The operations of the federal Central Valley Project ("CVP") and the State Water Project ("SWP") adversely affect the water quality, flows and levels in the southern Delta.
When the CVP began operations in the later 1940's and early 1950's it decreased the average annual flow of the San Joaquin River into the southern Delta by approximately 550 thousand acre feet (annual average). In addition, by delivering water to the western side of the San Joaquin Valley for agricultural use, the CVP in effect imports approximately 1 million tons of salt into the basin. The agricultural crops consume water but not salt and so the salts are concentrated, and each year anywhere from 400 - 700 thousand tons of salt enter the San Joaquin River either as surface drainage of subsurface accretions. This salt is sometime up to 5 times the concentration of the salinity standards downstream in the Delta. This concentrated salt caused substantial damage to local agriculture until water quality standards were adopted and New Melones Reservoir on the Stanislaus River began diluting the salts pursuant to its permits and federal authorization. Though such actions have improved the situation in the southern Delta, salt continues to be a major problem for agriculture.
The operation of the CVP and SWP export pumps in the southern Delta also cause other problems. The CVP export pumps operate generally 24 hours a day. They therefore both intercept and decrease the incoming tides which decreases the amount of fresher Delta water entering the area and further lower the low low tides. The SWP operates its export pumps using a forebay (Clifton Court Forebay) and generally takes water on and around the incoming or flood tides. This too decreases the amount of fresher Delta water entering the area but does not affect the low tides as much as the CVP. The net effects of these export pumps is to reverse flows in certain channels which exacerbates and creates null zones where the CVP salts from the San Joaquin River further concentrate. This concentration of salts results in salt buildup in the soils and adverse impacts to crop production and plant health.
The lowering of water levels also adversely impacts the ability of local diverters to operate their pumps or siphons. In most years, some local diverters cannot divert when needed, or cannot divert as much water as needed due to this artificial lowering of local water levels.
The above adverse impacts of the CVP and the SWP are experienced in most years and thus the landowners and farmers within the South Delta Water Agency continue to be harmed. Efforts to negotiate a contract or contracts to address these issues have not been successful. Currently the California Department of Water Resources (which operates the SWP) and the U.S. Bureau of Reclamation (which operates the CVP) refuse to negotiate with the South Delta Water Agency.
Below is a 1980 Report authored by the SDWA and the Bureau of Reclamation (during the brief time it was renamed) which quantifies the effects of the projects on the southern Delta. Though now 40 years old, it is still the most accurate description and analysis of the projects' effects.
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