Before 1933, what did parts of California’s Central Valley not have enough water for

The Central Valley Project (CVP) is a federal power and water management project in the U.S. state of California under the supervision of the United States Bureau of Reclamation (USBR). It was devised in 1933 in order to provide irrigation and municipal water to much of California's Central Valley—by regulating and storing water in reservoirs in the northern half of the state (once considered water-rich but suffering water-scarce conditions more than half the year in most years), and transporting it to the water-poor San Joaquin Valley and its surroundings by means of a series of canals, aqueducts and pump plants, some shared with the California State Water Project (SWP). Many CVP water users are represented by the Central Valley Project Water Association.

In addition to water storage and regulation, the system has a hydroelectric capacity of over 2,000 megawatts, and provides recreation and flood control with its twenty dams and reservoirs. It has allowed major cities to grow along Valley rivers which previously would flood each spring, and transformed the semi-arid desert environment of the San Joaquin Valley into productive farmland. Freshwater stored in Sacramento River reservoirs and released downriver during dry periods prevents salt water from intruding into the Sacramento-San Joaquin Delta during high tide. There are eight divisions of the project and ten corresponding units, many of which operate in conjunction, while others are independent of the rest of the network. California agriculture and related industries now directly account for 7% of the gross state product for which the CVP supplied water for about half.

Many CVP operations have had considerable environmental consequences, including a decline in the salmon population of four major California rivers in the northern state, and the reduction of riparian zones and wetlands. Many historical sites and Native American tribal lands have been flooded by CVP reservoirs. In addition, runoff from intensive irrigation has polluted rivers and groundwater. The Central Valley Project Improvement Act, passed in 1992, intends to alleviate some of the problems associated with the CVP with programs like the Refuge Water Supply Program.

In recent years, a combination of drought and regulatory decisions passed based on the Endangered Species Act of 1973 have forced Reclamation to turn off much of the water for the west side of the San Joaquin Valley in order to protect the fragile ecosystem in the Sacramento-San Joaquin Delta and keep alive the dwindling fish populations of Northern and Central California rivers. In 2017 the Klamath and Trinity rivers witnessed the worst fall run Chinook salmon return in recorded history, leading to a disaster declaration in California and Oregon due to the loss of the commercial fisheries. The recreational fall Chinook salmon fishery in both the ocean and the Trinity and Klamath rivers was also closed in 2017. Only 1,123 adult winter Chinook salmon returned to the Sacramento Valley in 2017, according to a report sent to the Pacific Fishery Management Council (PFMC) by the California Department of Fish and Wildlife (CDFW). This is the second lowest number of returning adult winter run salmon since modern counting techniques were implemented in 2003. By comparison, over 117,000 winter Chinooks returned to spawn in 1969

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