California’s hydraulic infrastructure has vaulted the state’s development forward, creating a thriving agricultural economy and supporting a population that now exceeds 38 million. But this entire infrastructure—a vast system of dams, reservoirs, and canals designed to transport water around the state—has been based on the assumption that historical precipitation levels were the norm in California and not the exception. We now know that this assumption was false. California, like much of the U.S. West, is facing the prospect of a water future characterized by longer and more severe droughts. In order for California to adapt to what appears to be a new climate regime, a systemic change to a century-old way of thinking about how the state stores and manages its water will be required. There will be no simple solution for California to engineer its way out of long-term or perhaps permanent drought, but first steps include recognizing the state’s true long-term climate patterns, identifying problems with the ways in which water has historically been allocated, adopting new conservation methods, and introducing substantive structural changes to the state’s economy, most notably in its agricultural sector, which consumes the overwhelming majority of the state’s developed water supply.
The creation of modern California has taken place during a relatively benign, and wetter than average, climatic period. Paleoclimatologists have uncovered evidence of past droughts in California that dwarf the scope of those in the written record. Upright tree stumps preserved in Lake Tahoe, the second deepest lake in the United States, point to a prolonged drought period that lasted for more than a thousand years during the mid-Holocene epoch (approximately 5,000 to 6,000 years ago), when the lake level had dropped by more than 20 feet.<sup1 Tree stumps discovered in Tenaya Lake in Yosemite National Park, Mono Lake and the Walker River on the eastern side of the Sierra Nevada, and other locations point to two megadroughts that spanned most of the medieval period—during the so-called Medieval Climate Anomaly—in California, from approximately AD 900 to 1100 and AD 1200 to 1350. Annual growth rings prove that many of these trees lived upward of 140 years and as long as 220 years.2
Megadroughts are not necessary to expose the fault lines in California’s water management, however. Far shorter droughts, none longer than six to seven years, have already demonstrated the inadequacies of California’s current water policy. The most significant California droughts of the past century include those of 1928–34, 1976–77, 1987–92, 2007–09, and the current drought that began in 2012. The brief but severe drought during 1976–77 was the driest on record for the past 500 years, as determined by paleoclimate data, and prompted the state’s first real efforts toward water conservation, which included widespread urban water conservation and mandatory rationing.3 During the drought of 2007–09, a statewide proclamation of emergency was issued for the first time.4 This was also the first drought to take place during a time of unprecedented environmental restrictions on agricultural water exports to the south of the Sacramento–San Joaquin Delta—the eastern portion of the estuary that extends from San Francisco Bay inland to the heart of California’s Central Valley at the confluence of the Sacramento and San Joaquin rivers. Decades of water exports delivered by federal and state projects had reduced freshwater flows through the Delta, resulting in deteriorating water quality, severe decline of endangered native fish species, and the near-collapse of the Delta ecosystem.5
California entered its current drought during a time of record warmth in the state. Higher temperatures are particularly problematic for water supply in California because the state’s hydraulic infrastructure was designed in large part to store snowmelt in reservoirs located in the foothills of the Sierra Nevada. Climate models, predicated upon higher temperature regimes, show pronounced impacts on the Sierra Nevada snowpack—the primary source of the state’s freshwater supply—with a loss of half or more by the end of the century.6 On April 1, 2015, the California Department of Water Resources measured the content of the Sierra snowpack at 5 percent of average for that date, the lowest percentage in any year in records dating back to 1950.7 By that time, reservoir levels throughout the state had already fallen to record or near-record lows.
In addition to surface storage, California relies heavily on groundwater, which accounts for close to 40 percent of the state’s agricultural and urban water needs. During drought periods, that percentage rises. Deprived of their full allocations of federal and state water, farmers increasingly mine groundwater from the state’s aquifers, hastening their depletion and leading to widespread land subsidence as the drained aquifers collapse. By 2014, the third consecutive year of drought, groundwater levels in many parts of the largely agricultural San Joaquin Valley (the southern half of the Central Valley) had fallen to more than 100 feet below previous historical levels, resulting in declining water quality, wells running dry—especially in economically disadvantaged small rural communities—and land subsidence and consequent damage to the state’s water delivery system and other infrastructure components.8 According to a NASA report, between May 2014 and January 2015 land in some parts of the San Joaquin Valley was sinking faster than ever before, at a rate of approximately 2 inches per month.9 Despite these severe problems, until the passage of the Sustainable Groundwater Management Act in September 2014, California was the only western state that had not enacted groundwater monitoring. Under the act, groundwater sustainability is to be achieved by 2040, but many argue that this is too little, too late, as groundwater levels are expected to continue to decline during the interim.10
The water challenges that the state faces are numerous and daunting: predicted longer and more severe droughts; greater risk of major wildfires, which will be particularly dangerous when they occur in densely populated areas at the wildland–urban interface; destruction of millions of drought-stressed trees from insect infestation; possible extinction of native fish species; deteriorating overall water quality and continuing decline of the Sacramento–San Joaquin Delta; and, somewhat ironically in an era of more severe drought conditions, greater risk of catastrophic floods as more precipitation falls as rain rather than snow and the pace of winter and early spring runoff accelerates.11
Adaptation to and amelioration of these conditions is both necessary and possible, and solutions will require efforts on a variety of scales from the hyperlocal to the regional. In April 2015, Governor Jerry Brown mandated a 25 percent reduction in urban potable water usage.12 Household conservation, including reduced watering of lawns—which accounts for the majority of urban water use—has already proven capable of meeting this target in much of the state.13 State regulations now limit the percentage of new housing lots that can contain lawns, but stronger incentives for xeriscaping—the planting of drought-tolerant vegetation—will be necessary. Substantial payments to homeowners to remove their lawns, such as those offered in other water-stressed western states, will facilitate a permanent reduction of urban water use, with minimal economic pain to residents.14
Agricultural priorities will need to change significantly as well, calling into question the future of California agriculture as it presently exists. The greatest demand for water in California comes from the agricultural sector, which accounts for approximately 77 percent of human water use in the state. Despite this disproportionate consumption, in recent years agriculture has accounted for just over one percent of the state’s gross domestic product (GDP) and about three percent of GDP if agricultural support industries are included as well. Agriculture and all related industries account for only about five percent of the state’s employment.15 For a transition to limited and more efficient agriculture to take place, crops that have the highest water demand must face the greatest scrutiny. Alfalfa, for example, consumes more than 15 percent of the state’s water, and approximately half of it is grown for export. Furthermore, almost all the state’s alfalfa crop is still grown using flood irrigation, rather than more efficient drip irrigation.16 Almonds, 80 percent of which are grown for export, require approximately another nine percent of the state’s water.17 From the perspective of natural resource economics, by exporting these water-intensive crops, California is actually exporting a significant amount of its limited water supply and is doing so for the benefit of a relatively small number of farmers, many of whom are wealthy absentee landowners or corporations.
Despite such evidence pointing to the need to restructure California agriculture, the political power of large agribusiness enterprises, along with willing cooperation from high-level elected officials, is driving the state toward an increased reliance on unsustainable engineering solutions, most notably in the case of the so-called Delta Tunnels. Under this latest multibillion-dollar plan to export water from Northern to Southern California, current methods of transferring water southward through Delta channels would be superseded by twin tunnels 40 feet in diameter and approximately 35 miles in length that would transport up to 9,000 cubic feet per second of Sacramento River water south of the Delta, bypassing the Delta’s channels entirely and further threatening the Delta’s endangered ecosystem. Meanwhile, even in the face of drought, farmers continue to increase acreage devoted to permanent planting of orchards and vineyard crops that require reliable year-to-year water supplies that the tunnels could provide, albeit at the expense of other parts of the state.18 The tunnels have become the most contested issue in California water politics in recent years, and the outcome remains uncertain, even as Northern California and Delta interests fiercely contest the plan.19,20
California has previously demonstrated the ability to dramatically reassess priorities for water use and is capable of doing so again, despite resistance from entrenched interests. During the 1870s and 1880s, Californians rapidly came to the realization that the state’s economic future would be better served by agriculture than by the highly water consumptive and environmentally destructive practice of hydraulic mining, debris from which was burying fertile farmlands and causing widespread flooding. Nearly a century and a half later, it is time for another reassessment. Questionable patterns of water consumption can best be addressed by treating water as a public commodity. Under such a legal and regulatory framework, which is already well under way in California, the public benefits of water are balanced with its value as an economic input. This can be accomplished, for example, by regulating groundwater more stringently and strengthening environmental review of water transfers, both of which can encourage a shift away from low-value and water-intensive crops. Integrating the management of groundwater and surface water, as well as the complex system of water rights that apply to them, will facilitate groundwater banking—the recharging of aquifers during wet periods for future use during drought—and thus improve water storage efficiency.21 Groundwater storage is both essential and more efficient than constructing expensive new surface storage (reservoirs), and can partially offset the shrinking Sierra Nevada snowpack. The water supply itself can be increased by constructing seawater desalination plants, such as the 50 million gallon per day Carlsbad Desalination Plant in Southern California, scheduled to come online in late 2015.22 As the experiences of Israel and other water-stressed nations have demonstrated, desalination plants have become cost-effective means of enhancing water supply, as has the recycling of gray water and sewage water.23
It has taken California more than a century to create its present hydraulic regime, and the climate for which it was designed no longer exists. It will take time to change course, but a multifaceted approach that includes revised priorities for water consumption, a stronger regulatory regime, groundwater banking, desalination, and conservation will go a long way toward avoiding escalating conflict over increasingly limited water allocations between urban residents, farmers, and fish and wildlife, many species of which are now protected under state and federal law. A livable and prosperous future is entirely possible for California, even under the challenge of climate change, but only if its people recognize that this future will be quite unlike California’s past.