The California Water Model: Resilience through Failure

by Nicholas Pinter, Jay Lund, Peter Moyle

This is a slightly-edited re-posting from May 5, 2019.

Sacramento 1862

Figure 1.  1861-62 flood in Sacramento.

A review of 170 years of water-related successes in California suggests that most successes can be traced directly to past mistakes.  California’s highly variable climate has made it a crucible for innovations in water technology and policy.  Similar water imperatives have led to advances in water management in other parts of the world.  A close look at California’s water model suggests that “far-sighted incrementalism” is a path to progress.  Given the complexity of water management systems, better scientific information and new policy tools must be developed coherently and collaboratively over time.  A history of learning from previous failures can guide progress towards stable, secure, and resilient water systems worldwide.  This includes learning from other regions and other “water models” – the one option clearly superior to innovating in response to your own mistakes is learning from the errors of others.

This post summarizes an article published in Hydrological Processes,  https://onlinelibrary.wiley.com/doi/epdf/10.1002/hyp.13447

Average runoff in California is about 100 km3/yr, but our ecosystems and parts of our economy have been water-limited for decades.  Part of the state’s challenge comes from the variability of its climate.  Average years are unusual, and instead long droughts are punctuated by years of heavy rain or snowmelt and flooding.  Nonetheless, the state has managed to thrive, with 40 million people, agricultural production exceeding $45 billion/year, and the world’s sixth largest economy.  California’s droughts and floods and tension between economic growth and environmental protection have pushed it to develop a diverse toolkit for managing water.

The toolkit consists of an integrated system of infrastructure, laws, institutions, and economic tools. This system, the ”California water model,” has evolved from the first Spanish settlement, through the gold mining era, the ascendancy of agriculture and major cities, to the recent broad mix of objectives that includes strong environmental protection. California has steadily adapted its water management by making mistakes and then learning from those mistakes. In 2017, for example, California avoided major flooding despite the winter being one of the wettest on record and major spillway failures. This was partly due to luck. Reservoirs began low from a drought and winter storms were widely spaced. And most flood infrastructure, particularly the flood bypasses, functioned well. California’s water model offers broad lessons for water managers, particularly in arid regions.

Water in California is framed by the state’s Mediterranean climate.  Summers are long and dry and most precipitation comes during the winter.  Historically, much of the water supply comes from mountain snowmelt (the state’s largest surface reservoir), reservoirs, and groundwater.  In addition to this seasonality, wet years often follow droughts, and vice versa, high variability accentuated by climate change. This near-perpetual alternating water crisis forces Californians to find innovative solutions.  Whereas other US states and other countries may have decades to settle into a false sense of security, California’s hydrologic extremes accelerate innovation.

In 2017, California emerged from a severe five-year drought.  The drought’s effects on agriculture were limited because past droughts had led to more flexible water markets, and farmers greatly expanding groundwater pumping.  Although the state lost about a third of its water supply, agricultural revenue losses were only 3%, and only about 6% of the land was fallowed.  This was in part because producers of lower-value crops sold or transferred their water to producers of higher value crops such as fruit, nuts, and vegetables and to urban water users.  The expanded groundwater pumping raised the visibility and impacts of long-term groundwater problems, which in turn led to passage of California’s Sustainable Groundwater Management Act, which will regulate groundwater in the future.

At the other extreme, California also has long history of damaging floods, and flood risk remains widespread today.  Winter storms of 1861-62, turned much of the Central Valley into an inland sea, and frequent levee breaches through the 19th and 20th centuries resulted in high costs to landowners and to the state. In less variable regions, the decades between major floods lead to a “hydro-illogical cycle” in meaningful steps avoid flood damage are forgotten in intervals between disasters.  Early on in California, repeated flooding led to construction of Yolo and Sutter Bypasses, which remain a world model for basin-scale flood management.  A costly 1986 levee failure (and national headlines from New Orleans in 2005) sparked new legislation and investment that has upgraded many California levees from some of the worst in the nation to some of the best.  Repeated flood disasters have kicked the state in the right direction, although much work always remains.  The near-disaster at Oroville Dam in February of 2017, where two spillway failures led to major evacuations, sparked scrutiny and investment at Oroville Dam and for aging water infrastructure across California.  Other regions with large dams, or contemplating new dams, should include Oroville’s lessons in their textbook.

sjv land subsidence

Figure 2.  Unchecked groundwater overdraft has brought ground-surface subsidence.  California’s San Joaquin Valley’s severe subsidence over the past century, continues locally today.  Photo courtesy of Michelle Sneed, US Geological Survey.

Despite successes, California’s water management faces continued challenges.  High on this list, protecting endemic aquatic species remains a vexing challenge.  Despite legal protections under federal and state regulations, California’s native fishes are in rapid decline, with 80% of species on paths towards extinction.  California will need to expand its toolkit – such as by accepting “reconciliation ecology” as a new model for maintaining natural diversity in the face of human pressures and a changing climate.

A prerequisite for providing and maintaining healthy aquatic ecosystems and adequate supplies of clean water is “far-sighted incrementalism” among water managers and political leaders.  Incrementalism involves addressing seemingly intractable problems by small forward-looking steps.  “Far-sighted,” at least in California, has involved forward-thinking planning among scientists, managers, and leaders during and after each water-related crisis.  The common response after a damaging flood is reactive – repair the levee breach and rebuild floodplain neighborhoods.  Far-sighted leaders see opportunities in such a crisis to move the system forward, usually incrementally, in a longer-term strategic direction (usually too controversial or difficult to achieve in one step).  California must continue to support organized and independent learning from and adapting to disasters and extremes.

 Lessons for managing water in a thirsty world

By 2050, an additional 2.3 billion people worldwide will face severe water stress, especially in Africa and southern and central Asia.  Already, 2.1 billion people worldwide lack access to safe drinking water. Three out of four jobs worldwide depend upon access to water and water-related services.  Water-limited regions and populations must prepare for changes in water management, addressing existing and emerging weaknesses and learning from mistakes, if possible from other areas, without repeating those errors.

Water management successes often rest on past failures – failures from which scientists, managers, and leaders learn and adapt.  This is especially true for California, where hydrologic variability frequently tests water systems and water policy.  As the world, especially the arid to semiarid world, looks for water solutions, the failures and lessons from California’s turbulent history can provide guidance for future global water resilience.

Nicholas Pinter, Jay Lund, and Peter Moyle are faculty in the Departments of Earth and Planetary Sciences, Civil and Environmental Engineering, and Wildlife, Fish, and Conservation Biology (respectively) and work together at the Center for Watershed Sciences at the University of California, Davis.  Email: npinter@ucdavis.edu; jrlund@ucdavis.edu; pbmoyle@ucdavis.edu

Further Readings

Auerswald, K, P. Moyle, S.P.Seibert, and J. Geist. 2019. HESS Opinions: Socio-economic and ecological trade-offs of flood management – benefits of a transdisciplinary approach. Hydrology and Earth System Sciences 23: 1035-1044.  https://www.hydrol-earth-syst-sci.net/23/1035/2019/  Open access.

Dettinger MD, Ralph FM, Das T, Neiman PJ, & Cayan DR. 2011. Atmospheric rivers, floods and the water resources of California.  Water, 3: 445-478.

Faunt, C., and M. Sneed, 2015.  Water availability and subsidence in California’s Central Valley.  San Francisco Estuary & Watershed Science, vol. 3, available fromhttps://ca.water.usgs.gov/pubs/2015/FauntSneed2015.pdf

Grantham, T.E., R. Figueroa, and N. Prat, 2013.  Water management in mediterranean river basins: a comparison of management frameworks, physical impacts, and ecological responses.  Hydrobiologia, 719: 451–482.

Independent Forensic Team, 2018.  Independent Forensic Team Report, Oroville Dam Spillway Incident, Jan. 5, 2018, https://damsafety.org/article/oroville-investigation-team-update

James, L.A., and M.B. Singer, 2008. Development of the Lower Sacramento Valley Flood-Control System: Historical Perspective, Natural Hazards Review, 9(3): 125-135.

Kelley, R., 1989.  Battling the Inland Sea, University of California Press, Berkeley, CA.

Konar M, Evans TP, Levy M, Scott CA, Troy TJ, Vörösmarty CJ, Sivapalan M. 2016. Water resources sustainability in a globalizing world: who uses the water? Hydrological Processes, 30: 330-336.

Lund, J.R., J. Medellin-Azuara, J. Durand, and K. Stone, “Lessons from California’s 2012-2016 Drought,” J. of Water Resources Planning and Management, Vol 144, No. 10, October 2018. (free download)

Lund, J., 2016.  You can’t always get what you want – A Mick Jagger theory of drought management.  California Water Blog, https://californiawaterblog.com/2016/02/21/you-cant-always-get-what-you-want-a-mick-jagger-theory-of-drought-management/.

Moyle, P., R. Lusardi, P. Samuel, and J. Katz. 2017. State of the Salmonids: Status of California’s Emblematic Fishes 2017.  Center for Watershed Sciences, University of California, Davis and California Trout, San Francisco, CA. 579 pp. https://watershed.ucdavis.edu/files/content/news/SOS%20II_Final.pdf

Multi-Benefit Flood Protection Project, 2017.  Projects, http://http://www.multibenefitproject.org/projects/.

OECD Organisation for Economic Co-operation and Development, 2012.  OECD Environmental Outlook to 2050: The Consequences of Inaction.  OECD Publishing, Paris.  http://dx.doi.org/10.1787/9789264122246-en

Opperman, J.J, P.B. Moyle, E.W. Larsen, J.L. Florsheim, and A.D. Manfree. 2017 Floodplains: Processes, Ecosystems, and Services in Temperate Regions. Berkeley: University of California Press.

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

Pinter, N., A. Damptz, F. Huthoff, J.W.F. Remo, and J. Dierauer, 2016.  Modeling residual risk behind levees, Upper Mississippi River, USA.  Environmental Science & Policy, 58, 131-140.

Pisani, D., 1984. From the Family Farm to Agribusiness: The Irrigation Crusade in California, 1850–1931. Berkeley: University of California Press.

Soulsby, C, Dick J, Scheliga B, & Tetzlaff D. 2017. Taming the flood—How far can we go with trees? Hydrological Processes, 31: 3122–3126.

Vahedifard, F., A. AghaKouchak, E. Ragno, S. Shahrokhabadi, and I. Mallakpour, 2017.  Lessons from the Oroville dam.  Science, 355: 1139-1140.

Van Lanen HAJ, et al. 2016. Hydrology needed to manage droughts: the 2015 European case.  Hydrological Processes, 30 https://doi.org/10.1002/hyp.10838

WHO & UNICEF World Health Organization and the United Nations Children’s Fund, 2017.  Progress on drinking water, sanitation and hygiene: 2017 update and SDG baselines. Geneva: World Health Organization (WHO) and the United Nations Children’s Fund (UNICEF).

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Experimental Habitats for Hatchery Delta Smelt

by Peter Moyle

Borrow pit on Bouldin Island that is now a pond maintained by ground water inflow. If expanded and deepened, and carefully managed, such ponds could become temporary rearing habitat for delta smelt. Photo by Peter Moyle.

The Delta smelt is either extinct in the wild or close to it; in the past year only a handful have been caught, with great effort. In contrast, the UC Davis Fish Conservation and Culture Laboratory (FCCL) has considerable success spawning and rearing the smelt in captivity. This coming winter, the FCCL will have as many as 40,000 smelt ready for release, when temperatures are low and the smelt are likely to spawn naturally. Such releases will be ‘experimental’ so not subject to the take provisions of the federal Endangered Species Act. In this blog, I support the concept that success of re-establishing smelt in the wild requires using multiple approaches.  In previous blogs and papers (Börk et al. 2020, Stompe et al. 2021), the idea of planting hatchery smelt in selected reservoirs was discussed. Here I first explore the problems of releasing fish back into the Delta and then describe an experimental reintroduction project taking advantage of the characteristics of Delta islands.

What do you do with 40,000 smelt?

It is a big question as to what to do, exactly, with 40,000 hatchery smelt. This is the job of the interagency Culture and Supplementation of Smelt Steering Committee (CASS) that has also has to deal with obtaining the many permits needed for any kind of release (CEQA, ESA etc.). Permitting will be a barrier to any action unless CASS decision makers are able to make risky decisions in short periods and get rapid action on the permits. My impression is that CASS prefers to use most of the fish for experimental releases, either as a one-time introduction of all fish or as series of smaller introductions made at selected sites where conditions appear favorable.  There are a number of problems with this approach:

  • The current Delta environment seems unsuitable for wild smelt. Cultured smelt will face the same problems as wild smelt, resulting in low survival. Börk et al. (2020) show that the factors put forth in the USFWS Biological Opinion as supporting recovery of smelt populations don’t hold up under close scrutiny.
  • Keeping track of even 40,000 small smelt in the big Delta is extremely difficult, if not impossible, given the small size of the smelt.
  • Hatchery smelt are genetically and behaviorally adapted for life in an aquaculture facility, so it is doubtful they will be able to quickly adjust to being released into a more natural environment. 
  • A strategy focusing on experimental releases into the Delta does not diversify risks but instead seems to be “putting all the eggs in one basket”.

Alternative: island ponds

Figure 1. Conceptual model of island experimental Delta smelt pond (diagram by Kelly Schmutte).

Mount and Twiss (2005) published a provocative analysis that showed most Delta islands (polders) were below sea level and were continuing to subside. Given weak levees, these polders are subject to sudden flooding, with huge costs to reclaim the land. But viewing flooded islands as habitat for fishes, including delta smelt, struck a number of biologists, including me, as a vision worth exploring. One variant of this idea was to deliberately flood islands and have gated openings so the water could be managed. This variant was not original, in that a private company called Delta Wetlands had actually purchased islands to flood them for water storage. While these big schemes never came to fruition, the idea of using flooded islands for fish conservation continued to be of interest. The version presented here proposes smaller, more manageable habitats, essentially large ponds, on subsided islands. This version developed through several Zoom meetings and involved scientists from Metropolitan Water District, UC Davis, and US Geological Survey.

The basis for this project is the need to spread risks for smelt introductions and to build a controlled food-rich habitat for conditioning hatchery smelt for improved survival in the wild. If this project is successful, it may be possible to propagate smelt in more or less natural ponds until the Delta ecosystem, or parts of it, has improved enough to support smelt on their own. The project is based on research, including findings of Jon Burau and others at USGS, on the hydrodynamic interactions between marsh and pelagic environments. The project includes ponds which are hydrologically-connected to artificial tidal marshes of varying sizes within a 43-acre plot on the northwest corner of MWD’s Bouldin Island (Figure 1, above).

Under current plans, one marsh-pond complex will be operated with water levels that will be raised and lowered for maximum night-time cooling; preliminary modelling by MWD indicates that under present conditions, water temperatures during the hot days of summer can be kept at or below 20°C. A second marsh complex will be operated to maintain maximum residence time for food (zooplankton) productivity. The ponds will be supplemented with cold, aerated groundwater (usually <17° C) during hot months in order to maintain water temperatures sufficient for a Delta smelt growth and survival. Temperature modelers at MWD are confident that sufficient design features can be developed to maintain appropriate conditions for smelt. Furthermore, bioenergetic studies of fish show that a robust food supply, which the project will include, can help compensate for the elevated metabolism of fish living in warmer water than might seem optimal. Finally, this site allows for the research and monitoring necessary for successful smelt supplementation efforts and Delta-wide tidal marsh design parameters. For example, the project could be useful for evaluating acclimation and release methods (particularly of early life stages, hatching frames, and mesocosms) and practices to reduce domestication selection through rearing in a more natural environment.

Figure 2. Drone photo of Bouldin Island, showing site of potential ponds for rearing Delta smelt. The existing facilities in the lower right foreground are eight experimental pools for examining (among other things) how floating mats of tules could provide a supply of invertebrates as smelt food.  New pools could be constructed immediately adjacent to these floating marshes as a near-term, cold weather conditioning facility while a permanent marsh-pond complex is being constructed in the center of the photo. The field in the center could be used in various ways to create ponds for Delta smelt rearing. The lighter colored area upslope of the pond site and edged by the dark green growths of blackberries, could be converted into marshes that drain into the ponds, as in Figure 1. The island is subsided so the ponds are about 20 feet below sea level. Sea level is the surface elevation of the water in the surrounding channels. Photo from Russ Ryan, MWD.

While MWD developed and funded the initial ‘proof of concept’ project, smelt stakeholders and experts will need to work together for the planning, funding, permitting, and monitoring of the project if the project is to succeed. It is urgent that a collaborative effort be made so that a project using 2000 or so hatchery smelt can be possible by the end of this year.   Assuming smelt are available, the project would be on-going in 2022. Time is of the essence, given uncertainties about the status of the smelt.  However, it is worth noting that the facilities and information produced as part of this project can also be applied to saving other native fish species in decline: splittail, Sacramento perch, longfin smelt, hitch, and tule perch.

Problems:

This pond project here has been presented in a positive light. But it is a high risk project for smelt because it involves creating new habitats by moving dirt and water around, on a subsided island. Such islands have a history of being flooded through levee failure, with additional risks caused by sea level rise, major flood events, and earthquakes. Climate change and drought may make water temperatures warmer than expected.  One way or another, it is likely that the created habitats will be invaded by non-native fishes such as Mississippi silverside. But any project in the Delta, including a straight-forward smelt re-introduction project, faces these same or similar problems; they will have to be dealt with in creative ways. The alternate path of doing nothing or doing too little leads to extinction.

Precedent

There is well-established precedence for the use of ponds in supplementation strategies of listed fish species as well as for Delta Smelt experimentation. The endangered Rio Grande Silvery Minnow is propagated in earthen ponds prior to release in the wild. The endangered Razorback Sucker is also grown out in seminatural and natural ponds before stocking, a practice which has improved growth rates and subsequent survival in the wild. Aquaculture ponds at the U.C. Davis Center for Aquatic Biology and Aquaculture have been employed extensively in research on Delta Smelt physiology and field trials in species-specific enclosures. 

Conclusion:

Re-establishing Delta smelt in its native Delta using hatchery smelt is an extremely difficult task, given how completely the habitat has been altered (Stompe et al 2001). Releasing fish directly into the wild is very risky and success will be hard to determine. Alternative projects need to be developed to spread risk. The Polder Pond Project proposed here is one such project. It proposes to rear Delta smelt in large ponds on a Delta island, on natural foods, which should prepare the fish better, at larger sizes, for release into the wild. The project also entails some risk for the Delta smelt needed for the project (ca. 2,000/year) but even if the smelt fail to adapt well to the ponds, useful information will be obtained on restoring native fishes to the Delta.

References

Bixby, R., and A. Burdett. 2013. Annual report 2011-2012; Resource utilization by the Rio Grande silvery minnow at the Los Lunas Silvery Minnow Refugium. Available at: ose.state.nm.us

Börk, K., Moyle, P., Durand, J., Hung, T., Rypel, A. L. 2020. Small populations in jeopardy: delta smelt case study. Environmental Law Reporter, 50(9), 10714-10722

Caldwell, C.A., Falco, H., Knight, W., Ulibarri, M., and W.R. Gould. 2019. Reproductive potential of captive Rio Grande Silvery Minnow. North American Journal of Aquaculture 81:47-54.

Day, J.L., Jacobs, J.L., and J. Rasmussen. 2017. Considerations for the propagation and conservation of endangered Lake Suckers of the western United State. Journal of Fish and Wildlife Management 8:301-312.

Mount J. and R. Twiss, 2005. Subsidence, sea level rise, seismicity in the Sacramento-San Joaquin Delta. San Francisco Estuary and Watershed Science. Vol. 3, Issue 1 (March 2005), Article 5. http://repositories.cdlib.org/jmie/sfews/vol3/iss1/art5.

Stompe. D., T. O’Rear, J. Durand, and P. Moyle. 2021 Home is where the habitat is. California WaterBlog  https://californiawaterblog.com/2021/07/04/home-is-where-the-habitat-is/

Watson, J.M., Sykes, C., and T.H. Bonner. 2009. Foods of Age-0 Rio Grande Silvery Minnows (Hybognathus amarus) reared in hatchery ponds. The Southwestern Naturalist 54:475-479.

Peter Moyle is Distinguished Professor Emeritus at the Center for Watershed Sciences, University of California, Davis.

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California’s Missing Forecast Flows in Spring 2021 – Challenges for seasonal flow forecasting

by John Abatzoglou, Anna Rallings, Leigh Bernacchi, Joshua Viers, Josué Medellín-Azuara

California’s 2021 water outlook became grimmer this spring as the state did not get fabulous February or miracle March precipitation. Unsurprisingly, spring streamflow forecasts from snowfed basins in the Sierra were far below average. For example, early April forecasts from California DWR called for April-July runoff to be between 59-70% of normal. Bad, but not terrible. Then came April, bringing little additional precipitation. To compound matters, April brought very warm temperatures for much of the state that led to rapid ablation (evaporation) of the Sierra snowpack. April began with snowpack around 60% of normal, but by month’s end was 20% of normal.

In early May a significant revision of forecasted spring flow estimated substantial reductions from forecasts of just one month earlier – in some cases a 28% reduction. Aggregated over the Sacramento River Basin, total forecasted flow for April-July dropped by 0.8-1.0 million-acre feet. This reduction in forecasted water supply turned a bad water year into a dreadful one with an amplified conundrum of long-standing water conflicts.

What led to such a drop-off in forecasts? Where did all that snow go if not into flow? While there is an official review of the procedures that led to the differences in forecasts underway, in this blog we look at five possible culprits.

Suspect #1: Lack of April Showers

April was dry. Much of the state had 10-25% of ‘normal’ April totals. April is never a drought buster, but the shortfall of April precipitation only worsened the developing drought. Aggregated over the Sierra Nevada, we estimate a shortfall of around 3” of precipitation in April 2021 that could otherwise contribute to streamflow, acknowledging that some of this became evapotranspiration. Certainly, some of the streamflow forecast revision could be from lack of rain, but unlikely enough to warrant such a large downgrade by itself.

Figure A: April 2021 precipitation percentiles relative to 1895-present period. Data source: West Wide Drought Tracker (Abatzoglou et al., 2017).

Suspect #2: Sublimation of water from snow to the atmosphere

There has been speculation that high rates of sublimation in April facilitated the rapid ablation of snow – limiting how much of the snow became streamflow. Sublimation – direct loss of water from the snowpack to the atmosphere – can be an important fate for snowpack, particularly in locations with strong winds, very low dewpoint temperatures, snow in tree canopies, and where snowpack energetics limit melt. In practice, sublimation is challenging to track. To get a sense for how important sublimation generally is for snowpack ablation, we look at long-term data from the Variable Infiltration Capacity macroscale hydrology model. While these data suggest that sublimation can be quite high in the interior West, up to 40% in the semi-arid areas of the West including in the eastern Sierra, it is much lower in more maritime locations such as the Sierra western slope where sublimation is generally below 10%.

Data source: Variable Infiltration Capacity model output.

In April, dewpoint temperatures were 1℃ below 1991-2020 normal which would have hastened sublimation a bit, and wind speeds were not unusual. Given the rapid pace of snowpack ablation, it is unlikely that sublimation was the primary culprit behind the missing flow. More generally, hydrologic model simulations show that a warming climate generally reduces sublimation and increases infiltration.

Suspect 3: Evapotranspiration

Evaporation from melted snow at the surface and overall evapotranspiration is another likely factor reducing flow. There is strong evidence suggesting April 2021 reference evapotranspiration (Eto) was near record high values for much of the region. The combination of warm temperatures, unusually clear skies, and low dewpoint temperatures facilitated this increase in atmospheric thirst for the month. But this would only be about 1” more than average ETo for April.

Figure C: April reference evapotranspiration (ET) aggregated broadly over the Sierra Nevada during 1979-2021. Data source: gridMET meteorological data and Climate Engine (Huntington et al., 2017).

Suspect 4: Dry antecedent conditions

Torrid dry conditions last year, depleted soil moisture through the summer of 2020, and an autumn with subpar precipitation had left soil moisture in the Sierra Nevada at near record low levels by April. Observations of soil saturation from the SNOTEL network show very low soil moisture throughout last winter and into early spring, with a distinct increase in late March and early April coincident with the drop in mountain snowpack.




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Figure D: Soil saturation data at 8” depth for the Echo Peak SNOTEL station. The black line shows that soils were parched through mid-March when snowmelt commenced. Data source: NRCS.

Likewise, hydrologic models depict a similar fate of soil moisture being very dry throughout much of the winter. This suggests some portion of snowmelt was taken up in soil moisture given the far-from-saturated state of the soils when the 2021 water year began.

Suspect 5: Snow Water Equivalent was overestimated

The 60% snow water equivalent (SWE) numbers on April 1st came from DWR-based snow stations. Measuring  snow over large areas is challenging and even a well-designed operational network might not adequately capture the distribution of snow across complex terrain. So perhaps the snow water volume in the Sierra was less than 60% of long-term average.

The single notable atmospheric river to hit California in 2021 in late January, bringing exceptional precipitation and snowfall to parts of central California and the Central Sierra. Given that it occurred at climatologically the coldest time of the year, it dropped heavy – in some cases record – snowfall in lower elevation mountains. For example, Calaveras Big Tree State Park (4800’ elevation) saw 76.5” of snow, over ¾ of their total for 2021 during this event. For this site, the 3-day snowfall total was the highest in the observational record. This provided a huge bump for snow at lower elevations but left higher elevations in a sizable deficit that expanded thereafter.

Colleagues, including Dan McEvoy, from the Desert Research Institute have been tracking snow droughts (less than usual accumulations of snow). Reductions in mountain snowpack have been sizable in recent years and are expected to increase in the coming decades. The ratio of SWE and cumulative precipitation since Oct 1st shown in the plot below, effectively tracks snow water storage efficiency. Curiously, for a snapshot of these data in late February all sites with SWE values above 85% of median SWE were at lower elevations (<7500’), despite seeing well below normal precipitation. Increased aerial surveying of snow, such as from Airborne Snow Observatories, may improve estimates of SWE beyond those with traditional snow survey and automated snow sensors.

Figure E: Distribution of percent of median snow water equivalent by elevation for SNOTEL stations in the Sierra at 23rd Feb 2021. The colors of the circles depict the percent of precipitation for the water year at each site. Data source: Dan McEvoy.

So, whodunit?

In a classic whodunit, five suspects are in the line-up for the case of the missing flow.

Lackluster April precipitation certainly contributed to the downward revisions in forecasted flow. In addition, the prime suspects of parched soils from 2020 and dry atmospheric conditions, acted together to steal snow from their typical streams. Michael Dettinger finds similar shortfalls in streamflow relative to precipitation since fall of 2019 across California and Nevada. Tessa Maurer and colleagues exploring catchment level feedbacks between ET and subsurface storage found that nonlinearities in the water balance can decouple precipitation and runoff during droughts. They also identify several confounding factors that may limit our understanding of hydrological feedbacks, including the loss of high-elevation runoff, often considered a drought mitigator, from temperature fueled increases in ET at high elevations or lateral redistribution of precipitation excess from higher elevations to unsaturated soil at lower elevations.

Suspects we can manage through forecasting

While we have focused on identifying the prime suspects for the missing streamflow, such scientific detective work may ultimately help improve forecasting accuracy and early seasonal warning systems for managing water. We highlight two fronts to improve forecasts.

First, modeling studies are showing that old rules of thumb are becoming less reliable for anticipating water resources in a changing climate and demand significant updates. Improved understanding of mountain processes that involve snow, soil, and vegetation may help improve forecasts. Previous studies show substantial changes in how water years play out with climate change in California – including more frequent dry and critically dry water years. Back-to-back snow droughts – like we experienced in 2020 and 2021 – are projected to become increasingly likely in the Sierra Nevada with continued warming. Likewise, we expect new types of water years that we have not seen in modern times that will challenge operational water forecasting and allocation decisions. More critical calculations will support better understanding to improve forecasts, allocations, and flexible management.

Second, incremental advances in sub-seasonal to seasonal climate forecasts have potential to inform water forecast and allocation decisions. For example, April forecasts issued in mid-March called for very dry and warm conditions for the state. Incorporation of such climate forecasts into water allocation forecasts may aid decision-making.

Further Reading

Abatzoglou, J. T., McEvoy, D. J. & Redmond, K. T. (2017) The West Wide Drought Tracker: Drought Monitoring at Fine Spatial Scales. Bull. Am. Meteorol. Soc. 98, 1815–1820

He, M., Anderson, J., Lynn, E., Arnold, W. (2021) Projected Changes in Water Year Types and Hydrological Drought in California’s Central Valley in the 21st CenturyClimate9, 26.

Huntington, J. L., Hegewisch, K. C., Daudert, B., Morton, C. G., Abatzoglou, J. T., McEvoy, D. J., & Erickson, T. (2017). Climate Engine: Cloud Computing and Visualization of Climate and Remote Sensing Data for Advanced Natural Resource Monitoring and Process UnderstandingBulletin of the American Meteorological Society98(11), 2397-2410.

Livneh, B., Badger, A.M. (2020). Drought less predictable under declining future snowpack. Nat. Clim. Chang. 10, 452–458

Marshall, A. M., Abatzoglou, J. T., Link, T. E. & Tennant, C. J. (2019). Projected Changes in Interannual Variability of Peak Snowpack Amount and Timing in the Western United States. Geophys. Res. Lett. 46, 8882–8892

Maurer, T., Avanzi, F., Glaser, S. D., and Bales, R. C.: Drivers of drought-induced shifts in the water balance through a Budyko approach, Hydrol. Earth Syst. Sci. Discuss. in review, 2021.

Null, S. E., & Viers, J. H. (2013). In bad waters: Water year classification in nonstationary climates. Water Resources Research, 49(2), 1137–1148.

Williams, A. P. Williams, A.P., Cook, E.R., Smerdon, J.E., Cook, B.I., Abatzoglou, J.T., Bolles, K., Baek, S.H., Badger, A.M. and Livneh, B. (2020). Large contribution from anthropogenic warming to an emerging North American megadrought. Science 368, 314 LP – 318

John Abatzoglou is an associate professor in the Management of Complex Systems Department at UC Merced.  Anna Rallings in a staff scientist and lab manager of the VICElab at UC Merced. Leigh Bernacchi is the program director of the Center for Information Technology Research in the Interest of Society and the Banatao Institute at UC Merced. Josué Medellín-Azuara is the associate director at the UC Davis Center for Watershed Sciences and an associate professor at the Department of Civil and Environmental Engineering at UC Merced. Joshua Viers is Campus Director of the Center for Information Technology Research in the Interest of Society and the Banatao Institute, Associate Dean for Research, School of Engineering at UC Merced and professor in the Department of Civil and Environmental Engineering at UC Merced.

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California isn’t running out of water; it’s running out of cheap water

by Wyatt Arnold

A California water myth which becomes especially pernicious in droughts is that California is “running out of water” (Hanak et al. 2009). Viewing California’s supply and demand pressures in terms of fixed water requirements perpetuates this myth and invariably places undue attention on building additional supply infrastructure. Instead, managing water as a scarce resource suggests a balanced portfolio of water trading, investments in conveyance, smart groundwater replenishment, and demand management. With such a balanced portfolio, 1) California’s water supply situation is not broadly dire, and 2) California’s vast and interconnected water infrastructure and groundwater resources can minimize most problems from the state’s highly variable climate.

An economics-driven model of California’s water system, the California Value Integrated Network (CALVIN), has provided such insight from several perspectives, including climate change, groundwater, water markets, and reservoir operations. But in many of these studies, authors lamented an unrealized potential to capture the impact of hydrologic variability more realistically. With perfect foresight, CALVIN was run with complete foreknowledge of 82-years of hydrology – giving exactly optimal solutions to managing reservoir over-year (“carryover”) storage through multi-year droughts, for example. Now, with access to high performance computing resources, a limited foresight carryover storage value function (COSVF) method (Draper 2001) has been applied to California’s entire system – more than 26 surface reservoirs and over 30 groundwater basins (Arnold 2021, Khadem 2018).  These model runs are the most comprehensive and realistic analyses of the potential for broad integrated portfolios of actions across water agencies to address California’s water supply problems.

So, what do these new limited foresight CALVIN results tell us about California’s water supply? Here are three things to get started:

  • From the standpoint of long-term average marginal economic value of water, perfect and limited foresight closely agree; however, limited foresight is more relevant for the risk averse, who prefer to minimize larger but rarer shortages at the cost of average performance.
  • Limited foresight results also suggest that, in general, increasing the storage capacity of reservoirs in California has a very low marginal economic benefit relative to other infrastructure investments like conveyance and groundwater pumping capacities.
  • A large range of carryover storage and conjunctive use operations yield similar statewide economic performance (summing water operation and scarcity costs statewide over 82 years of wet and dry conditions). Consideration of a broad portfolio of conjunctive use, trading, water conservation, and local infrastructure options may not significantly change major surface reservoir operations.

Economics of Carryover Storage

Many reservoirs in California have been drawn down to near record low levels in the current drought. People are alarmed that reservoir storages are so low after only two dry years and are speculating whether prudent decisions were made about storage management. Climate change is making these decisions riskier, yet modeling the historical record remains important as a frame of reference.

Here, I focus on Shasta, Oroville, and off-stream San Luis carryover operations suggested by the new limited foresight optimization results and compare with carryover storage simulated by two versions of the State’s reservoir system model, CalSim-II, to shed light on how and why the system’s carryover storage is so volatile.

Figure 1 shows the time series of carryover operations modeled through two of California’s notorious droughts. The first thing to notice is that total carryover storage varies a lot from year to year for all models. Second, all models tend to quickly draw down carryover storage in dry years – only perfect foresight CALVIN, knowing the exact length and depth of drought in advance, maintains and draws down carryover storage in the final year of drought. Third, CalSim-II simulated carryover storage – both the Water Storage Investment Program run and the recent Delivery Capability Report 2019 run – lie just above the sampled range of limited foresight runs, suggesting near-optimal operations (blue shaded region) during dry years and droughts.

Without a crystal ball, it is not economical to maintain too much carryover or drought surface water storage. The probability of refilling the following year is high, both due to the volume of carryover storage capacity relative to annual runoff and the low year-to-year correlation of annual runoff. Lower carryover storage raises groundwater pumping in the latter year(s) of drought, but also reduces average groundwater use and pumping costs and helps reduce groundwater overdraft (see Figure 2). Also, higher reservoir releases tend to reduce shortages where access to groundwater is limited, which lowers average shortage costs. Sustaining higher carryover volumes (upper end of the limited foresight range and CalSim-II alike) provides more surface supply in the latter year(s) of a drought, which reduces maximum shortage costs; however, the more risk-averse operation raises long-term average costs and the marginal value of groundwater that would eliminate overdraft. Limited foresight modeling (both optimization and CalSim-II) tends to use more groundwater in drier years (Figure 2), which points to groundwater’s importance as a buffer against hydrologic uncertainty.

Figure 1. Total carryover storage (ending September) of Shasta, Oroville, and San Luis as modeled by perfect and limited foresight CALVIN and CalSim-II Delivery Capability Report 2019 (CS-II DCR 2019) and Water Storage Investment Program (CS-II WSIP) historical runs. Drought periods of 1976-77 and 1987-92 are shaded in light tan. The limited foresight range is based on 26 near-optimal statewide solutions.
Figure 2. Total groundwater pumping volume in the Central Valley as modeled by CALVIN for perfect foresight, limited foresight, and with reservoir carryover storage fixed to CalSim-II Water Storage Investment Program historical run outputs.

Other Considerations for Carryover Storage

Water supply is not the sole objective of carryover storage operations. Federal and State operators of Shasta and Oroville reservoirs seek to maintain storage reserves for environmental requirements. For example, Shasta’s carryover storage objectives include maintenance of a cold-water pool to support Salmon habitat in the Sacramento River. Other economic objectives include recreation and hydropower. CalSim-II’s higher carryover storage relative to limited foresight CALVIN are partially attributable to these objectives in addition to Federal and State contractual water supply obligations to Sacramento and Feather River water rights holders. While CALVIN incorporates minimum environmental flow constraints, more complex environmental requirements such as cold-water pool management and some Delta operational constraints are less well represented. Nevertheless, the limited foresight CALVIN results provide a more realistic representation of the economic value of carryover storage in California’s multi-reservoir conjunctive use system.

Concluding Thoughts

Aggressive use of carryover water storage in California’s major reservoirs is economically prudent and reduces overall groundwater reliance. Water supply risks of lower carryover storage are further mitigated through greater system integration such as increased water trading, groundwater banking, and drought water use reductions. The higher risks of having low carryover storage, although not quantified here, appear to fall on California’s stressed ecosystems. A warming climate, expected to continue through at least mid-century even with aggressive global greenhouse gas mitigation, is changing runoff timing, magnitude, and frequency in ways that will make managing carryover storage more challenging. Future work should focus on this aspect and incorporate alternative hydrologic traces reflecting expected climate changes.

Further Reading

Arnold, Wyatt. 2021. The Economic Value of Carryover Storage in California’s Water Supply System with Limited Hydrologic Foresight. [MS, UC Davis]. Available at: https://watershed.ucdavis.edu/shed/lund/students/WyattArnoldThesis2021.pdf

Draper, A. J. 2001. Implicit Stochastic Optimization with Limited Foresight for Reservoir Systems. [PhD, UC Davis]. https://watershed.ucdavis.edu/shed/lund/students/DraperDissertation.pdf

Hanak, Ellen, Jay Lund, Ariel Dinar, Brian Gray, Richard Howitt, Jeffrey Mount, Peter Moyle, et al. 2009. “California Water Myths.” Public Policy Institute of California.

Khadem, M., C. Rougé, J. J. Harou, K. M. Hansen, J. Medellin‐Azuara, and J. R. Lund. 2018. Estimating the Economic Value of Interannual Reservoir Storage in Water Resource Systems.” Water Resources Research 54 (11): 8890–8908.

Wyatt Arnold recently completed a master’s degree in Civil and Environmental Engineering at the University of California – Davis.  He currently works for the California Department of Water Resources in the Climate Adaptation Program.

Data from CalSim-II runs are available on the California Natural Resources Agency OpenData site: 1) Water Storage Investment Program model (1995 Historical Detrended run) available at https://data.cnra.ca.gov/dataset/climate-change-projections-wsip-2030-2070, 2) Delivery Capability Report 2019 run available at: https://data.cnra.ca.gov/dataset/state-water-project-delivery-capability-report-dcr-2019 

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California isn’t running out of water; it’s running out of cheap water

by Wyatt Arnold

A California water myth which becomes especially pernicious in droughts is that California is “running out of water” (Hanak et al. 2009). Viewing California’s supply and demand pressures in terms of fixed water requirements perpetuates this myth and invariably places undue attention on building additional supply infrastructure. Instead, managing water as a scarce resource suggests a balanced portfolio of water trading, investments in conveyance, smart groundwater replenishment, and demand management. With such a balanced portfolio, 1) California’s water supply situation is not broadly dire, and 2) California’s vast and interconnected water infrastructure and groundwater resources can minimize most problems from the state’s highly variable climate.

An economics-driven model of California’s water system, the California Value Integrated Network (CALVIN), has provided such insight from several perspectives, including climate change, groundwater, water markets, and reservoir operations. But in many of these studies, authors lamented an unrealized potential to capture the impact of hydrologic variability more realistically. With perfect foresight, CALVIN was run with complete foreknowledge of 82-years of hydrology – giving exactly optimal solutions to managing reservoir over-year (“carryover”) storage through multi-year droughts, for example. Now, with access to high performance computing resources, a limited foresight carryover storage value function (COSVF) method (Draper 2001) has been applied to California’s entire system – more than 26 surface reservoirs and over 30 groundwater basins (Arnold 2021, Khadem 2018).  These model runs are the most comprehensive and realistic analyses of the potential for broad integrated portfolios of actions across water agencies to address California’s water supply problems.

So, what do these new limited foresight CALVIN results tell us about California’s water supply? Here are three things to get started:

  • From the standpoint of long-term average marginal economic value of water, perfect and limited foresight closely agree; however, limited foresight is more relevant for the risk averse, who prefer to minimize larger but rarer shortages at the cost of average performance.
  • Limited foresight results also suggest that, in general, increasing the storage capacity of reservoirs in California has a very low marginal economic benefit relative to other infrastructure investments like conveyance and groundwater pumping capacities.
  • A large range of carryover storage and conjunctive use operations yield similar statewide economic performance (summing water operation and scarcity costs statewide over 82 years of wet and dry conditions). Consideration of a broad portfolio of conjunctive use, trading, water conservation, and local infrastructure options may not significantly change major surface reservoir operations.

Economics of Carryover Storage

Many reservoirs in California have been drawn down to near record low levels in the current drought. People are alarmed that reservoir storages are so low after only two dry years and are speculating whether prudent decisions were made about storage management. Climate change is making these decisions riskier, yet modeling the historical record remains important as a frame of reference.

Here, I focus on Shasta, Oroville, and off-stream San Luis carryover operations suggested by the new limited foresight optimization results and compare with carryover storage simulated by two versions of the State’s reservoir system model, CalSim-II, to shed light on how and why the system’s carryover storage is so volatile.

Figure 1 shows the time series of carryover operations modeled through two of California’s notorious droughts. The first thing to notice is that total carryover storage varies a lot from year to year for all models. Second, all models tend to quickly draw down carryover storage in dry years – only perfect foresight CALVIN, knowing the exact length and depth of drought in advance, maintains and draws down carryover storage in the final year of drought. Third, CalSim-II simulated carryover storage – both the Water Storage Investment Program run and the recent Delivery Capability Report 2019 run – lie just above the sampled range of limited foresight runs, suggesting near-optimal operations (blue shaded region) during dry years and droughts.

Without a crystal ball, it is not economical to maintain too much carryover or drought surface water storage. The probability of refilling the following year is high, both due to the volume of carryover storage capacity relative to annual runoff and the low year-to-year correlation of annual runoff. Lower carryover storage raises groundwater pumping in the latter year(s) of drought, but also reduces average groundwater use and pumping costs and helps reduce groundwater overdraft (see Figure 2). Also, higher reservoir releases tend to reduce shortages where access to groundwater is limited, which lowers average shortage costs. Sustaining higher carryover volumes (upper end of the limited foresight range and CalSim-II alike) provides more surface supply in the latter year(s) of a drought, which reduces maximum shortage costs; however, the more risk-averse operation raises long-term average costs and the marginal value of groundwater that would eliminate overdraft. Limited foresight modeling (both optimization and CalSim-II) tends to use more groundwater in drier years (Figure 2), which points to groundwater’s importance as a buffer against hydrologic uncertainty.

Figure 1. Total carryover storage (ending September) of Shasta, Oroville, and San Luis as modeled by perfect and limited foresight CALVIN and CalSim-II Delivery Capability Report 2019 (CS-II DCR 2019) and Water Storage Investment Program (CS-II WSIP) historical runs. Drought periods of 1976-77 and 1987-92 are shaded in light tan. The limited foresight range is based on 26 near-optimal statewide solutions.
Figure 2. Total groundwater pumping volume in the Central Valley as modeled by CALVIN for perfect foresight, limited foresight, and with reservoir carryover storage fixed to CalSim-II Water Storage Investment Program historical run outputs.

Other Considerations for Carryover Storage

Water supply is not the sole objective of carryover storage operations. Federal and State operators of Shasta and Oroville reservoirs seek to maintain storage reserves for environmental requirements. For example, Shasta’s carryover storage objectives include maintenance of a cold-water pool to support Salmon habitat in the Sacramento River. Other economic objectives include recreation and hydropower. CalSim-II’s higher carryover storage relative to limited foresight CALVIN are partially attributable to these objectives in addition to Federal and State contractual water supply obligations to Sacramento and Feather River water rights holders. While CALVIN incorporates minimum environmental flow constraints, more complex environmental requirements such as cold-water pool management and some Delta operational constraints are less well represented. Nevertheless, the limited foresight CALVIN results provide a more realistic representation of the economic value of carryover storage in California’s multi-reservoir conjunctive use system.

Concluding Thoughts

Aggressive use of carryover water storage in California’s major reservoirs is economically prudent and reduces overall groundwater reliance. Water supply risks of lower carryover storage are further mitigated through greater system integration such as increased water trading, groundwater banking, and drought water use reductions. The higher risks of having low carryover storage, although not quantified here, appear to fall on California’s stressed ecosystems. A warming climate, expected to continue through at least mid-century even with aggressive global greenhouse gas mitigation, is changing runoff timing, magnitude, and frequency in ways that will make managing carryover storage more challenging. Future work should focus on this aspect and incorporate alternative hydrologic traces reflecting expected climate changes.

Further Reading

Arnold, Wyatt. 2021. The Economic Value of Carryover Storage in California’s Water Supply System with Limited Hydrologic Foresight. [MS, UC Davis]. Available at: https://watershed.ucdavis.edu/shed/lund/students/WyattArnoldThesis2021.pdf

Draper, A. J. 2001. Implicit Stochastic Optimization with Limited Foresight for Reservoir Systems. [PhD, UC Davis]. https://watershed.ucdavis.edu/shed/lund/students/DraperDissertation.pdf

Hanak, Ellen, Jay Lund, Ariel Dinar, Brian Gray, Richard Howitt, Jeffrey Mount, Peter Moyle, et al. 2009. “California Water Myths.” Public Policy Institute of California.

Khadem, M., C. Rougé, J. J. Harou, K. M. Hansen, J. Medellin‐Azuara, and J. R. Lund. 2018. Estimating the Economic Value of Interannual Reservoir Storage in Water Resource Systems.” Water Resources Research 54 (11): 8890–8908.

Wyatt Arnold recently completed a master’s degree in Civil and Environmental Engineering at the University of California – Davis.  He currently works for the California Department of Water Resources in the Climate Adaptation Program.

Data from CalSim-II runs are available on the California Natural Resources Agency OpenData site: 1) Water Storage Investment Program model (1995 Historical Detrended run) available at https://data.cnra.ca.gov/dataset/climate-change-projections-wsip-2030-2070, 2) Delivery Capability Report 2019 run available at: https://data.cnra.ca.gov/dataset/state-water-project-delivery-capability-report-dcr-2019 

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Home is where the habitat is

 by Dylan Stompe, Teejay O’Rear, John Durand, and Peter Moyle

            The San Francisco Estuary (estuary) is sometimes called the most invaded estuary in the world, and for good reason. Through many avenues, hundreds, if not thousands, of species have been introduced to San Francisco Bay, the Delta, and their rivers. Some introductions were byproducts of human activity and include organisms that “hitchhiked” on the bottom of boats or as stowaways in ballast water carried by international shipping vessels. Others were deliberate and undertaken either legally by the government or illicitly by individuals for biocontrol, fisheries, or disposal of unwanted pets.

            The U.S. Fish and Wildlife Service (USFWS) defines aquatic invasive species as “aquatic organisms that invade ecosystems beyond their natural, historic range.” Under this definition, any species brought into the estuary and establishes a self-sustaining population would be considered an aquatic invasive. However, we challenge that assertion given the current state of much of the estuary. If we focus on the historic range of an organism strictly as a function of geography, then the organisms introduced by people to the estuary are invasive aquatic organisms under the USFWS definition. If, however, if we interpret the natural range to encompass the habitats to which species are native, then many non-native species would be considered right at home in the estuary.

            For example, much of the Delta is made up of waterways that resemble southeastern lakes (such as Lake Okeechobee) much more so than they resemble the historic Delta habitat of sloughs and marshes. These new habitats are largely constrained by levees, eliminating the vast marshes and floodplains that once existed. Compounding these landscape changes are highly altered flow regimes. Upstream reservoirs capture water and control its release, dampening winter floods and increasing summer flows. The flatter hydrograph and modified landscape have made the Delta much more suitable habitat for many introduced species. These species are well-adapted to the low flows, increased water clarity, higher temperatures, large beds of aquatic weeds, and other features of the modern Delta. 

             Sadly, some native species, such as Delta smelt, are actually strangers to these altered habitats. While they are geographically native, the traits that once made them so abundant in the Delta are maladaptive in these new habitat conditions. Much like we would not expect Delta smelt to succeed if introduced to Lake Okeechobee, it should not be surprising that they are no longer successful in the warm, clear, and highly vegetated waters of the Delta.

            Take a breath! Contrary to what you may be thinking right now, we are not proposing to give up on species such as the Delta smelt. We are suggesting that trying to reestablish this species in poorly suitable habitats is extremely difficult. While there is a legal and moral obligation to help sustain Delta smelt and other critically endangered species, the Delta will require radical restoration for Delta smelt to persist in their native geographic range. State and federal agencies, as well as some private groups, have begun implementing a number of measures, including habitat restoration and hatchery supplementation, but these are slow to implement and unlikely to reverse the immediate extinction spiral (Börk et al. 2020). Rather than wait for better Delta solutions to emerge, creative solutions to sustain wild Delta smelt outside of the hatchery setting should be explored.

            One potential solution is to establish self-sustaining, non-hatchery-supplemented Delta smelt refuge populations in reservoirs with suitable conditions. A proof-of-concept has already been established by the Delta smelt’s cousin wakasagi (Hypomesus nipponensis), which was planted and is currently thriving in several Sierra reservoirs, such as Oroville, Rollins, and Almanor. Habitat requirements for these species are similar, and many reservoirs are cool, dark at depth, and have abundant zooplankton – conditions Delta smelt need. Wakasagi and Delta smelt will hybridize, so Delta smelt cannot be stocked into reservoirs that already contain wakasagi. But many reservoirs similar to Oroville and Almanor exist where wakasagi are absent: Mountain Meadows, Union Valley, Davis, Frenchman, and Britton, to name a few.

Figure 1. Lake Davis at sunset. “Lake Davis” by seabamirum is licensed with CC BY 2.0. To view a copy of this license, visit https://creativecommons.org/licenses/by/2.0/

This form of “assisted migration” has worked for another Delta fish that recently became extinct in its “natural, historic range”: Sacramento perch. Sacramento perch was once so abundant in the Delta that it supported a commercial fishery, but it is no longer found in its historic waters. It has avoided extinction, however, by its successful introduction to farm ponds and reservoirs across the American West. While these populations of perch are not strictly “native,” they have saved the species from extinction and preserve some of their cultural, ecological, and recreational value.

            Sometimes we daydream about what our estuary once looked like and the epic amounts of salmon, smelt, and other native species that once swam in its waters. Unfortunately, it’s wishful thinking to believe that the daydream will be anything more than that given the magnitude of change in the estuary. The Delta smelt inhabits a novel ecosystem that contains very little habitat that could be considered natural for it. Additionally, some invasive species, such as the overbite clam (Potamocorbula amurensis) and Brazilian waterweed (Egeria densa), have caused habitat shifts that are nearly irreversible and these species are going nowhere.  Further, they’re no doubt going to be joined by new species that will further alter the Delta from its historic state, such as the recently introduced alligatorweed (Alternanthera philoxeroides; Walden et al. 2019). Therefore, novel management strategies must be used to keep species such as Delta smelt from going extinct. So, this begs the question – if we have thousands of Delta smelt in a hatchery, why not take a page out of the Sacramento perch playbook and plant them in some reservoirs while we still have smelt to plant?

            Do the best you can with what you’ve got – the Delta is currently not the best we’ve got for Delta smelt. The best we got – it’s the reservoirs.

Dylan Stompe is a fisheries researcher and graduate student at the Center for Watershed Sciences. Teejay O’Rear is a fish ecologist at the Center for Watershed Sciences and lab supervisor for Dr. John Durand. Peter Moyle is Distinguished Professor Emeritus at the University of California, Davis and an Associate Director of the Center for Watershed Sciences. John Durand is a researcher specializing in estuarine ecology and restoration at the Center for Watershed Sciences.

Further Reading

Börk, K., Moyle, P., Durand, J., Hung, T., Rypel, A. L. 2020. Small populations in jeopardy: delta smelt case study. Environmental Law Reporter, 50(9), 10714-10722

Cohen, A.N., Carlton, J.T. 1998. Accelerating invasion rate in a highly invaded estuary. Science, 279(5350), 555-558.

Crain, P.K., Moyle, P.B. 2011. Biology, history, status and conservation of Sacramento perch, Archoplites interruptus. San Francisco Estuary and Watershed Science, 9(1).

Moyle, P.B. 2021. Can Japanese Smelt Replace Delta Smelt? California Water Blog. https://californiawaterblog.com/2021/02/07/can-japanese-smelt-replace-delta-smelt/

O’Rear, T., Moyle, P.B., Durand, J.R. 2018. Delta Smelt and Salmon Habitats Beyond the Estuary. Presentation. https://watershed.ucdavis.edu/library/delta-smeltand-salmon-habitats-beyond-estuary.

Walden, G. K., G. M. S. Darin, B. Grewell, D. Kratville, J. Mauldin, J. O’Brien, T. O’Rear, A. Ougzin, J. V. Susteren, P. W. Woods.  2019.  Noteworthy collections, California (Alternanthera philoxeroides). Madrono 66(1): 4-7.

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Drought Makes Conditions Worse for California’s Declining Native Fishes

Long Valley speckled dace and Whitmore Marsh, its last natural native habitat in the Owens Valley. Other habitats have been heavily modified by poor landuse and mostly dried up.  Photos by J. Katz and P. Moyle.

by Peter Moyle and Andrew Rypel

California is home to 131 kinds of native fishes that require freshwater for some or all of their life-cycle. Most of these fishes are found only in California and most (81%) are in decline (Moyle et al. 2015, 2020). Thirty-two (24%) are already listed as threatened or endangered by state and/or federal governments. Declines are usually the result of fishes losing the competition with humans for California’s water and habitat (Leidy and Moyle 2021). This competition is heightened by the ongoing severe drought.  Thus, there is a petition circulating to declare the delta smelt extinct to make supposedly large amounts of water available to farmers, even though the smelt is not extinct and the amount of water devoted to delta smelt is small (Börk et al. 2020). Winter-run Chinook are being vilified because they require cold-water releases from Shasta Reservoir even though the lack of cold water mostly results from poor management of the reservoir’s pool of water. In the Klamath River Basin, farmers are angry because they are not being provided with water from Upper Klamath Lake, blaming the demands of endangered suckers and salmon, even though juvenile salmon in the river are already dying in this extraordinary drought.

One response to these ongoing problems is federal and state financial relief for farmers.  For example, California politicians have proposed state and federal funding to improve canals that deliver water to farmers in the San Joaquin Valley. Yet deterioration of the canals was created by over-drafting ground water, causing land and canals to subside. Some $800 million in government funds is proposed to subsidize this infrastructure repair, that will mostly go to improving the ability of farmers to take water away from fish. An equivalent bill to improve access of native fishes to water or improve their habitats does not seem to be in the works.

              If native fishes are going to persist through this extended drought (there is no end in sight), a statewide program of monitoring, emergency, and preparatory actions is needed. This program needs to check on the condition of all native fishes annually, with the capacity to take action if key habitats are drying up or are otherwise becoming unsuitable.  Here are some examples that reflect the diversity of actions that are ongoing or needed to keep California’s native fishes viable despite the combined immediate threats of competition for water with people and loss of habitat by drought. In general, species listed under the federal Endangered Species Act (ESA) are more likely to have resources devoted to their recovery than are species that are not listed. More complete information on these example species can be found in Moyle et al. 2015, 2017.

              The central coast Coho salmon is listed as endangered under federal and state ESAs  because of loss of habitat combined with reductions in stream flows, often drought related. This fish has been brought back from the brink of extinction by a combination of intensive management of Lagunitas Creek (Marin County) and an innovative captive breeding program at the Dry Creek Hatchery. Coho have the advantage of being charismatic, as sleek sea-run fish that are highly visible when they spawn, reminding people that California coho once supported extensive sport and commercial fisheries.

              The Sacramento splittail once lived throughout the Central Valley and upper San Francisco Estuary.  The only population remaining today spawns on flooded vegetation especially in the Yolo Bypass. After spawning the fish return to their main rearing area, Suisun Marsh, followed by the juveniles a few months later.  They were listed as a federally threatened species for a short time but the designation was rescinded when studies revealed their remarkable resilience, even during short droughts. But their total distribution is increasingly restricted and persistence through long droughts will be increasingly difficult, without help, such as providing more reliable floodplain habitat for spawning.

              The northern California roach is a small minnow largely confined to springs and isolated small streams in the upper Pit River watershed in California and Oregon. Its original description as a distinct species in 1908 was largely ignored by subsequent workers. Baumsteiger and Moyle (2017), however, using genomic techniques, validated the species distinctiveness. Its current status, especially in California, is poorly known but most of its known habitats are degraded by poor land management (e.g., livestock grazing) and other factors, exacerbated by drought. This species may easily disappear unnoticed from California if steps not taken to protect it and its habitats.

              The Long Valley speckled dace is another small minnow headed for extinction because it had not been seen as unique. An unpublished genomics study reveals that it is quite different from other dace and has been isolated for thousands of years in the streams and marshes of the Owens Valley region. These habitats are disappearing as the water disappears.  Its last natural refuge is Whitmore Marsh, which is watered by a hot spring, now converted to a swimming pool.  The only other population is in a small pond monitored by CDFW at the White Mountain Research Station. Neither population can be regarded as secure.

              Green sturgeon are ancient survivors, reaching 2-3 m in length and living 50-75 years or more. Like salmon, they are anadromous, spending most of their time in the ocean.  Unlike salmon however, they spawn many times throughout their long lives. There are two distinct populations recognized, the southern green sturgeon and the northern green sturgeon. The former consists of small population that spawns in the Sacramento River, while the latter spawns in north coast streams, principally the Klamath River and the Rogue River (Oregon). The southern population is listed as a threatened species and is likely further threatened by drought-reduced flows in the Sacramento River. Thanks to its being ESA-listed, however, considerable resources have been devoted to it, so managers can take advantage of new knowledge of its life history requirements. The northern population in the Klamath River supports a small tribal fishery which is threatened by reduced flows and temperatures. The 2002 fish kill in the lower Klamath, caused by low flows in combination with disease, is famous for killing thousands of adult salmon and also killed a few green sturgeon.

              Clear Lake Hitch is a native fish that is found exclusively in Clear Lake, Lake County, where it was once an abundant food for the indigenous Pomo people.  Formerly, it ascended tributary streams by the thousands to spawn in the spring. Hitch numbers are greatly reduced due to alteration and diversion of its spawning streams and to predation by non-native fishes in the lake. Reductions in flows are particularly a problem in drought years. Furthermore, Clear Lake struggles with blue-green algae blooms, especially during hot summers, which functionally limits the oxythermal habitat of fishes like the Clear Lake hitch, and can also can fish kills (Till et al. 2019). Importantly, Clear Lake also has a history of native fish extinctions; the Clear Lake Spilttail (another species only found in Clear Lake) has not been captured since 1970 and is presumed extinct. Local people monitor the hitch populations but funding for habitat restoration and other actions is limited, so the future of these fish is far from secure, despite being listed as Threatened under the state ESA and despite its importance to Pomo culture.

Each of California’s native fishes have a similar story, even species not threatened with extinction. But the most threatened species need special attention. The more obscure species need be protected by champions who watch out for their welfare, such as the CDFW biologist who checks up on Red Hills roach in their tiny streams, ready to mount a rescue operation if needed. Ultimately, each species needs protection in their special habitats, preferably as a statewide system of managed watersheds that protect more than just threatened fish (Howard et al 2018). We discussed many of these issues at length in a recent blog post.

Winter-run Chinook salmon and Delta smelt are examples of species that have been saved from extinction so far by extraordinary measures, as prescribed under the state and federal ESAs. These acts have managed to prevent extinction of most listed California fishes so far, but drought, combined with threats from activities by people, is pushing ESA protections to the breaking point.

Further reading

Baumsteiger, J. and P.B. Moyle 2017. Assessing extinction.  Bioscience 67: 357-366. doi:10.1093/biosci/bix001

Baumsteiger, J. and P. B. Moyle. 2019.A reappraisal of the California Roach/Hitch (Cypriniformes, Cyprinidae, Hesperoleucus/Lavinia) species complex. Zootaxa 4543 (2): 2221-240. https://www.mapress.com/j/zt/article/view/zootaxa.4543.2.3  (available as open-access download)

Börk, K.S., P. Moyle, J. Durand, Tien-Chieh Hung, and A. L. Rypel. 2020. Small populations in jeopardy: A Delta Smelt case study. Environmental Law Reporter 50 ELR 10714 -10722 92020

Howard, J.K, K. A. Fesenmyer, T. E. Grantham, J. H. Viers, P. R. Ode, P. B. Moyle, S. J. Kupferburg, J. L. Furnish, A. Rehn, J. Slusark, R. D. Mazor, N. R. Santos, R. A. Peek, and A. N. Wright. 2018. A freshwater conservation blueprint for California: prioritizing watersheds for freshwater biodiversity.  Freshwater Science 37(2):417-431. https://doi.org/10.1086/697996

Leidy, R. A. and P. B. Moyle. 2021. Keeping up with the status of freshwater fishes: a California (USA) perspective.  Conservation Science and Practice. 2021;e474. https// doi.org/ 10.1111/csp2.474. 10 pages. Open Access.

Lennox R.J., D.A. Crook, P. B.  Moyle, D. P. Struthers, and S. J. Cooke 2019. Toward a better understanding of freshwater fish responses to an increasingly drought-stricken world. Reviews in Fish Biology and Fisheries 29:71-92  https://doi.org/10.1007/s11160-018-09545-9.  Open Access.

Moyle, P., J. Howard, and T. Grantham, 2020. Protecting California’s Aquatic Biodiversity in a Time of Crisis. California Water Blog. https://californiawaterblog.com/2020/05/03/protecting-aquatic-biodiversity-in-california/

Moyle, P.B., J. V. E. Katz and R. M. Quiñones.  2011. Rapid decline of California’s native inland fishes: a status assessment.  Biological Conservation 144: 2414-2423.

Moyle, P., R. Lusardi, P. Samuel, and J. Katz. 2017. State of the Salmonids: Status of California’s Emblematic Fishes 2017.  Center for Watershed Sciences, University of California, Davis and California Trout, San Francisco, CA. 579 pp. https://watershed.ucdavis.edu/files/content/news/SOS%20II_Final.pdf

Moyle, P.B., R. M. Quiñones, J.V.E. Katz, and J. Weaver. 2015.  Fish Species of Special Concern in California.  3rd edition.  Sacramento: California Department of Fish and Wildlife. https://www.wildlife.ca.gov/Conservation/Fishes/Special-Concern

Moyle, P.B., D. Stompe, and J. Durand. 2020. Is the Sacramento splittail an endangered species?  https://californiawaterblog.com/2020/03/03/is-the-sacramento-splittail-an-endangered-species/

Rypel, A.L., P.B. Moyle, and J. Lund, 2021. A Swiss Cheese Model for Fish Conservation in California. California Water Blog. https://californiawaterblog.com/2021/01/24/a-swiss-cheese-model-for-fish-conservation-in-california/

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.

Peter Moyle is Distinguished Professor Emeritus at the University of California, Davis and is Associate Director of the Center for Watershed Sciences. Andrew Rypel is a professor of Wildlife, Fish, and Conservation Biology and Co-Director of the Center for Watershed Sciences at the University of California, Davis.

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Mitigating Domestic Well Failure for SGMA and Drought in the San Joaquin Valley

by Rob Gailey and Jay Lund

Domestic wells serve sizable potable water demands in California and much of the world. These wells tend to degrade and fail with declining regional groundwater levels. In areas of irrigated agriculture, impacts to shallower domestic wells may occur from ongoing groundwater use and worsen during drought when agricultural pumping increases to compensate for diminished surface water supplies. Impacts on domestic wells include increased pumping lift, pump cavitation, well screen clogging, and wells running dry.  Our recent work examines the potential for managing these impacts in part of the San Joaquin Valley (shown in Figure 1) where groundwater sustainability plans were completed in 2020 as required by the Sustainable Groundwater Management Act.

Figure 1. Study area. Blue outlined area is the Central Valley. Dark orange filled area in the southern Central Valley is the San Joaquin Valley. Light orange filled areas with outlines are critically-overdrafted groundwater subbasins in the San Joaquin Valley. Only a portion of the area covered by these subbasins is considered based on limited data. Gray shaded areas indicate the portion of critically overdrafted subbasins considered in this work.
Chart, line chart

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Figure 2. Domestic well mitigation cost as a function of retirement age for the groundwater management parameters. MO is Measurable Objective, MT is Minimum Threshold,and DF is drought factor (relative to groundwater level declines during 2012-2016 drought).

As groundwater levels decline during drought, we consider mitigation actions and costs for additional pumping energy, lowering pumps, cleaning well screens, and replacing dry wells with deeper wells.  These actions allow continued domestic well use. Our analysis estimates: 1) the range and magnitude of mitigation actions, 2) their likely costs, 3) where and when impacts are likely to occur, and 4) labor and time needed to resolve problems for those who depend on domestic wells for drinking water. These actions and costs are driven by how drought declines in groundwater are likely to affect existing domestic wells of varying depths.

Estimated total mitigation cost for groundwater level declines to planned management targets (Measurable Objectives defined under the Sustainable Groundwater Management Act) ranges from $42 to $96 million for this part of the San Joaquin Valley, depending on well retirement age – information known only approximately (Figure 2). If groundwater levels decline further during drought to defined limits below the management targets (Minimum Thresholds defined in SGMA plans) allowed during periods of shortage, costs increase to $120 to $249 million. Costs for groundwater levels declining to the Measurable Objectives are comparable to those that would occur from a repeat of the 2012 to 2016 drought. Costs for declines to the Minimum Thresholds are somewhat more than those estimated for twice the groundwater level decline of the 2012 to 2016 drought. The highest costs are in the northern and central study area where well densities are greatest (Figure 3). The deeper Minimum Threshold groundwater levels increase the area and depth of mitigation needs. Including older wells significantly increases costs. 

Map

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Figure 3. Geographic distribution of mitigation cost for groundwater management limit (Minimum Threshold) with no retirement age. Costs are presented for each section of the US Public Land Survey System within the study area.

Although these costs are large for domestic well owners and users, they are quite small compared to the economic benefits to agriculture from additional pumping during droughts.  This remains true, even considering that the additional water pumped must be replenished after the drought, because the Sustainable Groundwater Management Act prohibits long-term groundwater overdraft.

Prices for agricultural water in this region during non-drought and drought periods are approximately $250 and at least $1,000 per acre-foot, respectively.  Because additional groundwater extraction during drought must be replaced after the drought (from additional water purchases and recharge or future reductions in non-drought pumping), the value of agricultural pumping during drought may be estimated as the avoided cost of purchasing water during drought (the difference between drought and non-drought prices conservatively estimated at $750 per acre-foot). For this cost savings and considering the estimated change in storage from the Measurable Objectives to the Minimum Thresholds, the value of drought pumping for agriculture in the study area is estimated at $9 to $27 billion, or approximately $2 to $5 billion per year over a five-year drought. This compares to $34 billion in agricultural revenue during 2019 for the eight counties in the San Joaquin Valley. Domestic well costs are less than two percent of the value to agriculture from managing to the Minimum Thresholds during droughts.

Despite uncertainty in estimating specific impacts (due to incomplete records on well construction, well retirement and groundwater hydrology), it seems clear that domestic well mitigation needs and costs from agricultural pumping are likely to be large. These include thousands of pumps being lowered in wells and hundreds of kilometers drilled for well replacement. The scope of mitigation may be still greater since 1) the study area includes only 59 percent of domestic well construction records for critically-overdrafted groundwater subbasins in the San Joaquin Valley and 2) additional mitigation work would be needed for shallow agricultural wells. Although other mitigation actions, such as expanding and consolidating centralized community water systems, would often be best, maintaining well supplies is often the best or only near-term option.

The estimated labor for the largest cost (well replacement) indicates the level of effort required to mitigate domestic well impacts. For the Measurable Objective, approximately 50 to 132 km of drilling would be required depending on assumed retirement age. The requirements increase to 148 to 347 km for drawdowns to Minimum Thresholds. The unknown future timing and magnitude of droughts, and therefore potential departures from Measurable Objectives to the Minimum Thresholds, creates uncertainty in the timing and intensity of needed mitigation. Given the substantial effort and scarce skilled labor to accomplish mitigation actions for domestic wells, there may be insufficient capacity (funds and skilled labor) to complete this work as impacts occur, so pre-mitigation for the most vulnerable areas should be addressed preventatively before impacts occur. 

Given the high costs to agriculture of making groundwater management plans more stringent, preventative mitigation should be undertaken for vulnerable, high-impact areas. Such measures could greatly reduce drought damages and interruptions for domestic well supplies, and reduce the cost and response time of mitigation. Assuming that mitigation measures do not create additional water quality problems, the cost of such mitigation is much less than the benefit to local agriculture from pumping additional groundwater during a multi-year drought.  Domestic well mitigation in advance of droughts is a cheap way to build drought storage for agricultural water supply.

Rob Gailey is a practicing hydrogeologist in California.  Jay Lund is a Professor of Civil and Environmental Engineering at the University of California, Davis, where he is also Co-Director for its Center for Watershed Sciences.

Further Readings

California Department of Food and Agriculture (2020) California agricultural statistics review 2019-2020

Gailey, R.M. and Lund, J.R., Managing Domestic Well Impacts from Overdraft and Balancing Stakeholder Interests,” CaliforniaWaterBlog.com, May 20, 2018.

Gailey RM (2020), California supply well impact analysis for drinking water vulnerability webtool, Community Water Center, January 2020.

Hanak E, Lund J, Arnold B, Escriva-Bou A, Gray B, Green S, Harter H, Howitt R, MacEwan D, Medellín-Azuara, Moyle P and Seavey N (2017) Water stress and a changing San Joaquin Valley, Public Policy Institute of California, March 2017.

Lund JR, Medellin-Azuara J, Durand J, and Stone K (2018), “Lessons from California’s 2012-2016 Drought,” J. of Water Resources Planning and Management, Vol 144, No. 10, October 2018.

State of California (2021), Household water supply shortage reporting system.

Stone K and Gailey R (2019), “Economic Tradeoffs in Groundwater Management During Drought,” CaliforniaWaterBlog.com, June 10, 2019.

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Ecosystem Restoration and Water Management

– Curated by Jennifer Cribbs (jecribbs@ucdavis.edu)

Note from the Curator:

Restoration implies returning to a prior state. A broken cup carefully glued, might appear nearly as whole as the original, but will always differ from the original. 

Ecosystem restoration attempts to return an evolving web of interconnected species and physical processes to a prior state. This endeavor raises complex questions: what prior state should be the restoration target? How do ecosystem needs and human values interact in determining the restoration goal? Is it most important to restore physical processes (process-based restoration) or populations of critical species (species-based restoration)? The following collection of art explores these questions and the connections between restoration and water management. 

The Voyage of Life (Thomas Cole 1842) source This quadriptych illustrates the stages of human life from childhood to youth to adulthood, and finally old age. The river symbolizes the passage of time and the uniqueness of every moment. As with human lives, it is impossible to restore a river to a previous point in time. However, process based restoration, as described by Wohl et al. (2015), focuses on restoring essential functions of the river rather than restoring to conditions at a previous point in time.  –Angelica Ortiz 

The Oxbow (Thomas Cole 1836)source Thomas Cole’s paintings epitomize the romanticism of the Hudson River School which reflects the desire to restore a different relationship between nature and society. Similarly, river restoration raises questions about what the relationship between nature and society should be. In The Oxbow, the landscape predominantly shows signs of humans extracting resources from nature. Whether that is the right relationship between nature and society remains an open question.    –Abbey Hill

Kintsugi tea bowl (17th Century Japan, Edo period, currently at Smithsonian’s Freer Gallery of Art) – source Kintsugi, meaning “golden joinery,” is a Japanese method of repairing broken ceramics. The technique uses lacquer and powdered gold or silver to emphasize, rather than hide, the cracks. Kintsugi shows that the object may never be wholly restored, but it can be beautiful and useful. Similarly, process-based restoration projects intend to restore the form and function of a river rather than return the system to an unimpacted or past state (Wohl et al., 2015). Rivers that are “broken” (i.e., impaired water quality, biodiversity loss) will not be made whole by restoration projects, but they will gain new form, function, and value for people and the environment.  –Eleanor Fadely

Glen Canyon Dam (Normal Rockwell 1969) – source The Navajo family in the foreground emphasizes the costs of Glen Canyon Dam–the people displaced, the ecosystems drowned, the river’s natural path arrested.  The dam dramatically influences flow regimes in the Grand Canyon, transforming the Colorado River below the dam from high sediment, high flood water, with variable temperatures to much lower sediment, smaller managed floods, and consistent cooler temperatures (Schmidt et al., 1998).  Options for managing the river range from traditional management (business as usual) to full scale restoration (removal of all dams) as well as options in between.  Schmidt et al. (1998) explores the benefits and drawbacks of these options, recognizing that it is impossible to turn back the clock in any ecosystem. –Jenny Cribbs

Tanner Springs Park, Portland Oregon by Atelier Dreiseitl & Green Works (2005) source  Can decentralized water treatment and reuse systems integrate into communities in an invisible or even beautiful way? Tanner Springs Park combines landscape architecture and water treatment. This formerly culverted creek collects runoff from the surrounding city in its bioswale, filtering contaminants and slowing water flow. Tanner Springs Park exemplifies how decentralized treatment and reuse systems can work in tandem with centralized water systems, combining economical sanitation with functional beauty.  –Eleanor Fadely

Jenny Cribbs is a masters student in Environmental Policy and Management and an incoming PhD student in Ecology at the University of California at Davis. This post is a product of a pandemic, remote, discussion-based class on Art and Water Management in Winter, 2021. Contributing authors Eleanor Fadely, Abbey Hill, and Angelica Ortiz all participated in this class; Jay Lund served as faculty facilitator.

Further Readings

Schmidt, J., Webb, R., Valdez, R., Marzolf, G., & Stevens, L. (1998). Science and Values in River Restoration in the Grand Canyon. BioScience, 48(9), 735-747. doi:10.2307/1313336

Wohl, E., Lane, S. N., & Wilcox, A. C. (2015), The science and practice of river restoration, Water Resources, 51, 5974–5997. doi:10.1002/2014WR016874.

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Jobs and Irrigation during Drought in California

Jobs and Irrigation during Drought in California

Farmworkers harvesting cauliflower in Monterey County. Photo by John Chacon/California Department of Water Resources

by Josué Medellín-Azuara and Jay Lund

During droughts organizations and stakeholders look for ways of getting the most from every water drop. This is not an exception in California where roughly 40 percent of all water use (on average) is agricultural, 10 percent to cities and the rest is uncaptured or environmental uses (mostly on the North Coast). Cities particularly in southern California have adhered to aggressive water conservation measures, and economically worthwhile irrigation efficiency improvements have already been adopted by thriving agriculture in the state. Yet the notion that applied water in agriculture is often wasteful is common in media drought coverage.

As it turns out, farmers strategically apply water to maintain higher net economic returns.  Farmers irrigate to supply crop evapotranspiration needs, plus a bit more to ensure each plant across a field is well watered and reduce management costs.  In some areas, salts need to be flushed from soils to avoid crop yield losses.  In most areas, most of the additional irrigation beyond immediate crop needs becomes groundwater recharge, which helps prepare for future droughts. Drier soils and higher temperatures during droughts may also demand higher applied water to compensate for additional temperature losses. 

With all these nuances in California agricultural water use, the regional economic benefits of growing crops are sometimes neglected. In California’s San Joaquin Valley, agricultural crop production and processing are nearly a fourth of gross revenues and a sixth of the region’s employment. Rural areas across the state depend disproportionately on irrigated agriculture.

The table below presents estimated irrigated crop area by major crop group, applied water and employment (Medellin-Azuara et al. 2015). While data in the table merits an update (keep posted for a follow-up blog), the story remains unchanged. Fruits, nuts and vegetables support most agricultural gross revenues, employment and income in California’s agriculture when combining hired and contract labor.

Figure 1 puts the story into perspective, if major crop categories are arranged in acreage from the highest value the lowest gross value and employment (from Table 1), nearly 85 percent of all employment and revenues are from growing fruits, nuts and vegetables, which are about half of California’s irrigated acreage.

Figure 1. Cumulative value and employment in California’s major crop groups (Lund et al. 2018). Prepared by Josue Medellin-Azuara with the assistance of Nadya Alexander, UC Davis Center for Watershed Sciences. Contact: jmedellin@ucmerced.edu

Droughts bring new challenges for supplying water even to highly profitable crops, including permanent crops. Adaptation and profits usually point towards reducing irrigation of field, grain and other less profitable agricultural commodities. One limiting factor is the feed crop needs of California’s highly ranked dairy’s sector. Silage corn is the preferred wet roughage for dairies to support high milk yield.

Some old and new insights are worthwhile mentioning:

  • The top 5 crop groups in revenue per unit of water use are grown on about 25 percent of California’s irrigated cropland and account for 16.4 percent of all the net water use. Those crops are responsible for two-thirds of all crop-related employment.
  • Grains, livestock forage and other field crops rank lower in revenue and jobs per drop because their farming is highly mechanized, requiring much less labor. These crop groups nonetheless are critical to the livestock industry. California’s dairy production is the largest in the country.
  • Vegetables, horticulture, fruits and nuts account for more than 90 percent of employment directly related to crop production.
  • Farm contractors, who provide bulk labor for growers, supply about half the labor force for most crop groups.
  • California agriculture accounts for more than 400,000 full-time jobs (or their equivalent, with nearly 200,000 in crop and animal production, another 200,000 in agricultural support services (contract labor).

California’s dynamic and highly adaptive agricultural sector is likely to continue increasing value and employment per unit of water use. Over the past 30 years there has been an intensification in value that retains commodities with the highest gross value and employment. Such value intensification along with a globalized economy prevent catastrophic economic (including employment) losses from drought in agriculture to occur, particularly when groundwater is available to maintain permanent crops.

Despite this robustness of agriculture overall, some hurdles merit additional planning and forethought. First, additional reductions in applied water might sound attractive, but should be put in the context of the farm (or basin) water balance and the need to recharge groundwater for droughts.  Second, within the first few years of implementing the Sustainable Groundwater Management Act, adhering to drought year provisions on water use and pumping will be a challenge, and some irrigated area reductions might occur.

Increased water pumping during drought will likely dampen higher overall agricultural economic losses once again.  Yet even if pumping adheres to drought year provisions in the groundwater sustainability plans, the effects on rural community wells from increased agricultural pumping nearby is a concern.

Growing water scarcity for agriculture is probably best managed using water markets and pricing so the industry and the state can make the most of limited supplies. Efforts to impose detailed arbitrary limits on crops and regions are unlikely to serve the economic and environmental interests of California, but rather further impoverish rural areas and distract from discussions needed for long-term progress.

Josué Medellín-Azuara, Jay Lund are respectively associate director and co-director at the UC Davis Center for Watershed Sciences. Medellín-Azuara is an associate professor at the Department of Civil and Environmental Engineering at UC Merced. Lund is a professor of Civil and Environmental Engineering at UC Davis.

Further reading

California Department of Water Resources. 2015. “Irrigated crop acres and water use.” Last visited April 24, 2015

Martin P. and Taylor E. 2013. “Ripe with Change: Evolving Farm Labor Markets int he United States, Mexico and Central America.” Migration Policy Institute, Washington, D.C. Last visited April 24, 2015

Medellin-Azuara J. and Lund J.R. 2015. “Dollars and drops per California crop.” California WaterBlog. April, 14, 2015

Sumner D. 2015. “Food prices and the California drought.” California WaterBlog. April 22, 2015

Lund, J., Medellin-Azuara, J., Durand, J., & Stone, K. (2018). Lessons from California’s 2012–2016 drought. Journal of Water Resources Planning and Management, 144(10), 4018067.

Medellin-Azura, J. Lund, J.R. and Howitt, R.E. Jobs per drop in the California Crops. California Water Blog, April 28, 2015.

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