Adaptive health management information systems

California’s 5-year drought has ended, even as its aftermath lingers. From 2012–năm 2016 much or all of California was under severe drought conditions, with greatly diminished precipitation, snowpaông chồng, and streamflow và higher temperatures. Water shortages to forests, aquatic ecosystems, hydroelectric power plants, rural drinking water supplies, agriculture, & cities caused billions of dollars in economic losses, killed millions of forest trees, brought several fish species closer to lớn extinction, & caused inconvenience and some expense to lớn millions of households và businesses. The drought also brought innovations và improvements in water management, some of which will better prepare California for future droughts. This paper summarizes the magnitude & impacts of the 2012–2016 California drought. The paper then Đánh Giá innovations arising from the drought in the larger historical context of water management in California. Lessons for California and for modern drought management are then discussed. Droughts in modern, well-managed water systems serving globalized economies need not be economically catastrophic, but will always have sầu impacts và challenges, particularly for native sầu ecosystems. In California & every other water system, droughts usefully expose weaknesses & inadequate preparation in water management. In this regard for California, managers of ecosystems and small rural water supplies had the most lớn learn.

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Drought is a temporary reduction in water availability below normal quantities. Droughts can be for only a few weeks or endure for years or centuries—in which they blover with changes in climate. In rain-fed agricultural systems, droughts of a few weeks can be devastating. Places such as California, with a long summer dry season và a Mediterranean climate, each year face what would be the worst drought ever seen in more humid American states.

From 2012 lớn 2016, California experienced one of its deepest, longest, and warmest historical droughts. Many effects from this drought khổng lồ forests, native fish populations, groundwater levels, và lvà subsidence will endure for decades. Lessons and innovations from the drought also will last for decades và improve California’s ability to manage future droughts. Past and future droughts are always present in managing water in California. California enters each drought with management institutions, policies, infrastructure, water storage conditions, and water demands influenced by past droughts. Future droughts are also in the minds of water managers as they make agreements, contracts, storage, infrastructure, and kinh doanh decisions to lớn dampen potential drought impacts.

Drought has always been a risk lớn humans and natural organisms. Historically, drought has shaped và destroyed civilizations & ecosystems. Droughts and sometimes-accompanying climate change have sầu been implicated in the decline and fall of civilizations (Shimada etal. 1991; Douglas etal. 2015; Krieger 2014; Staubwasser etal. 2003; Drysdale etal. 2005; Fagan 2009; Weiss 1997). For ecosystems, droughts can be pivotal events when invasive sầu species become established or shifts occur in species composition (Winder etal. 2011). Yet, western US water management systems have sầu become much more robust và adaptive than is commonly thought (Fleông xã 2016).

The onmix of drought is slow. The water stored in soils, slowly diminishing springs, reservoirs, and aquifers dampens the onset of drought. The duration of droughts in California can be long & uncertain, perhaps lasting years, decades, and even centuries, compared with hours to days for fires and floods or minutes for earthquakes (Stine 1994). Therefore, signaling the onphối and end of drought can be messy. Drought onphối is usually slow, varying in local intensity, with an uncertain & often varying duration. Like all forms of disaster, preparation greatly diminishes drought losses, and organization is central to lớn effective sầu preparation and response.

For humans, the impacts of drought vary with economic, infrastructure, and institutional conditions, as well as the drought’s hydrologic characteristics. The economic effects of drought depover on the economy’s reliance on water and the extent of regional and global trade. Global economic connections greatly reduce the impacts of drought (Sumner 2015; Lund 2016a). Global food trade largely eliminates the existential threats of drought khổng lồ civilizations, & greatly eases drought’s economic và public health impacts. Infrastructure networks và institutions that store, move, và reallocate water flexibly also greatly reduce drought impacts (Lund 2016a). Regional hydrosúc tích characteristics, such as large freshwater aquifers, can dampen drought effects.

However, actions taken khổng lồ minimize the impact of drought for humans often further jeopardize vulnerable ecosystems & other environmental resources. California has arguably restructured its infrastructure và economy lớn accommodate droughts, but many of these actions have further altered habitats & streams in ways that harm native species, which once were well adapted to California’s droughts using once-vast habitats connected to snowmelt, springs, groundwater, and seasonal floodplains. Losses lớn native species populations during drought are often not recovered before the next drought.

This paper Reviews California’s most recent drought, và places it in an historical & global context. Lessons are drawn for California & for drought management globally. Despite problems & revealed weaknesses, well-prepared water systems within globalized economies usually weather drought fairly well & improve over time with exposure lớn such extremes.

The California drought of 2012–2016 was unusually dry and warm with a frequency estimated between once in 20–1,200years. As a large diverse state, this range of estimates is reasonable. The drought’s unusually high temperatures depleted soil moisture more rapidly, yielding a drought frequency estimate of 1 in 1,200years, relative sầu to lớn past temperatures (Griffin và Anchukaitis 2014). Snowpaông xã also diminished from high temperatures, with a frequency estimate of 1 in 500years, assuming past temperatures (Belmecheri etal. 2016). The drought was frequently the worst of record by many metrics, but local assessment varies widely with location, area, and drought metric. Far longer và more severe droughts occurred in the Middle Ages (Stine 1994). Regional precipitation, streamflow, and water delivery reductions, relevant for regional water supplies, were often new lows, but more frequently have sầu been seen with approximate frequencies of 1 in 15–30years across the state (Lund 2016a). The drought was unusually dry, hot, và severe, by any reckoning.

The drought’s higher temperatures are important for how managers, engineers, & scientists prepare for future droughts. Warmer temperatures accounted for as much as 25% of the drought’s cumulative sầu moisture deficit (M. Dettinger, personal communication, 2017) & certainly reduced soil moisture & snowpaông chồng, reduced cold water in reservoirs, và increased river temperatures (Hanak etal. 2015b; Mount etal. 2017).

The California drought was caused largely by the formation of a “ridiculously resilient ridge” of high pressure in the Pacific Ocean off California, diverting atmospheric moisture away from California. The climatological causes of this ridge will be debated for some time (Swain 2015; Singh etal. 2016; Swain etal. 2017). The persistence of such a deep drought for several years over California is unlikely lớn be entirely random and is likely to have connection with some more Pacific-wide and global climate processes (Teng và Branstator 2017). Climate warming is thought lớn have sầu had some role (Diffenbaugh etal. 2015) và the pattern is consistent with predictions of climate change downscaled lớn California (Cayan etal. 2008; Dettinger 2005).

California already has an unusually variable climate. The literature suggests that climate warming will magnify both the frequency và magnitude of floods and droughts in California. The warmer temperatures of the most recent drought might be a harbinger for future drought & nondrought years with climate warming. Higher temperatures will worsen many drought impacts, especially for soil moisture, snowpack, streamflow, & temperature-sensitive ecosystems.

The drought reduced water deliveries from local, regional, state, and federal water projects at a time of historically high water demands. Table1 summarizes the reductions in Central Valley Project và State Water Project deliveries for each year of the drought (2012–2016) as well as the wet years before và after the drought (2011 và 2017), showing the drought’s development. Even in wet years (2011 & 2017), the water projects cannot satisfy all water demands. In addition, different water users are often shorted differently, reflecting different legal priorities due khổng lồ legislation and/or preproject water rights (e.g.,Sacramenlớn Valley “Settlement” & San Joaquin River “Exchange” contracts).

YearState water project (SWP)aCentral Valley project (CVP)b
201180%100%, except south of Delta junior agricultural contractors (e.g.,Westlands) 80%
201265%100%—North of Delta, wildlife refuges, San Joaquin Exchange, & Eastside (New Melones) contractors
75%—South of Delta urban
50%—Friant; 40%—south of Delta junior agricultural contractors
201335%100%—Wildlife, San Joaquin Exchange, and Eastside contractors
75%—North of Delta agriculture & settlement
70%–75%—Urban; 62%—Friant; 20%—south of Delta agricultural
20145%75%—Sacramento lớn Valley settlement and wildlife refuges
65%—San Joaquin Exchange contracts và wildlife refuges
55%—Eastside (New Melones) contractors; 50%—urban
0%—Other agricultural contracts (including Friant, Westlands)
201520%, except north of Delta urban 22–28%75%—Sacramenlớn Valley settlement, wildlife, San Joaquin Exchange contracts; 25%—urban
0%—Eastside (New Melones) & other agricultural contracts
201660%, except north of Delta urban 60–100%100%—North of Delta, wildlife, San Joaquin Exchange contracts
75%—Friant; 55%—urban; 5%—south of Delta agriculture
0%—Eastside (New Melones) contractors
201785%, except north of Delta urban 100%100%, all

a Data from California Department of Water Resources (2018a).

b Data from US Bureau of Reclamation (2018).

As the drought wore on, the water projects had less stored water & reduced their deliveries, reaching a low in 2014 và 2015. In these years, some water contractors (particularly Friant) received zero deliveries for the first time since the project began in the 1950s, & sometimes lacked alternative sầu water sources, forcing users to lớn drill new wells or purchase water from others with a contract allocation. Such adaptations reduced shortages và costs for many areas but brought their own costs and consequences.

Many other local and regional water suppliers, which provide most water used by Californians, were affected by the drought. Some were less affected, due to sizable upstream reservoirs (e.g.,Solano County và Coloravị River users), banked groundwater, or water market transfers và conservation (particularly in cities in southern California and the San Francisteo Bay areas). Some isolated local water supplies were more deeply affected.

Droughts thử nghiệm water systems. The 2012–năm nhâm thìn drought was broad và deep enough to test all water management sectors in California. Areas with the most severe impacts, in rough economic order, were agriculture (particularly San Joaquin Valley), forests, hydropower, rural groundwater supplies, recreation, the Sacramento-San Joaquin Delta, aquatic ecosystems, protected fisheries management, & cities (particularly hydraulically isolated cities). The state’s water accounting & water rights administration systems were also tested.


The drought was statewide và much of California’s agriculture saw substantial drought effects, although local groundwater buffered most agricultural impacts (Howitt etal. 2014, 2015a, b; Medellín-Azuara etal. 2015a; Medellín-Azuara etal. 2016). Of the approximate 30% drought reduction of surface water available for agriculture statewide, about two-thirds was replaced by additional groundwater pumping, adding approximately $600million per year in pumping costs (Table2 for 2015). The remaining 10% shortage in statewide agricultural water use was accommodated by fallowing or idling about half a million acres (approximately 6% of statewide irrigated crop area) & through bít tất tay irrigation of crops, shifting crops, và improving irrigation efficiencies.

DescriptionBase yearDrought change% change
Surface water supply (109 m3)22.210.7 loss−48%
Groundwater use (109 m3)10.48.0 increase72%
Net water use (109 m3)32.63.3 reduction−10%
Drought-related idle l& (hectares)500,000a225,000 more45%
Crop revenue ($)$35billion$900million loss−2.6%
Dairy và livestoông xã revenue ($)$12.4billion$350million loss−2.8%
Groundwater pumping cost ($)$780million$590million rise75.5%
Direct costs ($)N/A$1.8billion lossN/A
Total economic impact ($)N/A$2.7billion lossN/A
Direct farm jobs200,000b10,100 loss5.1%
Total job lossesN/A21,000 lossN/A

Source: Data from Howitt etal. (2015b).

a NASA-ARC estimate of normal Central Valley idle land.

b Total agriculture employment is about 412,000, of which 200,000 is farm production.

Total direct statewide economic losses khổng lồ agriculture from the drought were approximately $3.8billion for 2014–2016 (Howitt etal. năm trước, 2015b; Medellín-Azuara etal. 2016). Estimates are unavailable for the less severe years of 2012–2013. This included lost net revenues from crop production, dairy & livestock, & additional pumping costs.

Statewide crop revenue losses were approximately $1.7billion in 2014–2015, the deepest 2years of the drought (Howitt etal. năm trước, 2015a, b), for an approximate $45billion dollar/year agriculture industry. Seventy-two percent of these losses were in the southern Central Valley (15% in the San Joaquin basin & 57% in the Tulare basin). These losses were concentrated in parts of the Valley lacking access khổng lồ good groundwater. Agricultural areas adapted to lớn the drought by fallowing sizable acres of annual crops, reducing irrigation applications lớn some crops (bao tay irrigation), và shifting some annual crops lớn new orchards (with approximately 40% less water use in their first years) (Sanchez 2017).

Lower groundwater elevations from the drought will increase groundwater pumping costs for many years in parts of the southern Central Valley, with higher costs for dry wells và lost infrastructure capathành phố from subsiding lvà above sầu heavily overdrafted aquifers (MacEwan etal. 2017).

The drought greatly increased overdraft-related land subsidence, a long-term problem in parts of the San Joaquin Valley (Faunt & Sneed 2015; Sneed etal. 2013; Borchers etal. 2014). In some areas, new l& subsidence approached several feet during the drought. The greachạy thử economic impact of subsidence has been reduced conveyance capacities for some major San Joaquin Valley canals by up lớn 60% (Farr etal. 2017; Friant Water Authority 2017). Ironically, another major impact of drought-related subsidence is disrupting slopes that reduce floodway capacities. This groundwater-caused lvà subsidence is mostly from one-time dewatering of aquifer clay layers with little reduction in ability to lớn recharge aquifers (Borchers etal. 2014).


Perhaps the greakiểm tra impact of California’s drought was the death of 102million forest trees, which depover on soil moisture accumulated in the wet season for growth during the spring và summer (US Forest Service 2016; Stevens 2016). Low precipitation và snowpaông chồng greatly reduced soil moisture, and higher temperatures accelerated soil moisture depletion. Drier, weakened trees became more susceptible lớn disease & insect infestations. Similar losses of forest trees occurred from the shorter 1976–1977 drought (DWR 1978).

With a warming climate, this drought might be pivotal for ecological changes in California’s forests, particularly in tree density và species composition (Young etal. 2016). The millions of dead trees in California’s forests has implications for wildfires, erosion, and public safety. The economic costs of these forest impacts from drought have sầu not been estimated, but will continue lớn affect ecosystems, fire, và public safety for many years. Costs from additional wildfires và their public health impacts could become the largest economic & public health impact of the drought, spread years after the drought ends.


California’s hydropower production is closely tied to lớn annual runoff upstream of hydropower plants, with little over-year water storage (Madani và Lund 2009). Higher energy prices in the summer encourage hydropower reductions in other seasons, which is fortunately compatible with summer releases for downstream water supplies.

The deepest years of the drought (2014–2015) reduced hydropower production by more than 1/2 from its long-term average, going from about 13% of California’s electriđô thị use lớn about 5% (Table3). The economic cost of this lost hydropower from substituting more expensive gas–turbine generation was approximately $2billion, plus additional air pollution & greenhouse gasses (Gleiông xã 2016). California’s 2015 hydropower production was almost as low as in the short deep drought of 1976–1977 (DWR 1978).

Rural Groundwater Supplies

The drought increased attention to lớn problems of small water systems and rural domestic wells (Grosmê man 2017). These smaller systems lachồng economies of scale and are frequently poorer and less well organized. These factors make rural water systems (& rural public services generally) more vulnerable to lớn high costs, contamination, operation và maintenance problems, & drought. Rural water systems typically depover on shallower wells. Unlike larger water systems, small systems are not required khổng lồ have sầu drought contingency plans. Additionally, most small systems lachồng emergency or permanent connections to other water systems that can help during droughts.

As nearby water users with deeper wells pumped more during the drought, many rural households & small communities found their wells going dry. Tulare County alone reported almost 2,000 domestic well failures in năm ngoái (Tulare County 2017). Costs for additional pumping & rehabilitation for domestic và community wells in Tulare County from drought-related groundwater declines were estimated to be $10–$18million. Further costs occurred from actual dry wells. Overall, these costs are greater than for previous droughts due lớn lower initial groundwater levels (Gailey 2018; Kwon 2017; Medellín-Azuara etal. 2016).

Many small water systems were unprepared for the drought (Fencl và Klasic 2017). Bottled water was often used or potable water was delivered by trucks for household storage tanks (Hanak etal. 2015b). Various state departments provided financial and technical assistance for private domestic well owners and small systems with drought-related issues (Fencl and Klasic 2017). The Draft Executive Order Framework, issued by the California Department of Water Resources, gives counties 2years to determine how khổng lồ provide drought supplies for households currently outside of the drought contingency plans (Fencl và Klasic 2017).


Outdoor recreation also suffered from the drought. The skiing industry was particularly affected by the laông xã of snow & higher temperatures, particularly in 2014–năm ngoái, with shorter seasons and significantly fewer customers (Barber 2015; Kirkpatrick 2015). Whitewater rafting was somewhat buffered by upstream reservoirs. Lake recreation was affected by lower reservoir levels, particularly in 2014–2015. Some marinas in the Delta were overrun by alien aquatic plants prohibiting boat passage (Durvà etal. 2018). No detailed analysis or quantification has been done on the effects of drought on recreation for the 2012–năm nhâm thìn drought. A California Department of Water Resources report on the 1976–1977 drought demonstrates such an analysis (DWR 1978).

Sacramento–San Joaquin Delta

The Sacramento–San Joaquin Delta is the major hub of California’s water system và a continuing source of controversy (Lund etal. 2010; California Department of Water Resources and US Bureau of Reclamation 2016). During the drought, low inflows from northern California greatly reduced the ability to move water from wetter northern California khổng lồ drier southern regions and San Francisteo Bay area cities. Water exports from the Delta were greatly reduced. In 2011, before the drought, Delta water exports peaked at 6.5 MAF, dropping khổng lồ 1.8 MAF during the worst year of the drought (Table4).

In May 2015, DWR installed a temporary roông chồng barrier to lớn cthua trận False River in the western Delta to lớn reduce the need for additional freshwater outflow lớn San Francisteo Bay to lớn maintain low salinity in the central Delta. The barrier was removed in October năm ngoái. This followed decades of permanent flow barrier studies from the 1920s (Lund etal. 2010) & annual use of seasonal barriers in the southern Delta for fish và agricultural water chất lượng purposes since the 1990s, use of temporary drought barriers in the 1976–1977 drought, & proposals for drought barriers in the 2009 và năm trước drought years (California Department of Water Resources 2009). The barrier helped maintain only slightly relaxed water-unique standards for Delta agriculture & urban use and some south of Delta water exports with reduced fresh water releases from upstream dams. The barrier affected in-Delta water chất lượng & flow circulation, which continue lớn be studied (Durand etal. 2018). Export of zooplankton from the south Delta khổng lồ Suisun Bay may have sầu slightly reduced summer food resources for the Delta smelt. In addition, reduced water circulation may have sầu increased salinity in the lower San Joaquin River.

Regulatory Delta outflows khổng lồ support native ecosystems were also reduced during the drought by the State Water Board, allowing the salinity zone to move sầu eastward. This reduced environmental outflows by about 1.4 billion m3 (1.1million acre-ft, MAF) over the drought, but did not greatly reduce in-Delta water quality for export, agriculture, and urban use (Gartrell etal. 2017a, b). Much of this saved outflow was retained in reservoirs for potential additional dry years. At market prices for water south of the Delta (over $0.8/m3, $1,000/acre-ft), this amounted to approximately $1billion worth of environmental water made available for water users và storage. Populations of native fish in the Delta continued khổng lồ decline during the drought. Considerable controversy resulted from the uncompensated reductions in environmental flows khổng lồ favor other water users (State Water Resource Control Board 2015; Lund etal. 2014; Lund & Moyle 2014). State và federal regulations specify Delta water quality standards, export limitations, & salinity gradient location.

Aquatic Ecosystems

The benefits of organization & preparation for drought are evident in comparing drought management for urban và agricultural uses with fish và waterfowl in the drought (Hanak etal. 2015b; Moyle và Quiñones 2014; Jeffries etal. 2016). From 2013 to 2016, drought emergency ecosystem support spending totaled $66million and $67million from the state and federal governments. Lachồng of drought preparation for the environment increased the severity of the effects on ecosystems (Hanak etal. 2015b).

California supports 129 species of freshwater fish. Approximately two-thirds of these species are found only in California. Most of these species are either currently endangered or at risk of becoming endangered (Moyle etal. 2011; Hanak etal. 2015b). Low flows and high temperature from the drought reduced water quality & impaired habitat for native sầu fish species. Additionally, the drought’s lower flows, longer water residence times, & higher temperatures supported expansions of some invasive species, particularly aquatic vegetation (Dur& etal. 2018). Intervention by the State Water Resources Control Board required some to lớn reduce surface-water diversions or groundwater pumping, which affects flows in some salmon & steelhead streams. However, the State Water Resources Control Board also temporarily voided at least 35 environmental flow regulations during the drought (Hanak etal. 2015b; Mount etal. 2017).

Salmon populations suffered from higher temperatures và reductions of flow during the drought. The hardest-hit was the winter run of Chinook salmon, which historically spawned in cold water, high in the upper Sacramenlớn River watershed. They are now displaced & reduced to lớn habitat below Shasta Dam, where spawning is supported by cold water from the bottom of the reservoir. During the previous long drought (1991), cold water from the reservoir became depleted và caused high egg và juvenile mortality, leading to lớn their official listing as an endangered species, construction of a temperature-mixing control device on Shasta Dam, & regulatory và operational changes for Shasta Dam. During the first years of the 2012–năm 2016 drought, the cold water available behind Shasta Dam was enough khổng lồ maintain spawning & rearing habitat. However, by năm trước, lower reservoir levels, higher temperatures, and various management problems depleted cold water behind Shasta Dam before the outmigration of juveniles, leading to lớn substantial elimination of that year’s cohort of winter-run salmon. Despite the attention from this failure, a similar result occurred in năm ngoái, the drought’s deepest year. Juvenile salmon populations in these 2years were supported mostly by refuge hatchery releases (Durand etal. 2018).

Regarding waterfowl, California is a primary stop on the Pacific Flyway (Hanak etal. 2015b; Mount etal. 2017). However, draining of most natural wetlands in California has limited waterfowl to lớn wetlands managed as state và federal refuges, private l&, duck hunting clubs, và flooded farmland. Decreased drought water allocations for managed wetlands reduced fall & winter habitats for waterfowl. Wildlife refuges throughout the state collaborated to lớn identify where water supply should be allocated khổng lồ best support waterfowl habitat (Hanak etal. 2015b; Mount etal. 2017).

Isolated Cities

Cities isolated from California’s intertied water system had fewer options to lớn prepare for & adapt khổng lồ drought. Santa Cruz in năm trước required a 30% mandatory use reduction as local water supplies became depleted without other recourse (City of Santa Cruz Water Dept. 2016). This was the first sizable thành phố forced khổng lồ mandatory rationing by the absence of water during the drought. Late in the drought, Lake Cachuma, the primary water source for Santa Barbara County, was expected to lớn empty, despite increased supplies acquired from a small connection to lớn the State Water Project. In năm 2016, the City of Santa Barbara required a 30% water-use reduction and restrictions on residential & commercial water uses (City of Santa Barbara 2017). The đô thị banned all residential lawn irrigation in January 2017 (McPhate and Medina 2016), lifting the ban in March 2017 as Lake Cachuma began khổng lồ refill.

Cities better connected to other supplies were more able lớn prepare & adapt to lớn drought. Urban utilities in the San Francisteo Bay Area and southern California served by the State Water Project và Central Valley Project faced 80%–95% reductions in water allocations for 2014–2015. These cities responded with sizable voluntary water conservation actions, withdrawals from water stored in reservoirs and banked in local and distant groundwater basins, water purchased from more senior agricultural water users, & purchases or exchanges from neighboring water systems (Alamedomain authority Zone 7 2015; SCVWD 2016; ACWD 2016; MWDSC 2015; CCWD 2016). Water banked with agricultural water districts in the Tulare basin provided particularly important replacement urban water supplies. These preparations and interties to neighboring areas greatly reduced drought impacts, largely from agreements & interties developed since the 1988–1992 drought.

Water Accounting and Water Rights Administration

The 2012–năm 2016 drought highlighted California’s lachồng of a coherent water accounting system (Hanak etal. 2014; Escriva-Bou etal. 2016). Although water systems are connected by conveyance networks & hydrosúc tích processes, these water systems are governed và regulated independently with separate water accounting systems. During the drought, legislators and state regulators directed several efforts to incrementally improve water accounting policies (Escriva-Bou etal. 2016).

The 2014–năm ngoái water years were the first since the 1976–1977 drought when junior water rights were formally curtailed by the State Water Board. The 2014–năm ngoái curtailments were made easier by 2009 legislation requiring all water-right holders, not just those holding post-1914 state permits, khổng lồ report monthly water use. By năm trước, the first years of these new data were becoming available. In năm ngoái, Senate Bill 88 required surface-water-right holders to measure và report their monthly diversions annually (Escriva-Bou etal. 2016). The 2014 Sustainable Groundwater Management Act (SGMA) also created a timeline for local groundwater accounting & regulation, with potential state agency enforcement. Similarly, government agencies began expanding environmental flow regulations.

Although some water accounting policy improvements occurred during the drought, further actions are needed to lớn establish broadly effective water accounting in California. These actions include determining water availability, water rights và use quantities, & creating transparent and coherent water balance and information systems (Escriva-Bou etal. 2016).

Some of the biggest impacts of the 2012–năm 2016 California drought were similar to lớn those of the 1976–1977 drought, a shorter drought containing the driest year on record. An excellent assessment of the 1976–1977 drought found that the biggest economic impacts were for agriculture, forests, & hydropower production (DWR 1978). These sectors are inherently water-intensive sầu & can react khổng lồ water losses almost exclusively by reducing production. In the case of forest impacts, little can be done khổng lồ substantially manage or compensate for drought impacts (Butsic etal. 2017). Water-based recreational losses are also direct & often difficult to manage. Most problematic areas tended to lớn be less well organized institutionally và less well funded, such as the environment.

Perhaps the biggest lesson from the drought is how small the economic impacts of drought were relative sầu to lớn the size of the hydroxúc tích và ngắn gọn sự kiện. Total economic losses, on the order of $10billion over 5years, were less than 0.09% of the state’s $2.3trillion/year economy. The drought’s statewide economic impact was less than the effects from business cycles, federal policies, và international exchange rates. California’s statewide economy was substantially adaptable và robust for a temporary loss of approximately one-third of normal water supplies. Modeling studies show substantial economic adaptability and robustness to lớn still longer & deeper droughts (Harou etal. 2010).


This was not California’s first drought. California’s long history of drought has led to lớn the accumulation of infrastructure, institutions, và changes in water demands adapted khổng lồ droughts (Pisani 1984; Lund 2016c).

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Perhaps the best illustration of successful preparation is the contrast of urban drought impacts from California’s 1988–1992 drought và the most recent drought. The 1988–1992 drought brought deep widespread impacts lớn urban areas, often with mandatory cutbacks of 20–30%. Following the 1988–1992 drought, cities individually, regionally, và with state tư vấn instituted more effective sầu and permanent water conservation, regional intertie pipelines, local water storage projects, groundwater storage, wastewater reuse, water market arrangements, và contingency plans (Lund 2014b, 2015e, 2016c). As a result, of major cities, only Santa Cruz and Santa Barbara were forced to lớn implement mandatory water conservation by lachồng of water.

For all other cities & years, urban conservation efforts were voluntary, except for năm ngoái, the drought’s fourth and deepest year, when the Governor required 25% urban use reductions, given prospects for additional dry years. These state-required cutbacks varied locally by per-capita water-use rates from 8 to 40%. Given the high proportion of urban water use for landscape irrigation (discussed subsequently), the overall economic impact of this 1-year 25% urban water-use reduction was very small (Lund 2015a, b, c, d).

Groundwater Supplies for Agriculture

Most agriculture in California is blessed with large underlying freshwater aquifers, particularly in the Central Valley, which provides substantial drought water storage. Statewide surface reservoir storage capacity is approximately 52 billion m3 (42 MAF), but total groundwater storage is approximately 500 billion m3 (400 MAF), making groundwater the main stored water source for long droughts. Additional groundwater pumping supplied more than 70% of the drought reductions to lớn agriculture’s water supply.

However, long-term overdraft of approximately 2.5 billion m3/year (2 MAF/year) undermines the availability of groundwater for future droughts. In the San Joaquin Valley, groundwater overdraft is about 17% of the total water supply (Arnold etal. 2017). The 2012–2016 drought highlighted groundwater’s importance as a long-term và drought source, và the need to lớn protect groundwater availability. This spurred passage of California’s Sustainable Groundwater Management Act of năm trước, which requires reaching basin groundwater sustainability by 2040. An average net reduction of consumptive sầu use of approximately 2.2 billion m3/year (1.8 MAF/year) in the San Joaquin Valley will be needed to maintain groundwater for future droughts. Permanent fallowing of some irrigated areas, additional groundwater recharge in wetter years, và pressure to import additional water can be expected (Hanak etal. 2017; Nelson etal. 2016).

Economic Structure

California’s economic structure tremendously reduces drought vulnerability. Growth in California’s economy has been greatest in less water-consuming sectors for many decades. In the 1920s, agriculture was about 30% of California’s employment, và is less than 4% today. Manufacturing has shifted to lớn less water-consuming methods, and the service sector, where most growth has occurred, requires relatively little water. These changes make California’s economy overall much less dependent on abundant water supplies and less affected by drought water shortages. This shift has been driven by technological modernization, as well as economic globalization.

Globalization of California’s agricultural sector was particularly effective sầu in reducing drought impacts (Lund 2016c; Sumner 2015; York và Sumner 2015; Lund 2015b). Although the drought idled hundreds of thousands of crop acres và markedly reduced farm revenues, the drought’s effect on the statewide agricultural economy was relatively small. During the drought, farmers reduced economic losses by allocating water khổng lồ higher-valued crops, where California has a large nói qua of national and global production (Sumner 2015; York và Sumner 2015). Production và market prices for these specialty crops (particularly almonds) were svào during the drought, which bolstered agricultural revenues and employment (Medellín-Azuara etal. 2015b). California’s food staples, which are marketed more globally, saw no higher prices due lớn drought.

Sizable Lower-Valued Water Uses

Although California has a globalized economy, in which primary agricultural production is a small cốt truyện of GDP., agriculture is a major source of income and employment in rural areas và the Central Valley. Agricultural water use is approximately 80% of all human water use statewide; the rest goes to lớn cities và towns. Within agriculture, about 85% of employment & gross revenues from crops is from fruits, nuts, and vegetables, which use less than half of all irrigated area and agricultural water use (Fig.1). The remaining agricultural land & water use tư vấn grains and feed crops. Dairy và beef cattle production are about a fourth of all agricultural value & relies on feed from out of state and local silage production. Challenges for agriculture include labor shortages, droughts, permanent cutbacks khổng lồ protect groundwater, & competing economic land uses. Another challenge is the continued expansion of permanent crops, orchards và vines, which are more difficult to fallow in dry years, encouraging more attention to groundwater management.


Fig. 1. Crop shares of agricultural crop revenues & employment. (Data from California Employment and Development Department 2018; IMPLAN 2015.)

Urban water use has a similar economic structure, with about half of California’s urban water use being for landscape irrigation providing relatively little economic contribution. In 2015, the State mandated an average 25% reduction in urban water use, varying from 8% khổng lồ 36% locally, with cities having higher per-capita water use being required to lớn reduce use more. Reductions were accommodated mostly in landscape irrigation, with little economic impact, despite some inconvenience & loss of urban trees, sometimes referred lớn as the “war on lawns.”

Energy System Flexibility and Market

Hydropower is a highly variable source of California’s electrithành phố from year lớn year, ranging from 7% to lớn 21% of statewide electriđô thị production since 2002 (CEC 2017a, b). Market flexibility, cheap natural gas thermoelectric power, growing electriđô thị production from wind và solar sources, & long-term declining overall electriđô thị use dampened the impact of hydropower losses (CEC 2017a). Still, many power retailers added drought surcharges to lớn cover higher generation costs.

Water System Flexibility and Water Markets

In past droughts, even modest water trading amuốn willing sellers and buyers dampened economic impacts to agriculture & cities (Israel và Lund 1995). Water markets and exchanges were particularly important for shorted agricultural areas lacking access to lớn surface water. Urban water systems in southern California & the San Francisco Bay area activated long-term water market contracts for stored water và agricultural lvà fallowing. Irrigation districts and farmers lacking sufficient groundwater sought lớn purchase water from others, driving agricultural water prices as high as $1.7/m3 ($2,000/acre-ft), but often over $0.8/m3 ($1,000/acre-ft), approximately triple the recent non-drought-water market prices (Hanak etal. 2015b; Hanak etal. 2017).

Cooperative sầu operations, aided by greater availability of interties & anticipatory agreements, further supported water markets và exchanges khổng lồ make fuller use of available water across California’s extensive conveyance and storage network. Institutional flexibility và capability allowed deep and abrupt disruptions in water deliveries lớn Sacramenkhổng lồ Valley farmers from endangered species operations lớn be rapidly, if inconveniently, accommodated with little economic loss. San Francisco Bay area utilities faced with 80–95% reductions in State Water Project deliveries used markets và system flexibility to accommodate such cuts without severe water rationing.

Water markets face both infrastructure & institutional barriers. Many ideas for improving market effectiveness are discussed (Hanak etal. 2011). Although regulations và agency oversight impede or delay some transfers, within-district resistance due to future water security and other issues is also common. Cooperative agreements among water users, system operators, and government agencies might help smooth low-environmental-impact transfers.

Waterfowl Institutional Preparation and Response

Waterfowl in California benefitted during the drought from a combination of preparation, luông chồng, & creative sầu management (Hanak etal. 2015b). First, waterfowl are more Smartphone than fish and can therefore better adapt và move with drought conditions. Waterfowl require ponds with a small volume of standing shallow water, in contrast khổng lồ native sầu fish in streams or the Delta, which require constant fresh water flow. Luckily timed winter storms during the drought helped ease impacts to migrating waterfowl. Beyond this, California has a long-established system of federal, state, & private wetlvà wildlife refuges, with some coordination. This refuge and institutional infrastructure was well employed to lớn identify and address foreseeable gaps in waterfowl habitat at critical times. Such actions involved many groups. Perhaps the most creative action was the Nature Conservancy’s Bird Returns program, in which farmers bid for payments to lớn water fields at particular times & places to lớn support migrating waterfowl (Hallstein & Miller 2014).

The 2012–2016years were not California’s first multiyear drought, and the cumulative sầu lessons of past droughts did much khổng lồ shape the adaptive capacity and responses for the more recent drought. Although statewide economic impacts were modest, some areas were more acutely & chronically affected. Impacts were mostly in areas least prepared or organized or inherently difficult to lớn organize (forests, fish, and rural water systems).

The fear, impacts, & controversies of drought bring professional, popular, & political focus needed to make strategic water management improvements. Historically, major droughts have led to major innovations. This is also true for California, as summarized in Table5. Early droughts alerted immigrants from the humid eastern United States that California’s seasonally dry climate could be even drier. As the state’s agricultural economy grew, droughts in the 1920s và 1930s led to extensive sầu water infrastructure construction from the 1940s through the 1970s (Pisani 1984). The short, deep 1976–1977 drought surprised many agencies và led to lớn widespread urban conservation programs và early water-market activity (DWR 1978). The prolonged 1988–1992 drought also caught many urban and agricultural areas underprepared, leading lớn greatly improved urban interties, conjunctive use, & much more extensive sầu water markets. This drought also led to pivotal changes in environmental management with the follow-up listing of several endangered fish species. The short 2007–2009 drought precipitated new institutions for the Delta & improved collection of surface-water-use data.

California’s economy, society, and climate are dynamic. Each historical drought has been different hydrologically and impacted a different human economy with a substantially different water management và infrastructure. A region’s economic structure drives drought management & impacts. In addition, California’s economic structure has always been driven by its changing global economic roles, from shipping hides globally in the early 1800s, gold in the late 1800s, grain in the early 1900s, & markets for higher valued crops, wine, electronics, manufacturing, software, & tourism in the last century.

Changes in California’s economic structure drive changes in economic demands for water management (Pisani 1984). Improving technology và changing political institutions & social expectations also change what is possible và desired in water management (Kelley 1989). However, institutional arrangements can be slow khổng lồ evolve, và droughts (lượt thích floods and major lawsuits) provide the attention và sense of urgency often needed for strategic changes. Droughts, floods, và lawsuits help water systems adjust to accumulating historical changes (Hanak etal. 2011).

Adjustments are usually both technological and institutional, & typically build on existing institutions và infrastructure. The development of large regional and statewide water projects, responding to droughts in the early twentieth century, did not eliminate local water utilities và irrigation districts. Existing local districts continued to manage local supplies & merely contracted with regional wholesale projects. Existing & new local districts could then benefit from economies of scale with newer regional water management technologies (large dams and aqueducts) and financing institutions (Metropolitung Water District, CVPhường, SWP), with little loss of local advantages & sovereignty (Maass and Anderson 1978).

In examining the swings of technologies & innovations, often accelerated by droughts, changes in the most economical technological innovations are often accompanied by rebalancing of the portfolio of managing & regulating local, regional, state, & federal institutions. Large-scale regional water infrastructure development shifted initiatives in water management khổng lồ federal, state, và regional governments. Before this time, water systems were almost entirely local. Now that large reservoir & conveyance systems are largely completed, today’s newer water management innovations, such as water conservation, wastewater reuse, conjunctive use of ground & surface waters, và water markets, are often better led and financed locally, requiring adjustments in state and federal regulations and regional system operations. These adjustments challenge routine finance & regulatory structures, and often depover on droughts khổng lồ accelerate change.

The general drought robustness of California’s urban, agricultural, energy, và recreation sectors contrast starkly with weaknesses seen in environmental & ecosystem management. In part, the drought management successes of California’s economic sectors come from water delivery systems, levees, storage & conveyance infrastructure, management, and water allocations that disrupt conditions for native ecosystems in droughts và in wetter years. Drought buffering for the economy in part has been paid for by native ecosystems.

Many of California’s aquatic ecosystems remain chronically starved for habitat và water in all years, but especially in droughts. Therefore, native sầu species enter droughts with diminished và geographically limited populations, only to lớn encounter greater stresses during drought (Moyle et al. 2017). Chronic problems of water development for aquatic ecosystems include dams that bloông xã fish migration lớn upper watershed habitats, elimination of wetl& & floodplain spawning và rearing habitat by levees, entrainment of juvenile fish by water export pumping, & poor water quality. Most of California’s endemic species’ populations were at historical lows at the 2012–năm nhâm thìn drought onmix. By entering the drought with such low stocks, several species were pushed lớn the brink of extinction by higher water temperatures và lower flows.

As species approach extinction, federal & state agencies charged with species protection have sầu become more deeply involved. Droughts have sầu often accelerated the listing of endangered species và regulatory agency involvement due khổng lồ rapid reductions in native fish populations. For winter-run salmon & Delta smelt, this process began after the 1988–1992 drought, after long declines.

Droughts have sầu long-term environmental effects that may take many years and management changes lớn repair. Without the time, water, và habitat needed to lớn rebuild fish stocks, droughts ratchet down native sầu fish populations, with little recovery between droughts. The Delta smelt was listed as threatened in 1993, state endangered in 2010, & nearly disappeared from detection by năm 2016. Droughts also facilitate invasive organisms, beginning in the early 1900s with the invasive sầu teredo’s spread into lớn the Delta in drier years (Means 1928). More recently, invasive clams và vegetation have been aided by drought, disrupting food webs, stressing native sầu populations, and disturbing infrastructure & passage (Jeffries etal. 2016; Lehman etal. 2017).

Successful environmental & ecosystem management will require a more proactive sầu approach, involving planning, organization, & financing of effective sầu actions, including drought planning. Proactive drought-management approach has been effective sầu for urban và agricultural sectors, & for managing wetlands for waterfowl.

The 2012–2016 California drought brought a range of innovations likely lớn improve preparations for future droughts.

The năm trước SGMA, the first forceful state effort to make groundwater use sustainable, passed because of the drought, approximately 100years after California legislation first regulated surface water. A thoughtfully implemented SMGA will not only improve sầu prospects for dealing with future droughts by improving groundwater reserves but will also foster broader coordination, accounting, and tighter water management at local và regional scales (Hanak etal. 2017).

The drought brought local và state government pressure lớn reduce per-capita urban water use, which remains higher that most of the country and most other developed economies in dry regions (Cahill and Lund 2013). Urban areas face long-term state pressure to lớn reduce per-capita, mostly outdoor, water use from drought-driven legislation in 2009 và more recent drought legislation, executive orders, and regulations.

In năm trước & 2015, low inflows and depleted upstream storage raised concerns about seawater intrusion inkhổng lồ the Delta & led khổng lồ consideration of several temporary flow barriers khổng lồ reduce salinity intrusion và the construction in 2015 of a temporary salinity barrier in the western Delta. Future droughts will also likely use salinity barriers, perhaps with greater planning and preparation.

Another benefit of the drought was additional state and federal spending on drought-related water problems in California (Hanak etal. 2015a). Much of these funds were merely redirected or retitled from other water and environmental programs, và some helped to lớn directly relieve drought impacts to small communities và farmers, but some also led to longer-term infrastructure improvements and other long-lasting benefits.

The drought did not immediately result in broad improvements to lớn environmental management. Some notable innovations occurred for coordinating water-bird management (Hallstein & Miller 2014). California’s WaterFix và EcoRestore mandate over 8,000acres of tidal habitat restoration in the Delta, which may help buffer some threatened populations. Much attention was paid to lớn potential innovations from Australia (Mount etal. 2016). Perhaps the difficulties of managing forest và aquatic ecosystems from drought will motivate more effective efforts to come. Discussion of an environmental water right has begun, which may be one way lớn allow environmental flows to support postdrought recovery of vulnerable fish species và over drought ratcheting of ecosystems (Mount etal. 2017).

One of the most important benefits of the drought is the reminder lớn the broader society và political discourse that California is a dry place overall, where water must be carefully managed. This lesson is particularly poignant for the southern Central Valley, which has extensive & high-valued agricultural water demands in one of California’s drier regions, prone khổng lồ groundwater overdraft, & particularly vulnerable to lớn shortages of Delta water imports.

A final optimistic lesson is that if water is well managed, damages from drought (& floods) will usually be quite modest in the context of California’s overall society và economy. The combination of California’s global economy, urban và substantial agricultural preparation for drought, relatively abundant groundwater reserves, and substantial institutional flexibility greatly dampened the impacts of one of history’s most severe & lengthy droughts in California (Lund 2016b). Important problems and opportunities are also pointed out that should be addressed to both prepare for future droughts and improve sầu the water system overall.

Having demonstrated substantial economic robustness to severe drought allows California the opportunity khổng lồ more aggressively counter environmental damages. California has considerable wealth và flexibility to solve sầu its environmental and water chất lượng crises. Much of the resources needed to effectively manage the environment (e.g.,water, money, habitat restoration) are needed during interdrought periods, when resources should be more available. Investments in environmental preparation for drought could be as successful as they are for economic sectors.

The behavior of systems under unusual bít tất tay is an important opportunity to learn and improve, despite undesired impacts. The drought provided opportunities for “natural” ecological và institutional experiments that would otherwise be impossible lớn permit or be impractically expensive sầu. Drought-related reductions in flows & rises in temperatures were widespread. Major emergency changes to lớn infrastructure, such as the Delta emergency salinity barrier, provided opportunities lớn examine effects of major Delta changes on water quality, flow, và ecological conditions.

State & federal agencies & science programs were largely unprepared lớn take advantage of these scientific opportunities. Some important scientific work did occur (Durand etal. 2018; Jeffries etal. 2016; Lehman etal. 2017; Medellín-Azuara etal. 2018; Lord etal. 2018), although often less systematically. Scientific syntheses that assemble data, analyses, và lessons from the drought likely have great value.

Historically, major droughts in California have occurred at a rate of each generation experiencing approximately one major drought in a career. This often means that each drought is greeted by a new generation of professionals, lacking direct drought management experience. This infrequency of drought dampens personal incentives for institutions to learn from past droughts & prepare for the next drought. If climate warming & tighter water demands make drought more frequent, with two or more droughts expected in a career, agencies might make deeper drought preparations. More frequent droughts appear likely to lớn affect environmental protection agencies especially, with noted weaknesses in drought preparation.

The development and use of water-use data & estimates saw particular advances during the drought. Drought legislation in 2009 required all surface-water right holders to report monthly use lớn the State Water Board every 3years—for the first time applying lớn riparian and pre-1914 appropriative sầu water right holders. The 2010–2013 water-right use data became available in 2013. Although these data were often incomplete, they greatly improved water-use estimates for declarations of water unavailability by the state.

Errors in models & field data also became apparent during the drought. Models of stream and reservoir temperatures were forced khổng lồ operate outside their normal và calibrated ranges. Field measurements of reservoir temperature took on new significance và were sometimes found khổng lồ be gravely inaccurate for the salmon they were intended lớn protect (Dur& etal. 2018).

Droughts always heighten public, political, và agency interest in drought forecasting. This drought greatly increased funding and publicity for real-time predictions of drought & floods (often based on El Nino conditions). Such efforts have improved insights into lớn atmospheric processes, but long-term forecasting remains substantially unsuccessful (Cayan & Mount 2015; Schonher and Nicholson 1989).

Water management in California was unusually effective for the 2012–năm 2016 drought, with the exception of ecosystems & rural drinking water supplies. However, the drought highlighted several moderate khổng lồ severe problems, & helped bring attention and innovations—following a comtháng pattern of droughts bringing innovation.

Success in water management for California has always been dynamic. California’s semi-arid Mediterranean climate & ever-changing economy, society, and ecosystems require that water management constantly adapt, as it has for over 150years. Such adaptations are always imperfect and controversial, involving a messy awkward set of convenient past practices, present exigencies, & preparing for an imagined future.

Several overall conclusions arise from California’s most recent drought:

1.Droughts focus attention and encourage improvements in water management. Each major drought in California’s history has motivated improvements in water management, often responding to long-term problems and opportunities. The current drought highlighted the dependence of California’s agriculture on groundwater in dry periods, & led khổng lồ substantial legislation requiring more effective local groundwater management. Some improvements in water accounting, urban water conservation, & other areas were accelerated by the drought;


A diversified economy with deep global connections significantly buffers economic effects of drought. California and most modern economies depend less on abundant water supplies than in the past. Agriculture is California’s most water-dependent industry, about 80% of human water use, but despite its growth và prosperity, provides less than 4% of California’s jobs. High values for major export crops greatly reduced the impacts of fallowing about 6% of the least-profitable irrigated lvà during this drought. Despite local problems, the effect of major drought on California’s statewide economy was quite small (Howitt etal. 2014, 2015a, b). Urban areas, supporting most of the people and economic activity, have developed diversified portfolios of water supply và conservation activities that were quite successful during the California drought;


Major drought và climate change have sầu much less impact on irrigated water systems with diversified supply sources, particularly groundwater, and flexibility in operations with water networks và markets. California’s extensive và diverse water infrastructure allowed more than 70% of lost water supplies lớn be replaced by pumped groundwater for agriculture, requiring greater recharge of groundwater in the long term. Although costly compared with dryland agriculture, California’s irrigation infrastructure và network of reservoirs & canals greatly mute the effects of drought, and are particularly effective for protecting the most economically valuable crops & economic activities. With reductions in the least-profitable irrigated area, this system can be sustainable for many decades if properly managed;


Ecosystems were most affected by the drought, given the weak condition of many native species, even in wet years, due khổng lồ decades of losses of habitat and water và the growing abundance of invasive species. With each drought, humans become better at weathering drought, but effective institutions & funding are lacking lớn improve ecosystem management & preparation for drought. Forests are particularly vulnerable và difficult lớn protect from droughts. Dedicated environmental water rights & restoration and migration programs can help tư vấn ecosystems. Such actions are needed lớn break the cycle of cumulative drought impacts to lớn ecosystems and the environment;


Small rural water systems are especially vulnerable khổng lồ drought. Small systems often struggle in normal years, lachồng economies of scale, typically have only a single vulnerable water source, và commonly lachồng sufficient organization and finance; and


Every drought is different. Droughts are hydrologically unique events that occur under different historical, economic, & ecosystem conditions, and increasingly with different climate conditions. But all droughts provide opportunities và incentives lớn improve sầu and adjust water management khổng lồ changing economic and environmental conditions and priorities. In well-managed systems, each drought is greeted with improved preparations from previous droughts.

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This paper benefitted from work và conversations with many diverse stakeholders, agencies, researchers, and journalists during the drought, as well as insightful reviewer comments. This work was partially funded by the California Department of Food và Agriculture, the US Environmental Protection Agency (Assistance Agreement 83586701), & the S.D. Bechtel, Jr. Foundation. None of these funders reviewed, approved, or endorsed this sản phẩm.

ACWD (Alameda County Water District). năm 2016. Urban water management plan 2015–2020. Fremont, CA: ACWD.

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