Storing water has always been critical in California. Today the strategies are changing to meet a new generation of challenges. As our state moves forward with long-term plans to modernize our aging water system, expanding our water-storage capabilities is a central part of the equation.

In our grandparents’ era, water storage projects were a means to increase supply. Today they are more about building operational flexibility to meet 21st-century needs.

Under a new water policy paradigm formalized by the Legislature in 2009, our system of canals, reservoirs and conveyance facilities must be managed for the dual goals of a healthy ecosystem and a reliable water supply. We cannot meet that mandate without more places to “park” water — both above and below the Delta — for relatively short periods of time.

As an operational concept, that means catching water in high volumes during storm events, parking it for a time, and then releasing it to aid the environment, improve water quality, meet summertime demands or replenish groundwater basins.

Climate change — with its specter of higher peak flood flows and more extreme drought in the future — makes it even more important that we develop this kind of flexibility.

In the past, water storage projects involved building new dams across rivers in the foothills or other locations. The water might be stored for years before gradually being released. Today storage may be shorter term and closer to the user. Projects are located off-stream, with stored water released as needed, often in the same year.

Los Vaqueros Reservoir is a prime local example. Los Vaqueros, an off-stream reservoir operational since 1998, stores high-quality water pumped through state-of-the-art fish screens from the Delta when it’s available. The water is then used to boost water quality and bolster supplies during dry periods.

A recent expansion enlarged the reservoir’s capacity by 60 percent, immediately benefiting Contra Costa Water District customers and opening the door to potential partnerships with other Bay Area water agencies to store water at the centrally located reservoir.

To the north, a proposed off-stream storage project near Maxwell in the Sacramento Valley is entering a key planning phase with the release of environmental documents and a feasibility study this summer.

The proposed Sites Reservoir would safely divert water from the Sacramento River and store it for later use, adding significant flexibility to the state’s backbone water management system. Water stored in Sites would generate an array of benefits, from improved water supply certainty to better management of temperatures and flows for salmon and other species.

Other projects proposed on the San Joaquin River above the existing Millerton Reservoir and on the Sacramento River via enlargement of Shasta Dam would give water managers flexibility to pulse water downstream for environmental purposes and time the delivery of water out of the Delta when it is best for fishery management.

As state and federal agencies move closer to a decision on the Bay Delta Conservation Plan later this year, new storage capacity must be a key component of the state’s water solution. Additional storage will be critical to allow project operators to pump more water in wet years and less in dry and environmentally sensitive times for species.

It will take an “all-of-the-above” approach to create a sustainable water delivery system in California for the next century. That means investing in more storage to equip our system to meet today’s demands for ecosystem health, ease the pressure on Delta levees and provide a more reliable water supply.

No step would do more to set the state on the right course for the future.

Jerry Brown is general manager of the Contra Costa Water District. Thaddeus Bettner is general manager of Glenn-Colusa Irrigation District.