California’s largest river, the Sacramento, provides 35 percent of the state’s developed water supply.
Once called “the Nile of the West,” the Sacramento River drains the inland slopes of the Klamath Mountains, the Cascade Range, the Coast Ranges and the western slopes of the northern Sierra Nevada. The river stretches some 384 miles from its headwaters near Mount Shasta to the Sacramento-San Joaquin Delta.
The Sacramento-San Joaquin Delta is California’s most crucial water and ecological resource.
More than a century ago, farmers began building a network of levees to drain and “reclaim” what was then a marsh. Progressively higher levees were built to keep the surrounding waters out, the lands were pumped dry and the marsh was transformed into productive island farms, mostly below sea level. [See Sacramento-San Joaquin Delta Timeline].
The Sacramento-San Joaquin Delta always has been at the mercy of river flows and brackish tides.
Before human intervention, salty ocean water from the San Francisco Bay flooded the vast Delta marshes during dry summers when mountain runoff ebbed. Then, during winter, heavy runoff from the mountains repelled sea water intrusion.
The Sacramento-San Joaquin Delta has been the hub of California’s water system for more than 50 years and along the way water experts have struggled to balance the many competing demands placed on the estuary—the largest on the West Coast.
Those demands include meeting the needs of agricultural communities in the Central Valley, water deliveries through the Delta to the Bay Area and arid Southern California, and providing habitat for plants and wildlife.
Over times, the home of these species-the Sacramento-San Joaquin Delta ecosystem-has been impacted for many decades by human activities, such as gold mining, flood protection and land reclamation. Along the way, more than 200 exotic species have been intentionally or accidentally introduced.
Freshwater flows from the Delta meets saltwater from the ocean near Suisun Marsh located to the east of San Francisco Bay. Suisun Marsh and adjoining bays are the brackish transition between fresh and salt water. But the location of that transition is not fixed.
The Sacramento-San Joaquin Delta includes approximately 500,000 acres of waterways, levees and farmed lands extending over portions of five counties: Contra Costa, Sacramento, San Joaquin, Solano and Yolo.
With the Sacramento-San Joaquin Delta crucial to California’s overall water supply, roughly 1,115 miles of levees protect farms, cities, schools and people.
Since the 19th century, levees—from the French word ‘lever’, or ‘to raise’— have been erected to protect “reclaimed” marshland, popularly referred to as Delta islands. The levees were built to prevent flooding and allow cultivation of the rich soil while protecting public infrastructure such as highways and pipelines.
For more than 30 years, the Sacramento-San Joaquin Delta has been embroiled in continuing controversy over the struggle to restore the faltering ecosystem while maintaining its role as the hub of the state’s water supply.
Lawsuits and counter lawsuits have been filed, while environmentalists and water users continue to clash over the amount of water that can be safely exported from the region.
Landowners in California are entitled to pump and use a reasonable amount of groundwater from a basin underlying their land. When there is insufficient water to meet demand, property owners are expected to extract the safe yield—the rate at which groundwater can be withdrawn without causing long-term decline of water levels.
If the amount of groundwater withdrawn exceeds the safe yield amounts, the well can go dry.
Excess salinity poses a growing threat to food production, drinking water quality and public health. Salts increase the cost of urban drinking water and wastewater treatment, which are paid for by residents and businesses. Increasing salinity is likely the largest long-term chronic water quality impairment to surface and groundwater in the Central Valley.
Southern California’s Salton Sea—approximately 232 feet (70 m) below sea level—is the by-product of a man-made accident.
In 1905, the Colorado River broke through a series of dikes, flooding a basin known as the Salton Sink in the Imperial Valley and forming the Salton Sea in what had been an ancient lake bed occasionally fed by the river.
California’s central coast is home to the San Felipe Division of the federal Central Valley Project. Authorized in the 1960s and completed in 1988, San Felipe Division includes a 5.3-mile-long tunnel (the Pacheco Tunnel), pumping plant and other conduits.
It transports water west from the Central Valley’s San Luis Reservoir near Los Banos to supply Santa Clara and the high-tech Santa Clara Valley as well as parts of Santa Cruz, Monterey and San Benito counties.