Changes to Delta Operations Start Today: Balancing Water Needs for Millions of Californians and the Environment

California’s water system is complex and requires real-time adjustments to balance the needs of our state’s cities and farms and the natural environment. Starting today, the State Water Project (SWP) is adjusting operations to meet those needs.

The SWP’s pumping plant near Tracy diverts water from the Sacramento and San Joaquin rivers and lifts it into canals that flow to reservoirs and local water agencies. In March, the pumps moved approximately 125,000 acre-feet of water, enough to supply 375,000 households for a year. Today, San Luis Reservoir, an important parking spot for water that eventually flows to San Joaquin Valley farms and Southern California cities, is 90% full and holds 331,000 more acre-feet than it did last year at this time.

As of today, SWP pumping rates in the Delta have been reduced from approximately 1,200 cubic feet per second (cfs) to 600 cfs. Operators likely will maintain that lower rate through the end of May unless San Joaquin or Sacramento River flows increase beyond certain high-flow thresholds.

The pumping curtailment is required under a permit to protect five fish species listed under endangered species laws. Those fishery protection objectives have a large effect on water supply across California, because they restrict how much water may be captured by the federal and state water projects that serve 30 million people and four million acres of farmland. Scientists generally agree that spring outflow in March, April, and May improves habitat and food availability for Delta smelt and longfin smelt and improves migratory conditions for winter-run and spring-run Chinook salmon. Higher spring outflow also helps to minimize the number of fish pulled toward the pumping plant.

Future Spring Delta Water Project Operations

In future years, the SWP’s spring outflow requirement may be satisfied through a different method than simply reduced pumping. The State Water Resources Control Board is currently considering adoption of a program, called Healthy Rivers and Landscapes, that would expand fish habitat and increase springtime flows in the Sacramento and San Joaquin rivers and the rivers that flow to them, as well as Delta outflow. State, federal, and local water agencies negotiated the $2.6 billion Healthy Rivers and Landscapes program’s habitat and flow commitments because they believed it could serve as a faster, less economically disruptive way to balance competing uses of water than the strictly regulatory approach available to the State Water Board. State Water Board regulatory authorities are process-intensive, focused mainly on requiring additional water, and result in protracted litigation and uncertainty. A combination of increased fish habitat and increased springtime flows are believed to provide greater benefits than additional flow alone.

The SWP’s endangered species authorizations note that if and when the State Water Board adopts the Healthy Rivers and Landscapes program as part of its update of the water quality objectives that Delta water users must meet, then the pumping reductions and augmented springtime flows that water users committed to in the Healthy Rivers and Landscapes program will replace the spring outflow requirements in effect this year.

Targeted Research to Inform Water Project Operations

Science, monitoring, and learning from experimentation are foundational to the Healthy Rivers and Landscapes program. Participating agencies planned carefully how best to efficiently monitor the results of their efforts. They embedded their monitoring proposal in a Science Plan that is driven primarily by hypotheses about which actions might improve conditions for native fish. Signatories to the program are not waiting for State Water Board approval to launch scientific inquiries. Scientists with the California Department of Water Resources, which operates the SWP, and the California Department of Fish and Wildlife will be tracking the effects of the April and May pumping curtailment to better understand how flow enhances habitat conditions and, ideally, supports improved growth and survival of protected species.

Insights gleaned from this research should help state and federal agencies strike a better balance between capturing water supply and protecting native fish species and water quality. This can help accelerate a move away from rigid, calendar-driven regulations in an era of increasing whiplash between extreme wet and dry conditions. Neither storms nor fish populations move in line with a calendar of regulations. Adapting operations based on immediate conditions requires solid science, monitoring programs, and a willingness by regulators to consult, decide, and move quickly.

Better Infrastructure to Create Flexibility

Our new climate of increased aridity and more powerful storms also demands new infrastructure. Had it been in place this winter, the proposed Delta Conveyance Project could have moved 760,000 acre-feet of water into storage, enough to supply more than 2 million households for a year. The proposed project’s intakes on the mainstem Sacramento River in the north Delta would not be subject to the same restrictions as the pumping plants near Tracy, creating additional opportunities to convert high-flow storm runoff into water supply without violating federal and state endangered species and water quality rules.

California is both wetter and drier in a warming world. The trend of the last few decades is toward longer and more severe droughts and more extreme atmospheric rivers, with flashes from super wet to super dry in a single season. Keeping SWP deliveries reliable will require new regulatory frameworks and new infrastructure.