Drought and the Colorado River: Localizing Water in Los Angeles

By Erik Porse and Stephanie Pincetl

Parker Dam and Lake Havasu, 2009 (Photo Credit: Alan Stark, Flickr)

In October 2022, water agencies in Southern California with Colorado River water rights announced plans to reduce water diversions. The agencies offered voluntary conservation of 400,000 acre-feet per year through 2026. This annual total is nearly 10% of the state’s total annual usage rights for the Colorado River. The cutbacks help prepare for long-term implications of climate change for the river’s management, which are starting to be acknowledged. In urban Southern California, an important aspect of this need is reducing imported water reliance through investments in local water resources.

Diversion rights along the Colorado River are over a century old. In 1922, states signed an agreement to allocate the river’s resources. Native Americans were excluded, but some of the sovereign nations have subsequently gained water rights through legal decisions and agreements. Arizona did not ratify the compact until 1944. Within the 1922 agreement, the river’s originally estimated 16.5 million acre-feet of annual yield was divided, with 7.5 million acre-feet allocated to states in both the upper and lower basins. A paltry 1.5 million acre-feet was allocated to Mexico in the 1944 Treaty with Mexico. Subsequent research estimated the historic volume of available water on the Colorado closer to 14 million acre-feet, and from 2000-2020, average inflow volumes were 12.5 million acre-feet. These numbers leave the river dry at its ultimate destination, the Colorado River Delta in Mexico. In recent decades, no flows reached the Gulf of California until 2014, when agencies negotiated a timed release of flows from Lake Mead that wetted the Delta for a few days as part of an international agreement between the U.S. and Mexico (Minutes 319 & 323).

In 2022, the river’s available water was projected to be just 8.4 million acre-feet of inflows into Lake Powell, another year well below historical averages. Huge reservoirs along the river, namely Lake Mead and Lake Powell with over 50 million acre-feet of storage, buffer against dry periods. But today the reservoirs are nearly drained after decades of severe dryness. Existing agreements developed over 15 years outline how states in the Upper and Lower Basins must adaptively reduce demand during drought based on reservoir storage levels. Given the stark forecasts through 2024, in June 2022 the U.S. Bureau of Reclamation (USBR) issued an ultimatum to parties along the river: develop plans to reduce draws by 2 to 4 million acre-feet that address chronic overuse and align with agreed conservation plans, or be subject to federal determinations. Among the Lower Basin states, California was not required to reduce draws until Lake Mead reached 1,045 feet in elevation. As of November 30, 2022, its elevation was 1,043 feet. Recovering the basin’s reservoir levels will require continued conservation along with multiple wet years.

What would happen if Southern California lost access to Colorado River water for an extended period? Almost a decade ago, we looked at this question for urban areas in Los Angeles (L.A.) County. Cities use less than 30% of California’s 4.4 million acre-feet of Colorado River water allocations. This is mostly for the Metropolitan Water District of Southern California (MWD) and San Diego County Water Authority.  The remaining California water use from the Colorado River is for agricultural districts and Native American sovereign nations. The percentages can vary between years based on decades of complex water sharing and storage agreements. End-of-year projections for 2022 forecasted that MWD would receive 25% of California’s total Colorado River diversions. Within areas of Los Angeles, Orange, Riverside, San Bernadino, and San Diego Counties served by MWD, Colorado River water supplies are critical. MWD balances imported water supplies from the Colorado River and Northern California to maintain sufficient storage in its reservoirs, helping augment local groundwater, stormwater capture, and recycled water.

To investigate the impacts of reduced imported water supply in Los Angeles, we modeled scenarios of full (100%) to no (0%) imported water availability for L.A. County water agencies that supply 10 million people. We examined impacts on urban water operations, trees, and landscapes, along with opportunities to update existing groundwater rights allocations. At the time, we didn’t anticipate that as soon as 2022, L.A. County agencies could face little to no available new water allocations from both the State Water Project and Colorado Rivers.

Results present a window into water management futures in Los Angeles. Overall, L.A. County water agencies could likely reduce long-term water reliance on imported supplies, especially the Colorado River, to 30% of total demand. Agencies would need to boost stormwater capture and recycled water production, while also investing in many more climate-appropriate landscapes. In recent years, agencies have increased investments in these strategies. Continued conservation is also key. The modeled scenarios included water allocations for health and safety, as well as estimated irrigation requirements for the urban tree canopy (if irrigated appropriately). Total per capita use was 80-100 gallons per capita per day (gpcd) in scenarios with reduced imported water availability.

The analysis captured many current trends. For instance, water use in L.A. County has continued to decline, most recently facilitated by severe drought since 2020. Recent total urban per capita use was approximately 100 gpcd across Southern California agencies in 2019-2020. In modeled scenarios, landscape transformation was a key contributor to long-term conservation. In addition, agencies have continued to invest in stormwater capture and groundwater recharge projects, especially through the county-wide Safe Clean Water Program approved in 2018. Modeled scenarios also showed the importance of water storage, not only in MWD’s reservoirs, but also in groundwater basins. Groundwater continues to be an important source that has historically averaged 35% of supply in both L.A. County and urban Southern California more broadly. We didn’t model any new ocean desalination projects in L.A. County because no such plans were underway.

We also missed some key developments. The modeled scenarios included existing and planned recycled water projects at the time, but did not account for large scale water reuse projects by the Los Angeles Department of Water and Power (LADWP), MWD, and L.A. County Sanitation. Additionally, we modeled household water needs for health and safety as 50-55 gpcd, which was the legislative standard at the time. The current indoor standard is slated to drop to 42 gpcd through 2030. Last, we didn’t explicitly include significant policy and behavioral changes that have emerged. For instance, research supported by MWD estimated that a rebate-funded turf replacement project yields an additional two turf replacement projects not funded through incentives. So-called “non-functional” turf on commercial, industrial, and institutional properties will likely become much less common in Southern California.

Achieving equitable local water reliance will require key policy changes. Many of L.A. County’s groundwater basins were adjudicated years ago and the remaining ones have been brought under regulations through the Sustainable Groundwater Management Act or “SGMA”. In adjudicated basins, existing water rights for pumping will need to offer broader access to agencies that may be unable to fund new projects. This would further incentivize stormwater capture and would spur agencies to address current adjudications, including possible municipalization of pumping rights. New water financing strategies are also needed to pay for large water projects such as countywide water recycling. Agencies will need to increase retail rates to subsidize affordable water for low-income households (within Proposition 218 restrictions). Tradeoffs in water availability for recycled water and environmental instream flows will need to be resolved, likely through guidelines for seasonal releases.  Finally, increased and sustained funding streams for landscape transformation will be needed, supported by cooperation between water agencies and the landscaping and nursery industries. Nascent programs are already taking root.

Much work remains to adapt Southern California’s water use habits to future climate conditions. The Colorado River will remain an important source of supply for coming years, but expectations of availability will change. Southern California’s cities have significant fiscal resources and planning capacity to adapt. The hardest hit areas will likely be rural and agricultural communities in California that rely on Colorado River water. Yet, cities use food grown by farms and, over decades, water management practices between urban and rural agencies in the region have become entwined. The result is a system where everyone is affected. As we face more dry years in California and the Pacific Southwest, empathy for the livelihoods of fellow Californians is perhaps our most potent resource for climate adaptation.

Erik Porse is a Research Engineer at the Office of Water Programs at Sacramento State and an Assistant Adjunct Professor at UCLA’s Institute of the Environment and Sustainability.

Stephanie Pincetl is a Professor at UCLA’s Institute of the Environment and Sustainability and Founding Director of the California Center for Sustainable Communities at UCLA.

The results were part of projects from a multi-university team that also included Mark Gold, Diane Pataki, Terri Hogue, Katie Mika, Kim Manago, Elizaveta Litvak, Madelyn Glickfeld, and Felicia Federico.

Further Reading:

Davis, Margaret Leslie. 1993. Rivers in the desert: William Mulholland and the inventing of Los Angeles, 1st ed. HarperCollins Publishers, New York, NY.

Erie, Steven, HD Brackman. 2006. Beyond Chinatown: the Metropolitan Water District, growth, and the environment in southern California. Stanford University Press, Stanford, CA.

Felicia Federico, A. Youngdahl, S. Subramanian, C. Rauser, M. Gold. 2019 Sustainable LA Grand Challenge Environmental Report Card for Los Angeles County Water. UCLA

Galt, Joe. Sharing Colorado River Water: History, Public Policy and the Colorado River Compact. University of Arizona Water Resources Research Center. August 1997.

MWD. Integrated Water Resources Plan: 2020 Update. Technical Appendices. Los Angeles, CA.

MWD. 2020 Urban Water Management Plan. Los Angeles, CA. June 2021.

Mika, Kathryn B., E. Gallo, E. Porse, T. Hogue, S. Pincetl, and M. Gold. 2017. LA Sustainable Water Project: Los Angeles City-Wide Overview. UCLA, Los Angeles, CA

Ostrom, Elinor. 1965. Public Entrepreneurship: A Case Study in Ground Water Basin Management. Ph.D. Dissertation, University of California, Los Angeles

Ostrom, Vincent. 1962. “The political economy of water development.” The American Economic Review 52.2: 450-458.

Porse, Erik, KB Mika, E Litvak, KF Manago, K Naik, M Glickfeld, TS Hogue, M Gold, DE Pataki, and S Pincetl. 2017. “Systems Analysis and Optimization of Local Water Supplies in Los Angeles.” Journal of Water Resources Planning and Management. 143, no. 9 (2017): 04017049.

U.S. Bureau of Reclamation. Annual Operating Plan for Colorado River Reservoirs 2022. December 8, 2021.

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California WaterBlog: 2022 In Review

By Christine Parisek

The California WaterBlog is completing its 11th year. As we enter 2023, we take a moment to to thank our many readers, partners, authors, and friends. The California WaterBlog’s central mission is to provide stimulating ideas and commentary on critical challenges of water issues, resource management, and ecosystem restoration, in a digestible form. 

Figure 1. Word Cloud displaying frequent
      themes in 2022 WaterBlog titles.

In 2022, California WaterBlog published 49 blogs. This year, 64 unique authors contributed to California WaterBlog (an increase from last year), and on July 10th we surpassed our 500th blog post! The blog currently reaches readers in 74 countries worldwide with almost 14,000 subscribers and over 103,000 visitors this year. As usual, blog posts covered a breadth of themes, including Watershed outreach, the recent mass local die-off of white sturgeon, effect of drought on California’s intermittent streams, thiamine deficiency in salmon, native fishes and reservoirs, and being patient and persistent with nature.

Especially popular topics included California’s drought status and drinking water systems, environmental water rights, what to do when shift happens, a conservation bill you’ve never heard of [that] may be the most important in a generation (the Recovering America’s Wildlife Act), an exposé on the silent extinction of freshwater mussels, and farmer-researcher team science initiatives. We hope you continue enjoying CaliforniaWaterBlog and that the list below helps if you missed any blogposts.

Christine Parisek is a PhD candidate in the Graduate Group in Ecology at UC Davis and a science communications fellow at the Center for Watershed Sciences.

Table 1 (Further Reading). Top 17 blog posts in 2022, as ranked by “View” statistics.

6,128California’s 2022 Water Year – Both Wet and DryJay Lund
5,674Saving Clear Lake’s Endangered ChiPeter Moyle and Thomas Taylor
2,879Considerations for Developing An Environmental Water Right in CaliforniaKarrigan Börk, Andrew Rypel, Sarah Yarnell, Ann Willis, Peter Moyle, Josué Medellín-Azuara, Jay Lund, and Robert Lusardi
2,820Drought Year Three in California, 2022Jay Lund
2,746Who governs California’s drinking water systems?Kristin Dobbin and Amanda Fencl
2,580Continued drought early in a possibly wet yearJay Lund
2,283The Failed Recovery Plan for the Delta and Delta SmeltPeter Moyle
2,232Shift happensMiranda Bell-Tilcock, Rachel Alsheikh, and Malte Willmes
2,147A conservation bill you’ve never heard of may be the most important in a generationAndrew Rypel
1,957Follow the Water!Jay Lund
1,936Nature has solutions…What are they? And why do they matter?Andrew Rypel
1,758The Putah Creek Fish Kill: Learning from a Local DisasterAlex Rabidoux, Max Stevenson, Peter Moyle, Mackenzie Miner, Lauren Hitt, Dennis Cocherell, Nann Fangue, and Andrew Rypel
1,697Approaches to Water PlanningJay Lund
1,589Losing mussel mass – the silent extinction of freshwater musselsAndrew Rypel
1,483Five “F”unctions of the Central Valley FloodplainFrancheska Torres, Miranda Tilcock, Alexandra Chu, and Sarah Yarnell
1,434Unlocking how juvenile Chinook salmon swim in California riversRusty Holleman, Nann Fangue, Edward Gross, Michael Thomas, and Andrew Rypel
1,434Rice & salmon, what a match!Andrew Rypel, Derrick Alcott, Paul Buttner, Alex Wampler, Jordan Colby, Parsa Saffarinia, Nann Fangue, and Carson Jeffres
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The Collapse of Water Exports – Los Angeles, 1914

This is a re-post from 2019 with updated links for pictures and further readings.

by Jay Lund

Collapse of Los Angeles aqueduct pipeline through Antelope Valley from a major flood in February, 1914 (3-months after the aqueduct’s official opening)

“In February, 1914, the rainfall in the Mojave Desert region exceeded by nearly fifty per cent in three days the average annual precipitation.

Where the steel siphon crosses Antelope valley at the point of greatest depression, an arroyo or run-off wash indicated that fifteen feet was the extreme width of the flood stream, and the pipe was carried over the wash on concrete piers set just outside the high water lines. The February rain, however, was of the sort known as a cloud-burst, and the flood widened the wash to fifty feet, carried away the concrete piers, and the pipe sagged and broke at a circular seam. The water in the pipe escaped rapidly through the break under a head of 200 feet, and the steel pipe collapsed like an emptied fire hose for nearly two miles of its length. In some places the top of the pipe was forced in by atmospheric pressure to within a few inches of the bottom. The pipe is ten feet in diameter, and the plates are 1/4 and 5/16 of an inch thick. Many engineers pronounced the collapsed pipe a total loss, and advised that it be taken apart, the plates re-rolled and the siphon rebuilt.

The damage was repaired, however, by the simple expedient of turning the water on after the break was mended, relying on the pressure to restore the pipe to circular form. The hydraulic pressure, under gradually increasing head, restored the pipe to its original shape without breaking any of the joints or shearing the rivets, and a month after the collapse the siphon was as good as new. The total cost of repairing the siphon was only $3,000. It would have cost about $250,000 to take it apart and rebuild it.” [1]

Water management and policy has always faced challenges, even unexpected ones following great technical triumphs.  But sometimes challenges require only some simple creativity based on fundamental insights and a willingness to venture forth and adapt.  Sometimes.

Further reading

[1] Complete report on construction of the Los Angeles aqueduct, Los Angeles Board of Public Service Commissioners, Los Angeles, CA 1916. (pp. 20-21) https://openlibrary.org/works/OL13802476W/Complete_report_on_construction_of_the_Los_Angeles_aqueduct

[2] http://waterandpower.org/museum/Construction_of_the_LA_Aqueduct.html

[3] LADWP historic photo archives – https://tessa2.lapl.org/digital/collection/dwp/search

[4] YouTube – Construction of the Owens Valley Project

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The Largest Estuary on the West Coast of North America

By Jeffrey Mount and Wim Kimmerer

For decades the San Francisco Estuary, which includes San Francisco Bay and the Sacramento-San Joaquin Delta, has been routinely described as “the largest estuary on the west coast of North America.” This appeared in publications of all types, presumably to emphasize the importance and unique nature of the estuary. But this claim is wrong. While the San Francisco Estuary is quite large, with many unique features, the Salish Sea Estuary is the largest by far.

Estuaries were defined six decades ago as semi-enclosed bodies of water where rivers mix with ocean water. This definition reflected the scope of estuarine studies of that era, which were conducted mainly in large river mouths in Europe and eastern North America. This traditional view of estuaries may have influenced current thinking that the San Francisco Estuary is the largest. But, the definition of what constitutes an estuary has since been broadened to include all coastal enclosed water bodies, including those without substantial freshwater input (for example, Tomales Bay).

The San Francisco Estuary, including its historic wetlands, covers an area greater than 1,900 square miles (Figure). The Salish Sea Estuary—made up of Puget Sound, Strait of Juan de Fuca, Georgia Strait, and Desolation Sound—covers 7,200 square miles, almost four times larger. It is the biggest on the west coast and is even larger than the Chesapeake Bay Estuary.

Sources: Salish Sea Atlas (Flower 2021), Adapting to Rising Tides East Contra Costa Shoreline Flood Explorer. Prepared by Gokce Sencan, PPIC.

Notes: For the San Francisco Estuary, boundaries of a 100-year storm event were used as rough boundaries of the estuary. For the Salish Sea Estuary, the topographic map was adjusted to include elevations up to 2 meters (approximately 6 feet). Actual areas of estuaries might be smaller due to factors like historical modifications and rounding in calculations.

This contrast in size stems from the geologic processes that originally formed the two estuaries.

Most large estuaries are formed by sea level rise. From around 19,000 years to 5,000 years ago, melting of continental glaciers induced a rapid rise in sea level that inundated valleys and canyons formerly occupied by rivers and streams around the globe.

Before the late Pleistocene/Holocene rise in sea level, the ancestral Sacramento River emerged from the Central Valley through the Carquinez Strait and spread out into an alluvial plain in what is now San Pablo and San Francisco Bay. The river then flowed through a narrow canyon at the Golden Gate and formed a large delta adjacent to the Farallon Islands, more than 300’ below present sea level.

By the time early Native Americans arrived, perhaps more than 10,000 years ago, there were vast floodplains, marshes, riparian forests and massive dune fields in what is San Francisco Bay. As sea level rose, brackish and freshwater tidal marsh formed along shorelines throughout the area. About 5,000 years ago, sea level rise pushed into the area near the confluence of the Sacramento and San Joaquin rivers. Here, accumulation of organic material and river sediment kept up with sea level rise—which slowed considerably—forming the Sacramento-San Joaquin Delta.

Until they were subsequently drained or filled, the marshes formed by sea level rise throughout the estuary were the unique characteristic of the relatively shallow San Francisco Estuary. They fueled what must have been one of the most productive estuarine ecosystems in North America, teeming with abundant fish and wildlife (today it has become rather unproductive owing to changes in hydrology, loss of wetlands, and the introduction of countless species from around the world).

The origins of the Salish Sea are quite different, but it is, by modern definitions, an estuary. The glaciers that covered much of the North American continent 25,000 years ago spilled over into the Salish Sea region, carving steep-walled, deep canyons. The ice in some regions was nearly a mile thick, with its base grinding out canyons well below sea level. Around 16,000 years ago these glaciers retreated rapidly, completely disappearing as the oceans began to rise and flood glacial outwash sediments in Juan de Fuca Strait, Puget Sound, and Georgia Strait. Depths in the Salish Sea today reach more than 2,000 feet in some areas. It is one of the deepest estuaries in North America: even deeper than the St. Lawrence Estuary, which is by far the largest. And unlike the San Francisco Estuary, which has one large watershed at its head, many rivers discharge into the former glacial canyons.

The San Francisco and Salish Sea Estuaries are the West Coast’s largest. Their differences in origin shape their hydrodynamics, salinities, and ecology, along with their human uses. But the differences in origins also led to big differences in size. As important as the San Francisco Estuary is to the region’s history, economy, culture, and biodiversity, it is not the biggest. That crown goes to the Salish Sea Estuary.

Jeffrey Mount is a senior fellow at the Water Policy Center, Public Policy Institute of California and founding director at the UC Davis Center for Watershed Sciences. Wim Kimmerer is Estuary and Ocean Science Center Research Professor, San Francisco State University, Romberg Tiburon Campus.

Further reading

Johnson, K. A. and G. W. Bartow, eds. 2018. Geology of San Francisco, California, United States of America. Association Engineering Geologists, Geology of Cities of the World Series.

Lasmanis, R. and E. S. Cheney, eds. 1994. Regional Geology of Washington State. Washington Division of Geology and Earth Resources, Bulletin 80.

Malamud-Roam, F., M. Dettinger, L. B. Ingram, et al. 2007. Holocene Climates and Connections between the San Francisco Bay Estuary and its Watershed: A Review. San Francisco Estuary and Watershed Science, 5 (1).

McLusky, D. S. and M. Elliott, M. 2004. The Estuarine Ecosystem: Ecology, Threats and Management. New York: Oxford University Press.

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The 2020-2023 drought continues for a fourth year?

by Jay Lund

After three years of drought and two dry months, plus two wet weeks, into California’s “wet” season for 2023, California has become unsettlingly settled into this long drought.  Most cities have decreased their water use, some more than others.  Agricultural fallowing has been modest statewide, but large in the Sacramento Valley, with major economic effects in areas depending on rice-growing.  Impacts to native fish and forests have been accumulating, and are dire in some cases.

What is California’s water situation in early December 2022?

What are some drought lessons so far?

What are prospects and preparations for additional dry years?

Storage in Major Surface Reservoirs

Reservoir levels remain low, but within California they are slightly improved from last year at this time.  Nevertheless, there is little surface water reserve to be drawn down if this winter remains dry, and much of that would be needed for Delta outflows to keep the Delta freshish this coming summer.

The ongoing depletion of lower Colorado River water storage means that overall storage available to California is diminished (perhaps including any remaining California water “banked” in the Colorado River basin), and embroils California with increasingly dire Colorado River issues, especially for the Salton Sea.

The immense Colorado River reservoirs have been draining rapidly, about 3 million acre-ft in the last year, to supply about a third of water use in the lower basin and Mexico (about 9 maf). Continued drawdown in these reservoirs could jeopardize the ability to use some dam outlet structures this coming summer.

The good news is these low reservoir levels make flooding less likely this water year, so far at least.

Surface Storage as of October 31, 2022 (water year 2023):

Precipitation so far

It remains too soon to say much about precipitation for the 2023 water year.  After the first 2 months, precipitation is currently 85% of average for northern California.  So far, it has not been wet, but there is time for this to change, with the wettest months of the water year still ahead. The last week has put some water in this wet season, but the water year is still young.

Snowpack so far – Very early, but with the last week or so of storms, California is at 150% of average for this time of year.  An unusual time recently where snow is above average and total precipitation is a bit below average.

Drought damages so far

Just before Thanksgiving, a group led from UC Merced produced an insightful report on the impacts of this drought on agricultural water use, production, and economic performance (Medellin-Azuara et al. 2022).  The table below summarizes from this report, and adds results from the worst two years of the previous drought (from Howitt et al. 2014, 2015).

Condensed Summary of Recent Drought Impacts to Agriculture:

Note: *2014 and 2015 estimates were done using somewhat different methods and baselines, and not corrected for inflation, and so are only roughly comparable.

Some pretty interesting preliminary results stand out (highlighted in the table), which are discussed more in the original reports:

  1. All four drought years were similarly dry overall, but 2015 was the worst.
  2. There was a big and unusual shift of surface water supply reductions in 2022 to the Sacramento Valley from the Tulare basin, helping explain the large fallowing of rice lands in the Sacramento Valley in 2022.
  3. Additional groundwater pumping due to drought seems to have diminished in the post-SGMA drought years, unless this difference stems from differences in estimation methods. (I’ll be hopeful for now.)
  4. Net water shortages were more balanced across river basins in the 2021-22 drought years, shifting fallowing more to the Sacramento Valley from the Tulare basin.
  5. Economic losses in terms of value added from crop and livestock production seem pretty similar across droughts, but job losses were a little larger recently.
  6. These newer agricultural drought impact studies are more complete.

Some of these differences might be due to differences in methods and baselines, especially between the two droughts.  We’ll have to see how more detailed post-drought analyses come out.  It would be nice to see such regular assessments on ecological and rural community drought impacts.

The quantities of water shortages and land fallowing during these drought years is roughly what we should expect to see permanently with the implementation of SGMA. 

Prospects for another dry year

The likelihood of additional dry years is high enough to prepare for more drought.  Low reservoirs and declining groundwater make such preparations even more prudent.  DWR’s minimal initial State Water Project water allocations for the coming year are along this line.

DWR recently released an interesting survey of urban water shortage likelihoods for next year.  There was widespread expectation of an additional dry year, with quite a few agencies expecting cuts in their regular water sources.  However, of hundreds of sizable urban water suppliers, very few expected great difficulty in accommodating these water source reductions, having made preparations for alternative sources (from groundwater, purchases from farmers, additional water conservation, etc.).  Urban areas appear to be mostly well prepared, as they should be.  Urban water use supports over 90% of California’s economy and population, while using about 10% of its water.

Groundwater levels are declining.  DWR’s new SGMA website shows local and regional trends in groundwater levels (and is a great advance in groundwater data communication).  For the Central Valley, there continues to be sizable declines in groundwater levels in many areas, particularly the San Joaquin Valley and now in parts of the Sacramento Valley.  The need to replenish the additional pumping of this drought, as well as accumulating overdraft since 2014, during the hopefully coming wet years will extend the agricultural impacts of this drought for many years to come, especially if 2040 sustainability targets are to be met.

Rural communities often struggle in drought and from accumulating groundwater contamination.  State aid seems more available and organized than in previous droughts.  But we still have a long way to go on these problems.

Ecosystems impacts of drought remain California’s sector with the least drought management success.  For waterbirds, we seem relatively well organized and mostly successful.  But not for most fish and forests, with post-drought impacts extending for many years from wildfires and more species becoming more endangered.

What to do?

The previous drought highlighted the need to manage groundwater and resulted in California’s Sustainable Groundwater Management Act.  This drought confirms the need to move solidly and deliberately to implement this law at the aquifer level, which will reduce irrigated acreage by 500,000 – 1,000,000 acres permanently.  This will be painful, but necessary for long-term rural health, prosperity, and ecosystems across drought and wetter years.  State and county education and development programs can help ease and accelerate this unavoidable transition.

This drought highlights the growing urgency and unavoidability of reducing agricultural and urban water uses, and the needs to rationalize environmental water management and rural water supplies. 

In the meantime, stay calm and hopeful, but prepare for both floods and drought, as usual.

Further reading

Precipitation data: https://cdec.water.ca.gov/precipapp/get8SIPrecipIndex.action

Reservoir data: https://cdec.water.ca.gov/reservoir.html

Groundwater data: https://sgma.water.ca.gov/CalGWLive/#groundwater

Here is a data garden to play in:  http://cdec.water.ca.gov/reportapp/javareports?name=8STATIONHIST

Medellín-Azuara, J., et al. (2022). Economic Impacts of the 2020-2022 Drought on California Agriculture (2022). A report for the California Department of Food and Agriculture. Water Systems Management Lab. University of California, Merced 35p. Available at http://drought.ucmerced.edu

Howitt, R.E., D. MacEwan, J. Medellín-Azuara, J.. Lund, D.A. Sumner (2015). “Economic Analysis of the 2015 Drought for California Agriculture”. Center for Watershed Sciences, University of California – Davis, Davis, CA, 16 pp.

Howitt, R.E., Medellin-Azuara, J., MacEwan, D., Lund, J.R. and Sumner, D.A. (2014). Economic Analysis of the 2014 Drought for California Agriculture. Center for Watershed Sciences, University of California, Davis, California. 20p.

Jay Lund is a Professor of Civil and Environmental Engineering and Vice-Director of the Center for Watershed Sciences at the University of California – Davis

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Managing source water for maximum benefit in a challenging climate

By Amber Lukk and Ann Willis

Figure 1. A site in the study reach of the Little Shasta River during summer baseflows. (Image credit: Amber Lukk).

In drought-prone northern California, limited water resources, private water rights allocations, and inefficient transport and use of water resources causes tension between freshwater conservation and private landownership (Garibaldi et al. 2020, Vissers 2017). In the face of a changing climate, drought curtailments will likely become more frequent, ratchetting stress on all water users (Vissers 2017). From an engineering perspective, efficiently managing water rights as arid landscapes become drier and less predictable will be essential to preservation of working landscapes and the environment.

Water purchases and leases are a common tool for securing water rights for environmental purposes. California recently considered a budget proposal to allocate $1.5 billion to buy-back private agricultural water rights to mitigate drought and support ecological uses (Bork et al. 2022). However, water right purchases can be incredibly expensive, and understanding which water rights are most likely to achieve maximal environmental benefit is vital for optimized management. Especially in coldwater habitats, the quality of water sources included in buy-backs will determine success of such efforts.

In our recent study (Lukk et al. In Press), we explore these concepts using a case study of a stream where water rights affect both spring-fed and surface water sources. The study focused on restoration of a portion of the Little Shasta River (Siskiyou County, Northern California) through reconnection of Evans Spring. This natural coldwater spring was historically a tributary to the Little Shasta, but is currently diverted for agricultural use. In the study, we explore effects of increasing stream flow using alternative water sources (e.g., in-stream runoff versus off-channel springs) to enhance coldwater habitat along a working cattle ranch.

Of the simulated scenarios, piping water directly from Evans Spring to the Little Shasta showed the greatest thermal benefits, with a maximum temperature reduction of 2.7°C. This scenario (Piping Scenario B) would provide substantive ecological benefits, especially for salmonids of conservation concern. The addition of surface water runoff, however, did not provide thermal benefits to the Little Shasta River. But while piping spring water provided the largest temperature benefit, this same strategy sacrifices potential benefits of off-channel habitat and restoration of the historical spring-fed channel. The trade-offs associated with piping versus historical channel restoration are important, as one option provides immediate benefit to existing habitat during current conditions when extreme low flows and warmer stream temperatures occur during the summer; the other reflects a more long-term conservation strategy.

No matter which option is pursued, the implications of these findings are that the source of water transfers is vital to success of an environmental water dedication. Water management practices aimed at increasing quantity of water dedications often overlook water quality in favor of an emphasis on quantity alone. When planning water inputs to a coldwater ecosystem, especially for the purposes of conservation, the water quality of the source water should be taken into consideration. Natural coldwater sources have considerable value for California’s native ecosystems, whereas their thermal quality is of little value for agricultural uses (Garbach et al. 2014). In contrast, other dedications may increase the amount of water available to streams, but result in little benefit because they have marginal ecological quality.

Figure 2. Results from the temperature model showing the differences in water temperature between the baseline measurement and the projected values from each alternative management scenario.

With the challenging unpredictability of freshwater resources, understanding the best possible uses for high-quality coldwater sources may provide the greatest benefits to the environment as well as adjacent working landscapes. For coldwater ecosystems, preservation of natural thermal regimes will be key to conservation efforts in the face of a changing climate (Willis et al. 2021). Prioritizing different water sources and when to use them may provide considerable benefits for the future of water resource and stream management in California.

Amber Lukk is an Assistant Specialist at the Center for Watershed Sciences. Dr. Ann Willis was a Senior Research Engineer at the Center for Watershed Sciences and is currently the California Regional Director at American Rivers; her research focuses on water management for stream conservation in working landscapes.

Further Reading:

Börk, K., A.L. Rypel, S. Yarnell, A. Willis, P. Moyle, J. Medellin-Azuara, J. Lund, and R. Lusardi. 2022. Considerations for developing an environmental water right in California. https://californiawaterblog.com/2022/06/12/considerations-for-developing-an-environmental-water-right-in-california/rBlog

Garbach, K., Milder, J.C., Montenegro, M., Karp, D.S., and DeClerck, F.A.J. 2014. Biodiversity and ecosystem services in agroecosystems. Encyclopedia of Agriculture and Food Systems 2: 21-40. https://doi.org/10.1016/B978-0-444-52512-3.00013-9

Garibaldi, L.A., F.J. Oddi, F.E. Miguez, I. Bartomeus, M.C. Orr, E.G. Jobbagy, C. Kremen, L.A. Schulte, A.C. Hughes, A.C., C. Bagnato, G. Abramson, P. Bridgewater, D.G. Carella, S. Diaz, L.V. Dicks, E.C. Ellis, M. Goldenburg, C.A. Huaylla, M. Kuperman, H. Locke, Z. Mehrabi, F. Santibanez, and C.D. Zhu. 2020. Working landscapes need at least 20% native habitat. Conservation Letters 14: e12773. https://doi.org/10.1111/conl.12773

Lukk, A.K., R.A. Lusardi, and A.D. Willis. In Press. Water management for conservation and ecosystem function: modelling the prioritization of source water in a working landscape. Journal of Water Resources Planning and Management.

Vissers, E. 2017. Low Flows, High Stakes: Lessons from Fisheries Management on Mill, Deer, and Antelope Creeks During California’s Historic Drought. Hastings Environmental Law Journal 23:169. https://repository.uchastings.edu/cgi/viewcontent.cgi?article=1026&context=hastings_environmental_law_journal

Willis, A.D., R.A. Peek, and A.L. Rypel. 2021. Classifying California’s stream thermal regimes for cold-water conservation. PLOS ONE 16(8): e0256286. https://doi.org/10.1371/journal.pone.0256286

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The Flow of California Water Policy – A Chart

by Jay Lund

California water policy is often discussed and depicted as being impossibly complex.  In its essentials, it can be seen much more simply, as in the flow chart below.  Without extreme events (such as floods and droughts), the policy process would be simpler, but ironically less effective, and less well funded.

California’s remarkable water history shows that frequent extreme events have activated enough innovation and preparations over 170 years such that floods, droughts, and earthquakes are now much less threatening to California’s population and economy.  However, frequent failures have not yet motivated adequate preparation and management for ecosystems and rural water supplies.

Given predictions of climate and ecological disasters, the future looks simultaneously bright, terrible, and worse for those not prepared.

Further reading

Pinter, N., J. Lund, and P. Moyle. “The California Water Model: Resilience through Failure,” Hydrological Processes, Vol. 22, Iss. 12, pp. 1775-1779, 2019.

Dynamic inaction – https://www.thedailybeast.com/when-in-doubt-mumbledynamic-inaction-may-be-our-best-hope; https://www.youtube.com/watch?v=EcDvJTazDd0

Yes Minister – https://en.wikipedia.org/wiki/Yes_Minister

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Are native fishes and reservoirs compatible?

By Peter B. Moyle and Anna M. Sturrock

Oroville Reservoir during severe drought. The ‘bathtub ring’ of steep barren ground makes poor habitat for native fishes even when the reservoir is full. Photo credit: Californiaglobe.com

The question addressed in this blog comes from a new PPIC report that calls for reforms in management of environmental water stored behind dams in California. The report shows it is possible to manage water in ways that are compatible with maintaining a natural ecosystem in streams below and above dams (Null et al. 2022). An appendix to this report focuses on fishes (Moyle et al. 2022). It provides information on how dams and reservoirs affect native fish populations and supports the need for improved water management to avoid future extinctions.

California has a unique assemblage of fishes native to its rivers and streams. Most of the 129 or so species are found no place else. They are a fascinating mixture of endemic freshwater fishes that cannot live in salt water, and endemic sea-run (anadromous) fishes that migrate long distances through both fresh and salt water environments. There are exceptions, of course, such as delta smelt and splittail, which live in the mixing zone between salt and fresh water. All of these fishes are adapted to a climate that generates extreme floods and droughts, and everything in between, on an irregular basis. This naturally variable climate is also changing, becoming more volatile and making extreme conditions worse and more frequent. Unfortunately for the fish, we humans do not like these extremes nor the unpredictability in water availability; we therefore have built massive infrastructure, centered around dams, to generate a more stable water supply.

In particular, we built dams to store water in reservoirs to get us through extreme droughts and floods and then cement canals to keep a constant flow of water to our farms and cities. There are over 1400 reservoirs in California alone, some of them among the largest in North America. Most rivers in the state support at least one dam-reservoir combination. You would think all this impounded water would provide good habitat for native freshwater fishes. Indeed, some reservoirs in their early years did support high numbers of native fishes such as hardhead, pikeminnow, and hitch. When some of the larger reservoirs filled in the 1950s and 60s, native fishes were so abundant that fisheries agencies talked about solving the ‘hardhead problem’. These native fishes were regarded as trash fish (Rypel et al. 2021) throughout western USA because anglers did not like them and assumed they suppressed populations of game fishes through competition and predation. One solution was the use of fish poisons to kill all the fish in a river before a dam was built. The most egregious example of this was poisoning of the Green River in Utah before the closure of Flaming Gorge Dam. This operation killed millions of fish, native and non-native, including many species (e.g., Colorado pikeminnow, razorback sucker) that are now listed as endangered, even in California. In California, poisoning operations (euphemistically called ‘chemical control operations’) aimed at native fishes in reservoirs were a routine management practice up into the 1980s.

Hardhead, a native California fish that was once abundant in reservoirs but now is uncommon in most of its native range. Photo credit: Ken-ichi Ueda, downloaded from Creative Commons.

The hardhead problem eventually went away on its own after introduced predators, such as largemouth bass, smallmouth bass, striped bass, and channel catfish, became established and devoured and/or out-competed all the native fishes. The non-natives could even thrive in storage reservoirs that were systematically drawn down during summer months, leaving a ‘bath-tub ring’ of exposed dirt along reservoir edges. The raw dirt provides no cover or food for juvenile native fishes that wash in from upstream areas. Most of the non-natives could also complete their entire life cycle in reservoirs, because many of these species are endemic to natural lakes and other warmwater habitats before introduction in California. Only a few native species, such as prickly sculpin, Sacramento sucker, and rainbow trout appear to have adapted to reservoir life and remained abundant in them.

For many native species (24 out of 129), dams and reservoirs have played a predominant role in placing them on an extinction trajectory (Moyle et al. 2022; ‘Dam Impacts’ rated ‘high’ or ‘critical’ in figure below). But, not surprisingly, dams tend to be one of multiple, interacting factors causing their declines, including non-native species and climate change. Over half of California’s native fishes have been rated as headed for extinction, with seven already extinct.

The dominant fishes in most reservoirs today are non-native species, with each reservoir supporting some combination of the 50 non-native species thriving in the state. By and large, reservoir fishes are popular among Californian anglers because they support recreational fisheries for black basses, sunfishes, catfishes, and other familiar fishes in their warm surface waters and rocky bottoms. Such fish are the basis of important sport fisheries elsewhere, especially in the southeastern USA, where game fishes are held in high esteem and managed intensively by fisheries agencies. In California, the reservoir fisheries are pretty much taken for granted, with little concern for harmful effects on native fishes.

But harm to natives by dams is not confined only to reservoirs with non-native fishes. Dams block access to major upstream spawning and rearing areas of salmon, steelhead, and other native fishes. In California, 70% of critical upstream habitat for salmon and steelhead has been blocked. Below the dams, their habitats are often drastically changed by the absence of high flow events that shift and reshape the riverbeds. Such flows create the complex off-channel habitats needed for juvenile rearing and to maintain a diverse fish fauna. The so-called tailwaters below a dam may be cold enough to support salmon and trout, but the embedded substrate limits invertebrate production for food and makes digging nests (redds) for spawning difficult to impossible. As water warms up with distance from the dam, and as flows are further reduced by diversions, non-native species such as carp, catfishes, and basses become dominant in the warm pools of remnant, diked river channels. The habitat, flow and thermal regimes below dams typically bear little resemblance to the historic regimes that supported native fishes and cued important physiological and ecological events. The key ingredient for native fish habitat (cool, high-quality water), is greatly reduced or absent. This water is increasingly stored in reservoirs and not available to native fishes at the right times.

Overall conservation status, vulnerability to climate change, and impacts of dams and reservoirs on native fishes (n =129). See Moyle et al. (2022) for a summary how these ratings of fish species were created and the sources of information. The key findings are that 51% of the fishes are in severe decline overall, that 78% are highly vulnerable to decline due to climate change, and that that dam and reservoir management is endangering 42% of the remaining extant species.

Dams and reservoirs have played a large role in the decline of our native fishes. However, there is a growing need to protect native fishes before even more face extinction and become listed under the Endangered Species Act. It is clearly time to improve management of stored water for native fishes. In our rapidly changing climate, using reservoirs to store designated environmental water could allow such water to be deployed flexibly during droughts and to play a pivotal role in saving endangered fishes from extinction. Nevertheless, major policy changes that revolutionize our ability to store and manage water to benefit native fishes are not likely in the near future. The water is simply too important to California’s economy. However, the restoration of native fishes to lower Putah Creek, a highly managed stream (Yolo and Solano Counties) does provide an example of success with relatively low water costs. Null et al. (2022) provide a framework for creating such successes statewide. The key is making restoration of native fishes a designated function of reservoirs instead of being an afterthought. “Making ecosystem health a primary objective of reservoir operations would enable better overall management of hydrologic uncertainty and ecological risks (p3).” Without such a change, California fishes will likely become just another statistic in the world extinction crisis. It would be better if, instead, California emerged as leader in coping with environmental change through better management of its water. The state’s unique native fish fauna needs all the help it can get!

Peter Moyle is Associate Director of the Center for Watershed Sciences and Distinguished Professor Emeritus at the University of California, Davis, USA. Anna Sturrock is Lecturer in Marine Ecology and UKRI Future Leaders Fellow, University of Essex, Colchester UK.

Further reading:

Moyle, P., A. Sturrock, and J. Mount 2022. California’s Freshwater Fishes: Conservation, Status, Impacts of Dams, and Vulnerability to Climate Change. Storing Water for the Environment, Technical Appendix A. San Francisco: Public Policy Institute of California.

Null, S., J. Mount, B. Gray, K. Dybala, G. Sencan, A. Sturrock, B. Thompson, and H. Zeff. 2022. Storing Water for the Environment: Operating Reservoirs to Improve California’s Freshwater Ecosystems. San Francisco: Public Policy Institute of California. https://www.ppic.org/publication/storing-water-for-the-environment/

Rypel, A.L., C.A. Parisek, J. Lund, A. Willis, P.B. Moyle, Yarnell, S., and K. Börk. 2020. What’s the dam problem with deadbeat dams?, https://californiawaterblog.com/2020/06/14/whats-the-dam-problem-with-deadbeat-dams/

Rypel, A.L., Saffarinia, P., Vaughn, C.C., Nesper, L., O’Reilly, K., Parisek, C.A., Miller, M.L., Moyle, P.B., Fangue, N.A., Bell‐Tilcock, M. and Ayers, D., 2021. Goodbye to “rough fish”: paradigm shift in the conservation of native fishesFisheries46(12): 605-616.

Schreier, A., P.B. Moyle, N.J. Demetras, S. Baird, D. Cocherell, N.A. Fangue, K. Sellheim, J. Walter, M. Johnston, S. Colborne, L.S. Lewis, and A.L. Rypel. 2022. White sturgeon: is an ancient survivor facing extinction in California? https://californiawaterblog.com/2022/11/06/white-sturgeon-is-an-ancient-survivor-facing-extinction-in-california/

Willis, A., R. Peek, and A.L. Rypel. 2021. Dammed hot: California’s regulated streams fail cold-water ecosystems. https://californiawaterblog.com/2021/08/29/dammed-hot-californias-regulated-streams-fail-cold-water-ecosystems/

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White sturgeon: is an ancient survivor facing extinction in California?

by Andrea Schreier, Peter B. Moyle, Nicholas J. Demetras, Sarah Baird, Dennis Cocherell, Nann A. Fangue, Kirsten Sellheim, Jonathan Walter, Myfanwy Johnston, Scott Colborne, Levi S. Lewis, and Andrew L. Rypel

Sturgeons belong to an ancient family of fishes that once lived alongside dinosaurs. This resilient group of fishes survived a meteor strike, shifting seas and continents, and the onset of the Anthropocene. In California, sturgeon populations have persisted through periods of extreme overfishing, sedimentation and mercury contamination from hydraulic mining, species invasions, and alteration of rivers by dams and levees (Zeug et al. 2014, Gunderson et al. 2017, Blackburn et al. 2019). However, sturgeons remain highly vulnerable to human activities due to their long lifespans, late age-at-maturity, periodic reproduction, and long migrations between freshwater rivers and the ocean.

Suddenly, the future of these ancient fish does not seem so secure. Between late August and early September, 2022, hundreds of sturgeon perished in the San Francisco Estuary. According to Jim Hobbs, program manager for the Interagency Ecological Program at the California Department of Fish and Wildlife (CDFW) Bay Delta office, “the white sturgeon carcass count total will be over 400 and the total for green was 15. ” Because dead sturgeon tend to sink rather than float, the total number of perished individuals is almost certainly much greater. The dead fish that were found were mostly adults and subadults (Figures 1-3), likely taking advantage of abundant and productive food resources in these habitats. Concurrent with the fish kill, the San Francisco Estuary was experiencing a bloom of the ‘red tide’ alga Heterosigma akashiwo, which has been implicated as a possible cause of death of the sturgeon. H. akashiwo produces toxins dangerous to fishes and also reduces the oxygen available in the benthic habitat preferred by sturgeon. Poisoning, asphyxiation, or both could have contributed to the mass mortality. Never before has such a massive kill of sturgeons been recorded in our estuary. 

Unfortunately, mass mortality events of sturgeon in human-dominated environments are not altogether unusual. In fact, other sturgeon mortality events were reported this summer in Idaho, Canada and Europe. The frequency and severity of major mortality events for sturgeon and other fishes is predicted to increase substantially in the future, especially as effects of extreme heat waves become more prevalent in aquatic ecosystems (Till et al. 2019, Tye et al. 2022).

Figure 1. Adult white sturgeon washed up on the shorelines of San Pablo Bay and South San Francisco Bay in late August through early September, 2022. Photos by Anonymous. Similar images of green and white sturgeons were documented via the iNaturalist SF Bay Harmful Algae Bloom 2022 Project Page; and many more were reported to the CDFW, San Francisco BayKeeper, and San Francisco Estuary Institute hotlines and to the interagency California Sturgeon Research email. These citizen reports are currently being verified and collated by CDFW to document the timing, magnitude, and distribution of the mortality event.
Figure 2. Some stretches of San Francisco Bay shoreline contained high densities of sturgeon carcasses during the mortality event. For example, on August 30 at Point Pinole, a one-mile stretch of beach contained twenty-one fresh sturgeon carcasses, ranging in length from 0.7-2.2 meters. Photo by Kirsten Sellheim.

Unfortunately, of the 27 species of sturgeon alive today, all are considered by the IUCN to be in danger of extinction in the wild. For most species there are major gaps in our knowledge of life-histories to improve conservation (Jarik and Gessner 2018). In California, we have two species of sturgeon: green sturgeon (Acipenser medirostris) and white sturgeon (Acipenser transmontanus). Sacramento River green sturgeon are listed as ‘threatened’ under the US Endangered Species Act (ESA), and thus research on that species has increased, even recently (e.g., Colborne et al. 2022; Thomas et al. 2022). Ironically, although green sturgeon are much less abundant, we seem to currently know more about the ecology of this species than white sturgeon, which is not ESA-listed. Beginning in the late 1860’s, white sturgeon in the San Francisco Bay-Delta estuary have supported a burgeoning commercial fishery for both caviar and meat. However, the fishery declined precipitously and commercial harvests were banned in 1917 by the State of California. The white sturgeon population in the San Francisco Estuary was not deemed to have recovered enough to support a sport fishery until 1954. Since, white sturgeon have been abundant enough to support a popular recreational fishery, in which fish weighing over 100 pounds and over 100 years in age are caught (but see Blackburn et al. 2019). They are also the basis of pioneering aquaculture operations in the state. Yet despite their cultural, ecological, and economic importance, we still know relatively little about the life-history of white sturgeon in our waters (but see Walter et al. 2022). This is primarily due to the long life span and motile life-history of the species, which makes it difficult to track abundances over long periods of time. Recent work using fin ray microchemistry to reconstruct migratory histories of individual fish suggest high variation in migratory behaviors, with some spending most of their time in freshwater and others residing almost their entire lives in a brackish (estuarine) environment (Sellheim et al. 2022).

Figure 3. Social media posts by local naturalist Damon Tighe @damontighe and others captured the magnitude of the mass mortality event in the San Francisco Estuary. https://twitter.com/damontighe/status/1564755695253454848

Sturgeons are the redwoods of the San Francisco Estuary. This past summer, the H. akashiwo (red tide) bloom spread like a wildfire and wiped out a huge and still unknown fraction of the estuary’s old-growth fishery. Although white sturgeon have proven resilient in the past, there is no reason to be sanguine about their future now, especially in California. Here, white sturgeon live at the southernmost edge of their geographic range, making them especially vulnerable to climate change. And because California white sturgeon don’t reproduce until they are 10-16 years old (Moyle 2002), and their offspring don’t survive well in drought years, it will likely take decades to replace the adult fish lost to this mass mortality event. Continued harvest at current rates will delay, or possibly prevent, recovery of this ancient species (Blackburn et al. 2019). Action needs to be taken now to protect California white sturgeon to assure this ancient population survives long into the future. Given known population trends, combined with the scope of this event, future ESA listing of white sturgeon is plausible. The authors of this blog are collectively hoping white sturgeon avoid the same fate as those before it. Some possible actions to arrest such a future include:

1. Consider temporarily making fisheries for white sturgeon catch-and-release, while recruiting sturgeon anglers as citizen scientists to help with life-history investigations. A conservative strategy makes sense here given the large uncertainty surrounding how many fish actually perished in the mass mortality event. The current mortality estimate of hundreds likely represents only a proportion of the total number killed, as dead sturgeon in aquaculture have been observed to sink rather than float. Temporary catch-and-release fisheries have been enacted in other regions with valuable fisheries that have quickly declined, with the option to be reopened once the population improves.

2. Provide transparent updates to stakeholders and the public on the causes of the kill, number of fish killed as a proportion of the total population size, and possible management actions.

3. Continued support and expansion of existing long-term sturgeon monitoring efforts, to include all life-history stages and habitats, in order to determine population size and dynamics, and life-history requirements. In particular, how does management of the San Francisco Estuary and water resources more generally affect the populations? What are the ecological and physiological thresholds and tolerances for green and white sturgeon? While monitoring is notoriously expensive, it is in the long run, much cheaper than trying to recover an ESA-listed species.

4. Determine the causes of all sturgeon kills, major and minor, in part by expanded water quality and harmful algal bloom monitoring throughout the estuary. Funding may also be needed for rapid responses to mass mortality events including robust carcass surveys and necropsies to verify cause of death. This would include more research into the causes of the red-tide blooms in the San Francisco Estuary.

Andrea Schreier is an Adjunct Associate Professor and Director of the Genomic Variation Lab at University of California Davis. Nicholas Demetras is an Associate Specialist at the University of California Santa Cruz and NOAA Fisheries. Sarah Baird is a Staff Research Associate in the Department of Wildlife, Fish & Conservation Biology at University of California Davis. Dennis Cocherell is a Lab Manager and Staff Research Associate in the Department of Wildlife, Fish & Conservation Biologyat University of California Davis. Nann A. Fangue is a Professor and Chair of the Department of Wildlife, Fish & Conservation Biology at University of California Davis. Kirsten Sellheim is a Science Operations Manager and Senior Scientist at Cramer Fish Sciences. Jonathan Walter is Senior Researcher at the Center for Watershed Sciences at University of California Davis. Myfanwy Johnston is a Senior Scientist at Cramer Fish Sciences. Scott Colborne is a postdoctoral researcher at University of California Davis. Levi S. Lewis is a Researcher and PI of the Otolith Geochemistry & Fish Ecology Laboratory at University of California Davis. Andrew L. Rypel is a Professor and the Peter B. Moyle and California Trout Chair in Coldwater Fish Ecology at University of California Davis, and the Director of the Center for Watershed Sciences.

Further Reading:

Blackburn, S.E., M.L. Gingras, J. DuBois, Z.J. Jackson, and M.C. Quist. 2019. Population dynamics and evaluation of management scenarios for white sturgeon in the Sacramento-San Joaquin River basin. North American Journal of Fisheries Management 39: 896-912.

Colborne, S.F., L.W. Sheppard, D.R. O’Donnell, D.C. Reuman, J.A. Walter, G.P. Singer, J.T. Kelly, M.J. Thomas, and A.L. Rypel. 2022. Intraspecific variation in migration timing of green sturgeon in the Sacramento River system. Ecosphere 13: e4139.

Gundersen, D.T., S.C. Zeug, R.B. Bringolf, J. Merz, Z. Jackson and M.A. Webb. 2017. Tissue contaminant burdens in San Francisco estuary white sturgeon (Acipenser transmontanus): implications for population recovery. Archives of Environmental Contamination and Toxicology, 73: 334-347.

Jarik, I. and C.R.J. Gessner. 2017. Sturgeon and paddlefish life history and management: Experts’ knowledge and beliefs. Journal of Applied Ichthyology 34: 244-257.

Moyle, P.B. 2002. Inland Fishes of California, Expanded and Revised. Berkeley: University of California Press.

Sellheim, K., M. Willmes, L. Lewis, J. Sweeney, J. Merz, and J. Hobbs. 2022. Diversity in habitat use by White Sturgeon revealed using fin ray geochemistry. Frontiers in Marine Science 9: 859038.

Thomas, M.J., A.L. Rypel, G.P. Singer, A.P. Klimley, M.D. Pagel, E.D. Chapman, N.A. Fangue. 2022. Movement patterns of juvenile green sturgeon (Acipenser medirostris) in the San Francisco Bay Estuary. Environmental Biology of Fishes https://doi.org/10.1007/s10641-022-01245-5

Till, A., A.L. Rypel, A. Bray, and S.B. Fey. 2019. Fish die-offs are concurrent with thermal extremes in north temperate lakes. Nature Climate Change 9: 637-641.

Tye, S.P., A.M. Siepielski, A. Bray, A.L. Rypel, N.B.D. Phelps, and S.B. Fey. 2022. Climate warming amplifies the frequency of fish mass mortality events across north temperate lakes. Limnology and Oceanography Letters Published Online.

Walter, J.A., G.P. Singer, D.C. Reuman, S.F. Colborne, L.W. Sheppard, D.R. O’Donnell, N. Coombs, M. Johnston, E.A. Miller, A.E. Steel, J.T. Kelly, N.A. Fangue, and A.L. Rypel. 2022. Habitat use differences mediate anthropogenic threat exposure in white sturgeon. BioRxiv doi: https://doi.org/10.1101/2022.08.31.505999.

Zeug, S.C., A. Brodsky, N. Kogut, A.R. Stewart, and J.E. Merz. 2014. Ancient fish and recent invaders: white sturgeon Acipenser transmontanus diet response to invasive-species-mediated changes in a benthic prey assemblage. Marine Ecology Progress Series, 514: 163-174.










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Spawning of the living dead: understanding how salmon pass thiamine deficiency to their young

By Abigail E. Ward and Miranda Bell-Tilcock

This is no ordinary witch’s brew. It’s one part of the recipe to study thiamine deficiency in our California Central Valley Chinook salmon (Oncorhynchus tshawytscha) populations. In 2019, hatcheries noticed an eerie and shivering change in juvenile Chinook salmon. Offspring were laying on their side at the bottom of tanks, swimming in corkscrew motion (see video below), or not surviving at all. In other words, for many juvenile salmon, they were not quite dead, only slightly alive.

After much deliberation and study by pathologists from USFWS, CDFW and UC Davis, it was diagnosed that salmon were experiencing thiamine deficiency (lacking in Vitamin B1). When fish received a bath in thiamine, individuals went from mostly dead to fully alive!

But now, we are left with a major question: how did these fish became thiamine deficient in the first place? And if this is being seen in our hatchery fish, what about the fish in the wild? To understand thiamine deficiency in salmon, we need to understand the past, present, and future using an array of different samples.

Kavi McKinney showing a recently removed salmon eye.

Eyes – To understand the past, we need look no further than deep into salmon eyes (right). The lens within the eye is an onion like structure that can be peeled to reveal multiple layers. Each of these layers represents a different period of the salmon’s life and takes approximately 1-2 months to form, telling us more about what the fish was consuming in the ocean, in essence generating a retrospective diet journal (Bell-Tilcock 2021). For example, one extant hypothesis surrounding thiamine deficiency is that salmon were eating too many anchovies in the ocean. Anchovies are rich in thiaminase, which can break down thiamine in a fish if consumed in large enough quantities. We are also looking to use the lens to better understand diet of Chinook salmon more generally during years when thiamine deficiency occurred.

Matthew Salvador removes a muscle sample for thiamine analysis.

Muscle – To bridge the past to the present, we extract a muscle plug from the salmon (left). When salmon migrate back into rivers to spawn, they are no longer feeding. They use all remaining energy reserves for spawning migration and to produce progeny. Similar to salmon eye lenses, stable isotopes in muscle tissue can reveal dietary patterns. Unlike eye lenses, however, this allows us to understand recent diet, typically just the last few months, before they returned from the ocean. However, muscle tissue also provides clues into present conditions when analyzed for thiamine. Combined, muscle tissues allow us to see how salmon are storing thiamine in tissues, and compare concentrations to other tissues in their bodies. 

Kevin Kwak with CDFW extracts blood from a female spring-run Chinook salmon at Feather River Hatchery

Blood – To understand the present, we extract vials of blood from freshly spawned salmon (right). Just like for humans, we can analyze the blood of salmon to obtain a profile of vitamins and micronutrients circulating their system. Blood Thiamine concentrations will further contextualize patterns seen in tissues, eyes and other organs.

Liver – In addition to the blood, we also extract a slice of liver to understand the present. The liver is a key factor in metabolism, and thiamine concentrations provide another indication of thiamine deficiency. In comparing liver concentrations to those of the muscle and eggs, we can test for severity of deficiency since the liver conserves thiamine more than other tissue types. 

Abbie Ward collects eggs from spring-run Chinook salmon at Feather River Hatchery in Oroville.

Eggs – And finally to understand the future, we examine eggs (progeny) from the recently departed (left). With a small sample of eggs, we can understand how much thiamine is being passed from the mother to her progeny. Egg thiamine concentrations also help mitigate against thiamine deficiency in future populations by understanding how patterns change across different runs, at different rates, and different times. Hatchery managers can then use this information to adjust treatments of both thiamine injections for adults and thiamine baths at fertilization. It also helps researchers cue in on which fish we may want to target for eye lens and muscle research to better understand life-history variations. 

Taken together, these samples collectively help us better understand the threat thiamine deficiency poses to our Chinook salmon populations, and aides in developing new research methods for future studies surrounding this complicated problem. Collaborations with multiple labs and agencies is critical in solving the wicked problems that fish face in today’s climate and human-dominated landscapes.

Researching these parts and pieces may make us feel like witches and wizards at times, mixing potions and casting spells on these fish to magically heal them. But in the end, our hope is that each ingredient listed here would lead us to answers to ensure our Central Valley Chinook are not living mostly dead, but rather, mostly alive. 

Further reading:







Bell-Tilcock, M.N., C.A. Jeffres, A.L. Rypel, M. Willmes, R.A. Armstrong, P. Holden, P.B. Moyle, N.A. Fangue, J.V.E. Katz, T.R. Sommer, J.L. Conrad, and R.C. Johnson. 2021. Biogeochemical processes create distinct isotopic fingerprints to track floodplain rearing of juvenile salmon. PLoS ONE 16(10): e0257444 .

Bell-Tilcock, M., C.A. Jeffres, A.L. Rypel, T.R. Sommer, J.V.E. Katz, G. Whitman, and R.C. Johnson. 2021. Advancing diet reconstruction in fish eye lenses. Methods in Ecology and Evolution 12: 449-457.

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