The scope of water's role in California is just as diverse and complex as the state's climate, geography, and urban, agricultural, and economic landscapes. This is a state that stretches nearly 700 miles in length, hosts both the highest and lowest points in the Lower 48 states, and has climate zones that range from coastal to highlands to deserts. Its average annual rainfall varies from over 150 inches in the northwestern mountains to less than two inches in Death Valley. The Golden State has seen mega-floods and extended years of drought. California also has the largest population, largest economy, and largest agricultural values of any state. And the state's very livelihood is significantly impacted by the amount of water that falls from the sky, how that water is stored and transported, and how it is used (or not used).
The precipitation patterns over the state are also diverse, with nearly three-quarters of the rain that falls coming down in the northern third of the state, while three-quarters of the population resides in the central and southern thirds. Further complicating the equation is California's Mediterranean climate; most of its precipitation falls between October and April, but the greatest demand for water is in the warm and dry summer months.
California Water: A History
The management of its water has been one of California's greatest challenges dating back to the earliest settlements in 1769, when “Alta California” was settled by the Spanish. One of the initial challenges was the issue of water rights, as California was divided into missions, pueblos, and ranchos. These entities were located on rivers and streams, and under Spanish law they were granted rights to divert and use water for water supply and irrigation. These rights became important as the state was further settled, and a series of court decisions over the next 200 years held them to be valid. One of the original pueblos, El Pueblo de Nuestra Señora la Reina de los Ángeles, which became the city of Los Angeles, benefited greatly, as it was granted first rights to all of the native waters of the Los Angeles River and the connected groundwaters.
The mid-19th century saw huge changes to the California landscape, both politically and figuratively, as Alta California was ceded to the United States following the Mexican–American War in 1848 and gold was discovered in 1849. The subsequent Gold Rush pushed the non-native population from 10,000 to over 100,000. It also brought about the practice of hydraulic mining, where water flow was concentrated through a series of flumes and penstocks and then used to blast away entire hillsides to expose the valuable ore. And from these activities came the need for laws to allocate water between various users and the impacts of that water downstream.
The burgeoning state was further tested by the Great Flood of 1862, which caused record flooding from one end of the state to the other as much of the Central Valley was turned into an inland sea. (see Weatherwise, January/February 2007, “California Washed Away: The Great Flood of 1862”).
Through the end of the 19th century, the combination of these factors and a series of court rulings led to a complicated patchwork of water and irrigation districts, with the State of California and the United States Army Corps of Engineers attempting to manage the competing forces of industrial, agricultural, human, and environmental use.
At the turn of the 20th century, Los Angeles had depleted most of its local sources of water and began looking afar to meet its needs for a clean water source. This ended up being nearly 250 miles away in the Owens Valley, on the east side of the Sierra Nevada. By 1905, the City of Los Angeles had acquired almost all of the riparian land and water rights in the Owens Valley, often through rather questionable means. This led to the construction of the Owens Valley Aqueduct, which began delivering water to aquifers in the San Fernando Valley eight years later. But even this did not quench the region's thirst for water as Los Angeles's population grew to a half-million in 1920 and 1.2 million in 1930. To meet these needs, Los Angeles also bought up much of the groundwater rights in the Owens Valley and expanded its reach farther north to the tributaries feeding Mono Lake. These measures were not without controversy, and the aqueduct was dynamited several times by protesters.
This same time period saw certain parties in the San Francisco Bay Area seeking to assure adequate water for their future growth, and they too looked toward the Sierra Nevada. Their solution was to dam the Tuolumne River at the mouth of Hetch Hetchy Valley, not only to store water but also to generate hydroelectric power. The development of this valley, said by some to be just as magnificent as nearby Yosemite Valley, was fought by John Muir and the fledgling Sierra Club, and it was not until 1934 that Hetch Hetchy water flowed from taps in San Francisco. (Even today there are efforts to drain and restore Hetch Hetchy to its wild river status.)
During this same timeframe, these efforts to manage water in the state were being aided on a parallel track by the federal government, which was promoting the populating and development of the western United States. The cornerstone of these efforts was the Reclamation Act of 1902, signed by President Theodore Roosevelt in 1902, that established the United States Bureau of Reclamation to assist in the reclamation of western lands, primarily for agriculture.
California also began looking outside of its borders for water, in this case the Colorado River that drains a large portion of the southwestern United States. The first effort to divert some of the flow of the Colorado into the Imperial Valley began shortly after the turn of the twentieth century, with the construction of the Imperial Canal. However, in 1905, upstream snowmelt and flooding caused the failure of a series of dikes and flooded the lowlands in the center of the Imperial Valley. By the time the river had been diverted back to its original channel in 1907 the ancient and highly saline lakebed had been filled to form the landlocked 343-square-mile Salton Sea.
The 1922 Colorado River Compact set forth allotments of the river's average annual flow to 16.5 million acre-feet (MAF) shared among Arizona, Nevada, California, Colorado, New Mexico, Utah, and Wyoming, along with 22 Native American tribes, parks and wildlife areas, plus Mexico. The annual allocation to California is 4.4 MAF flowing through the All-American and Colorado River Aqueducts. The 80-mile-long All-American, completed in 1939, was a replacement for the Imperial Canal; it carries 3.1 MAF into the Imperial Valley. Two years later, the 223-mile-long Colorado River Aqueduct began carrying its annual allotment of 1.2 MAF to Southern California coastal communities from Ventura County in the north to San Diego County in the south.
The state's largest water supply undertaking was the Bureau of Reclamation's massive Central Valley Project (CVP), which began in the 1930s and continued into the 1950s. The CVP delivers 7 MAF annually from a total of 18 dams and reservoirs, 11 hydroelectric plants, and 500 miles of canals and aqueducts that stretch from Lake Shasta in the north to the Bakersfield area in the south. In addition to delivering water for irrigation to much of the Central Valley (i.e., the Sacramento and San Joaquin Valleys and the adjoining Delta), the CVP provides some of the water used in the urbanized areas of the San Francisco Bay Area and Central Valley towns.
The final piece in California's surface water infrastructure puzzle is the State Water Project (SVP), which was built and is managed by the California Department of Water Resources. Constructed in the 1960s and 1970s, the SVP is anchored by Lake Oroville on the Feather River in the Northern Sierra Nevada. Behind Lake Shasta, it's the state's second largest reservoir. On average, 2.3 MAF are delivered via the SVP through the lower Sacramento River and California Aqueduct to the San Joaquin Valley and over Tehachapi to Southern California, with branches taking water to parts of the Bay Area and south-central coastal communities.
In total, there are more than 1,000 major reservoirs, of which the 200 largest have a storage capacity of 41 MAF. Eleven of these have a capacity of 1 MAF or more, with Shasta Lake the largest at 4.5 MAF. The larger reservoirs not only store water, but they also control flooding as well as produce on average 15% of the state's electrical power.
Another vital component of California's waterscape is below the surface of the earth: its groundwater. In total, there is about 10 times the amount of groundwater as there is in all of the surface reservoirs combined; though not all of it is accessible or consumable. This hidden resource typically accounts for about 30% of the water used by urban areas and agriculture, and in drought years this figure can rise to 60%. By far the biggest users of groundwater are the agricultural interests, which use about 85% of the water brought to the surface from under the Central Valley. Groundwater is also at least a portion of the water supplies, as it is used by about 75% (approximately 30 million) of Californians. And for 6 million people, primarily in the Central Valley, it is their only source of water. Historically, it been treated as a “nest egg in the (water)bank” when surface flows are diminished. But groundwater is not a bottomless pit, and, just like other water resources in the state, its use requires careful management.
The groundwater under California's surface resides in beds (aquifers) of alluvial sediments that are made up of sand, gravel, and rocks, not large underground lakes as is often the public's perception. These aquifers fill (recharge) naturally from surface water by gravity through semi-porous surface soils and are trapped from below by impermeable bedrock. They can also be recharged through intentional efforts of over irrigating, percolation ponds, or pumping water back into the ground.
When more water is withdrawn from these aquifers than is recharged, the aquifers shrink due to compaction, with the result being less volume for storage and also the subsidence (sinking) of the land above. The largest groundwater aquifers in California are in the Central Valley, and these account for about three-quarters of the groundwater pumped for surface use. They are also the area of the largest subsidence recorded on the planet, with some areas having sunk 30 feet over the past decades. Other areas in the state that also experience subsidence, but to a lesser degree, are the Sacramento, Santa Clara, and Antelope Valleys. In all of these areas, not only is the groundwater potential reduced, but billions of dollars in damage to roads, canals, and other infrastructure have occurred.
Unfortunately, there has been little in the way of regulation for California's groundwater or incentives to better budget its use. As more water is pumped from the ground, the water table lowers and wells must be dug even deeper to reach it. In some areas of the San Joaquin Valley, where water was plentiful at less than a 100 feet below the surface a decade ago, wells are now having to be dug to 1,000 feet and at costs of up to $300 per foot. Not only are these deeper wells expensive, but they use larger amounts of energy to bring the water to the surface. A lowered water table also has ecological impacts, such as saltwater intrusion and increased concentration of manmade pollutants.
In addition to water for urban and agricultural uses, a significant percentage of California's water is designated for the “environment.” This usage falls into three broad categories: water that is “wild and scenic,” with flows that are unrestricted in rivers per state and federal mandates; water used to maintain specific habitats within streams and other watercourses for fish, migratory birds, and other wildlife; and water used to maintain water quality. In broad terms, this “environmental water” accounts for nearly half of the water that is potentially usable in the state.
A System Stressed by Drought
In total, California's water budget is used and misused by just about every group that has an interest in getting its fair share or blaming another group for using a disproportionate amount. In broad terms, about 200 MAF of water falls onto the California landscape as precipitation in an average year. From this total, 115 MAF are recycled into the atmosphere through evapotranspiration, and another 20 MAF flow into the Pacific from the North Coast western drainages. Of the remaining 65 MAF, 35 MAF are used by agriculture, 21 MAF go to environmental balance, and the last 9 MAF are used by urban areas for human consumption and industry.
When things are flowing smoothly, all of the parts of California's waterscape run in balance, based on average uses. But in reality, this balance is severely tested during periods of droughts or floods. The current drought has impacted California for the past five years (2012–2016), with most areas of the state having a deficit equal to an entire years' worth of rainfall. This scale of deficit has broad reaching effects, impacting not just the water available immediately from the tap but also California's water over the long term. The reduced runoff from the wet season's rain and snow translates into a further drawdown of groundwater resources, subsidence, and the permanent loss of some groundwater capacity. Likewise, the resulting reduced water allocations can lead to a relaxation of environmental standards, higher salinity in some areas, and long-term harm to native species of flora and fauna. The recent drought is also responsible for a two-thirds drop in hydroelectric power generation, falling from 21% of the state's power in 2011 to only 7% in 2015. The resulting offset in power generation had to be made by increased natural gas–fueled energy generation with the associated costs and pollution.
Agriculture, California's largest user of water, was also severely impacted by the drought. The agriculture-rich San Joaquin Valley was hit especially hard, with reduced runoff from the Sierra Nevada, reduced allocations from the Central Valley Project, and a dramatic decrease in economically available groundwater. Short-term annual losses directly to agriculture are estimated to be on the order of a billion dollars, but the impacts are far-reaching, with fallow fields and a downturn in the region's economy that includes double digit unemployment. In the long term, it will takes years for groundwater supplies to recover, but on the positive side, it has led to more sustainable irrigation practices for many crops.
Though it only accounts for about 5% of California's water use, the highly visible “urban water” sector has been asked, and in some areas mandated, to reduce consumption by 20–35%. In many communities, conservation efforts have seen both brown lawns and a switch to drought-resistant landscaping.
The most recent California drought also is being exacerbated by the climate change, and it may be a look into the future. Most global warming scenarios show the state's semi-arid climate becoming even more arid as the warmer atmosphere stresses water supplies.
Water has been a controversial factor in California from the days of its first settlers in the 18th century, as the myriad user groups have attempted to divide this scarce and valuable resource. These same dynamics will be at play in the 21st century, as the state's demand for water grows.
JAN NULL, Certified Consulting Meteorologist, is a California native, founder of Golden Gate Weather Services, a part-time faculty member at San Jose State University, and a former Lead Forecaster with the National Weather Service.