After researching the pumping station I refer to as “the Powerhouse,” I hoped to find an online resource that would explain when the pumps are activated. It made me realize that, after all these years, I actually don’t know much about that specific pumping station. Does it really generate power, or is it simply a pumping station? Where does the water come from, and why is it sometimes muddy when the flows at Check 12 are clear?
Daily Water Flows in and out of O’Neill Forebay
The forebay is part of the Central Valley Project and serves as a balancing reservoir between the San Luis Reservoir and the California Aqueduct. Three Pump Stations that effect fishing the O’ Neill Forebay
- Dos Amigos Pumping Plant: Located miles downstream of the O’Neill Forebay down the outlet of Oneill Forebay which is near the Mederos Launch. The Dos Amigos Pumping Plant is responsible for lifting water from the California Aqueduct to higher elevations as the aqueduct continues southward toward the San Joaquin Valley and Southern California. The plant moves water that has already passed through the O’Neill Forebay, meaning it doesn’t directly pump water into the forebay, but it affects downstream water distribution. After water is released from the O’Neill Forebay into the California Aqueduct, it flows by gravity to Dos Amigos, where the plant then lifts the water to allow it to continue its journey through the aqueduct system south.
These two plants play critical roles in managing the water movement into and out of the O’Neill Forebay, part of the larger Central Valley Project.
San Luis Reservoir and Trash Racks
The pumping plant located at the San Luis Reservoir dam is called the William R. Gianelli Pump-Generating Plant. This facility is part of the San Luis Reservoir complex and is integral to the operation of both the reservoir and the broader Central Valley Project. It is s located at the base of the San Luis Dam, on the San Luis Reservoir.
- Pumping:
- When water is abundant or during periods of low energy demand, the plant pumps water from the O’Neill Forebay up into the San Luis Reservoir for storage.
- The plant is responsible for pumping water into the San Luis Reservoir from both the California Aqueduct (State Water Project) and the Delta-Mendota Canal (Central Valley Project).
- The water is stored in the San Luis Reservoir, serving as a reserve for agricultural, urban, and industrial uses during dry periods.
- Generating Power:
- During peak electricity demand or water releases, the stored water from the San Luis Reservoir flows back down through the Gianelli Pump-Generating Plant to the O’Neill Forebay.
- As water flows through, it spins the turbines in the plant, generating hydroelectric power.
- The power generated can reach up to 424 megawatts (MW) of electricity, making it a significant contributor to the state’s renewable energy portfolio.
Where does the water go?
Water released from the San Luis Reservoir can be directed either into the Delta-Mendota Canal or the California Aqueduct, depending on operational needs. Here’s a breakdown:
- California Aqueduct: A significant portion of the water stored in San Luis Reservoir typically flows into the California Aqueduct. This water is primarily used to supply agricultural, municipal, and industrial needs in the Central Valley and Southern California. The aqueduct is a major part of the State Water Project (SWP), and it receives water from the San Luis Reservoir when it is pumped into the aqueduct system. The exact amount varies based on annual allocations and demands. Roughly 30% of the State Water Project’s water is delivered to urban areas in Southern California. A significant portion of this urban water goes to the greater Los Angeles area, although this water also serves other urban centers like San Diego and the Inland Empire. Agriculture uses about 70% of the aqueduct’s total water supply.
- Delta-Mendota Canal: Another portion of the water from San Luis Reservoir is released into the Delta-Mendota Canal, which supplies water mainly to agriculture in the western San Joaquin Valley. The canal serves users who are part of the federal Central Valley Project (CVP). Similar to the aqueduct, the amount of water sent to the Delta-Mendota Canal depends on the year’s water allocations, which are based on precipitation, snowpack, and other hydrological factors. The primary recipient of Mendota Canal water, particularly for irrigation in the western San Joaquin Valley. the Mendota Canal is primarily focused on delivering water for agricultural irrigation, with additional allocations for environmental and municipal purposes. The actual distribution fluctuates based on water availability and policy decisions made by federal agencies.