A California Water Crisis   

A NextGen Blog post by Lauren Rose, University of Exeter
All Photos © Alison M. Jones

This is the latest post to our NWNL NEXTGEN BLOG series. Since 2007, NWNL has supported watershed education with college internships and blogging opportunities. This NWNL NEXTGEN BLOG series posts student essays; sponsors a forum for our student contributors; and invites upper-level students to propose work focused on watershed values, threats and solutions.

Lauren graduated from University of Exeter (UK) and University of Queensland (Australia) with a degree in Zoology. She is currently pursuing a Master’s in Island Conservation and Biodiversity at the Jersey International Centre of Advanced Studies. She believes coordinated stewardship and nature-based solutions best help our expanding human populations live in harmony with the natural world. Following her earlier blogs on the Columbia River Basin, Lauren is continuing her research on North American water issues with this extremely thorough look at California’s Megadrought – a NWNL Spotlight since 2014.  For those who would like to read Lauren’s short “Background on Climate Change,” written in preparation for this post, there is an addendum at the end of this report (above her footnote references).

The US Water Crisis

In the United States in particular, climate change-induced heat waves of greater frequency and severity are increasingly evident.1United States Environmental Protection Agency Since the 1960s, these waves have occurred three times more often. Since records began in 1895, the average temperature has increased by 1.3°F to 1.9°F, with eight of the top 10 warmest years on record having occurred since 1998. Flooding, cyclone activity and drought have become increasingly common, as a result of the rising and fluctuating US climate.2United States Environmental Protection Agency

Throughout the arid and semi-arid western US, climate change stressors, coupled with growing demands, have led to water requirements beginning to exceed possible supply.3Luoma, S.N., et al. Ultimately, water drives the economy of the western US, thus droughts and water shortages will have implications for millions of people and the effects will be felt throughout the country.4Luoma, et al..

California’s San Joaquin River Valley, irrigation canal almost empty during drought

Estuaries, an essential habitat, are experiencing severe damage due to increased droughts.5Ade, C., Hsestir, E.L. and Lee, C.M Providing ecosystem services and harboring biodiversity, they have become one of the most endangered habitats on earth.6Barbier, E.B., et al. Droughts can cause a decreased water flow and connectivity within estuaries, thus altering their water rate of flow, clarity, and salinity.7Wetz, M.S., and Yoskowitz, D.W. When combined with other threats facing estuaries, drought can considerably exacerbate the situation.

All these issues are especially evident in California which has had more frequent and extreme dry periods than any other US state.8Dettinger, M., et al. Particularly in this region, freshwater is a scarce and precious resource, and recent droughts have made this fact even more evident.9Luoma, S.N., et al.

Sacramento–San Joaquin Delta (California’s “pumping heart”)

The Sacramento–San Joaquin Delta is a critical area within a larger water supply system that extends throughout much of the western U.S. Just northeast of San Francisco, it is the largest delta on the Pacific coast of North America.10Luoma, et al.. This delta began forming about 10,000 years ago, when rising sea level slowed the flow of the Sacramento and San Joaquin Rivers, allowing their sediment loads to settle. Since then, human activity has shaped and transformed the delta into a patchwork of around 57 islands, separated from each other by over 1,000 km of waterways.11California Department of Water Resources

Aeriel view of San Joaquin River wandering among island and other rivers in the CA Delta

This delta is essential for California’s water storage and distribution. It manages around 45% of the state’s total runoff, and is also vital for commercial shipping and the generation and storage of natural gas. Furthermore, Silicon Valley, a nearby thriving center for the electronics industry, receives approximately half of its water directly from this delta.12Lund, J., et al. California’s entertainment industry, the US largest export, is concentrated in cities also dependent upon this delta.13Farhi, P. and Rosenfeld, M.

In addition to sending water to large California communities, this delta is also incredibly valuable for economic and environmental reasons. California’s entertainment industry generates over $47 billion annually, and the agricultural industry in California produces around this in sales. California is responsible for 40% of U.S. agricultural production, and is almost the sole US producer of almonds, walnuts and pistachios.[mfn]Luoma, et al..[/mfn] The delta exports water to around 25 million inhabitants and irrigates around 3 million acres of farmland.14Lund, J., et al.,15Mount, J., et al. This has created a gross domestic product of $2.2 trillion; accountable for 13% of US economic output.[mfn]Luoma, et al..[/mfn]

Lettuce field with precision drip irrigation east of the Central Valley city of Los Banos

The delta also serves as a critical habitat for threatened and endangered species, and is one of 25 recognized worldwide biodiversity hot spots.16US Fish and Wildlife Service,17National Marine Fisheries Service. The San Francisco Bay is home to over 750 species of plant and animals, including culturally and economically important species such as salmon, and sturgeon.18Myers, N., et al. Additionally, migratory waterfowl use this California Delta and its adjacent San Francisco Bay as feeding grounds and as a nursery during breeding season.[mfn]Luoma, et al.[/mfn] Although the diversity of bird fauna is mostly likely only a small fraction of what it once was, as climate change begins to cause species range shifts, this delta may become a critical refuge from changing conditions. Worsening this issue, in addition to climate change pressures, more than 100 industries, wastewater treatment plants and urban stormwater now discharge effluent full of pollutants into the Delta.19Aan Geen, A., et al.

Although 40% of California’s water supply originates in groundwater wells, this delta is essential for storage and capture of the majority of California’s freshwater.20California Department of Water Resources Long-term impacts of climate change in California have created growing uncertainty about water supply and provoked suitable management strategies.[mfn]Luoma, et al.[/mfn] As droughts become progressively more common in California, effective water management has become a critical policy issue.

California Megadrought

The previous 2012-2016 drought saw groundwater levels drop in 88% of wells, with 22% falling by over 10 feet in that 1 year.[mfn]Luoma, et al.[/mfn] Compared to the droughts of the 1920s and 1970s, this megadrought has produced a combination of record-breaking high temperatures and low snowpack. Unfortunately, this will become characteristic of droughts to be expected in future years – very likely to be worse. A temporary rock barrier was constructed across one of the delta’s channels and remained there for a few months. A project to prevent the Pacific Ocean’s salt water from mixing with the river’s freshwater and promote water storage in depleting reservoirs cost $US 28 million.21Walton, B. Overall, it proved very successful. A retrospective study found that while the barrier was in place, there were no catastrophic differences in hydrodynamics, nutrient distribution or phytoplankton biomass.22Kimmerer, W. However, if such fixtures were to become more permanent, impacts may become more severe.

Only two years after the end of the most recent devastating drought, California is facing another drought – although some say California is in a continuing megadrought.  As a result of recent and escalating dry conditions in California, on May 10, 2021, Governor Newsom declared a drought emergency for 41, out of 58 counties.23Newburger, E. Construction began on yet another emergency drought barrier in the Sacramento-San Joaquin Delta to preserve the state’s precious water supply.

Fremont Weir Wildlife Area on the Sacramento River, with marker for river levels

One study, analyzing tree rings, found that California may be entering the worst period in its history of continuous droughts in more than 1,200 years. The 1,500 reservoirs in the state are currently only at 50%  capacity and local authorities have begun issuing restrictions.24Canon, G. The capacity of reservoirs within the delta is around 1.1 times the average annual runoff, thus creating flexibility for within-year fluctuations in precipitation and temperature, but not when confronted with consecutive droughts.25Lund, J. The effects of the current drought began to show early this spring, when the annual winter rains failed to quench the already dehydrated reservoirs. The U.S. Drought Monitor shows that by May, 93% of the south-west U.S. and California was in drought, with 38% of the region classified at the highest degree, with conditions only worsening as temperatures rise.26Canon, G.

Exasperated by the effects of climate change, the California Delta soon will not be able to support growing   local populations or demands from agriculture.[mfn]Luoma, et al.[/mfn]However, the delta itself poses challenges to effective water management; the year-to-year variability; and strong seasonal fluctuations in water supply, climatic influence, and high earthquake damage potential. Within the next 35 years, there is a 60% chance that an earthquake of magnitude 6.5 or greater will occur around or in the Delta.33 Although California will likely recover both economically and socially, there is great uncertainty on how the ecosystem will respond to this current megadrought due to its slow and chronic effects. Additionally, there is no unified vision for the delta and so monitoring programs and contradicting plans are uncoordinated and thus, less successful, affordable and sustainable.[mfn]Luoma, et al.[/mfn]

Tractor parked on dry sandy soil, San Joaquin River Basin

As of early September, 2021, San Francisco and a collection of Central Valley irrigation districts are suing the State of California for implementing drought restrictions that have blocked or restricted “senior” water holders from diverting water from the delta. In response, state officials highlighted that restrictions are necessary to preserve water supplies, prevent saltwater intrusion and protect the local environment. The Sacramento–San Joaquin Delta delivers two-thirds of the state’s drinking water; and so urgent and extreme actions are crucial in any bid to preserve this precious resource for all local residents, farmers, and wildlife.27Newburger, E. This may be the first of many disputes that will inevitably occur across the US Southwest in decades as droughts become more frequent and severe.  Sacrifices and compromises must be made at all levels of society, whilst also tackling climate change, the cause of these water shortages.

The Future of California

Movements have been made to protect California’s water supply and the Sacramento-San Joaquin Delta in particular. In 2014, the Groundwater Management Act was passed. It required groundwater basins to be monitored and protection plans to be developed. Effective implementation and action are the next stage. The construction of barriers has previously proved effective as a short-term solution. However, as droughts become more severe and frequent, this will no longer be an appropriate or effective solution. California should shape the Sacramento-San Joaquin Delta into a resilient ecosystem; one with the ability to absorb disturbance and adapt to change, whilst retaining its original function, structure and identity. To be effective, conservation efforts and local decisions need to include a more diverse array of stakeholders and general public to ensure a variety of views, values and cultures. California needs “all hands on deck” if it is to create a delta system that can simultaneously benefit local communities, maintain ecological services, and improve habitat quality for wildlife and human use.

Lastly, California’s recent wildfires have posed an additional need for water. Climate change will only make these wildfires more common and devastating. Other nations are not as financially or technologically fortunate as California, and so mitigating the efforts of, and adapting to drought, comes with even more challenges and restrictions for them. California will hopefully use its more fortunate position to design and test the most robust drought mitigation and adaptation strategies, and then share this technology with other nations. If watershed stewards, scientists and political entities work together, climate change can be slowed, biodiversity collapse can be averted and a healthier global ecosystem maintained.

Boat seen from tour of Sacramento-San Joaquin River Delta

ADDENDUM:  A Background on Climate Change, by Lauren Rose

Since the Industrial Revolution, average global surface temperatures have risen by 1.1°C and have caused a multitude of cascading issues.28IPCC Increasing consumer demands have resulted in humans directly modifying roughly 77% of land and 87% of oceans, making ecosystems even more vulnerable to future change.29Ganivet, E. As the global human population nears 8 billion people, the environment has been placed under extreme pressure to meet these growing requirements. Increased production, technology and transport have led to an unnatural spike in greenhouse gases, with the unsustainable burning of fossil fuels being a primary culprit. In June 2021, atmospheric carbon dioxide (CO2) levels were the highest on record over the past 800,000 years, reaching 418.94 parts per million (ppm).30Earth Systems Research Laboratory/National Oceanic and Atmospheric Administration

The impacts of climate change can vary significantly, from increases in the frequency and severity of extreme weather events to reductions in corporate financial performance.31Earth Systems Research Laboratory/National Oceanic and Atmospheric Administration ,32Secinaro, S., et al. These can subsequently cause food insecurity from variations in crop success and can threaten thousands of species with extinction.33Ray, D.K., et al.,34IPBES Specifically, climate change has impacted coastal areas disproportionally, as they are naturally vulnerable ecosystems, and since over half of the global population resides within 200 km of the coastline.35Neumann, B.,,36Small, C., and Nicholls, R.J. In a worst-case scenario, climate change would result in biodiversity collapse, a sixth mass extinction and the end of humanity as we know it.37Ceballos, G., However, by utilizing the scientific knowledge we have, coordinating efforts between multiple stakeholders and with a sprinkle of optimism, crisis can and will be averted.

Two ways in which climate change can be tackled is through mitigation and adaptation. These include such strategies as using renewable energy sources, improving livestock and agricultural practices, taxing fossil fuels alongside afforestation and similar carbon sequestration projects. Mitigation deals with the causes of changing temperatures to minimize the possible impacts of climate change. Adaptation aims to reduce the negative impacts of climate change when opportunities may arise. Both must be used in combination to achieve climate change goals and create more resilient ecosystems to survive the inevitable impacts of changing climates.


[CDWR] California Department of Water Resources. (2014) Groundwater sustainability program draft strategic plan, March 2015, Available from: http://www.water.ca.gov/groundwater/sgm/pdfs/DWR_GSP_DraftStrategicPlanMarch2015.pdf.

[CDWR] California Department of Water Resources. (2015) Where rivers meet—the Sacramento–San Joaquin Delta, Sacramento (CA): CDWR, Available from: http://www.water.ca.gov/swp/delta.cfm.

[EPA] United States Environmental Protection Agency (2021) Climate Change Indicators: Weather and Climate, https://www.epa.gov/climate-indicators/weather-climate.

[ESRL/NOAA] Earth Systems Research Laboratory/National Oceanic and Atmospheric Administration. (2021) CO2 earth, viewed 15 July 2021, <http://co2now.org&gt;.

[NMFS] National Marine Fisheries Service. (2009) Biological opinion and conference opinion on the long-term operations of the Central Valley Project and State Water Project, Long Beach (CA): NOAA NMFS, Southwest Region. page 844.

[USFWS] US Fish and Wildlife Service. (2008) Formal Endangered Species Act consultation on the proposed coordinated operations of the Central Valley Project (CVP) and State Water Project (SWP), Sacramento (CA): USFWS, page 396.

Ade, C., Hsestir, E.L. and Lee, C.M. (2021) Assessing Fish Habitat and the Effects of an Emergency Drought Barrier on Estuarine Turbidity Using Satellite Remote Sensing, Journal of the American water resources association, https://doi.org/10.1111/1752-1688.12925.

Barbier, E.B., Hacker, S.D., Kennedy, C., Koch, E.W., Stier, A.C. and Silliman, B.R. (2011) The Value of Estuarine and Coastal Ecosystem Services, Ecological Monographs, 81(2): 169–93. 

Canon, G. (2021) ‘Truly an emergency’: how drought returned to California – and what lies ahead, The Guardian, Available at: https://www.theguardian.com/us-news/2021/jun/07/california-drought-oregon-west-climate-change.

Ceballos, G., Ehrlich, P. R., and Dirzo, R. (2017) Biological annihilation via the ongoing sixth mass extinction signalled by vertebrate population losses and declines, Proceedings of the National Academy of Sciences, 114(30): e6089–e6096.

Dettinger, M., Anderson, J., Anderson, M., Brown, L.R., Cayan, D. and Maurer, E. (2016) Climate change and the Delta, San Francisco Estuary and Watershed Science, 14(3): https://escholarship.org/uc/item/2r71j15r.

Farhi, P. and Rosenfeld, M. (1998) American pop penetrates worldwide: first of three articles, The Washington Post, Made in America, October 25, 1998, http://www.washingtonpost.com/wp-srv/inatl/longterm/mia/part1.htm.

Ganivet, E. (2020) Growth in human population and consumption both need to be addressed to reach an ecologically sustainable future, Environment, Development and Sustainability, 22: 4979–4998.

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Kimmerer, W., Wilkerson, F., Downing, B., Dugdale, R., Gross, E., Kayfetz, K., Khanna, S., Parker, A. and Thompson, J. (2019) Effects of Drought and the Emergency Drought Barrier on the Ecosystem of the California Delta, San Francisco Estuary and Watershed Science, 17(3): https://doi.org/10.15447/sfews.2019v17iss3art2.

Lund, J., Hanak, E., Fleenor, W., Bennett, W., Howitt, R., Mount, J. and Moyle, P.B. (2010) Comparing futures for the Sacramento-San Joaquin Delta, University of California Press, Berkeley, page 230.

Lund, J., Hanak, E., Fleenor, W., Howitt, R., Mount, J, and Moyle, P. (2007) Envisioning futures for the Sacramento–San Joaquin Delta, Joaquin Delta San Francisco (CA): Public Policy Institute of California, Available from: http://www.ppic.org/content/pubs/report/R_207JLR.pdf.

Luoma, S.N. Dahm, C.N., Healet, M. and Moore, J.N. (2015) Challenges Facing the Sacramento–San Joaquin Delta: Complex, Chaotic, or Simply Cantankerous? San Francisco estuary and watershed science, 13(3): doi: https://doi.org/10.15447/sfews.2015v13iss3art7.

Moore, J. and Shlemon, R. (2008) Levee system fragility. In: Healey, M.C., Dettinger, M.D. and Norgaard, R.B. eds. The state of bay–delta science, 2008. Sacramento (CA): Delta Science Program, pages 103–120. Available from: http://www.science.calwater.ca.gov/pdf/publications/sbds/sbds_final_update_122408.pdf.

Mount, J., Gray, B., Chappelle, C., Gartrell, G., Grantham, T., Moyle, P., Seavy, N. and Szeptycki, L. (2017). Technical appendix: eight case studies of environmental water management during the 2012-16 drought, in: Mount, J., Gray, B., Chappelle, C., Gartrell, G., Grantham, T., Moyle, P., Seavy, N. and Szeptyck, I L. eds. Managing California’s freshwater ecosystems: lessons from the 2012-16 drought. San Francisco (CA): Public Policy Institute of California, page 45.

Myers, N., Mittermeier, R.A., Mittermeier, C.G., da Fonseca, G.A.B. and Kent, J. (2000) Biodiversity hotspots for conservation priorities, Nature, 403: 853–858.

Neumann, B., Vafeidis, A.T., Zimmermann, J. and Nicholls, R.J. (2015) Future coastal population growth and exposure to sea–level rise and coastal flooding – a global assessment, PLoS ONE, 10: e0118571.

Newburger, E. (2021) San Francisco, irrigation districts sue California over drought-related water restrictions, CNBC: Climate, https://www.cnbc.com/2021/09/10/san-francisco-irrigation-districts-sue-california-over-water-cuts.html.

Ray, D.K., West, P.C., Clark, M., Gerber, J.S., Prishchepov, A.V. and Chatterjee, S. (2019) Climate change has likely already affected global food production, PLoS ONE, 14(5): e0217148.

Secinaro, S., Brescia, V., Calandra, D. and Saiti, B. (2020) Impact of climate change mitigation policies on corporate financial performance: Evidence–based on European publicly listed firms, Corporate Social Responsibility and Environmental Management, 27(6): 2491–2501.

Small, C., and Nicholls, R.J. (2003) A Global Analysis of Human Settlement in Coastal Zones, Journal of Coastal Research, 19(3): 584–599.

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Wetz, M.S., and Yoskowitz, D.W. (2013) An ‘Extreme’ Future for Estuaries? Effects of Extreme Climatic Events on Estuarine Water Quality and Ecology, Marine Pollution Bulletin, 69(1): 7–19.

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