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California Water Projects in Sustainable Agriculture

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California is the third largest, and most populous state in United States and has the fifth largest economy in the world. California has a large agriculture industry worth $49.8 billion in 2018 which is 2.8 percent of the state’s economy according to Northern California Department of Food and Agriculture (CDFA).   California agricultural products include more than 400 commodities. Over a third of the country’s vegetables and two-third of the country’s fruits and nuts are grown in California.  According to CDFA the total agricultural export totaled $21.7 billion. The top valued agricultural products include dairy products, almonds, grapes, pistachios, lettuce, walnuts, floriculture, and tomato.  

Central valley of the state is a main agriculture area, where more than 250 crops are grown and about 75% of irrigated land in California is in the Central Valley. Part of the Central Valley, the Sacramento-San Joaquin Delta or California Delta is an important agricultural, ecological, and economical resource. The Delta is formed by Sacramento River and San Joaquin River. Delta covers 738,000 acres interlaced with hundreds of miles of waterways. Much of the land is below sea level and relies on more than 1,000 miles of levees for protection against flooding.

Map of the Central Valley’s four major regions (from USGS: https://ca.water.usgs.gov/projects/central-valley/about-central-valley.html)

The Delta is unique and valuable resource and an integral part of California’s water system. According to the California Department of Water Resources (DWR) it receives runoff from 40 percent of the State’s land area including Sacramento, San Joaquin, and east side streams. Its land and waterways support communities, agriculture, and recreation and is the focal point for water distribution throughout the State. The Delta is a tidal estuary.  Tidal action and Delta outflow create a gradual salinity gradient from the Pacific Ocean into the interior Delta.

Two major water export facilities are dependent on Delta waterways and the levees. Banks

pumping plant provides water to the State Water Project (SWP) via the California Aqueduct

while the Tracy (Jones) pumping plant provides water to the Central Valley Project

(CVP) via the Delta Mendota Canal. These water projects operate under strict guidelines

By California State Water Resources Control Board. Upstream reservoir releases, Delta canal’s operation by gates, and amount of pumping are controlled to satisfy the salinity standards.

Meeting the salinity standards at specified locations of the Delta while controlling upstream reservoir releases, and amount of pumping are challenges faces by operators. Computer models are used to help decision making and in Delta operations. 

The SWP operates to balance the needs of water delivery and environmental protection.  The sustainability of California’s water resources depends on the environmental health of the Sacramento-San Joaquin Delta. In cooperation with the federal Central Valley Project (CVP) the SWP operates to limit salinity intrusion into the Sacramento-San Joaquin Delta and Suisun Marsh by supplementing freshwater outflows to the ocean and limiting water exports from the Delta during certain times of the year.

Sunflower field with surface irrigation, Davis, California

The SWP is a water storage and delivery system of reservoirs, aqueducts, power plants and pumping plants extending more than 700 miles—two-thirds the length of California. Planned, constructed, and operated by the Department of Water Resources, the SWP is the nation’s largest state-built, multi-purpose, user-financed water project. It supplies water to more than 27 million people in northern California, the Bay Area, the San Joaquin Valley, the Central Coast and southern California. SWP water also irrigates about 750,000 acres of farmland, mainly in the San Joaquin Valley.

A tomato field in Davis, California.

SWP was designed to deliver nearly 4.2 million acre-feet of water per year. Water is received by 29 long-term SWP Water Supply Contractors who distribute it to farms, homes, and industry. Water supply depends on rainfall, snowpack, runoff, water in storage facilities, and pumping capacity from the Delta, as well as operational constraints for fish and wildlife protection, water quality, and environmental and legal restrictions.

The SWP was designed to provide many additional benefits:

  • Flood control
  • Power generation
  • Recreation – SWP lakes and reservoirs provide opportunities to swim, picnic, waterski, boat, fish, hike, bike, camp, and horseback ride.
  • Fish and wildlife habitat –The SWP is operated to protect fish and wildlife with fish hatcheries, fish screens and passages, habitat restoration, and restricted pumping schedules.

To be continued…

Nimal C. Jayasundara
Nimal C. Jayasundara
Ph.D., PE. Water Resources Engineer, California Department of Water Resources, California.

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