Managing source water for maximum benefit in a challenging climate

By Amber Lukk and Ann Willis

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

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

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

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

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

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

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

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

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

Further Reading:

Börk, K., A.L. Rypel, S. Yarnell, A. Willis, P. Moyle, J. Medellin-Azuara, J. Lund, and R. Lusardi. 2022. Considerations for developing an environmental water right in California.

Garbach, K., Milder, J.C., Montenegro, M., Karp, D.S., and DeClerck, F.A.J. 2014. Biodiversity and ecosystem services in agroecosystems. Encyclopedia of Agriculture and Food Systems 2: 21-40.

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

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

Vissers, E. 2017. Low Flows, High Stakes: Lessons from Fisheries Management on Mill, Deer, and Antelope Creeks During California’s Historic Drought. Hastings Environmental Law Journal 23:169.

Willis, A.D., R.A. Peek, and A.L. Rypel. 2021. Classifying California’s stream thermal regimes for cold-water conservation. PLOS ONE 16(8): e0256286.

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The Flow of California Water Policy – A Chart

by Jay Lund

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

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

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

Further reading

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

Dynamic inaction –;

Yes Minister –

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Are native fishes and reservoirs compatible?

By Peter B. Moyle and Anna M. Sturrock

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

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

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

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

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

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

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

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

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

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

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

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

Further reading:

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

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

Rypel, A.L., C.A. Parisek, J. Lund, A. Willis, P.B. Moyle, Yarnell, S., and K. Börk. 2020. What’s the dam problem with deadbeat dams?,

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

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

Willis, A., R. Peek, and A.L. Rypel. 2021. Dammed hot: California’s regulated streams fail cold-water ecosystems.

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

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

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

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

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

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

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

Figure 3. Social media posts by local naturalist Damon Tighe @damontighe and others captured the magnitude of the mass mortality event in the San Francisco Estuary.

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

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

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

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

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

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

Further Reading:

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

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

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

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

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

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

Thomas, M.J., A.L. Rypel, G.P. Singer, A.P. Klimley, M.D. Pagel, E.D. Chapman, N.A. Fangue. 2022. Movement patterns of juvenile green sturgeon (Acipenser medirostris) in the San Francisco Bay Estuary. Environmental Biology of Fishes

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

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

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

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

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

By Abigail E. Ward and Miranda Bell-Tilcock

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

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

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

Kavi McKinney showing a recently removed salmon eye.

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

Matthew Salvador removes a muscle sample for thiamine analysis.

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

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

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

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

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

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

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

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

Further reading:,in%20converting%20food%20into%20energy,Researchers%20Probe%20Deaths%20of%20Central%20Valley%20Chinook,Possible%20Ties%20to%20Ocean%20Changes&text=Deficiency%20in%20Vitamin%20B1%20linked,mortality%20in%20California%20fish%20hatcheries.

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

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

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Innovative Approaches for Flood Insurance Affordability

by Kathleen Schaefer

People have been asking if Hurricane Ian will push the National Flood Insurance Program (NFIP) into an affordability crisis?  Some argue the NFIP is already there.

Two weeks ago, the Greater New Orleans, Inc.’s Coalition for Sustainable Flood Insurance (CSFI) reported that NFIP’s new pricing strategy makes NFIP insurance premiums unaffordable. The report’s authors assert that increasing NFIP premiums and fees will lead to fewer households with flood insurance, and recommend slowing premium increases until an affordability program can be developed and funded. An examination of historical NFIP purchases by California households supports this assertion. We suggest a different affordability approach—a community-scale public/private partnership that makes insurance affordable by focusing on community resiliency and recovery.

The NFIP is the primary means for businesses, homeowners, and renters to insure for flood risk. The NFIP is the world’s largest single-peril insurance operation. Since 1978, the NFIP has paid over $72 billion in claims, helping approximately 2 million policyholders recover (Maurstad, 2021). A primary goal of the NFIP is to increase the number of households with flood insurance.

On October 1, 2021, FEMA implemented a new premium pricing method — Risk Rating 2.0 (RR2.0). Under RR2.0, the NFIP uses the same type of catastrophic loss modeling as private flood insurers. Under year one of RR2.0, FEMA estimated premiums would increase for 77% of current policyholders, some increasing as much as $240 per year. (FEMA 2018). The CSFI study estimates fully implemented RR2.0 increases in some areas of Texas and Florida could be $1009 to $3134 per year. A UC Davis estimate, covered in a previous California Water Blog, suggests that for California, changes from RR2.0 will be mixed.

FEMA asserts that RR2.0 is needed to make the program financially stable and to modernize setting premiums. The NFIP program was over $20 billion in debt even before Hurricane Ian. Program administrators also believe that premiums, based on actuarily sound rates, will help to communicate flood risk to the public and policyholders (Maurstad, 2021). While this may be true, as premium costs increase, the number of insured households decreases.

Nationally, the number of NFIP policies in force has declined from an all-time high in 2009 of 5.70 million policies in force to a low of 4.54 million by June 2022 (Insurance Information Institute 2021) as quoted in (CSFI 2022). In California, except for a spike in 2015, the number of NFIP policies has also steadily declined (Figure 1). The spike in policies correlates with Godzilla El Niño media stories in the major media markets. California’s Mediterranean climate oscillates between wet and dry winters (Swain et al., 2018). The sharp increase in policies suggests that some consumers respond to media reports of upcoming wet winters with a decision to buy flood insurance.  

Figure 1. Total number of California residential NFIP purchases annually from January 1, 2009, to December 31, 2021, compiled from NFIP Open Source data. Except for 2015, the number of NFIP policies has decreased from a high in 2009 of more than 300,000 policies to less than 200,000 in 2021.

How does price affect insurance purchase decisions?

To evaluate the impact of price on buying habits of California households, NFIP purchase records were broken into full risk-rated and non-full risk-rated policies. Full risk-rated policies are generally required to be purchased by a lender and usually exceed $1000/year. Non-full risk-rated policies are grandfathered or preferred risk policies, and generally cost less than $600/year.

When the price and take-up rate data for full risk-rated policies (more expensive and generally mandatory purchases) are separated from those of non-full risk rated (cheaper, discretionary purchases), an interesting pattern emerges. When premiums exceed $1000 per year, the total premiums paid steadily decline (Figure 2). When premiums are less than $600 annually, the total premium paid increases (Figure 3). This suggests that keeping premiums below $600 per year would increase both premium income and the number of households protected by insurance (as well as the NFIP’s potential financial exposure).

Figure 2. Fully Rated Residential Policies. Comparison of the (A) number of policies, (B) total premium paid, and (C) median policy price for fully rated residential policies during the period from 2009 to 2021. Graph A shows that California’s total number of residential NFIP policies has steadily declined. Graph B shows that the total paid residential premium peaked in 2010 and again in 2015 and has generally declined. Graph C shows that the median policy price increased sharply after HIFFA was passed in 2014. This set of graphs shows that the total number of policies and the total premium paid generally decline when the median policy price exceeds $1000. Source: FEMA open source data compiled with R software.
Figure 3.  Non Fully Rated Residential Policies. Comparison of the (A) number of policies, (B) total premium paid, and (C) median policy price for fully rated residential policies during the period from 2009 to 2021. Graph A shows that the total number of residential NFIP policies issued in California increased significantly with media news of a wet winter, but declined over time. Graph B shows that the total residential premium paid peaked in 2015 and has generally stayed about the same since that year. Graph C shows that the median policy price increased sharply after HIFFA was passed in 2014. This set of graphs shows that the total number of policies and the total premium paid remain stable when the median policy price is less than $600.  Source: Data compiled from NFIP Open Source data using R open source software.

Almost all studies of variables thought to affect insurance purchase decisions (e. g. price, personal beliefs, risk awareness, and income) have been for Texas, Florida, the Midwest or the Gulf Coast (Atreya, Ferreira, and Michel-Kerjan 2015; Michel-Kerjan, E., and Carolyn Kousky. 2010a; Browne, Mark J, and Robert E Hoyt 2000). California may be different. Our floods are primarily from atmospheric rivers, not hurricanes (Konrad & Dettinger 2017). California’s flood storage systems (e.g. Oroville, Shasta, and Folsom Dams) work in tandem with water storage systems. California has a Mediterranean climate that goes for months or sometimes years with no significant rainfall. And in the last 20 years, California has invested billions in upgrading and improving flood control infrastructure. These California characteristics can change flood risk and influence flood insurance purchasing decisions.

When the historical record of total non-risk rated premiums (cheaper discretionary policies) is broken into components. It shows many California households purchase flood insurance in the fall at the onset of expected wet weather. If the media alerts the public of an impending “Godzilla El Niño”, more homeowners respond by purchasing flood insurance. It also shows that when the seasonal trend and random effects are filtered out, aggregated premium payments show a clear upward trend.

Figure 4. A statistical decomposition of total NFIP premiums for non-fully rated policies in California’s four largest flood insurance markets: Los Angeles, Orange, Sacramento, and San Diego Counties. Purchases by month show a clear seasonal and upward purchase trend and the impact of media stories on the “Godzilla El Nino”—Source: Data compiled from NFIP Open Source data using R open source software.

This analysis suggests that if policies are priced around $600 or less, there is a willingness to buy. However, once the policy exceeds $600, homeowners are less willing or able to purchase flood insurance. For many California residents, this corresponds to a price of roughly one to two percent of the annual household income. Instead of creating a new bureaucracy to support subsidies and low-income grants, California might build public/private partnerships at the community level that deliver a base level of insurance to everyone for $600. Global reinsurers have expressed an interest in providing $100,000 to $300,000 of coverage to consumers in the SFHA for less than $600. A $100,000 policy would cover 85% of all NFIP historical claims payments in California.

While some reinsurers have expressed willingness to provide $100,000 worth of coverage for $600, getting to a price of $600 in some communities may mean that the community or the state may need to pick up the first layer of loss. This might take the form of a $10,000 recovery payment. A community-based resiliency and recovery program providing a $10,000 recovery payment that might be accepted as meeting the NFIP deductible would save residents 30-40% on an NFIP policy. It would also provide a financial incentive for communities to manage their flood risk proactively.

Getting to a price of $600 might also mean that the State might cover the top layer of risk, the risk greater than $100,000. The Paterno Decision showed that the state of California might ultimately have to pay should a State Plan of Flood Control Levee fail. A community-based insurance resiliency and recovery program provides a way for the state to manage this risk proactively. It would also provide a financial incentive for the State to continue to invest in flood management, even during times of drought.

A pilot community-based resiliency and recovery program has been initiated for Delta Legacy Communities. With the support of California and DWR, other pilot programs are being explored in the Central Valley and along the coast. The concepts of a community-based resiliency and recovery program, while still evolving, are the result of a multi-year collaboration with private industry, academia, the Department of Water Resources, and the Department of Insurance.


This analysis suggests several things. Expensive flood insurance is a poor tool to use to communicate flood risk. If premiums could be held to between 1 to 2% of the annual income, the NFIP would likely increase total premiums collected and increase the number of insured households. Focusing on reducing risk rather than establishing affordability plans is likely to be more successful. California has an opportunity to lead the nation in innovative insurance arrangements. In this, Public/Private/Community/Academic partnerships are critical to providing more affordable, accessible flood insurance.

Further reading

Atreya, Ajita, Susana Ferreira, and Erwann Michel-Kerjan. 2015. “What Drives Households to Buy Flood Insurance? New Evidence from Georgia.” Ecological Economics 117: 153161.

CSFI. 2022. “An Evaluation of Risk Rating 2.0 Impacts on National Flood Insurance Program Affordability.” Coalition for Sustainable Flood Insurance.

Browne, Mark J, and Robert E Hoyt. 2000. “The Demand for Flood Insurance: Empirical Evidence.” Journal of Risk and Uncertainty 20 (3): 291306.

FEMA. 2018. “An Affordability Framework for the National Flood Insurance Program.” Report to Congress. Washington, D.C.: FEMA.

———. n.d. “Flood Insurance Manual, Effective October 1, 2018 | Fema.Gov.” Flood Insurance Manual, Effective October 1, 2018. Accessed March 31, 2019.

Insurance Information Institute. 2021. “Spotlight on: Flood Insurance”. Retrieved July 8, 2022, from Insurance Information Institute:

Michel-Kerjan, E., and Carolyn Kousky. 2010a. “Come Rain or Shine: Evidence on Flood Insurance Purchases in Florida.” Journal of Risk and Insurance 77 (2): 369397.

Konrad, C. P. and Dettinger, M. D. 2017. “Flood runoff in relation to water vapor transport by atmospheric rivers over the Western United States, 1949–2015.” Geophysical Research Letters, 44(22):11–456.

Maurstad, D. 2021. U.S. Senate Committee on Banking, Housing, and Urban Affairs: Hearing Entitled Reauthorization of the National Flood Insurance Program, Part II. Washington, DC. Retrieved from

 Swain, D., Baird Langenbrunner, J David Neelin, and Alex Hall. 2018. “Increasing Precipitation Volatility in Twenty-First-Century California.” Nature Climate Change 8 (5): 427.

Kathleen Schaefer is a PhD student in Civil and Environmental Engineering at the University of California – Davis and a former Regional Engineer with FEMA.

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Being patient and persistent with nature

By Andrew L. Rypel

Upper Putah Creek, April 2018, photo downloaded from
Former UC Davis graduate student Mackenzie Miner showing a Putah Creek Chinook salmon carcass. Photo from

In the coming weeks, fall-run Chinook salmon (Oncorhynchus tshawytscha) will appear in Putah Creek again to spawn. The fact that any salmon spawn in Putah Creek is a small miracle, and testimony to the resilience of salmon and a small army of people that worked tirelessly to restore and care for the ecosystem. UC Davis Emeritus Distinguished Professor Peter B. Moyle was one of the linchpins in making this happen. Field data from the classes he taught at UC Davis were used in the legal proceedings to improve the creek in the late 1990s, partly because no one else studied the stream. Like many California rivers, flows are an organizing ecological factor, driving the assembly of native and non-native fishes in Putah Creek (Marchetti and Moyle 2001). Since the Putah Creek Accord in 2000, several changes to water management have proved beneficial to native fishes (Keirnan et al. 2012, Jacinto 2020). These include increased spring flows, reduced water temperatures, increased summer flows to prevent the creek from drying, and fall attraction flows for migratory native fishes, like salmon. There was hope at that time that collectively these actions might one day bring anadromous salmon back to the system. These hopes were realized in fall 2013, when <10 adult Chinook salmon were found in the stream. Most of the recolonizing salmon turned out to be strays from California hatchery efforts (Willmes et al. 2020). Numbers increased in most years since (Chapman et al. 2018), until an unfortunate fish kill last year coincided with an usual early fall storm. One step forward and two steps back. Actions are being taken this year and future years to prevent a repeat and put the Putah Creek salmon population back on the growth trajectory. But, recovery is clearly not rapid.

Ecosystems are unsurprisingly highly complex and dynamic. Disturbances are common, and interactions among species can be intense and important (Winemiller 1989). Perhaps for these reasons, populations express tremendous heterogeneity in space and time (Rypel 2021; Blog digesting this paper). On top of this are myriad ways humans impact ecosystems: climate change, habitat loss and fragmentation, invasive species, pollution, overfishing, and genetic manipulation. It’s no wonder nature is hurting globally. This week, World Wildlife Fund (WWF) released a sobering report highlighting the perilous state of biodiversity on Earth. The report emphasized the decline of freshwater biodiversity. And although there are issues with precision of numbers presented in the report, the overriding signal of biodiversity decline is unmistakable, especially in freshwater. We are impacting freshwater environments on scales never seen before, and the losses continue to mount.

Food web depiction of a floodplain river (Cano Maraca), Venezuala from Winemiller 1989. This web includes interactions between 72 predators and 113 prey and clearly shows the degree to which food webs can be exceedingly complex. Recovery of broken links may also be complicated.

It’s easy to ‘get down’ about Earth’s sad news, and even be paralyzed by it. But many bright spots also exist. At the university, daily, I see large bunches of young people absolutely determined to help protect and recover our Planet, including its frail biodiversity. There are growing examples of ecosystem rehabilitations that actually work, species coming off the Endangered Species Act, and examples using Indigenous knowledge showing how management can be protective, inclusive, and honorable (Morin et al. 2021). Quietly, the largest dam removal in US history is being prepared in California and Oregon. This effort is vital to Indigenous peoples of the Klamath River whose families have depended on the river for generations, and is an opportunity for new partnerships. While conservation success stories are more rarely identified in the media, when one looks closely, they are there. And there is a motif to these stories, not always, but generally. 

The success stories are not overnight. They are usually built the hard way – through collaboration, relationships, years of investment, long-term monitoring, and of course, sound science. Any small survey of the success stories clearly shows that nature is often ready to come back – when we give it a chance. We saw glimpses of this dynamic during Covid lockdowns, when animal behaviors quickly started to shift. Yet fuller or even modest ecological recoveries can take years, decades, and maybe longer. Several examples from my own work support this notion. Spring-run Chinook salmon were reintroduced into the San Joaquin River in 2013 and 2014; and while there have been successes, there is still a long way to go, and water quantity remains a principal limiting factor in recovery. On the other side of the Delta, we are actively trying to use agricultural floodplains (rice fields) to mimic natural floodplains. And again, while there have been some successes, and much promise for the future, there remains a road ahead, with much science still needed to work the whole thing out. In some cases, the need to take a long view is necessary just from a life-history standpoint. For example, recovering long-lived sturgeon, redwood or elephant populations will necessarily take decades given their low replacement rates. Further, the sheer intensity of impacts humans are delivering to Earth cannot be underestimated (Vitousek et al. 1999; Folke 2021). And because it took us a long time to get into these messes, it may take equally long or longer to dig back out. In some cases, ecosystems may never come back the same. Just as people need time to heal from an injury or traumatic event, so too, ecosystems need our patience when we begin working to bring them back from the brink, or even the damned.

Persistence may be equally important. Persistence is needed in paying attention to detect, understand, and address complex problems. Persistence is necessary for adapting to changes in socioecological conditions, which are often exceedingly complex. Persistence is important for navigating our political system, sometimes multiple times. Political priorities shift because of changes to political leadership, budgets, events, and crises du jour. Persistence to follow through over the long haul often separates successful from less successful recovery projects. And because persistence is in many ways a personality trait, sustained long-term efforts require long-term commitments from people – all of us – to ensure that ecological recoveries reach their full potential. This is hard work, and I’m not sure everyone who contributes to these efforts is ever fairly recognized for their important labor.

Walking along Putah Creek now, it is easy to take for granted all the work needed to get to this point. Those involved over the long haul see this. It took 13 years for Chinook salmon to find Putah Creek again. It took another 10 to get the numbers back up. And it might take at least another 10 to really start getting it right. That’s 33 years in the right direction – a career for someone. And yet still more work remains. Sometimes, we tell ourselves or our loved ones to be patient and give one another grace. This same way of thinking is probably true with nature, and us, especially as we heal.

Estuary of the Klamath River, Redwood National Park, CA. Downloaded from

Further Reading:

Chapman, E., E. Jacinto, and P. Moyle. Habitat restoration for Chinook salmon in Putah Creek: a success story,

Folke, C., S. Polasky, J. Rockström, V. Galaz, F. Westly, M. Lamont, M. Scheffer, H. Österblom, S.R. Carpenter, F.S. Chapin III, K.C. Seto, E.U. Weber, B.I. Crona, G.C. Daily, P. Dasgupta, O. Gaffney, L.J. Gordon, H. Hoff, S.A. Levin, J. Lubchenco, W. Steffen, and B.H. Walker. 2021. Our future in the Anthropocene biosphere. Ambio 834-869.  

Jacinto, E.E. 2020. Long-term rehabilitation of a native freshwater fish assemblage in California. MS Thesis, University of California, Davis.

Kiernan, J.D., P.B. Moyle, and P.K. Crain. 2012. Restoring native fish assemblages to a regulated California stream using the natural flow regime concept. Ecological Applications 22: 1472-1482.

Marchetti, M.P., and P.B. Moyle. 2001. Effects of flow regime on fish assemblages in a regulated California stream. Ecological Applications 11: 530-539.

Morin, J., T.C.A. Royle, H. Zhang, C. Speller, M. Alcaide, R. Morin, M. Ritchie, A. Cannon, M. George, M. George, and D. Yang. 2021. Indigenous sex-selective salmon harvesting demonstrates pre-contact marine resource management in Burrard Inlet, British Columbia, Canada. Scientific Reports 11: 21160.

Rypel, A.L., G. Singer, and N.A. Fangue. 2020. Science of an underdog: the improbable comeback of spring-run Chinook salmon in the San Joaquin River,

Rypel, A.L. 2021. Spatial versus temporal heterogeneity in abundance of fishes in north-temperate lakes. Fundamental and Applied Limnology 195: 173-185.

Rypel, A.L. 2021. Sometimes, studying the variation is the interesting thing.

Rypel, A.L., D.J. Alcott, P. Buttner, A. Wampler, J. Colby, P. Saffarinia. N. Fangue, and C.A. Jeffres. 2022. Rice and salmon, what a match!

Vitousek, P.M., H.A. Mooney, J. Lubchenco, and J.M. Melillo. 1997. Human domination of Earth’s ecosystems. Science 277: 494-499.

Willmes, M.,  E.E. Jacinto, L.S. Lewis, R.A. Fichman, Z. Bess, G.P. Singer, A. Steel, P.B. Moyle, A.L. Rypel, N.A. Fangue, J.J.G. Glessner, J.A. Hobbs, and E.D. Chapman. 2021. Geochemical tools identify the origins of Chinook Salmon returning to a restored creek. Fisheries 46: 22-32.

Winemiller, K.O. Must connectance decrease with species richness? The American Naturalist 134: 960-968.

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Losing mussel mass – the silent extinction of freshwater mussels

by Andrew L. Rypel

Fig. 1. Sampling a healthy freshwater mussel population in the unregulated Sipsey River, Alabama. Photo credit: Andrew Rypel

Note: this is a re-post from August 2020.

Throughout my career I’ve spent some time studying the fascinating ecology and conservation issues of freshwater mussels (Fig. 1). For me, learning about mussels has fortified a recurring theme of the natural world – that everything is connected and that small changes in one part of a system can yield unexpected changes elsewhere, often many years later. More importantly, freshwater mussels are essentially threatened everywhere. And because we don’t often hear about them, it is hard to save them, because public will is so critical to generating change.

What is a freshwater mussel?

Some basics. Freshwater mussels, along with freshwater snails (another taxonomic group in major trouble) are varieties of molluscs. Most molluscs on Earth live in saltwater, however several families live in freshwater. Freshwater bivalves (order Unionidae) are one of the major clades of these species. This group’s fossil record extends back to the upper Devonian (416-365 million years ago or “mya”). In North America, first fossils appear to have emerged in the Triassic (250-200 mya). So these animals are not quite as old as fish (>400 mya), but certainly old.


Now here’s where it gets really interesting. [Caution…your mind may explode like mine once did!] With some exceptions, most juvenile freshwater mussels are obligate parasites on fishes. This means they cannot complete their life cycle without using fish as hosts. Baby mussels (glochidia) attach to the gills and fins of fish hosts. In some cases the host fish for a mussel is highly specific, e.g., mussel species x must use fish species y. In other cases, mussels are generalists which can use a range of fish species. By studying these obscure dynamics, a web of interactions begins to emerge between mussels and fishes that is ecologically vital.

Perhaps more interesting is how mussels transmit the glochidia to the fish. Because mussels are mostly sedentary, they have evolved lures to attract their fish hosts. The lures are often part of the mussel’s mantle and are loaded with magazines of baby glochidia. Once a fish bites the lure, the glochidia are ejected onto the host fish. Some lures are basic while others can be exceedingly ornate. Lures resemble all types of potential fish prey including bluegill, minnows, darters, sculpins, salmon, and aquatic insect larvae. Elaborate superconglutinate lures even emerge from the mussel as though on a mucus string, with the same goal of attracting a host fish to bite. In these cases, the mussel literally appears as though it is “going fishing”. Check out the following video of a mantle lure in action!

Ecosystem services

Freshwater mussels perform a variety of important functions in aquatic ecosystems, well-reviewed by Vaughn 2018. For example, mussels regulate water quality through biofiltration. They also process and store excess nutrients in ecosystems. An interesting thought experiment is to consider the role oysters (a similar group of animals) have in regulating water quality in Chesapeake Bay. According to the Chesapeake Bay Foundation, oysters once filtered the entire ecosystem (estimated ~19 trillion gallons of water) every week. However, with declining oyster abundance, it now takes oysters > 1 year to filter the Bay just once. To what extent do mussels similarly promote water quality in freshwater ecosystems? And what might their losses mean?

Freshwater mussels were important to Native American cultures. Mussels seemed to be highly central to mound-building societies of the midwestern and southern USA. However, shell mounds (or “middens”) were also common on the West Coast, notably in San Francisco – driving down “Shellmound Street” might be one major clue! Shell mounds were created by tribes as sacred ceremonial places and as burial sites. Most mussel shells in archaeological sites are “unworked”, meaning mussels were used as food. But, their low caloric value means mussels were probably supplementary food and used more frequently during times of food scarcity. In the Columbia River, mussels were harvested by tribes well into the 20th century and prepared for consumption mainly by steaming. Shells were also for pottery-making, utensils, and jewelry. Because shells are relatively well-preserved, middens can also reveal how mussels and aquatic ecosystems responded to human activities. For example, one genus of mussels in southeastern USA (Epioblasma spp.) showed relatively constant abundance at archaeological sites over a 5000 year period; but around 1000 years ago, mussel abundances declined rapidly with the rise of maize and bean cultivation. In the last 100 years, Epioblasma spp. have declined substantially further due to ecosystem alterations such that species are now listed under the US Endangered Species Act.

In addition to filtering, mussels support fish populations by engineering benthic habitats to be more suitable for fishes like darters, minnows, dace and sculpins that require firm and complex structures. Mussels also are useful in monitoring water quality because they are among the first species that disappear as water quality declines (Augspurger et al. 2003). Because mussel organs are exposed constantly to ambient environmental conditions, they are figurative “canaries in the coal mine” for aquatic environmental change. Mussels support aquatic and terrestrial foodwebs by providing energy to diverse species including fishes, otters, muskrats, raccoons, waterfowl, crayfish, turtles, frogs, salamanders and people. 

Fig. 2. (Left) Loading mussels on scows along the Mississippi River, IA for use in the pearl button industry. Photo by Hugh M. Smith (1899) in Mussel Fishery and Pearl-Button Industry of the Mississippi River, Bulletin of the United States Fish Commission. (Right) Common cutting technique used in pearl-button manufacturing. Photo from Coker (1921) Fresh-water Mussels and Mussel Industries of the United States, Bulletin of the United States Bureau of Fisheries, vol. 36, 1917-1918.

The market for mother-of-pearl buttons was a leading factor in initial mussels declines and extirpations in North America (Fig. 2). Another factor was pearl hunting, even though pearls from native freshwater mussels are mostly rare and imperfect. Gossip in Rome during the 1st century speculated that one reason Julius Caesar invaded England was to search for pearls in mussels from local streams, and that he returned with a piece of armor decorated in pearls (Haag 2012). In the USA, there were two “pearl rushes” – one in the mid-late 19th century, and a second round in the 1950s related to a new process of culturing pearls in Japan. These rushes had horrible consequences for mussel populations, particularly long-lived species.

Diversity, California & Decline

While Class Bivalvia contains ~20,000 living species worldwide, only ~1000 species are known to live in freshwater, and 850 of these species are in the Order Unionida. Estimates suggest there are ~300 species of freshwater mussels in North America. Like many North American taxa, a diversity hotspot for freshwater mussels is the southeastern USA where a lack of glaciation and a correspondingly old evolutionary landscape promote local evolution and high diversity. 

While freshwater mussel diversity is low in California (3-4 native species), these organisms can be locally abundant. Mussels therefore play underappreciated roles in our ecosystems, and in many locations are apparently in significant decline. Native California mussels include the Western Pearlshell (Margaritifera falcata), the Western Ridged Mussel (Gonidea angulata), the California Floater (Anodonta californiensis), and possibly the Oregon Floater (Anodonta oregonensis) (Fig. 3). The Western Pearlshell is notable for its long life, often exceeding 60 years. These mussels are so old, they can be used to reconstruct past climates, parallel to the ways tree-rings can be used (Black et al. 2015). Ecologically, their host fishes are likely trouts and/or salmon. As recently as 1942, Western Pearlshells were a dominant species in the Truckee River with at least 20,000 individuals surveyed; however only 120 mussels were found recently (Murphy 1942, Howard 2008). Today, the only known populations of Western Pearlshell Mussel in the Tahoe basin are in the Upper Truckee River, Trout Creek, and the Truckee River. Western Ridged Mussels are also native to California and are the dominant native mussel species in the Rocky Mountains and to the West. This species is also in decline across the western USA and sculpins might be a host fish. Finally, the California Floater is common in large rivers and pools of streams. Floaters of the genus Anodonta are frequent specialists on floodplain lakes and pools. We frequently encounter floater shells on banks in the Yolo Bypass and in farm ponds. Speckled dace and sculpin are known host fishes for the California floater (Main et al. 2016), but it is likely that this mussel is a generalist species.

Fig. 3. Photos of native freshwater mussels in California. (Upper Left) Adult and juvenile Western Pearlshells alongside invasive Asian clam. Picture from (Lower Left) Adult specimen of California Floater, photo from (Right) External, internal and hinge of the Western Ridge Shell. Photo from

There is great variation in the life-histories of different freshwater mussel species (Haag and Rypel 2011). Some species are exceptionally long-lived. The freshwater pearl mussel (Margaritifera margaritifera) regularly lives >100 years of age. One specimen from Finland had an estimated age of 162 years – this individual was born 37 years before California became a US State. If you go marine, some bivalves live even longer; a specimen of Arctica islandica from the coast of Iceland in 2006 lived 507 years!

In a classic examination of the conservation status of freshwater mussels in North America, Williams et al. 1993 noted 72% (213 of 297) of species are endangered, threatened or of special concern 21, and 7.1% of species had probably gone extinct. These are the highest rates of imperilment of any other known group of freshwater taxa. According to the Xerces Society, crayfishes, freshwater fishes, amphibians, dragonflies have imperilment rates of 51%, 37%, 36%, and 18% respectively. As another contrast, imperilment rates for flowering plants, mammals and birds are 33%, 16% and 14%, respectively. Mussels are…uniquely endangered.

California problem – California solution?

While mussels are declining globally, the mussel problem is also a California problem. Studies in the Truckee River showed a 99.4% decline in abundances of a long-lived mussel (Murphy 1942, Howard 2008). Howard et al. 2015 re-surveyed 450 historical records from 116 sites throughout California,  showing freshwater mussels re-occured at only 47% of these sites. Mussel losses were especially acute in southern California, with 13 of 14 streams having lost their mussels. Yet while loss of native mussels is occurring in many ecosystems, the addition of invasive mussels is simultaneously wreaking havoc on others. Invasion of the Sacramento-San Joaquin Delta by Asiatic clams (Corbicula spp.) is a commonly-studied mechanism for changing zooplankton and fish communities. The ecology of invasive mussels in California and the West will be a good topic for a future blog post.

Like many natural resource issues, we have inherited and contributed to the freshwater mussel problem, which will require hard and focused work to correct. The mechanisms for losses remain elusive. Commonly cited factors include loss of fish hosts, poaching and overharvest, pollution, invasive species and climate change (Haag 2012). Substantially more basic information is needed on the status and distribution of native mussels in California. Where are our mussels? What are their host fishes? Is there cryptic diversity? What are trends in diversity and abundance? What are the impacts of water and riparian land management and invasive species? How have native fish declines impacted mussels? 

A “mussel-building program” in California could take many shapes. I suggest a draft 4-point plan that might be useful to consider:

1. A statewide inventory: A statewide inventory of freshwater mussel abundance and diversity is long overdue. Currently no native California mussel is listed at the state or federal level as threatened or endangered, even though some of these species are already identified as in jeopardy or extirpated from other Western states. A statewide inventory could occur with a series of targeted grants or directed actions, or using a special research unit within one of the relevant state agencies. These data are needed to assess if some of our native mussel species, populations, and ecosystems should be protected. New environmental DNA (eDNA) tools hold promise for such an endeavor.

2. Sentinel sites: Long-term data shows trends over time. Without these data, scientists have little hope of adequately investigating hypotheses of species declines or developing models for testing potential conservation solutions. A series of sentinel sites (e.g., 10-15) strategically located around the state could monitor freshwater mussel populations over time. Sentinel sites/data would give an immediate benefit to scientists struggling to understand mussel dynamics across our large and complex landscape.

3. Conservation hatcheries?: Some eastern US states are developing mussel hatcheries to recover rare species after habitat issues are corrected. In many cases, older decommissioned hatcheries and aquaculture facilities are being repurposed for conservation aquaculture. Are mussel hatcheries a possibility in California? If mussel species were to become listed at some point, hatcheries may be needed to achieve goals. While hatcheries are never intended to replace natural reproduction, they can be an emergency back-up plan for populations and species.

4. Look for win-wins: Strategic prioritization is needed to locate restoration opportunities that would benefit fishes and freshwater mussels. Because mussels rely on suitable fish hosts, loss of fish hosts from habitats will eventually crash mussel populations. Yet because mussels live long lives, mature adults can subsist for decades without host fishes following landscape fragmentation by dams and other structures. This pattern is often referenced in the ecological literature as a “extinction debt” (Timan et al. 1994). Restarting natural mussel recruitment necessitates recolonization by native fishes. Ecosystems with a high potential for boosting native mussel populations could then be prioritized for restoration. Rehabilitation might include large dam removals, but also could be as simple as adjusting the myriad in-stream culverts that also block fish passage to headwater streams, some of which contain mussels. Strategic prioritization along these lines also ties in with existing mechanisms for restoration funding and climate resilience (e.g., through Propositions 1 and 68). In short, the future of mussels is closely tied to the future of fishes – we need to save them together.

Key lessons can be found when examining the demise of mussels. Healthy lands = healthy watersheds = healthy rivers and lakes often = healthy mussels (and fishes and amphibians and plants) = healthy societies. California has so often been a leader in environmental conservation efforts, and needs to be once again.

Andrew Rypel is an Associate Professor and the Peter B. Moyle and California Trout Chair of coldwater fish ecology at the University of California, Davis. He is a faculty member in the Department of Wildlife, Fish & Conservation Biology and Acting Director of the Center for Watershed Sciences

Fig. 4. Freshwater mussels sampled on a survey of the Marais des Cygnes National Wildlife Refuge 2011. Photo by Tim Menard, USFWS. Downloaded from

Further Reading

America’s freshwater mussels are going extinct — Here’s why that sucks

A freshwater mussel apocalypse is underway – and no one knows why

California floater mussel take fish for an epic joyride

Nature’s britta filter is dying and nobody knows why

Oyster fact sheet

The tiny clams that ate the Bay-Delta

There Were Once More Than 425 Shellmounds in the Bay Area. Where Did They Go?

Scientists find 507-year-old clam. Are older ones out there?

Black, B.A. J.B. Dunham, B.W. Blundon, M.F. Raggon, and D. Zima. Spatial variability in growth-increment chronologies of long-lived freshwater mussels: Implications for climate impacts and reconstructions. Ecoscience 17: 240-250.

Haag, W. R., 2012. North American freshwater mussels: Natural history, ecology, and conservation. Cambridge University Press, Cambridge UK.

Helama, A., and I. Valovirta. The oldest recorded animal in Finland: ontogenetic age and growth in Margaritifera margaritifera (L. 1758) based on internal shell increments. Memoranda Soc. Fauna Fennica 84: 20-30.

Augspurger, T., A.E. Keller, M.C. Black, W.G. Cope, and F.J. Dwyer. Water quality guidance for protection of freshwater mussels (Unionidae) from ammonia exposure. Environmental Toxicology and Chemistry 22: 2569-2575.

Howard, J. K. 2008. Strategic inventory of freshwater mussels in the northern Sierra Nevada Province. Final Report by Western Mollusk Sciences, San Francisco, CA to US Forest Service PSW Regional Office, Vallejo, CA. 65 pp.

Howard, J.K., J.L. Furnish, J.B. Box, and S. Jepsen. 2015. The decline of native freshwater mussels (Bivalvia: Unionidae) in California as determined from historical and current surveys. California FIsh and Game 101: 8-23.

Haag, W.R., and A.L. Rypel. Growth and longevity in freshwater mussels: evolutionary and conservation implications. Biological Reviews 86: 225-247.

Maine, A., C. Arango, and C. O’Brien. Host Fish Associations of the California Floater (Anodonta californiensis) in the Yakima River Basin, Washington. Northwest Science 90: 290-300.

Murphy, G. 1942. Relationship of the fresh-water mussel to trout in the Truckee River. California Fish and Game 28: 89-102.

Timan, D., R.M. May, C.L. Lehman, and M.A. Nowak. Habitat destruction and the extinction debt. Nature 371: 65-66.

Vaughn, C.C. 2018. Ecosystem services provided by freshwater mussels. Hydrobiologia 810: 15-27. 

Williams, J.D. M.L. Warren, K.S. Cummings, J.L. Harris, and R.J. Neves. Conservation Status of Freshwater Mussels of the United States and Canada. Fisheries 18: 6-22.

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Happy New Water Year 2023!

by Jay Lund

Happy New Water Year, 2023!  (October 2022 – September 2023)

The first New Year celebration for California’s water wonks is October 1, the beginning of the new Water Year, the nominal beginning of California’s wet season.  California sometimes has its first big rain storm earlier, and sometimes later, but by convention the wet season begins October 1.  It is a time when reservoir levels are reduced to prepare for potential floods (not an issue this year because of already-low reservoir levels) and when notices of flood vulnerability are sent to many residents of low-lying areas (which remain vulnerable during the coming wet season despite relatively low reservoir levels upstream).

Outlook for 2023 Water Year

The outlook for the 2023 water year is that it is far too early to tell.  We have had some precipitation in September, which helped suppress wildfires, but didn’t contribute much to water supply.  Hopefully we will have more and larger storms starting this month, but not so much as to cause floods.

Reservoir levels in California are mostly well below average for this time of year, and soil and groundwater levels remain below average from the past three years of drought.  The Colorado River reservoirs are in trouble.  Temperatures (and watershed evapotranspiration) seems persistently high.  All this means that water shortages in this new water year will be magnified even if 2023 is dry to even moderately wet.

At this time of year, media and pundits ponder the entrails of El Nino, La Nina, and ENSO indices for prognosticating how wet the coming year will be.  But for northern California, ENSO is poorly correlated with runoff, as seen in the figure below (Schonher and Nicholson 1989).  Jan Null just blogged his statistical analysis of El Nino, La Nina, and precipitation for different basins in California with seemingly similar findings.

ENSO and Sacramento Valley Annual Runoff

The statistical truth seems to be that there is little well-documented skill in predicting what the current water year will bring until well into the water year, perhaps even February or March.

Effects of the last three drought years endure

Even if the coming year is wet enough to fill reservoirs, there will be enduring effects of the last three drought years (and earlier drought years).  The most recent drought years are likely to have increased dead or dying trees in as-yet unburned watersheds, contributing to increases in fire risk and air quality problems for some years to come.  And the reductions in groundwater levels from recent drought years will make achieving groundwater sustainability more difficult (Escriva-Bou et al. 2020). 

“Drought management” must extend well beyond hydrologic drought years, just as most flood management, preparations, and investments must occur in non-flood years.

Prepare for both dry and wet, perhaps both in the same year

Californians and California’s water managers need to prepare for the new water year to be both wet and dry, as both dry and wet years are possible.  Even dry years sometimes include flood or near-flood events, at least locally.

Welcome to California water management.  Hope for the best, but prepare for the worst.

May Water Year 2023 be wetter than California’s 2022 and drier than Florida’s 2022!

Further reading

Escriva-Bou, A., et al. (2020), How reliable are Groundwater Sustainability Plans?,, 20 May.

Null, Jan (2022), La Niña and California Precipitation, October.

Schonher, T. and S. E. Nicholson (1989), “The Relationship between California Rainfall and ENSO Events,” Journal of Climate, Vol. 2, Nov. pp. 1258-1269.

You can play with the figure’s data yourself, with data cheerfully supplied from DWR’s CDEC: and NOAA:

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

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Federal Disaster Assistance to California

By Ryan Miller and Nicholas Pinter

Following a major flood or other natural disaster, the US federal government provides disaster assistance to individuals and local and state jurisdictions to help them recover. Over the past ~20 years, these federal payments have totaled nearly $150 billion (in 2020 dollars), including over $20 billion for recovery from Hurricane Katrina and $15 billion from Hurricane Sandy. We analyzed 20 years of federal data to assess patterns of FEMA disaster assistance, focusing on aid to California, peer states, and FEMA assistance across the US.

A principle conclusion is that California has received less federal disaster assistance on a per-capita basis than most peer states and less than United States averages for all disaster types. The imbalance is especially pronounced for flood-related events, and reinforces previous findings that California has relied less on federal flood funding, including National Flood Insurance Policy claims, than most states over the past 20-30 years. In addition, delay times in receiving FEMA Public Assistance funds showed wide variations, with delays ranging from a few days up to almost 16 years.


We analyzed 20 years of information about three types of assistance from the Federal Emergency Management Agency (FEMA), including: Public Assistance (PA) to repair public infrastructure, Individual Assistance (IA) provided to individual victims of disasters, and Hazard Mitigation Assistance (HMA) spent to reduce future losses. FEMA also underwrites flood insurance payments from the National Flood Insurance Program (NFIP), a type of post-disaster funding analyzed separately (see Pinter, N., R. Hui, K. Schaefer, and D. Conrad, Dec. 14, 2016. California, Flood Risk, and the National Flood Insurance Program. California Water Blog: In addition, other federal agencies and programs, for example the Small Business Administration, also sometimes invest in post-disaster recovery.

Patterns in Disaster Aid

Public Assistance (PA) payments nationwide (Figure 1a) vary each year, but show increasing numbers of “Billion Dollar Disasters” in recent years (NOAA, 2022; Most PA payouts nationwide (66.1%) were for hurricanes, with peaks in 2006 (after Hurricane Katrina) and 2018 (after Harvey). Non-hurricane flooding is the second-largest category of PA funding (20.4%), followed by fires (8.6%; reconstruction in the wake of the September 11 Terror Attacks were coded as ‘Fire’, explaining the spike in in 2002-2003). Payouts for all other disaster types represented less than five percent of the total.

Figure 1a: Public Assistance payouts nationally, 2000-2019 (2020 Dollars).
Figure 1b: Public Assistance payouts to California jurisdictions, 2000-2019 (2020 Dollars).

PA allocations to California (Figure 1b) differ from the national pattern. Most PA projects in California in recent years have been for fire, with the largest expenditures in 2018, following the Tubbs, Carr, and Camp fires. In other years, total PA spending in California was in the low tens of millions of dollars.

California also draws far less in PA funds per capita than most other U.S. states – particularly for flooding (Table 1; Figure 2). A handful of small Mountain West and Midwestern states received over $1,000 per capita in PA during 2000-2019, while several states received less than $10 per capita. The average per-capita PA expenditure nationwide was over $251, more than 23x higher than $10.90 per-capita in California.

The simplest explanation for state-to-state differences in federal disaster relief allocations is that disasters are rare and somewhat random, and that 20 years might not do justice to long-term disaster occurrence. However, the data (e.g., Figure 3) hint at political factors at work. The five most populous states – California, Texas, New York, Florida, and Pennsylvania — each received less than $50 per capita in PA during 2000-2019, compared to over $250 per capita nationwide. Other states such as Idaho, Wyoming, and New Hampshire received over $1,000 per capita over the same period. Perhaps influential politicians from small states steer PA funding to the less populous states they serve.

Figure 2. Flood-related Public Assistance expenditures per capita in the United States (2020 Dollars).
Figure 3. Flood-related Public Assistance expenditures per capita versus total population.

Patterns in California

In California, the counties receiving the most Public Assistance per capita (Table 2; Figure 4) were predominantly small and rural and mostly in Northern California, while those receiving the least PA per capita were all in the San Joaquin Valley.

Figure 4. Cumulative per-capita flood-related Public Assistance payments in California (inflation-adjusted to 2020).

Payment Times

FEMA’s PA database includes the date that federal funds were obligated to local jurisdictions and the date funds were fully received (Table 3-4). Lag times varied from just 2-3 days for some projects up to 5,800 days (almost 16 years). Average PA payment times in California are about the same as elsewhere in the US, for both flood and non-flood related disaster declarations. California had a greater share of moderate delays than elsewhere in the country: nearly 40% of the funds disbursed in California had payment delays of 1-2 years, compared to 22% nationwide (Figure 6). Conversely, California had fewer extreme delays, with less than 1% of lag times >3 years, comparing to nearly 20% nationwide.

Over the past 20 years, the time to process PA funding has increased (Figure 5). Larger states have longer delays than small states. Puerto Rico and Louisiana had the longest delays, probably from the complicated assistance projects following Hurricanes Maria and Katrina.

Figure 5. Mean days elapsed before payment of federal funds, including funds received in California (blue line) and throughout the United States (grey line).
Figure 6. Distribution of all disbursed PA funds (2000-2020; not inflation-adjusted) according to payment delay.


The imbalance between what California has received over the past 20 years from FEMA disaster assistance programs relative to other states mirrors imbalances documented in California’s claims from the National Flood Insurance Program (Pinter et al., 2016). The results here raise the same question as raised in discussions of California’s role in the NFIP – whether California “has just been lucky” (avoided major floods in the last 21 years), or rather “has flood risk … been overestimated or successfully managed or reduced” (Pinter et al., 2016). The analyses here – which normalize FEMA disaster payments to population as well as independent measures of flood exposure – suggest California has indeed managed its flood risk better than other areas of the US. We encourage California policymakers and flood managers to continue investing in floodplain management and flood-risk reduction.

Ryan Miller is a PhD Candidate in the Geography Graduate Group at the University of California, Davis. Nicholas Pinter is the Shlemon Chair in Applied Geosciences in the Department of Earth and Planetary Sciences at UC Davis and is Associate Director, Center for Watershed Sciences.

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