlorination stations to disinfect the water. The main conduit starts at Casitas Dam with a capacity of 121 cubic feet per second.