Hydraulic Model Study of Tehama-Colusa Canal

The California Department of Water Resources (DWR) conducted feasibility-level engineering and environmental studies under the Integrated Storage Investigations Program. The U.S. Bureau of Reclamation (USBR) was the lead federal agency for the EIS/R. As part of the investigation, DWR and USBR evaluated alternatives using the Tehama-Colusa canal to provide up to 5,000 cubic-feet-per-second (cfs) of conveyance capacity to deliver water to the proposed Sites Reservoir. To evaluate the existing canal's capacity, and to assist in the design of alternatives to increase the capacity, a hydraulic model was developed. HEC-RAS was applied between Mile Posts (MP) 0.51 and 66.07, and included 16 check structures, 20 inverted siphons, 33 bridges, and numerous other crossings. The canal was designed and built in reaches using standard cross sections for each reach. A spreadsheet was developed to automatically create the HEC-RAS geometry file from these standard sections and individual station invert elevations, obtained from construction plan/profile drawings. After the various structures were added, the model was calibrated to recent moderately-high flows, and then applied to evaluate a range of alternatives. The alternatives included raising the canal's lining and structures, and widening the canal to achieve new design flow capacities.