Evaluating Intake Pipeline Hydraulics to Optimize Contra Costa Water District’s Rock Slough Intake

Contra Costa Water District (District) has several water sources, including an intake from the San Joaquin River at Rock Slough. Water from this source was originally conveyed to the District’s water treatment plants via 6.5 km of unlined canal with a capacity of 9.9 cubic meters per second (m³/s). The District has been executing a project to convert the canal into a buried 3-m diameter reinforced concrete pipeline (RCP). As of December 2020, four of five segments totaling 4.5 km have been converted to pipe, with approximately 2 km of canal remaining. Changing this system from an open channel gravity system to a closed conduit system required a complete hydraulic redesign of the conveyance system. A hydraulic model was developed to evaluate a wide range of operating scenarios to accommodate both current and future conditions. The hydraulic model identified limitations in the intake system and a path forward for the District to maintain the system’s 9.9 m³/s conveyance capacity.