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The Bay Delta


For centuries, the Sacramento-San Joaquin River Delta was a vast plain with seasonal and tidal flooding, creating 1,000 square miles of brackish tidal marsh, narrow, branching tidal channels, and freshwater marshes.

Following 19th century European settlement and 20th century water supply, agricultural and urban development, these original habitats of the Delta have been replaced by sub-sea level, levee-protected islands and simplified, deep, wide, armored waterways.

Today there are approximately 1,100 miles of levees in the Delta protecting 625 square miles of productive agricultural areas and 500,000 residents in both, rural communities and urban areas. The fertile peat soil produces $800 million annually in agricultural crops .

The Delta is home to more than 700 plant and animal species, many of which are threatened or endangered. The mixing of fresh water and salt water (brackish water) in Suisun Bay and the Delta provides essential estuarine habitat for migratory fish like salmon and resident fishes like delta smelt (photo bottom right) and longfin smelt. In addition, the Delta also provides critical refuge for migratory birds traveling the pacific flyway.

The Delta also serves as the hub of California’s water system. A portion of the snowmelt and rain from the Sierra Nevada and other points to the north runs into the rivers that supply the Delta and from there makes its way south, to provide drinking water to 25 million Californians, including those in Santa Clara County, and irrigation water to Central Valley farmers.

After decades of alterations, the Delta is far from the natural estuary it once was. The Delta’s ecosystem is impacted by several factors including loss of habitat, proliferation of invasive species, contaminants, and water operations. This has led to declining fish populations and increasing regulatory restrictions that have decreased State Water Project (SWP) and federal Central Valley Project (CVP) water exports over the past several decades in order to protect threatened and endangered fish species.