Water availability and land subsidence in the Central Valley, California, USA
- 4.3k Downloads
The Central Valley in California (USA) covers about 52,000 km2 and is one of the most productive agricultural regions in the world. This agriculture relies heavily on surface-water diversions and groundwater pumpage to meet irrigation water demand. Because the valley is semi-arid and surface-water availability varies substantially, agriculture relies heavily on local groundwater. In the southern two thirds of the valley, the San Joaquin Valley, historic and recent groundwater pumpage has caused significant and extensive drawdowns, aquifer-system compaction and subsidence. During recent drought periods (2007–2009 and 2012-present), groundwater pumping has increased owing to a combination of decreased surface-water availability and land-use changes. Declining groundwater levels, approaching or surpassing historical low levels, have caused accelerated and renewed compaction and subsidence that likely is mostly permanent. The subsidence has caused operational, maintenance, and construction-design problems for water-delivery and flood-control canals in the San Joaquin Valley. Planning for the effects of continued subsidence in the area is important for water agencies. As land use, managed aquifer recharge, and surface-water availability continue to vary, long-term groundwater-level and subsidence monitoring and modelling are critical to understanding the dynamics of historical and continued groundwater use resulting in additional water-level and groundwater storage declines, and associated subsidence. Modeling tools such as the Central Valley Hydrologic Model, can be used in the evaluation of management strategies to mitigate adverse impacts due to subsidence while also optimizing water availability. This knowledge will be critical for successful implementation of recent legislation aimed toward sustainable groundwater use.
KeywordsSubsidence Groundwater/surface-water relations Compaction USA Geohazards
Ressource en eau et subsidence dans la Vallée Centrale, Californie, Etats-Unis d’Amérique
La Vallée Centrale de Californie (Etats-Unis d’Amérique) couvre environ 52,000 km2 et constitue l’une des régions agricoles les plus productives du monde. Cette agriculture dépend fortement d’apports d’eaux de surface canalisées et de pompages d’eaux souterraines, pour répondre à la demande en eau d’irrigation. Parce que la vallée est semi-aride et que la ressource en eau de surface est très variable, l’agriculture dépend beaucoup des eaux souterraines locales. Dans les deux-tiers sud de la vallée, la Vallée de San Joaquin, les prélèvements d’eaux souterraines historiques et récents ont provoqué des rabattements importants et étendus, ainsi qu’une compaction du système aquifère et une subsidence des terrains. Au cours des périodes de sécheresse récentes (2007–2009 et 2012 jusqu’à maintenant), les prélèvements d’eaux souterraines ont augmenté en raison d’une réduction de la ressource en eaux de surface et de changements dans l’occupation des sols. La baisse des niveaux piézométriques, approchant ou dépassant les niveaux historiques bas, ont engendré une accélération et un accroissement de la compaction et de la subsidence, qui sont probablement irréversibles. La subsidence a provoqué des problèmes opérationnels, de maintenance et de conception pour l’adduction d’eau et pour les canaux, dans la Vallée de San Joaquin. La prévision des effets d’une poursuite de la subsidence dans la région est importante pour les agences de l’eau. Tandis que l’occupation des sols, la recharge des aquifères, et la ressource en eaux de surface continuent à évoluer, le suivi du niveau des eaux souterraines à long-terme, la surveillance de la subsidence et la modélisation sont cruciaux pour comprendre les dynamiques des usages historiques et à venir des eaux souterraines résultant de la baisse conjointe des niveaux d’eau et des stocks d’eaux souterraines, ainsi que la subsidence associée. Les outils de modélisation, tel que le modèle hydrologique de la Vallée Centrale, peuvent être utilisés dans l’évaluation des stratégies de gestion pour atténuer les impacts négatifs dus à la subsidence, en optimisant la ressource en eau disponible. Cette connaissance sera cruciale pour une mise en œuvre réussie de la législation récente qui a pour objectif une utilisation durable des eaux souterraines.
Disponibilidad de agua y subsidencia del terreno en el Central Valley, California, EEUU
El Central Valley en California (EEUU) abarca alrededor de 52,000 km2 y es una de las regiones agrícolas más productivas del mundo. Esta agricultura se basa en gran medida en las desviaciones de las aguas superficiales y en el bombeo del agua subterránea para satisfacer la demanda de agua para riego. Debido a que el valle es semiárido y la disponibilidad de agua superficial varía sustancialmente, la agricultura depende en gran medida del agua subterránea local. En los dos tercios meridionales del valle, el Valle de San Joaquín, el bombeo de agua subterránea histórico y reciente ha causado una extensa e importante depresión, la compactación del sistema acuífero y la subsidencia del terreno. Durante los períodos de sequía recientes (2007–2009 y 2012-presente), el bombeo de agua subterránea aumentó debido a una combinación de una disminución en la disponibilidad de agua superficial y a los cambios de uso del suelo. La profundización del nivel freático, que se aproxima ó sobrepasa los más bajos niveles históricos, ha causado una renovada y acelerada compactación y una subsidencia que en su mayor parte probablemente sea permanente. La subsidencia causó problemas operacionales y de mantenimiento y del diseño constructivo para la provisión del agua y para los canales del control de inundaciones en el Valle de San Joaquín. La planificación por los efectos de la subsidencia continua en la zona es importante para los organismos encargados del agua. Como el uso de la tierra, el manejo de la recarga de los acuíferos y la disponibilidad de agua superficial continuarán variando son críticos el monitoreo y modelado del nivel del agua subterránea y de la subsidencia a largo plazo para la entender la dinámica del uso histórico y continuado del agua subterránea la que resulta en descensos adicionales del nivel y del almacenamiento de agua subterránea y de la subsidencia asociada. Las herramientas de modelado, como el Modelo Hidrológico del Central Valley, se pueden utilizar en la evaluación de las estrategias de gestión para mitigar los impactos adversos debido a la subsidencia y al mismo tiempo para optimizar la disponibilidad de agua. Este conocimiento será crítico para la exitosa implementación de la reciente legislación dirigida al uso sustentable del agua subterránea.
(美国)加利福尼亚中央谷地面积大约52000平方公里,是世界上生产粮食最多的地区之一。这里的农业主要依赖引来地表水和抽取地下水满足灌溉用水需求。因为谷地为半干旱地区,地表水的可利用量变化很大,因此农业很大程度上依赖地下水。在谷地南部三分之二地区,即San Joaquin谷地,历史上和最近的抽取地下水导致了很大的、广泛的水位下降、含水层系统压实和沉降。下降的地下水位接近或超过历史上最低水位,加速了很可能是永久性压实和沉降。沉降引起了San Joaquin谷地引水和防洪渠道运营维护和建设设计方面的问题。规划这个地区持续沉降的影响对水管理机构来说至关重要。因为土地利用、管理的含水层补给及地表水可利用量仍然在变化,历史上和持续的地下水利用造成了水位和地下水储量进一步下降及地面沉降,长期地下水位和沉降监控及模拟对于了解其地下水利用动力学至关重要。模拟工具诸如中央谷地水文模型可用于管理战略的评估,以便在优化水可利用量时,缓解沉降造成的不利影响。这些知识对于成功实施近年来的地下水可持续利用的立法非常关键。
Avaliação hídrica e subsidência de terreno no Vale Central, Califórnia, EUA
O Vale Central, na Califórnia (EUA), abrange cerca de 52,000 km2 e é uma das regiões agrícolas mais produtivas do mundo. Essa agricultura depende fortemente de desvios de águas superficiais e bombeamento de águas subterrâneas para atender a demanda de água para irrigação. Devido ao vale ser semiárido e a disponibilidade de águas superficiais variar substancialmente, a agricultura depende fortemente de águas subterrâneas locais. Nos dois terços do sul do vale, o vale de San Joaquin, bombeamentos históricos e recentes de águas subterrâneas têm causado significativos e extensos rebaixamentos, compactação do sistema aquífero e subsidência. Durante os períodos de seca recentes (2007–2009 e 2012-presente), o bombeamento de águas subterrâneas tem aumentado devido a uma combinação de menor disponibilidade de águas superficiais e mudanças no uso da terra. O declínio dos níveis freáticos, se aproximando ou ultrapassando os baixos níveis históricos, tem provocado a compactação acelerada e renovada, e subsidência que provavelmente é mais permanente. A subsidência tem causado problemas operacionais, na manutenção e em projetos de construção para distribuição de água e de controle de enchentes em canais no vale de San Joaquin. O planejamento para os efeitos da subsidência contínua na área é importante para agências de água. Como o uso da terra, a gestão de recarga de aquífero e disponibilidade de águas superficiais continuam a variar, o monitoramento de longo prazo do nível das águas subterrâneas e da subsidência e modelagem são fundamentais para entender a dinâmica de uso histórico e contínuo das águas subterrâneas, resultando em níveis de água adicionais e declínio no armazenamento de águas subterrâneas e subsidência associadas. Ferramentas de modelagem, como o Modelo Hidrológico do Vale Central, podem ser utilizadas na avaliação de estratégias de gestão para mitigar os impactos adversos devido à subsidência e ao mesmo tempo otimizar a disponibilidade de água. Esse conhecimento será fundamental para a implementação bem sucedida da recente legislação voltada para o uso sustentável das águas subterrâneas.
Introduction and background
Partially in response to these water-level declines and associated aquifer-system compaction and land subsidence, an extensive surface-water delivery system was developed to redistribute some of the water from north to south and east to west. Surface-water imports from the Delta-Mendota Canal since the early 1950s and the California Aqueduct since the early 1970s resulted in decreased groundwater pumping in some parts of the valley, which was accompanied by a steady recovery of groundwater levels and a reduced rate of aquifer-system compaction and land subsidence in some areas (Ireland 1986). For brevity, throughout this paper, the term subsidence will be used to refer to aquifer-system compaction and the associated land subsidence.
The objective of this paper is to describe changes in water availability and competition for water in the Central Valley as well as to evaluate the influence of climate variability and human action on subsidence, particularly during the latest drought periods. In response to the competition for water, a number of water-related issues have gained prominence: surface-water availability, conjunctive use, managed aquifer recharge, land-use change, subsidence, and effects of climate variability. Independent of climatic variability, which is discussed later, surface-water deliveries have declined in recent years due to water-quality and biologic issues principally in the Sacramento-San Joaquin Delta—the ‘heart’ of the state’s water delivery system (Ingebritsen and Ikehara 1999)—and agreements associated with surface-water allocations (Fig. 2). For example, the agricultural service contract allocation from the Central Valley Project south of the Delta was less than 50 % of the 1952–1990 average for each of the years 2009–2011 and has been less than two thirds that allocation for each year since 2000 (B. Martin, San Luis Delta Mendota Water Authority, written communication, 2015).
Climate variability has had profound effects on the Central Valley hydrologic system. During droughts, surface water is less available and groundwater pumpage increases. During the droughts of 1976–1977 and 1987–1992, diminished availability of surface water led to reduced surface-water deliveries and increased groundwater pumpage, thereby reversing the overall trend of groundwater-level recovery and re-initiating subsidence in the San Joaquin Valley. Following each of these droughts, recovery to pre-drought water levels was rapid and subsidence virtually ceased (Swanson 1998; Galloway et al. 1999). During the more recent droughts of 2007–2009, and 2012–present, groundwater pumping and subsidence has increased in some parts of the valley.
To provide information to stakeholders addressing these issues, the US Geological Survey (USGS) Groundwater Resources Program supported a detailed assessment of groundwater availability of the Central Valley aquifer system that includes: (1) the present status of groundwater resources; (2) how these resources have changed over time; and (3) tools to assess system responses to stresses from future human uses and climate variability and change. The principal product of this assessment is a tool referred to as the Central Valley Hydrologic Model (CVHM) that accounts for integrated, variable water supply and demand, and simulates surface-water and groundwater flow, and subsidence across the entire Central Valley system (Faunt 2009; Figs. 1 and 2).
The CVHM simulates groundwater and surface-water flow, irrigated agriculture, subsidence, and other key processes in the Central Valley on a monthly basis. This model was developed at scales relevant to water management decisions for the entire Central Valley aquifer system. Subsidence, an important consequence of intense groundwater pumpage in susceptible aquifer systems, especially in the San Joaquin Valley, is specifically simulated. Recently, this model was extended through water year 2014 by including a scenario based on updated surface-water inflows and deliveries, updated land-use maps, and climate data (precipitation and reference evapotranspiration). In part, this extension was done to simulate the impact of land-use changes, managed aquifer recharge, and the more recent droughts on subsidence.
Land-use changes, managed aquifer recharge, and drought
Based on the CVHM simulation, since the majority of the surface-water delivery system has been in place (early 1970s), on average about 43 % of the water supply of the Central Valley has been met by groundwater (ranging from about 30 % during wet years to 70 % during extremely dry years). Central Valley farmers have drilled more wells and increased their groundwater pumping to compensate for reduced surface-water supplies and increased water demands of permanent crops. During the recent drought (2012-present), groundwater is used to meet about 70 % of the demand. The proportion is expected to increase in the near future if surface water availability declines or remains at current levels, particularly given the increase in permanent crops.
The increased pumping has stressed the aquifer system, which has had an overall loss in groundwater storage for decades. Since 1962 groundwater storage in the Central Valley aquifer system has been depleted at an average rate of 1.85 km3/year and at more than twice this rate during the latest drought (Fig. 2). This rate is likely to increase if dry conditions persist. Despite the worst drought in modern history, California agriculture realized record profits in 2013 and 2014, driven in part by US economic growth and expanding international markets (California Department of Water Resources 2014); however, under state laws enacted in 2014, the Central Valley groundwater basin must be sustainable by 2042. In order to meet these requirements, dramatic changes will need to be made.
Chronic lowering of groundwater levels (not including overdraft during a drought if a basin is otherwise managed)
Significant and unreasonable reduction of groundwater storage
Significant and unreasonable seawater intrusion
Significant and unreasonable degraded water quality, including the migration of contaminant plumes that impair water supplies
Significant and unreasonable land subsidence that substantially interferes with surface land uses
Depletions of interconnected surface water that have significant and unreasonable adverse effects on beneficial uses of the surface water.
Land subsidence and groundwater levels
The magnitude and rate of subsidence varies based on the hydraulic and mechanical properties of the saturated geologic materials constituting the aquifer system and on the consolidation history of the aquifer system. Therefore, the extent of subsidence was compared with the extent of fluvial fans from the Sierra Nevada (Weissmann et al. 2005; Figs. 1 and 5) and also to groundwater levels (Fig. 6a). In general, valley deposits sourced from the Coast Ranges and the non-glaciated fluvial fan deposits sourced from the Sierra Nevada are finer grained and more compressible than the coarser-grained sediments, resulting in greater subsidence under equivalent applied stresses (declining groundwater levels). Conversely, the upper reaches of the large drainage area glaciated fluvial fans that are relatively coarser grained and have much lower rates of subsidence (Fig. 5). Following the theory of aquifer-system compaction embodied in the aquitard drainage model (Galloway and Burbey 2011), the consolidation history of an aquifer system establishes the preconsolidation stress, which is often represented by the previous lowest groundwater level (highest effective or intergranular stress). The relation of current groundwater levels to the previous lowest water level controls whether subsidence is inelastic (permanent) or elastic (recoverable). Permanent subsidence occurs as a result of rearrangement of fine-grained materials when the preconsolidation stress is exceeded (current water levels lower than historical lows); whereas recoverable (elastic) subsidence occurs when the preconsolidation stress is not exceeded (current water levels higher than historical lows).
Since spring 2008, groundwater levels are at all-time historical lows (for period of record) in most areas of the southern San Joaquin Valley and portions of the Sacramento Valley. These areas exhibit groundwater levels more than 15 m below previous historical lows experienced sometime prior to 2000. There are many areas of the San Joaquin Valley where recent groundwater levels are more than 30 m below previous historical lows and correspond to areas of recent subsidence. According to the California Department of Water Resources (2014), groundwater levels in 55 % of the long-term wells (1,718 of 3,124) in the San Joaquin Valley and 36 % of the long-term wells (216 of 599) in the Sacramento Valley are at or below the historical spring low levels. Groundwater levels declined during these periods in response to increased pumping, approaching or surpassing historical low levels. As groundwater levels dropped, subsidence occurred in many areas.
The large recently subsiding areas in the San Joaquin Valley include areas that subsided historically; however, some of the areas of maximum subsidence have changed. The Tulare-Wasco area (Figs. 5 and 7) had substantial subsidence both historically and recently, the Los Banos-Kettleman City area (Figs. 5 and 7) has substantially less subsidence recently compared to historically—where maximum subsidence during 1926–1970 was about 4 m (Ireland 1986)—and the El Nido area has substantially more subsidence recently compared to historically (Ireland 1986; Sneed et al. 2013; Farr et al. 2015). More than 120 mm of subsidence occurred over a large part of the southern subsiding area during 2007–2010 (Fig. 5). In some places nearly 900 mm of subsidence occurred during this period. The maximum rate of recent subsidence (250 mm/year) is about twice the maximum rate that occurred historically in the area (200 mm/year).
The largest subsidence magnitude in the San Joaquin Valley during 2007–2014 was measured and simulated near El Nido (Figs. 5 and 7). The interferograms are the only measurements that captured the maximum magnitudes of subsidence because the CGPS stations and extensometers are located on the periphery of the most rapidly subsiding area (Fig. 5). The interferograms indicated a local maximum of about 540 mm during January 2008–January 2010, or 270 mm/year, which is among the highest rates ever measured in the San Joaquin Valley. The subsidence measured at nearby CGPS station P303 was about 50 mm during the same time period, indicating a large subsidence gradient between the two locations (Figs. 5 and 6b). The years 2010–2012 was a non-drought period but a continued high rate of subsidence occurred during this period near El Nido (Fig. 6b). Much of the area where subsidence is occurring near El Nido has little access to surface water for irrigation supplies regardless of climate conditions. This fact, coupled with changing land use explains the continued high rate of subsidence. Residual (delayed) compaction due to the slow equilibration of fluid pressures in relatively thick, interbedded, low-permeability fine-grained units in the aquifer system also may be a factor. Vertical displacement at P304 indicates that most subsidence occurred during drought periods and very little occurred between drought periods (Fig. 6a). This area received surface water, when it was available between drought periods. The cessation of subsidence between drought periods, when water levels recovered, indicates that residual compaction was not very important in this area. Assuming the same rate of subsidence occurred during 2007–2014 as occurred during 2008–2010 at the local subsidence maximum near El Nido, about 2 m of subsidence may have occurred during 2007–2014. The CVHM simulates slightly more than 2 m of subsidence in this area (Fig. 7).
In parts of the El Nido subsidence area, where the planting of permanent crops has increased, groundwater was either the primary source of water or groundwater pumping increased when surface-water availability was reduced, and groundwater levels declined to near or below historical lows during 2007–2010 and 2012–2014. The area with the highest rate of subsidence is correlated with rates of groundwater extraction where groundwater is used to irrigate (year-round) permanent crops (vineyards and orchards) that are replacing non-permanent land uses such as rangeland, field crops, or row crops (USDA 2000–2013; Fig. 3). The correlation between high rates of subsidence and water levels near or below historical lows indicates that the preconsolidation stress was exceeded and the subsidence is mostly permanent near El Nido.
The Pixley subsidence area is really more extensive than the El Nido subsidence area, but subsided at a lower rate during 2007–2014. Similar to the El Nido area, the interferograms provided the only measurements that captured the maximum subsidence magnitudes because the CGPS stations and extensometers are located on the edges of the most rapidly subsiding area (Fig. 5). The interferograms indicated a maximum subsidence of about 180 mm during January 2008–January 2010 (Fig. 5). If it is assumed that the rate of subsidence during 2007–2014 was equivalent to the rate during 2008–2010 at the local maximum near Pixley, about 0.7 m of subsidence may have occurred there during 2007–2014. Published subsidence rates during 2007–2010 ranged from about 0.2 to 0.25 m/year (Farr and Liu 2015; Farr et al. 2015), which are smaller than the 0.34 m/year rates, described as preliminary by LSCE et al. 2014). Farr et al. (2015) utilized InSAR to estimate subsidence rates in the Central Valley between May 2014 and January 2015, i.e., in the third year of California’s ongoing severe drought. They measured as much as 0.35 m of subsidence near the local maximum subsidence area near Pixley for the 8-month period (equivalent to a rate of about 0.5 m/year).
Data from the four CGPS stations and two extensometers near the periphery of the Pixley subsidence area show seasonally variable subsidence rates, with different interannual characteristics. Vertical displacement at P564 and P565 indicated that most subsidence occurred during drought periods and very little occurred between drought periods. This suggests that this area received other sources of water, most likely surface water, when it was available between drought periods, and also that residual compaction was not very important in this area. Vertical displacement at P056 and P566 indicated subsidence at fairly consistent rates during and between drought periods. These fairly consistent subsidence rates are in areas with limited surface water availability and where groundwater is the primary water source. CGPS and extensometer data indicated an increased subsidence rate during 2014, the third year of drought. In the Pixley area, groundwater pumping continued or increased when surface-water availability was reduced, and groundwater levels declined to near or below historical lows during 2007–2010 and 2012–2014. Similar to the El Nido area, because the high rates of subsidence in the Pixley area are correlated with groundwater levels near or below historical lows, the subsidence is interpreted to be mostly permanent. Similar subsidence magnitudes for these periods are simulated by CVHM but the spatial patterns are somewhat different. These differences are attributed in part to the grouping of farms and agencies accepting surface-water deliveries and calculating demand for the water accounting in this part of the CVHM.
Groundwater pumping has resulted in subsidence which has caused damage to infrastructure in the San Joaquin Valley. Bridges, roads, buried irrigation pipelines, land leveling of fields, and wells have been altered and/or damaged by subsidence in the San Joaquin Valley (Sneed et al. 2013). In particular, serious operational, maintenance, and construction-design problems for the California Aqueduct, the Delta-Mendota Canal, the Outside Canal, and other regional and local water-delivery and flood-control structures have been documented (Sneed et al. 2013; LSCE et al. 2014). Costs to address damage to surface-water conveyance infrastructure are estimated at more than $1.3 billion (2013 dollars) during 1955–1972; cost estimates for subsidence-related damages incurred in subsequent years are unavailable (LSCE et al. 2014).
Summary and conclusions
Groundwater and surface water are generally used conjunctively in the Central Valley (Williamson et al. 1989; Faunt 2009). During recent drought periods (2007–2009 and 2012–present), groundwater pumping has increased. This increase is likely related to, among other things, the combination of declines in surface-water allocations, drought and land-use changes. In response, groundwater levels declined to levels approaching or surpassing historical low levels, which has caused subsidence that is mostly permanent. In the San Joaquin Valley, this subsidence has caused alterations or damages to bridges, roads, buried irrigation pipelines, land leveling of fields, and wells (Sneed et al. 2013; LSCE et al. 2014). Large areas with recent subsidence in the San Joaquin Valley—El Nido and Tulare-Wasco and Los Banos-Kettleman City areas (LSCE et al. 2014)—do not have CGPS or borehole extensometers in the areas of maximum subsidence (Fig. 5); therefore, the actual subsidence rate cannot be monitored continuously.
Planning for the effects of continued subsidence in the area will be important for water agencies. As land use, managed aquifer recharge, and surface-water availability continue to vary, long-term groundwater-level and subsidence monitoring and modelling are critical to understanding the dynamics of historical and continued groundwater use resulting in additional groundwater-level and groundwater-storage declines, and associated subsidence. In some circumstances, the subsidence may occur long after the groundwater pumping has declined. Modeling tools such as the CVHM, can be used in the evaluation of management strategies to mitigate adverse impacts due to subsidence while also optimizing water availability. This knowledge will be critical for successful implementation of California’s recent legislation aimed toward sustainable groundwater use. Furthermore, the CVHM and other numerical models can be used to simulate a variety of scenarios to evaluate the various implementation plans and ensure the long-term resilience of the Central Valley’s interconnected hydrologic system.
This paper was encouraged by Devin Galloway (guest editor for the theme issue ‘Land Subsidence Processes’, Hydrogeology Journal) and supported by the USGS Groundwater Resources Program. Peer reviews by Kevin Dennehy (USGS), Lenny Konikow, and Jim Borchers and input from Devin Galloway greatly improved the manuscript. Errors of omission and commission are the sole responsibility of the authors.
- Bertoldi GL, Johnston RH, Evenson KD (1991) Ground water in the Central Valley, California: a summary report. US Geol Surv Prof Pap 1401-A, 44 ppGoogle Scholar
- California Department of Water Resources (2014) Summary of recent, historical, and estimated potential for future land subsidence in California. http://www.water.ca.gov/groundwater/docs/Summary_of_Recent_Historical_Potential_Subsidence_in_CA_Final_with_Appendix.pdf. Accessed 14 September 2015
- Farr TG, Liu Z (2015) Monitoring subsidence associated with groundwater dynamics in the Central Valley of California using interferometric radar. In: Lakshmi V (ed) Remote sensing of the terrestrial water cycle. Geophysical Monograph 206, American Geophysical Union, Washington, DC, pp 397–406Google Scholar
- Farr TG, Jones C, Liu Z (2015) Progress report: subsidence in the Central Valley, California. http://water.ca.gov/groundwater/docs/NASA_REPORT.pdf . Accessed 14 September 2015
- Faunt CC (ed) (2009) Groundwater availability of the Central Valley Aquifer, California. US Geol Surv Prof Pap 1766, 225 ppGoogle Scholar
- Galloway DL, Riley FS (1999) San Joaquin Valley, California: largest human alteration of the Earth’s surface. In: Galloway DL, Jones DR, Ingebritsen SE (eds) Land subsidence in the United States. US Geol Surv Circ 1182:23–34,. http://pubs.usgs.gov/circ/circ1182/. Accessed 14 September 2015
- Galloway DL, Jones DR, Ingebritsen SE (1999) Land subsidence in the United States. US Geol Surv Circ 1182, 175 ppGoogle Scholar
- Ingebritsen SE, Ikehara ME (1999) Sacramento-San Joaquin Delta: the sinking heart of the state. In: Galloway DL, Jones DR, Ingebritsen SE (eds) Land subsidence in the United States. US Geol Surv Circ 1182, pp 83–94. http://pubs.usgs.gov/circ/circ1182/. Accessed 14 September 2015
- Ireland RL (1986) Land subsidence in the San Joaquin Valley, California, as of 1983. US Geol Surv Water Resour Invest Rep 85-4196, 50 ppGoogle Scholar
- Poland, JF, Lofgren, BE, Ireland, RL, Pugh, AG (1975) Land subsidence in the San Joaquin Valley, California, as of 1972. US Geol Surv Prof Pap 437-H, 78 ppGoogle Scholar
- Luhdorff and Scalmanini Consulting Engineers (LSCE), Borchers JW, Grabert VK, Carpenter M, Dalgish B, Cannon D (2014) Land subsidence from groundwater use in California, report prepared by LSCE with support by the California Water Foundation. http://californiawaterfoundation.org/wp-content/uploads/PDF/1397858208-SUBSIDENCEFULLREPORT_FINAL.pdf . Accessed 14 September 2015
- Sneed M, Brandt J, Solt M (2013) Land subsidence along the Delta-Mendota Canal in the northern part of the San Joaquin Valley, California, 2003–10. US Geol Surv Sci Invest Rep 2013-5142, 87 pp, doi:. 10.3133/sir20135142 . Accessed 14 September 2015
- Swanson AA (1998) Land subsidence in the San Joaquin Valley, updated to 1995. In: Borchers JW (ed) Land subsidence case studies and current research. Proceedings of the Dr. Joseph F. Poland Symposium on Land Subsidence, Sacramento, Calif., October 4–5, 1995, Association of Engineering Geologists, Special Publ. no. 8, pp 75–79Google Scholar
- United States Department of Agriculture (USDA) (2000–2013) California County Agricultural Commission reports: National Agricultural Statistics Service. http://www.nass.usda.gov/Statistics_by_State/California/Publications/AgComm/Summary/index.asp. Accessed 14 September 2015
- Weissmann GS, Bennett G, Lansdale AL (2005) Factors controlling sequence development on Quaternary fluvial fans, San Joaquin Basin, California, USA. In: Harvey A, Mather A, Stokes M (eds) Alluvial fans: geomorphology, sedimentology, dynamics. Geol Soc Lond Spec Publ 251:169–186Google Scholar
- Williamson AK, Prudic DE, Swain LA (1989) Ground-water flow in the Central Valley, California. US Geol Surv Prof Pap 1401-D, 127 ppGoogle Scholar
Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.