Peripheral Canals: Way Past, Past, and Present

Comparing Export Strategies
Courtesy of Public Policy Institute of California.

Redistributing water from northern to southern California has challenged dreamers, planners, and engineers almost since California's statehood in 1850.

The image at right outlines the basic options for obtaining water supplies from the Delta: sending water through the Delta; a peripheral canal; using two peripheral canals to move water around the Delta; and regional self-sufficiency in water use, including using less water (conserving).

The "peripheral canal" idea has been around since the 1940s. At the heart of it is the hope that irrigators would receive water that has not had to pass through the Bay-Delta estuary prior to delivery to their fields. Water quality upstream of the Delta is better and more desirable for delivery to taps of California's cities.

Diversions from the Delta remove water from the tidal estuary and ecological nurseries that exist there, including the expanse of the Suisun Marsh where many species of fish rear their young.

Canal alignment around the Delta, 1946.

Courtesy of US Bureau of Reclamation, Central Valley Basin: Our Rivers: Total Use for Greater Wealth, Senate Document 113, 1946. Click to enlarge.

Originally from the US Bureau of Reclamation, such a canal would divert water from Sacramento Valley rivers around the Delta to enable fresh water to reach the pumps or irrigate San Joaquin Valley lands on the way. In the map at left, a dreamed-of Folsom-Newman Canal would divert water from the American River near Folsom Dam, and a "Hood-Clay Pump Canal" would divert Sacramento River water in the north Delta to the Folsom-Newman, and this water would flow by gravity south to a point on the Delta Mendota Canal near San Luis Reservoir.

Further east, a "Folsom-Ione Canal" would take water from Folsom Lake to a conceptual "Ione Reservoir" on the Mokelumne River, and an Ione-Mendota Canal would leave the Ione area, pick up additional water from a "Cooperstown Reservoir" on its way to the Mendota Pool (where the Delta Mendota Canal ends). The Folsom Newman canal would be joined to the Ione-Mendota canal by an Elliot-Wallace pump canal. All of this water would not see the Delta until after it had irrigated eastern San Joaquin Valley lands and drained into the Mendota Pool and other San Joaquin River tributaries.

A Peripheral Canal alignment, 1978

Peripheral Canal alignment, 1978
Courtesy of California Department of Water Resources, Bulletin 76: Delta Water Facilities, 1978.

In the 1960s and 1970s, other peripheral canals that would divert the Sacramento River at Hood around the "periphery" of the Delta region. This canal would have been about 43 miles long and would have delivered canal water directly to the state and federal pumps near Tracy. The 1982 design for the canal would have enabled it to carry 15,000 cubic feet per second.

The "release points" shown on the plan would enable the Department of Water Resources to provide flows from the canal into existing channels of the Delta in hopes of addressing flow needs for salmon migration and water quality and water level concerns. Determining the procedures and protocols for operating the canal, however, would mean that the public would have to trust the Department and the water contractors to protect fish and water quality.

Instead, a public referendum (Proposition 9) on the legislature's approval of bonds for such a peripheral canal was defeated in June 1982 by a vote of 63 to 37 percent of the electorate.

At the time, some observers of California water politics believed the peripheral canal was dead. But it was not.

CalFED's "isolated conveyance facility" alignment, 1998

CalFED Alternative 3 1998.jpg
Courtesy of the CalFED Bay-Delta Program.

But by 1998, the CalFED Bay Delta Program planning process to address Delta ecological and water supply concerns developed three alternatives for moving water through or around the Delta, including what CalFED planners called an "isolated conveyance facility." This plan called for a smaller capacity canal, around 5,000 cubic feet per second. The CalFED plan also included an ecosystem restoration plan, a multi-species habitat conservation plan, a levee repair strategy, reservoir planning studies, an ambitious science program to study Delta estuarine and river systems, a water transfer program, an "environmental water account" program to mitigate export pumping losses of fish and of water to contractors, and programs for water use efficiency and drinking water quality. This plan failed to receive sufficient funding, and has been all but discontinued (except for the science program).

Next: Bay Delta Conservation Plan