Field courses help young people see the real world

by Andrew L. Rypel

It was perhaps unsurprising I wound up a field ecologist. Raised in Wisconsin, I spent almost all my childhood free time roaming largely unchaperoned in nature, pre-internet. It was there that I developed a deep love for nature, water and fish that would stay with me my whole life. It was a privileged upbringing. And yet somehow it was years later, when I was 22 and taking a university field course, that I finally figured out I wanted to pursue an academic career in fish and ecology. It’s unclear how many biologists can trace their paths back to experiences like these, but I suspect there are many. Field courses are so impactful, and we need them now, more than ever before. 

As a young college student, I struggled at my mid-sized liberal arts college to find a curricula that connected my outdoors interests (nature, fishing, camping, hiking) together. Years later, I recognized that field broadly as ecology, but at the time, I didn’t know that’s what I was searching for. Most of the science courses and majors at my institution were annoyingly pre-health focused. I briefly toyed with the idea of a double major in English and a natural science field. Eventually I declared the best major I could find – environmental science (awarded through the geology department) with biology as a minor. At that time, environmental programs were somewhat rare at many US institutions, so I was happy enough I had majored in something vaguely reflecting my values.

Group photo from 2002 “Biology of the Southern Appalachians”. Yours truly looking dour and scraggly in the back row. Photo from Meredith Latimer.

I finally took my first real field course during my Master’s program in fisheries several years later at Auburn University (War Eagle!). The course was Biology of the Southern Appalachians, taught by Professor George Folkerts. It hadn’t been offered in years, and I had privately heard it was something special. Now, I could write an entire series of blogs on George, but most people who know Auburn, or natural history of the southeastern USA, or Tuesday trivia night in Auburn – all knew George. He was gentle, patient, brilliant, and a walking encyclopedia of biodiversity and ecology, especially rare and declining organisms like bog plants, salamanders, turtles, beetles, arthropods of longleaf forests – basically everything. I consider him one of my “academic parents”, and he was later a close friend.

Geoge took about 15 students including myself (~50/50 undergrad/grad) in vans for the better part of two months collecting plants and animals from Auburn, AL northeast to parts of Maryland. It was one of the best periods in my life. To help write this blog, I resurrected my old field notebook from the course to recall some of what we collected. For example, I see that we collected a black racer snake, hiked through a stand of smoke trees, observed cave bats, snorkled for freshwater mussels, observed rare bog turtles, collected aquatic insects, seined for fishes, captured a jumping mouse with our bare hands, used live traps for small mammals, sampled terrestrial snails, collected at least five species of cockroach (!), identified millipedes, collected a baker’s dozen species of salamanders, hiked to the top of Clingman’s Dome to see the completeness of the damage done to forests by acid rain and the balsam woolly adelgid, visited a cataract bog with stands of live mountain sweet pitcher plants (I described them as uniformly tall, beautiful, and with insects trapped in the pitchers). And this list was just for the first half of our trip!

From the dusty bottom of moving boxes – my field notebook from 2002. 

One afternoon, early in the trip, we were hiking through Joyce Kilmer National Forest in NC – famous for its old growth tulip trees. We’d been hiking for maybe an hour or so when George stopped at the base of a large tulip tree. He sat down, pensively, and swigged some water out of his canteen. He then said something I’ve never forgot, “Don’t let anyone tell you to get into the real world. Science and academics is the search for knowledge. And it’s more real than anything you’ll ever find in the “real world”.”

I’d never considered science as a career before then. Was I good at that? I had always figured I would get a fisheries degree, find a great job at a state or federal agency, and move back near home. Over time, I came to learn that I was good at science, and it became a passion. I wanted to understand how things worked – and I wanted to use that information to improve conservation, especially for my beloved fishes.

Over the years, I’ve come to realize my experience wasn’t unique. Many students elect to pursue environmental and science-based careers after taking field courses. We observe this frequently at the Center for Watershed Sciences at UC Davis. Many of our students, alumni, and staff began their journeys after taking Ecogeomorphology (EcoGeo for short). The brain child of Jeff Mount and Peter Moyle, EcoGeo is an interdisciplinary idea, where upper level undergraduate students study watershed issues in multidisciplinary teams. The course culminates with an extended summer field trip to the watershed where field research is conducted. UC Davis teams have traveled to places like the Kobuc River (AK), Santa Cruz Island (CA), Grande Ronde (OR/WA), Skeena River (BC), Copper RIver (AK), and the Grand Canyon (several times). So many UC Davis students have started careers with these courses; it is one of the great and enduring legacies of the Center, and one that I would like to see multiplied in coming years.

UC Davis EcoGeo students and instructors are gathered in the Grand Canyon in the nightly Circle of Science, where each night a student makes a presentation on some issue relevant to river management. Then everyone discusses how the topic relates to different disciplines. Photo credit: Joe Proudman

Of course, field courses are inherently important and impactful. We also know these courses are effective at generating extraordinary learning outcomes. Elkins and Elkins (2007) demonstrated that for introductory geology information, there was significantly higher improvements in basic geoscience understanding for field course students compared to 29 other introductory geoscience courses from across the United States. Durrant (2015) showed that aside from basic intellectual gains, students of field courses themselves realized integrative learning gains had taken place while attending a field course. These results suggest field courses also work on sharpening metacognition or ‘thinking about how you think’ – considered one of the higher forms of human thought. 

Finally, field courses can reset our values framework. For many young people, especially those without privilege, nature has never been fully experienced. Our society, especially in California, is increasingly urban, populated, and disconnected from nature and wilderness. We work and manage within reconciled contexts – urban parks, working landscapes, backyard ecology. These frameworks are necessary to realistically preserve and manage the ecological function we have left. Yet there is also a need to visit, study and protect the best – wild places – where the true real word is right in front of you. It is important for humans to experience these environments. 

In an alarming study by Soga and Gaston (2016), we see that children especially are having decreased basic contact with nature. For example, the percentage of children who had never fished increased from ~20% in 1998 to ~50% in 2009. The percentage of children who had never climbed a mountain increased from ~50% in 1998 to ~70% in 2009. Other simple indicators of participation (climbing trees, catching bugs, birdwatching) have all declined in young people over time. This is scary – and may do us in faster than many other existential threats that we worry about! 

It is rightful to ask, “How will our society be capable of protecting nature if many have never fully experienced it?” Field courses don’t solve this problem alone, but they do address the root of the problem for those who take them. Field courses also represent an opportunity to aid in diversifying the fields of natural resource management and conservation, which are notably lacking in recruitment and retention of women and people of color. For our part, we will journey on. Maybe you’ll see some of our graduates out on the river, or fighting for science-based decision-making in a meeting or public forum near you.

Further reading

UC Davis Center for Watershed Sciences education webpage,

Durant, K.L. 2015. The Integrative Learning Value of Field Courses. Journal of Biological Education 49: 385-400.

Elkins, J.T., and N.M.L. Elkins. 2007. Teaching Geology in the Field: Significant Geoscience Concept Gains in Entirely Field-based Introductory Geology Courses. Journal of Geoscience Education 55: 126-132.

Soga, M., and K.J. Gaston. 2016. Extinction of experience: the loss of human-nature interactions. Frontiers in Ecology and the Environment 14: 94-101.

Posted in Uncategorized | Leave a comment

Episode 1: “Unraveling the Knot” Water movement in the Sacramento-San Joaquin Delta – reprise

By Bill Fleenor, Amber Manfree, and Megan Nguyen

This is a re-posting from January 22, 2017.  Reminders on how things work are sometimes useful. (The whole series, with links below, is thought-provoking.)

In 2010, John DeGeorge of RMA, Inc used animated model results to illustrate specific flow and water quality issues in the Delta to the State Water Board. The Center for Watershed Sciences, working with John and using RMA software, has assembled a series of narrated animations to show some major forces acting on Delta flows and water quality. The goal is to “Unravel the Knot” of California’s Delta – at least some it – in terms of flow and water quality.

In Episode 1 we start with general background of California water and the role and significance of the Delta.

The main points are:

  • The Sacramento-San Joaquin Delta watershed covers 40% of California and most of the water used in the state by humans. Rain and snowmelt feed rivers, supporting a wide variety of habitats and large populations of wildlife.
  • The Delta is a critical hub in California’s water infrastructure, conveying fresh water from the wetter northern part of the state to farms and cities in the drier south. Water deliveries supporting intensive agriculture and supplying urban areas have spurred enormous economic growth. This has come with significant environmental tradeoffs.
  • The Delta is largely tidally influenced, and potential for rapid large-scale flooding of sunken island interiors, combined with sea level rise impacts, threaten its use as a conduit for water delivery, and raise the possibility of sudden, sweeping environmental changes.
  • Understanding how water moves in the Delta can help in planning for the future. This video series examines each component of water movement separately, and explains how shifts in water management, levee failure, and sea level rise might change the Delta and California’s water supply in the years ahead.

William Fleenor is a senior researcher who specializes in hydrodynamics and hydraulic modeling at the UC Davis Center for Watershed Sciences (formally retired, but still great to have around). Amber Manfree is a postdoctoral researcher with the UC Davis Center for Watershed Sciences (now an independent professional). Megan Nguyen is a GIS researcher at the Center for Watershed Sciences (now doing great work for CalTrout).  Voice talent was generously provided by Dr. John Durand, a professional researcher at the UC Davis Center for Watershed Sciences.

Further Reading

A Tale of Two Deltas: A Comparison of Transport Processes in the Predevelopment and Contemporary Delta (Jon Burau, as summarized by Maven, 2016)

Episode 1: “Unraveling the Knot” – Water movement in the Sacramento-San Joaquin Delta – Introduction

Episode 2: “Unraveling the Knot” – Water movement in the Sacramento-San Joaquin Delta – Tidal Forces

Episode 3: “Unraveling the Knot” – Water movement in the Sacramento-San Joaquin Delta – Managing Flows

Posted in Uncategorized | Leave a comment

Realty Meets Climate Reality

My husband and I fell in love a couple of months ago. It was with a house by a river. (See what I did there?) This is the river that was a stone’s throw away when we were engaged 13 years ago. The river we’ve brought our children to every summer of the past decade. The river I love to paint, paddle, swim in and stare at. This place could be our forever home.

The house is where I spent my first night after moving to California 15 years ago. It belonged to my boss, the editor of the town’s daily newspaper. He left years ago. When the house popped up for sale, my husband and I started to dream, penciled out some numbers and were stunned to realize we might just be able to make it happen.

One of the reasons we love the place is how close it is to the river. Looking at the realtor site I thought, “Hmmm, maybe that river is a little too close.” But my former boss had never had flooding issues and I didn’t recall it being a problem. I shrugged and went back to searching “cabin décor” on Pinterest.

A couple weeks later when we visited the place, we stood on the gravel bar below the property, my husband’s eyes all wild and dreamy looking across the water, and he said to me, “You know, I think our biggest concern with this place is that we’ll never want to leave it.”

Man beside river

He was wrong.

The biggest concern is it is smack dab in the middle of the floodway. Not just a 500-year or 100-year floodplain. The. Flood. Way. Like, if a flood were to occur of any significance, this is where it would go. I found this after doing what I should have done immediately: looked at the FEMA flood map for the home’s address.

Granted, the neighborhood hasn’t flooded since 1964, before it was even a neighborhood. But it did flood. And if there’s anything I’ve learned by writing about the environment for 20 years, and accompanying UC Davis flood experts like Nicholas Pinter to rivers across the U.S., it’s that if it’s a floodplain, flooding is a matter of “when” not “if” — and it will likely happen sooner than expected.

Expert advice

I used an already scheduled coffee chat as an opportunity to show Pinter a printout of the FEMA map of the property, hoping beyond hope that I had somehow misread it, or that he would tell me it probably wasn’t that bad. Keep in mind, Pinter is a man who has spent the better part of his career guiding people away, not toward, living on floodplains.

Me: So, I’m considering buying riverfront property.

Pinter: [Grimace]

Me: I know, you thought you taught me better. Here’s the map. [Map shown with hash marks running right through property.]

Pinter:  Kat… [Shakes head in dismay. Furrows brow.]

Me: I’m in that “in love” stage where heart is overriding head. We probably won’t get it, but I thought I’d show you while I have you here.

Pinter: [Pauses.] Look, you have to ask yourself, are you ready to drop everything and move everything to the attic whenever a big storm is coming? Are you willing to go up after a flood and muck it out, with all the mud and the stench? Are you ready to lose the house?

Great questions. Ones that made me even angrier at climate change than I was before. Even without climate change, that house would be risky; with it, we’d almost surely be mucking it out of the mud eventually. Atmospheric rivers that bring large amounts of rain at once are among the many weather events expected to intensify with climate change in the coming years.

Mapping risk

I started to look at just where I could live in this state that has the beauty and naturalness I so strongly crave in my suburban household existence but that isn’t vulnerable to disaster. I overlaid maps of California’s earthquake, wildfire and flood zones and the answer was: Not many. Certainly very few places I could afford.

Still lovestruck, my mind went into a rather whiny rationalization and validation mode: Well, if all of these people live in these risky places and aren’t agonizing over it, why shouldn’t I be one of them? (Yes, I hear myself.) Should all the people of Miami, Houston, the Caribbean, every coastal city on the planet just not live there? Or maybe we could raise the house? Or if it floods, maybe we could build a cool, livable treehouse and Airbnb it—does flood insurance cover that? (This is called grasping.)

I went online and found exactly zero stories, threads or tweets of people saying it was totally worth it to buy property within a floodplain. Meanwhile, there were hundreds of comments warning against it.

My sister and her husband just bought a home in the Bay Area. It’s a renovated A-frame in the hills, surrounded by trees. Lovely. And totally at fire risk. But given they both like and want to keep their jobs and friends, they don’t have much choice but to buy insurance and hope for the best.

Luckily, I don’t have to buy our dream house by the river. It’s a choice. But we all need a place to live, and the choices are becoming more limited in this state and others especially vulnerable to climate change.

As you may have guessed, we decided not to buy the river house. I haven’t given up on the idea of living within earshot of a river someday, but my home will have to be elevated and out of the flood zone.


The proposition did make me think in a very personal way about climate risk, resiliency and how I feel about impermanence.

“I just need it to last 50 years,” I found myself thinking when the realtor’s documents for an offer were still on my kitchen countertop. But really, there is no way to guarantee permanence for anywhere I can imagine living. Not my current home and certainly not my dream one.

live oak view from below, looking up

I recently stood under an 800-year-old live oak in New Orleans, a city slowly sinking back into the ocean. That tree emerged while Genghis Khan was coming to power. It lived among the native Chitimacha people, held strong as the French, Spanish and Americans laid claim to its land, and grew within earshot of a new music—jazz—rising out of the French Quarter. It absorbed the waters of Katrina and patiently watched as people started taking selfies in front of its curving limbs. It’s as permanent as anything my eyes can take in and yet it, too, will be gone soon.

The Earth will go on forever, in one form or another. But it is changing, and we’ll somehow need to be both open-eyed and resilient to where it wants to take us.

Kat Kerlin is an environmental science writer and media relations specialist at UC Davis. She’s the editor of the Science & Climate website and its “What Can I Do About Climate Change?” blog, from which this piece is re-posted. @UCDavis_Kerlin

Posted in Uncategorized | 1 Comment

Striped Bass: An Important Indicator Species in the Delta

Peter and an inconvenienced bass

by Peter Moyle

The striped bass is a favorite sport fish in the San Francisco Estuary (SFE), especially the Delta, because of its large size, sporting qualities, and tasty flesh. Historically, it supported major commercial and sport fisheries but the commercial fishery was shut down long ago and the sport fishery is in long-term decline. The decline of adult fish is reflected in decline of juvenile striped bass as well. Juvenile abundance in the major fish surveys of the SFE track the decline of delta and longfin smelt well. These declines are a good indication that major changes have taken place in the pelagic (open water) environment in the upper SFE, creating problems for pelagic fishes in general.  Nevertheless, adult striped bass, which are voracious predators, have been accused of causing the declines through predation, although there is little evidence for this (see and

The factors causing the decline of many fish and fisheries in the upper SFE have made their management controversial, usually because of the correlation of declines with increased water exports from the Delta and upstream of the Delta, as well as with invasions of ‘ecosystem engineers’ such as overbite clams. To address this problem better, the California Fish and Game Commission is developing new policies for managing Delta fish and fisheries, with a special focus on striped bass.  The commission sets policy that guides management actions of the state Department of Fish and Wildlife. The proposed policies essentially require fishing regulations to be based on scientific studies and on ecosystem-based management. They give CDFW considerable flexibility in setting regulations and management actions.

The striped bass angling community is passionate about their fishery and is largely in agreement (as far as I can tell) with the basic policies.  However, they also want special emphasis to be placed on increasing striped bass abundance, so as to restore some of the former glory to the fishery and to be assured that management regulations and actions will not perpetuate the decline.  The anglers are well aware of efforts in the past that were made, unsuccessfully, to make non-native striped bass the ‘scapefish’ for declines of native fishes.

In part because of my past blog posts, striped bass anglers asked me to address the commission on October 9th, 2019, on issues related to the importance of striped bass in the SFE ecosystem.  I had five minutes to talk as one of numerous speakers.  What follows is a slightly modified version of my remarks.

I appreciate the efforts of the commission to develop a holistic fisheries management policy for the Delta and for striped bass in particular.  I encourage continuation of the policy that treats striped bass as an important member of the SFE ecosystem, including the Delta, and to avoid actions designed to further reduce its declining abundance even further. In fact, I encourage that steps be taken to increase striped bass numbers naturally because it would reflect an improvement in conditions in the Delta ecosystem for native fishes as well.

I write this as an academic researcher who has studied fishes of the estuary for nearly 50 years, including establishing a Suisun Marsh monitoring program that has sampled fish monthly since January, 1980. One of the principal fishes captured in our samples over the decades has been striped bass; this has given me an appreciation for their importance to the estuary’s ecosystem.  For example, we have determined that Suisun Marsh is a major nursery area for Delta fishes, especially striped bass, and that the juvenile striped bass decline is not as evident there as it seems to be elsewhere in the estuary. We have also found that in the turbid water of the marsh, adult striped bass feed largely on sticklebacks, gobies, and sculpin: not salmon, not smelt.

In the past, my attitude towards striped bass has been ambiguous because they are a non-native species and much of my research has focused on conserving native species.  However, striped bass are also one of the best studied fish species in the Delta, whose population fluctuations have a mostly downward trend. They are a good indicator of the ‘health’ of the estuary, including its ability to support native fishes.  Long-term fisheries monitoring in the Delta and estuary started when fish sampling programs were established in the 1950s and 1960s to explicitly track impacts of the State Water Project and the Central Valley Project on striped bass fisheries (e.g., Fall Midwater Trawl Survey, Summer Tow Net Survey). These surveys are still ongoing. Importantly, they have also been the principal source of status information on other species such as delta smelt. In fact, until recently the trends in juvenile striped bass numbers closely followed those of endangered Delta smelt and longfin smelt.  This indicates that these species have a similar response to the major changes that have taken place in the Delta in the past couple of decades.

I recognized this in my 2002 book Inland Fishes of California where I concluded the striped bass account with:

“The striped bass is a very resilient species and is now a permanent part of the California fish fauna….The best thing that can be done for striped bass is to restore the estuary to a condition that allows it to support more fish of all kinds, but especially native species (p  362).”

Striped bass were introduced into California in 1879 with explosive success. They have become naturalized, adapting, over 140 years, to an estuary that bears little resemblance to the one into which they were introduced. For example, there are 23 other non-native fish species permanently established in the estuary, as well as 150-200 non-native invertebrate species.  Today’s Delta ecosystem is best termed a novel ecosystem because of the strong presence of the non-native species from all over the world and because of the extensive alteration of its physical structure.  Striped bass remain one of the best species for monitoring this novel system because they use the entire estuary to complete their life cycle with different life stages having different ecological requirements. It is highly likely that adaptations of striped bass to this estuary now have a genetic basis, as has been shown for American shad, introduced at about the same time, with a similar life history.

In 2019, I was part of an Independent Scientific Advisory Panel which wrote a report for the Delta Science Program on Developing Biological Goals for the Bay-Delta Plan (Dahm et al. 2019)In this report, we recommended getting away from using just endangered fishes as the principal species to monitor ecological conditions in the Delta. These species are becoming so rare that they have limited value in determining the quality of habitat for a spectrum of native and other desirable fishes. We recommended instead that new metrics be developed that integrate information from multiple species, native and non-native, including striped bass.  The importance of striped bass stems from our extensive knowledge of its life history and the fact that its population tracks the condition of the pelagic portions of the ecosystem well.

What all this means is that regulations for managing striped bass should not be aimed at reducing its population but rather at increasing, or at least stabilizing, it.  We especially need management actions that reduce removal of large fish from the system.  The largest fish are females that produce the most and highest quality eggs that ultimately become the juvenile fish that are particularly sensitive to annual changes in estuarine conditions. As these juvenile fish progress through their life cycle, their abundance and health at each stage reflect the impacts of multiple factors that stress the ecosystem, from contaminants to altered foodwebs. The striped bass should be treated as a species that not only supports a valuable fishery but as an important indicator of the ability of the San Francisco Estuary, especially the Delta, to support a diverse and vibrant ecosystem.

Thank you for listening. I appreciate your considerable efforts to design management strategies that are flexible and science- based.

Further reading.

Dahm, C., W. Kimmerer, J. Korman, P. B. Moyle, G. T. Ruggerone, and C.A.Simenstad. 2019. Developing Biological Goals for the Bay-Delta Plan: Concepts and Ideas from an Independent Scientific Advisory Panel. A final report to the Delta Science Program. Sacramento: Delta Stewardship Council. Report,\

Hasselman, D.J., P. Bentzen, S.R. Narum, and T. P. Quinn. 2018. Formation of population genetic structure following the introduction and establishment of non-native American shad (Alosa sapidissima) along the Pacific Coast of North America. Biological invasions 20(11): 3123-3143.

Mount, J., B. Gray, K. Bork, J. E. Cloern, F. W. Davis, T. Grantham, L. Grenier, J. Harder, Y. Kuwayama, P. Moyle, M. W. Schwartz, A.Whipple, and S.Yarnell. 2019.  A Path Forward for California’s Freshwater Ecosystems.  San Francisco: Public Policy Institute of California. 32 pp.

Moyle, P. B.  2002.  Inland Fishes of California. Revised and Expanded. Berkeley: University of California Press. 502 pp.

Moyle, P.B.  and W.A. Bennett, 2011. Striped bass control: cure worse than disease? California WaterBlog, January 31.

Moyle, P.  A. Sih, A. Steel, C. Jeffres, and W. Bennett. 2016.  Understanding predation impacts on Delta native fishes. UC Davis Center for Watershed Sciences California WaterBlog. May 22.

Stompe, D. and P. Moyle, 2018. Striped bass in the San Francisco Estuary: insight into a forgotten past.  California WaterBlog, November 18,

O’Rear, T. and P. Moyle 2019. Remarkable Suisun Marsh: a bright spot for fish in the San Francisco Estuary.

Peter Moyle is a Distinguished Professor, Emeritus, with the Department of Wildlife, Fish, and Conservation Biology and an Associate Director with the Center for Watershed Sciences at the University of California – Davis.

Posted in Uncategorized | 2 Comments

A Change of Plans

1957 Water Plan map

Development map from the 1957 California Water Plan

by Jay Lund

The 1957 California Water Plan was ambitious for its time, and successful in its own way for a time. This plan was the ultimate major water project development plan arising from a century of struggles to orient and organize a society transplanted from the humid eastern US to California’s highly variable Mediterranean climate – a poor society experiencing abrupt climate change due to relocation.

The direction of water planning in California changed decades ago.  Following the 1976-77 drought, the environmental, engineering, and economic limits of State planning became increasingly apparent to local water agencies and users.  Local and regional water planning and investments have grown in importance and sophistication, and few areas realistically seek major new water supplies from the state (although they do seek state funding). State water plans have wandered and diminished in content, while growing in volume over this period.  (In contrast, state flood planning has improved markedly, as federal flood roles have diminished.)

In recent years, California Governors have sponsored a parallel, but more focused and nimble, State water planning effort.  Governor Brown’s administration established a California Water Action Plan, which established state policy initiatives with a fairly precise list of state agency actions in about 30 pages.  A breadth of fresh air which was useful in bringing together the State’s widely flung water-related agencies and programs.

Governor Newsom’s administration recently released a draft Water Resilience Portfolio plan, of slightly greater length (if you chop off the ponderous appendix 3).  This plan also emphasizes diverse relatively precise policy initiatives for state agencies, often in support of local and regional water problem-solving and with some aspirations to bring state agencies together.  It is a good read, clearly reflecting intense and diverse discussions over several months.

Among the plan’s many important and useful proposals, Proposal 28.2 seems especially timely: “Broaden the impact of the California Water Plan, required every five years by law, by increasing alignment and coordination between contributing state agencies. Assess progress toward regional water resilience in Water Plan updates. Inventory recurring state-published water-related plans and assess whether each should be continued, modified, consolidated, or discontinued.”

Effective water management is fundamental to the public health, economic prosperity, environment, and social well-being of Californians.  How to modernize planning for water’s many changing roles in California’s now-richer dynamic economy, diverse society and governmental structure, and struggling ecosystems, with a highly variable and changing climate is an important topic for policy discussion.

Further Readings

California Department of Water Resources, California Water Plan, 1957.  Now buried on the DWR web site at:

California Department of Water Resources, Central Valley Flood Protection Plan, 2012.  A very useful recent state plan now buried on the DWR web site at:

California Resources Agency, California Water Action Plan, 2014.

California Resources Agency, Draft Water Resilience Portfolio, 2020.

Lund, J. (2012), “Can solid flood planning improve all California water planning?,”, posted

Jay Lund is a Professor of Civil and Environmental Engineering at the University of California, Davis.

Posted in Uncategorized | Leave a comment

Rapid changes in the Sacramento-San Joaquin Delta both diminish scientific certainty and increase science’s value

Hump of hope

(source: Jessica Hagy) Change and discomfort can lead to improvement; too much discomfort leads to panic.

by Jay Lund

Conditions in the Sacramento-San Joaquin Delta are changing, changing in new ways, and changing rapidly.  Changes are rampant not only in climate, but also in ecosystem structure, economic structure and globalization, invasive species, infrastructure, water demands, environmental regulations, and societal objectives.  Although the Delta always has  changed, often rapidly, we are seeing new types of changes.

Major ongoing and expected changes for the Delta will be driven by:

  • Climate change, particularly rising temperatures and sea level
  • Continued species invasions
  • Worsening struggles for native and listed species
  • Continued Delta land subsidence, perhaps accelerated by higher temperatures
  • Greater economic demands for Delta water exports from implementing the Sustainable Groundwater Management Act
  • Growing water quality concerns for urban and agricultural water uses
  • Rising costs for levee maintenance, rehabilitation, and repair of failures
  • Frustration with the seeming ineffectiveness of traditional environmental regulations
  • Rising concern with inequalities in wealth and opportunities

These changes will be substantial, multi-faceted, and often rapid.  Some changes will be irreversible.  Many changes are inevitable.  Some will say today’s Delta is doomed.

It will be important for California to develop a scientific program that can help guide difficult policy and management discussions and decision-making through these challenges.  Changes in the organizational structure of policy and management also may be needed.  Even though some aspects of the Delta are doomed to change, many aspects will endure, and others will thrive differently, particularly if policy and management decisions adapt well. The Delta of the future will be different, and different sorts of science and management may be needed.

Managing with rapid changes

California has always had to manage with rapid changes in climate (with its wet and dry seasons and extreme variability between floods and droughts), population, economic structure (from mining to agriculture, to industry, to post-industrial within 150 years), and prevailing political philosophy (decentralization to centralization and back again).  Managing with such changes has made California unusually successful, but not without awkwardness, environmental and economic damage, and often prolonged dithering, delays, and controversy.

Although not all changes can be managed, a wide range of responses can help.  Options range from infrastructure (levees, conveyance, barriers, habitat development, channel changes), operations (export pumping, operable and emergency barriers, upstream water operations, and land uses), new approaches to environmental management (such as those proposed by the SWRCB and being negotiated), and changing (often reducing) demands for water and land, and environmental and land use expectations.

These actions should be viewed within a portfolio of activities organized to better manage the Delta.  No portfolio of actions will be perfect.  Even the best responses will have major costs to various interests, balanced and allocated somewhat by government.  We are not doomed with change, but we are in trouble.

Better organization and information can reduce overall costs and better inform their allocation.

Science for managing with rapid changes

Given rapidly-changing conditions, science is both more important and more challenged.

For rapidly changing conditions,

  • Ecological science, which traditionally had focused on equilibrium relationships among species and static environmental conditions, may be unable to respond to management needs through reliance on traditional long-term observations and experiments.
  • Social sciences, relying predominantly on collections of past and present data, must deal with rapid changes in demography, economic structure, and societal objectives in real time to give advice for changing times in the future.
  • Engineering must design and prepare for a wider range of conditions and societal expectations, which will change with time.
  • Physical sciences must develop insights with changing and uncertain boundary conditions and interactions with changes in ecological, engineering, and social conditions.

Most people seem both impressed and disappointed with today’s ability of science to provide insights into the Delta’s problems and solutions.  Science will be hard pressed to keep up with changes and help policy-makers, managers, and the public keep ahead of such changes.

Managing with inadequate management and science

Even if science cannot keep up with changes in conditions, the value of well-employed science increases when it helps make policy and management decisions better than they would be otherwise.  Effort is needed to make the organization and resources of science for the Delta’s problems more forward-looking and useful across the many agencies and interests which make Delta decisions.

Uncertainties and changing conditions make adaptive management both more difficult and more necessary.  Adaptive management requires an ongoing effort for scientific synthesis, usually using computer models, to more explicitly and rapidly integrate new knowledge into a logical science-based framework, so that it can be applied to develop insights for policy and management.

There will be failures.  But our use of science will be more successful if we develop effective organization and resources to respond to and learn from failures, rather than delay in hopes of developing and implementing a perfect plan.  Preparing for the likelihood of failures involves establishing farsighted policies for responding when species are becoming extinct, subsided lands flood, and salinity intrudes during drought – responding in ways that strategically improve long-term Delta conditions.  Despite our best efforts, artfully failing into solutions may be more promising and feasible than the technical and political development of ideal plans for responding to change.


The Delta is changing and will inevitably change in important ways that will affect all of California.

Science will become more important for managing the Delta, even as knowledge becomes less perfect due to rapid changes in conditions.  Without well-organized forward-looking science, management decisions and actions are likely to be still more imperfect.

Rapidly changing conditions for the Sacramento-San Joaquin Delta challenge both our organization and objectives for Delta science and management.  We must prepare for a changing Delta future, and for our limited ability to understand and manage.  (Otherwise, discomfort can become excessive.)

Further reading

Arax, M. (2019), The Dreamt Land: Chasing water and dust across California, Knopf, 527pp.

Berbela, J. and E. Esteban (2019), “Droughts as a catalyst for water policy change. Analysis of Spain, Australia (MDB), and California,” Global Environmental Change, Vol. 58, 101969.

Hollings, C.S. (ed.) (1978), Adaptive Environmental Assessment and Management, London:  John Wiley and Sons.

Kelley, R. (1989), Battling the Inland Sea, UC Press, Berkeley, CA.

Lund, J.R., J. Medellín-Azuara, J. Durand, and K. Stone (2018), “Lessons from California’s 2012-2016 drought,” J. Water Resour. Plan. Manag. 144 (10), 04018067.

Madani, K. (2019), “The Value of Extreme Events: What Doesn’t Exterminate Your Water System Makes it More Resilient,” Journal of Hydrology, Vol. 575, 269-272

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

Wiens, J., et al. (2017), “Facilitating Adaptive Management in California’s Sacramento–San Joaquin Delta,” San Francisco Estuary and Watershed Sciences, Vol. 15, No. 2, July, 15 pp.

Jay Lund is a professor of Civil and Environmental Engineering at the University of California – Davis.

Posted in Uncategorized | Leave a comment

Futures for Delta Smelt

by Peter Moyle, Karrigan Bork, John Durand, Tien-Chieh Hung, Andrew Rypeldelta_smelt

A recent biological opinion (BiOp) released by the U.S. Fish and Wildlife Service (FWS) concluded that a proposed  re-operation of California’s largest water projects will avoid driving the federally threatened Delta smelt to extinction. The plan proposes increasing water exports from the Central Valley Project and State Water Project, which will reduce water available for ecosystems and local uses. Both projects move water through pumps in the California Delta, a productive but sensitive ecosystem and home to the Delta smelt.

Under the federal Endangered Species Act (ESA), the FWS reviews federal agency actions to ensure that they will not drive listed species into extinction. In 2009, FWS reviewed the operation of the state and federal pumps that export water from the Delta and concluded in a BiOp that operation of the massive pumps jeopardizes the smelt’s continued existence. FWS required reduced pumping and other measures to protect the smelt, and those measure are currently in effect.

In 2019, the FWS again reviewed this new plan for the pump operations and concluded that many of the 2009 protections were actually not necessary and that the pumps could export significantly more water without jeopardizing the smelt. It draws this conclusion in two ways. First, the opinion notes that “recent abundance trends strongly suggest [the smelt] is in the midst of demographic collapse” and will likely go extinct without intervention. Based on this existing trajectory, the opinion concludes it won’t be the project’s fault when smelt disappear. Second, the opinion implies that, because agencies will spend $1.5 billion on habitat restoration, a production hatchery for smelt, and other measures, the net effect for the smelt will be positive. Based on these considerations, FWS concluded that the new operation plan would not drive the smelt to extinction, although it acknowledges extinction might happen anyway.

But the BiOp considers a very narrow question. The BiOp does not consider whether the plan is likely to improve the smelt’s status, and this BiOp in particular constrains its analysis so it does not meaningfully consider what is likely to happen to the Delta smelt under the new plans.

So, moving away from the narrow BiOp and considering the smelt in a broader context, what is going to happen to smelt in the wild? Is extinction likely?  This essay explores some issues affecting Delta smelt and suggests possible futures. This blog is a short version of a longer white paper (with references) available at:

The basic problem

The estuary where Delta smelt evolved no longer exists, and smelt are poorly adapted for the new conditions. Much of the water that once flowed through the estuary is stored or diverted upstream or exported by the south Delta pumps (Hobbs et al. 2017; Moyle et al. 2016, 2018). The smelt’s historical marsh habitats are now artificial channels and levees protecting agricultural islands. These hydrologic and physical changes make the Delta prone to invasion by non-native organisms, some of which disrupt food webs and confound restoration. Lower flows allow salts, toxic chemicals, and nutrients to accumulate. Harmful algae blooms occur regularly. As climate change further disrupts flows and increases temperatures, little historical habitat is left for sensitive species like smelt.

A tipping point

Smelt populations have probably been in gradual decline since at least the 1950s (Figure 1), but their population has collapsed since the 1980s, tracking the increase in water exports (Figure 2). This correlation is compelling, but other major system changes took place in the same period.  In the late 1980s, an invasive clam spread through the Delta, removing much of the smelt’s planktonic food supply. Concurrently, invasive weeds spread across the Delta, transforming former Delta smelt habitats into clear, food limited, lake-like environments. From 1969-89, the Delta tipped away from good smelt habitat to a novel ecosystem unfavorable to smelt.  This shift is practically irreversible, and the shift put the Delta smelt on a trajectory toward extinction as a wild fish. It is currently largely absent from surveys that once tracked its abundance.

smelt zero.png

Figure 1. Indices of Delta Smelt abundance in the Delta’s two longest-running fish sampling programs, the Summer Townet Survey (for juvenile smelt) and the Fall Midwater Trawl Survey (mostly pre-spawning subadults). Figure by Dylan Stompe.


Figure 2. Annual water export (left axis) from the south Delta by the State Water Project (red) and federal Central Valley Project (blue) in million acre-feet. Gray bars show droughts, when pumping was reduced primarily because of low inflows. Annual inflows of water to the Delta in million acre-feet (right axis) are open circles. Data: Figure: Moyle et al. 2018

Is habitat restoration the answer?

The BiOp relies in part on habitat restoration under California’s EcoRestore and other programs to support flagging smelt populations. There is little guarantee that this will make much difference to smelt, although many other native species will benefit.

First, the area under restoration is insufficient. Delta smelt originally inhabited an area about the size of Rhode Island, moving opportunistically to find appropriate conditions. Because Delta smelt are migratory and pelagic, smelt will overlap with restoration sites only occasionally. Successful habitat restoration would have to include multiple sites adjacent to water corridors, with abundant food and cool water, and in areas suitable for both spawning and rearing. Instead, the restoration approach has been more opportunistic than strategic, with restoration often focused on wetlands with willing sellers, regardless of suitability. We have little working knowledge whether we can build, connect, and manage these sites to benefit smelt.

Second, some projects rely on the idea that just creating tidal wetlands will be sufficient. It will not. Most Delta restoration sites are vulnerable to invasion by non-native species, which can subvert habitat solutions. Successful restoration sites require intensive, continuous management to meet even minimum expectations of restored habitat, and there is little incentive to actively manage “natural” restoration sites.

Third, current smelt populations are too small to be able to see an immediate (annual) response to habitat changes alone. Whatever steps are taken to protect smelt may be too little too late.

Finally, while water users hope that restoration provides an alternative to water use, this is not realistic. Successful restoration requires water flowing across the landscape. Moving water promotes the exchange of nutrients, controls introduced species, distributes food production, and creates habitat structure. Flows help restorations mimic natural environments and improves their effectiveness. Flows give managers better control of where Delta smelt end up during the spring, summer and fall. Habitat with minimal outflow is an empty promise.

If we are serious about providing the outflow required for habitat for smelt and other fishes, a substantial environmental water right is needed to provide reliable water to interact with physical habitat to produce food and shelter. Allocation of a sufficient water right is difficult to envision, given the current conflicts in the Delta, but California’s Bay Delta Plan, currently under development, generally proposes significant water for Delta fish, based on a percentage of the rivers’ natural flows. If this water were treated as a right under the control of an ecosystem manager, Delta smelt might have a chance of more than extinction avoidance—they might recover.

Hatchery Smelt

The BiOp also relies on hatchery supplementation of wild stocks to mitigate smelt impacts. The UC Davis Fish Conservation and Culture Laboratory (FCCL) has maintained a genetically managed Delta smelt population since 2008, but low wild smelt numbers complicate its operation. FWS allows FCCL to incorporate 100 wild Delta smelt into its population annually, to maintain genetic diversity, but recently the FCCL has been unable to capture 100 individuals. Without those fish, inbreeding might rapidly increase and add further uncertainty to the success of supplementation.  Other hatchery supplementation programs, such as those for salmon, have had limited success in re-establishing self-sustaining wild populations. The smelt efforts will likely follow suit (Lessard et al. 2018).


 Based on our experience and research in the Delta, any benefits from the habitat restoration and hatchery plans in the new opinion are too uncertain to reliably offset negative impacts of increased water exports. The Delta has changed so much that suitable habitat for Delta smelt is increasingly lacking. Large-scale restoration projects that provide habitat and food for smelt will at times need increased outflows.  Desperate measures such as a production smelt hatchery and establishment of smelt in reservoirs may provide a veneer of ‘saving’ smelt for a while, but they seem unlikely to prevent extinction in the long run. In short, the smelt are likely to continue on their extinction trajectory. The following seem the most likely alternative futures for Delta smelt, in rough order of likelihood:

  1. Extinction of the wild population in 1-5 years, with a population of increasingly domesticated hatchery smelt kept for display and research purposes.
  2. Persistence of a small wild population in a few limited intensively managed habitats, until these habitats cease being livable from global warming and other changes.
  3. Global extinction after wild populations disappear and hatchery supplementation or replacement fails.
  4. Replacement of the wild population with one of hatchery origin, continuously supplemented.
  5. Persistence of wild populations as the result of supplementation and through establishment of reservoir populations.

The authors are at the University of California – Davis, Center for Watershed Sciences.

Further reading

Hobbs, J.A, P.B. Moyle, N. Fangue and R. E. Connon. 2017. Is extinction inevitable for Delta Smelt and Longfin Smelt? An opinion and recommendations for recovery.  San Francisco Estuary and Watershed Science 15 (2):  San Francisco Estuary and Watershed Science 15(2). jmie_sfews_35759. Retrieved from:

Lessard J., B. Cavallo, P. Anders, T. Sommer, B. Schreier, D. Gille, A. Schreier, A. Finger, T.-C. Hung, J. Hobbs, B. May, A. Schultz, O. Burgess and R. Clarke (2018) Considerations for the use of captive-reared delta smelt for species recovery and research, San Francisco Estuary and Watershed Science 16(3), article 3.

Moyle, P. B., L. R. Brown, J.R. Durand, and J.A. Hobbs. 2016. Delta Smelt: life history and decline of a once-abundant species in the San Francisco Estuary. San Francisco Estuary and Watershed Science14(2)

Moyle, P.B., J. A. Hobbs, and J. R. Durand. 2018.  Delta smelt and the politics of water in California. Fisheries 43:42-51.

Moyle, P.B., K. Bork, J. Durand, T-C Hung, and A. Rypel. 2019. “Futures for Delta Smelt”. Center for Watershed Sciences white paper, University of California – Davis, 15 December,


Posted in Uncategorized | 4 Comments

Jobs per drop irrigating California crops

Various crops grown in Monterey County. * FOR EDITORIAL USE ONLY *

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

By Josué Medellín-Azuara, Jay Lund and Richard Howitt

Reposted from Apr 28, 2015 (an oldie, but goodie!)

Some of the most popular drought stories lately have been on the amount of what water needed to produce food from California, as a consumer sees it — a single almond, a head of lettuce or a glass of wine. The stories are often illustrated with pictures of common fruits, nuts and vegetables in one column and icons of gallon water jugs representing their water usage in the other.

But there are more than two columns to this story. The amount of water applied to crops also translates into dollars and jobs — the main reasons for agriculture’s existence in California. 

Here are multiple columns of data to better understand California’s crop water use and the revenues and jobs it is intended to produce.

Prepared by Josué Medellín-Azuara, Research Scientist, UC Davis Center for Watershed Sciences.

Prepared by Josue Medellin-Azuara with the assistance of Nadya Alexander, UC Davis Center for Watershed Sciences. Contact:

The charts below illustrate the data. A principal conclusion is that crops with the highest economic “pop per drop” — revenue per net unit of water — also usually have the highest employment per land area and water use.barchart





Other observations from the data:

  • As a global food basket for fruits, vegetables and nuts, California’s net crop water use in 2010 was about 20 million acre-feet on 9.4 million acres of irrigated land. Gross revenues were about $36.7 billion.
  • The top 5 crop group 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 the farming is highly mechanized, requiring relatively little 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 about 400,000 full-time jobs (or their equivalent), including 172,000 in crop production, 29,000 in livestock and dairies and 193,000 in agricultural support services (contract labor). Some studies suggest that many California farm jobs  are part-time, with an average of two jobs for each full-time equivalent job.

California agriculture will use less water this year and in the long run. Several factors will lead to long-term reductions in farm water use in many areas of the state. Those include the state’s new groundwater legislation, ongoing salinization and urbanization of cropland, and increasing environmental water requirements.

The drought has raised understanding of these inevitable reductions. But the growing market value of California’s specialty crops and growing yields per acre and per gallon will keep California agriculture healthy in most cases

Growing scarcity of water 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 distract from discussions needed for long-term progress.

Josué Medellín-Azuara, Jay Lund and Richard Howitt are with the UC Davis Center for Watershed Sciences. Medellín-Azuara is a research scientist, Howitt is a professor emeritus of agricultural and resource economics, and Lund is a professor of civil and environmental engineering and director of the center.

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

Posted in Agriculture, Drought | Tagged , , , , , | 2 Comments

Turbidity and Insights on Flow-Habitat-Fish Abundance Curves in Policy-making

by Jay Lund

California’s water policy community continues to be embroiled on how best to manage what remains of California’s native aquatic ecosystems, particularly for the Sacramento-San Joaquin Delta and its tributaries.  One aspect of this controversy is the dedication and use of habitat and flow resources to support native fishes.

There is general agreement that California’s native fishes need both water and aquatic habitat.  After this, water management for native ecosystems becomes more complex, uncertain, and controversial.

Various authors have produced or explored relationships between native fish abundance, flow, and habitat for California’s Sacramento-San Joaquin Delta (see some under further readings below).  For policy-making, there is a tendency and probably a need to simplify the world by trying to believe such relationships.  Scientifically, the policy insights from such relationships might be quite limited, but such curves might have some utility nonetheless for helping us stagger towards better management.

Consider the alternative general fish abundance-outflow-habitat curves in the figure: flow-habitat-abundance curves

Axes. Even the axes for this plot will be a gross simplification.  For net outflow, it is quite important to know: a) when outflows occur seasonally, together with Delta inflow conditions, b) internal Delta flow conditions, c) the recent time history of Delta inflow and internal flow, and d) upstream habitat conditions that supply nutrients, prey, and young for species of interest.  Similarly, the habitat area is a gross amalgam of different types of habitat being managed differently in different parts in the Delta and upstream to provide different habitat, food, and nutrients at different times of year suitable for different native species.  Such grotesque simplification is a cost of the simplicity needed to start organizing a problem.

Thresholds for extinction.  On the diagram, there should be general agreement that some minimum thresholds of Delta outflow and habitat are needed for native species to subsist (dotted lines).  We should despair on knowing such thresholds exactly.  Thresholds for extinction are unlikely to be fixed and could easily vary with species, hydrologic conditions, antecedent conditions, and how these annual conditions are managed seasonally and locally within the Delta.  These thresholds should be seen something like vibrating limits, where even getting near them increases risks for extinction and costs for future species recovery.  Quantifying such limits as policies will be unavoidably controversial and scientifically perilous.

More flow and habitat help fish abundance.  There is general agreement that more flows and more habitat, if properly managed seasonally and geographically, should lead to more fish.  Consider the dashed diagonal line on the diagram, along which fish abundance always increases with northeast movement.

Substitution of resources for fixed fish abundance.  Now pick some arbitrary point on the diagonal, beyond the zone of certain extinction, a point that supports a fish abundance of n with equal dedications of aggregated habitat and flow.  Is this the best way to have an abundance of n fish?  Maybe a little more flow with a little less habitat (or vice versa) might result in more fish or less economic cost for providing flow and habitat for n fish?

Four possible shapes for a habitat-flow-fish abundance curve are suggested for achieving n fish.  These are curves A, B, C, and D on the diagram. These curves would shift outward for greater fish populations, and inward towards the extinction thresholds for smaller fish populations.  (For explication, the quantification of fish here is just as grotesque, averaged, and un-nuanced as the quantification of flow and habitat. These curves also vibrate stochastically, implying some probability of stable recovery increasing with higher populations.)

No substitution of flow and habitat.  Curve A shows no possibility for substituting flow for habitat in supporting fish.  Here, each fish needs fixed amounts of both habitat and flow, with fish abundance limited only by the most limiting resource.  Any extra flow or habitat above the limiting amount is wasted, except that, given uncertainties, an additional resource reduces the likelihood that resource is limiting, but makes it more likely that other resources are limiting.

Fixed rate of substitution.  If a constant fixed substitution of flow for habitat exists, then line C describes how flow and habitat trade-off to produce a fixed aggregated fish abundance.  From a management perspective, if flow is more easily gotten politically or economically than habitat, then fixed substitutability would lead investing all in flow (as near the threshold as one dared), to get the most fish.

Substitutions that encourage balance.  Where the total habitat and flow consists of heterogeneous sub-areas of habitat and flow with different abilities to support fish abundance, then some substitutability of flow and habitat will occur from investments in different mixes of sub-areas.  So spatial heterogeneity could create a degree of substitutability, perhaps like curve B.  For this curve, fish abundance would likely increase quickly as one exceeds a flow or habitat extinction threshold, and be maximized with a balancing of fish and flow investments.  For curve B, maintaining a given fish abundance n with less and less flow or habitat requires more rapid increases in the other resource to compensate (perhaps across different sub-areas), until the extinction threshold is approached.

Some substitutions encourage extremes.  If additional flow or habitat above an extinction threshold only slowly improves fish abundance, then curve D seems the likely flow-habitat-abundance curve shape.   This seems a perilous ecosystem to manage because, like the linear case of curve C, one is tempted to maximize abundance by investing all in flow or habitat (not both) as close to the extinction threshold of the other resource as one dares.

Keep out of the zone of extinction.  Of course, this discourse is only useful if enough flow and habitat resources exist to escape the zone of extinction, defined by the thresholds.  Indeed, one needs to invest in both resources to be far from them, as their exact locations vary with time and have uncertainty.

Other important things.  Alas, this diagram tempts the suggestion that flow and habitat (even as grossly considered here) are the only important factors.  The management of invasive species, ocean conditions, climate change, and other things may shift these curves with time, gently or abruptly.

Conclusions.  So, what can be learned from this?

  1. Managing flow and habitat for native Delta fishes is an unavoidably grotesque, complex, and uncertain problem. Whatever policies and management are adopted will probably not work as hoped for.  So a considerable effort is needed in developing institutions, resources, science, and synthesis that can adaptively manage.
  2. If we think we know the general shape of the substitutability of flow and habitat in supporting fish abundance, it leads us to either investing predominantly one resource or the other as near the extinction threshold as we dare if substitutability is constant (curve C) or concave (curve D), with more balanced investments in flows and habitat if there is no substitution (curve A) or weak substitution (curve B). The shape of substitution trade-offs determines the best strategic approach.
  3. If there is no substitutability of flow and habitat for fish abundance (curve A), yet both are vital, then it is important to seek the proper balance of resources. A balanced strategy also is best, but less strongly, if increasing flow or habitat would be needed to make up for a scarcity of the other (curve B) and both resources are costly.
  4. In all cases, managers should stay away from the extinction zone. Some flow-habitat-abundance shapes tempt one to find and manage at the edge of extinction edge, despite its instability.  For these substitution shapes (curves C and D), how close should we dare get to the extinction threshold?
  5. To find the proper balance and avoid extinction thresholds requires vigorous science-based adaptive management, based on ecological or mechanistic theory and models supported by field data and experiments.
  6. Although these general policy lessons have some value, settling on an initial resource policy and allocation can obscure the more difficult problems of how to manage these resources locally within the Delta seasonally and inter-annually. This more challenging detailed level of management and science must be workable for the ideal curve shapes and policies discussed above to hold true.

Hopefully this adds more insight than turbidity.

Jay Lund is the Director for the Center for Watershed Sciences and Professor of Civil and Environmental Engineering at the University of California – Davis.  This blog benefited (probably not enough) from conversations with John Durand, Peter Moyle, Wim Kimmerer, and Cathryn Lawrence.

Further readings

Bennett, W.A., and P. B. Moyle.  1996.  Where have all the fishes gone: interactive factors producing fish declines in the Sacramento-San Joaquin estuary. Pages 519-542 in J. T. Hollibaugh, ed. San Francisco Bay: the Ecosystem. San Francisco: AAAS, Pacific Division.

Grimaldo, L. F., T. Sommer, N. Van Ark, G. Joes, E. Hoilland, P.B. Moyle, B. Herbold, and P. Smith. 2009. Factors affecting fish entrainment into massive water diversions in a freshwater tidal estuary: Can fish losses be managed? North American Journal of Fisheries Management 29:1253-1270.

Hanak, E., J. Lund, A. Dinar, B. Gray, R. Howitt, J. Mount, P. Moyle, and B. Thompson. 2011.   Managing California’s Water. From Conflict to Reconciliation.  PPIC, San Francisco. 482 pp.

Healey, M., W. Kimmerer, G. M. Kondolf, R. Meade, P. B. Moyle, and R. Twiss. 1998.  Strategic plan for the Ecosystem Restoration Program. CALFED Bay-Delta Program, Sacramento. 252 pp.

Kimmerer, W. (2002), “Physical, Biological, and Management Responses to Variable Freshwater Flow into the San Francisco Estuary,” Estuaries Vol. 25, No. 6B, p. 1275–1290 Dec.

Kimmerer, W., E. Gross, and M. MacWilliams (2009), “Is the Response of Estuarine Nekton to Freshwater Flow in the San Francisco Estuary Explained by Variation in Habitat Volume?,” Estuaries and Coasts (2009) 32:375–389.

Kimmerer, W., T. Ignoffo . K. Kayfetz, and A. Slaughter (2018), “Effects of freshwater flow and phytoplankton biomass on growth, reproduction, and spatial subsidies of the estuarine copepod Pseudodiaptomus forbesi,” Hydrobiologia 807:113–130.

Lund, J., E. Hanak, W. Fleenor, W., R. Howitt, J. Mount, and P. Moyle. 2007. Envisioning futures for the Sacramento-San Joaquin Delta. San Francisco: Public Policy Institute of California. 284 pp.

Moyle, P. B., R. Pine, L. R. Brown, C. H. Hanson, B. Herbold, K. M. Lentz, L. Meng, J. J. Smith, D. A. Sweetnam, and L. Winternitz.  1996.  Recovery plan for the Sacramento-San Joaquin Delta native fishes. US Fish and Wildlife Service, Portland, Oregon.  193 pp.

Nobriga, M. and J. Rosenfield (2016), “Population Dynamics of an Estuarine Forage Fish: Disaggregating Forces Driving Long-Term Decline of Longfin Smelt in California’s San Francisco Estuary,” Transactions of the American Fisheries Society, Volume 145, 2016 – Issue 1


Posted in Uncategorized | 9 Comments

Is it drought yet? Dry October-November 2019

by Jay Lund

So far, October and November 2019 has been the driest (or almost the driest) beginning of any recorded water year with almost zero precipitation. (The 2020 water year began October 1, 2019 – so you might have missed a New Year’s party already.)

Should we worry about a drought yet?

Yes, this is California, where droughts and flood can happen in any year, and sometimes in the same year.  Water managers should always worry about drought (and floods) at all times in all years, especially during the November-March wet season.

No, not especially anyway, because we are still early in the 2019 wet season, most precipitation falls later in the water year, and there is not strong correlation between October-November precipitation and total water year precipitation.

The California Department of Water Resources does a great job assembling current and historical data on water conditions, updated daily on the California Data Exchange Center website.  It is a wonderful data playground.

Plotting historical 1921-2018 northern Sierra precipitation for October+November against water year total precipitation gives the following scatter-plot, correlation, and statistics.

Water year precip scatter plot

Having little precipitation in October + November still means the year overall could be wet or dry, but averages a bit drier

From this plot, statistically, every inch lost in October+November precipitation averages 1.4 inches less total water year precipitation for the northern Sierras.  Since October+November averages 9.3 inches of precipitation historically, if it does not rain for the rest of November (a storm is in the forecast), then we would have on average 13 inches less than average northern Sierra precipitation this year. (Average historical northern Sierra precipitation is 50 inches.)  Although this is not good news, it is not doom.  Given the high variability of California’s climate and poor correlation between monthly precipitations, anything could happen.

It is comforting that California’s reservoirs are relatively full today, which provides something of a buffer against dry years and shorter droughts.  And the last few wetter years also have refilled groundwater some from the last drought.

The these recent dry months lengthened this year’s fire season (if anyone had not noticed).  With a warming climate and more houses in fire-prone areas, any fire season extension due to dry weather becomes increasingly threatening.


Will California have a drought? Yes.

Is the next drought beginning this year?  Perhaps, but probably not.  Still, water managers should (and usually do) prepare for drought, even if recent months had been wet – because it will become dry eventually.

I am looking forward to rain (and hopefully snow).  A good storm is forecast for later this week, so we get at least some precipitation in November, slightly improving odds of a wetter year.

Jay Lund is a professor of civil and environmental engineering and director of the Center for Watershed Sciences at UC Davis. 

Further Reading

Lund, J. (2015), “The California Drought of 2015: January,”, January 5, 2015.

California Weather Blog,

L’Heureux, M., “Seeing Red Across the North Pacific Ocean”, October 23, 2019:  A recent discussion on Pacific blobs affecting drought in California.

Posted in Uncategorized | Leave a comment