Design of Combined Service and Auxiliary Spillway at Auld Valley Reservoir

The design features are described of a single-entrance, dual-service spillway/auxiliary spillway at Auld Valley Reservoir of the Metropolitan Water District of Southern California. The spillway employs a modified side channel, in which the side wall opposite the primary weir may be overtopped during large spills from the reservoir. Another spillway entrance is thus created, leading into a secondary valley which becomes an auxiliary spillway. The indeterminate hydraulics of the intricate three-weir system are reviewed and a computerized solution is presented of the applicable theoretical relationships. Model studies are described, which were conducted to confirm the technical feasibility of the design concept and the flow distribution in the spillway system. A FORTRN IV computer program is presented in the appendix, together with a sample output of the program.