Efforts to preserve natural wilderness areas in California go back at least to 1890, when the US Congress created three national parks in the Sierra Nevada: Sequoia, Grant (now part of Kings Canyon), and Yosemite. Three years later, some 4 million acres (1.6 million hectares) of the Sierra Nevada were set aside in national forests. In 1892, naturalist John Muir and other wilderness lovers founded the Sierra Club which, with other private groups of conservationists, has been influential in saving the Muir Woods and other stands of redwoods from the lumbermen's axes. Over the next century, numerous other natural areas were designated national parklands. Among the most recent were Death Valley National Park (1994), Joshua Tree National Park (1994), and "Rosie the Riveter" World War II Home Front National Historical Park (2000).
California's primary resource problem is water: the southern two-thirds of the state account for about 75% of annual water consumption but only 30% of the supply. Water has been diverted from the Sierra Nevada snow runoff and from the Colorado River to the cities and dry areas largely by means of aqueducts, some 700 mi (1,100 km) of which have been constructed in federal and state undertakings. In 1960, California embarked on one of the largest public works programs ever undertaken in the United States when voters approved a bond issue to construct the California Water Project, designed to deliver 1.4 trillion gallons of water annually to central and southern California for residential, industrial, and agricultural use. Other purposes of the project were to provide flood control, generate electric power, and create recreation areas.
Maintaining adequate water resources continued to be a problem in the 1990s. As the result of a US Supreme Court decision, southern California lost close to 20% of its water supply in December 1985, when a portion of the water it had been permitted to draw from the Colorado River was diverted to Arizona. In 1982, California voters turned down a proposal to build a canal that would have delivered water that flows into San Francisco Bay to southern California; no other plans to cope with the impending shortage were approved at that time. In December 1994 the state and federal governments joined together to form the Bay Delta Accord, intended to restore the environmentally threatened San Francisco Bay area through a combination of better conservation efforts and public and private investment. In November 1996 voters approved a bond issue valued at nearly $1 billion to implement the Accord.
Air pollution has been a serious problem since July 1943, when heavy smog enveloped Los Angeles for the first time; smog conditions in October 1954 forced the closing of the city's airport and harbor. Smog is caused by an atmospheric inversion of cold air that traps unburned hydrocarbons at ground level; perhaps two-thirds of the smog particles are created by automobile exhaust emissions. In 1960, the state legislature passed the first automobile antismog law in the nation, requiring that all cars be equipped with antismog exhaust devices within three years. (Federal laws controlling exhaust emissions on new cars came into effect in the 1970s.) The city's smog problem has since been reduced to manageable proportions, but pollution problems from atmospheric inversions still persist there and in other California cities. Nonetheless there is reason for optimism—in 1996, for example, Southern California had the best air quality ever measured in the post–World War II era. A key factor was introduction of a reformulated gasoline touted as the cleanestburning in the world—which reduced polluting emissions by 15% when put into use in 1996. The state inspection-and-maintenance program is also being reformed and updated, focusing on the small number of cars linked to as much as 50% of vehicular pollution in the state.
In early 1995, the Environmental Protection Agency (EPA) approved a California ozone-reduction plan that ordered car manufacturers to design and produce cars that will be 50% to 84% cleaner than the ones sold in 1990. In 1998 new regulations were introduced to give tax credits to Californians who drove very low emission vehicles. In 2001 regulators proposed offering credits for use of a shared fleet of vehicles. California's plan that 10% of the 2003 cars offered for sale would be zero emission vehicles (ZEV) was not realized.
State land-reclamation programs have been important in providing new agricultural land and controlling flood damage. One of the earliest such programs, begun shortly before 1900, reclaimed 500,000 acres (200,000 hectares) by means of a network of dams, dikes, and canals in the swampy delta lying within the fork of the Sacramento and San Joaquin rivers. In 1887, a state law created irrigation districts in the southeastern region; the Imperial Valley was thus transformed from a waterless, sandy basin into some of the most productive agricultural land in the United States.
Flood control was one of the main purposes of the $2.6 billion Feather River Project in the Central Valley, completed during the 1970s. Ironically, in the western portion of the Central Valley, farmland is now threatened by irrigation water tainted by concentrated salts and other soil minerals, for which current drainage systems are inadequate. One drainage system, the San Luis Drain, originally intended to carry the water to San Francisco Bay, was stopped short of completion and goes only as far as the Kesterson National Wildlife Refuge, where, according to the US Fish and Wildlife Service, the tainted water has caused birth defects in birds.
In the 1980s, the state legislature enacted stringent controls on toxic waste. California has also been a leader in recycling waste products—for example, using acid waste from metal-processing plants as a soil additive in citrus orchards. In 2003, the Environmental Protection Agency's database listed 903 hazardous waste sites, 96 of which were on the National Priorities List, in California.
The California Department of Water Resources is responsible for maintaining adequate groundwater levels, enforcing water-quality standards, and controlling floodwaters. The state Department of Conservation has overall responsibility for conservation and protection of the state's soil, mineral, petroleum, geothermal, and marine resources. The California Coastal Commission, created in 1972, is designated by federal law to review projects that effect California's coastline, including offshore oil leasing, which has become a source of concern in recent years. In 2001, California received $320,783,000 in federal grants from the EPA; EPA expenditures for procurement contracts in California that year amounted to $41,087,000.