California’s largest river, the Sacramento, provides
31 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
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 freshwater tidal estuary on the West Coast.
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.
The federal Safe Drinking Water Act sets standards for drinking
water quality in the United States.
Launched in 1974 and administered by the U.S. Environmental
Protection Agency, the Safe Drinking Water Act oversees states,
communities, and water suppliers who implement the drinking water
standards at the local level.
The act’s regulations apply to every public water system in the
United States but do not include private wells serving less than
According to the EPA, there are more than 160,000 public water
systems in the United States.
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
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 California’s Central
As part of the historic Colorado River Delta, the Salton Sea
regularly filled and dried for thousands of years due to its
elevation of 237 feet below sea level.
The most recent version of the Salton Sea was formed in 1905 when
the Colorado River broke
through a series of dikes and flooded the seabed for two years,
creating California’s largest inland body of water. The
Salton Sea, which is saltier than the Pacific Ocean, includes 130
miles of shoreline and is larger than Lake Tahoe.
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.