Uncertainty in modeling, an Art Gallery

Water resource planners regularly rely on computer models to illuminate relationships between human- and natural-systems. Anyone who has tinkered with one of California water supply models knows this is a deeply left-brained exercise. During Winter 2021, as part of Jay Lund’s Art and Water class, water resource engineering students took a break from creating and analyzing mathematical models to exercise the right side of their brains and enjoy some art. Please enjoy this collection of art pieces curated by a group of graduate students who can’t quite figure out how to unplug…

“War (The First Discord)” (19th c.) – DeScott Evans

This piece illustrates the struggle and discord that can occur in hydrologic modeling practice. As these cherubs fight over the apple shown in the bottom left, we can imagine two experts fighting to model nuanced environmental processes to create a “more perfect” model. In the heat of battle, they fail to consider how the model informs effective policy and meaningful change. Is creating the most accurate model always worth the toil, resources, and effort? Instead, the cherubs could collaborate to share the apple and create a model that worked well enough to inform policy and promote meaningful change. – Abbey Hill

Composition II in Red Blue and Yellow” (1930) –  Piet Mondrian 

Uncertainty in modeling is inescapable. Instead of making the solution very complicated, why not make things easier? This painting by Mondrian consists only of straight lines and blocks of colors. We can’t predict the variability of precipitation and other key variables in the future, but simplified (Mondrian-esque) models can still be useful and inform water-saving policies. –  Zhendan Cao

Tree Cathedral (Cattedrale Vegetale) – Giuliano Mauri (2010)

This work of Earth art represents both the carefully planned infrastructure and unavoidable uncertainty inherent to modeling. Just as models build on known and existing systems, this work originates with the architectural history of Gothic cathedrals. However, models must also allow space for flexibility, which Wilby and Dessai (2010) describe as a “framework for robust adaptation.” The Tree Cathedral is built with rigid support structures to manipulate the tree growth pattern, but as time passes, the support cages rot and fall away, allowing the trees to stand on their own. The adaptable and flexible nature of the Tree Cathedral becomes apparent over the years as it continues to grow. Will the tree canopies form the roof of the Cathedral as planned? Will the trees continue to grow as intended? Uncertainty is central to the beauty of the Tree Cathedral and to the functioning of models. There is no way to control or plan for every possible eventuality. Will the Tree Cathedral stay standing, or will exposure to the elements cause it to fall? How will future climate outcomes compare to model predictions of increased drought or storms?  – Eleanor Fadely

“Bad Lemon (Creep)” (2019) Kathleen Ryan

Emerging artist Kathleen Ryan creates intricate mosaics of precious gemstones to create larger-than-life monuments to spoiled fruit. The artist’s process resembles that of a water resource planning model-builder. The modeler finds beauty when complex mathematical feedbacks and uncertainties nest neatly together and produce reasonable results. Stepping back and applying modeling to real-life scenarios (such as climate change and drought) reveals rotten dilemmas for water resource managers.  – Lindsay Murdoch

Dove (1949), The Flying Dove with a Raibow I and II (1952) and The Dove of Peace (1949) by Pablo Picaso; and The Birds by Georges Braque (1960)

This collection of Dove sketches by Pablo Picasso presents a parallelism between different models used in water planning, design and operation. If a real dove represents the watershed to water managers, the first painting illustrates the utopic model that perfectly simulates/forecasts existing hydrology, incorporating all heterogeneity and complexity. The second sketch would be physically-based, spatially distributed hydrologic models to predict hydrologic processes, accurate depiction of the dove, with some spatial heterogeneity at fine spatial resolutions, represented by the feather details. The next simple dove sketch would illustrate simpler physically based models with a few hydrologic processes, clearly depicting a dove but with less detail. The second to last sketch nicely relates to conceptual models in which each block represents a separate hydrologic process, for instance Tank Model (Sugawara 1972) for subsurface runoff and baseflow, that individually do not provide useful information, but when arranged meaningfully, can produce realistic watershed outputs (Klemes 1982). Thus, generating the dove shape. Finally, George Braque’s painting illustrates an empirical model in which the resemblance to a dove is exclusively due to its construction using watershed data. As such, if provided to other water managers, they might recognize them as a different bird or even E letters with humps, showing that empirical models are useful for the specific watershed they are developed for. – Francisco Bellido

Autumn Rhythm by Jackson Pollock (1950)

Despite the shocking global trend of rising temperature, its local implications can be obscure. As some pointed out, “There is a low level of agreement amongst climate models even about the sign of the seasonal rainfall” over large areas. Future climate projections do share some similarities with Jackson Pollock’s paintings. In this notable piece called “Autumn Rhythm”, the artist used a variety of dripping and pouring methods to create disordered lines and patches. This certainly reminds us about the numerous uncertainties embedded into climate predictions. Viewers often appreciate this painting for its randomness, abstractness, and the delivery of vitality and flow. As engineers, we also hope to uncover trends and beauty in the turmoil of the future.

Bridge Over a Pond of Water Lilies – Claude Monet (1993)

A low level of agreement amongst climate models on projected changes in key variables such as the magnitude of warming or the magnitude and sign of seasonal precipitation has led many to recommend dynamic adaptive management as an alternative to taking big actions now. There is undeniably some common sense to this “wait and see” approach. However, adaptive management merely supplants uncertainties in projecting climate with a myriad of other uncertainties such as the social, economic, and political environments around decisions planned to be made in the future, environments which may in fact be more conducive to decisions made today. Imagine Claude Monet’s universally admired painting, “Bridge Over a Pond of Water Lilies”, without the bridge – does the scene appear more untamed and wild? The notion of adaptive management is like the bridge: its elegant structure transforms the landscape into an orderly, calm and serene atmosphere. But it only appears that way. In reality, the chaotic unpredictability of the environment is more likely to undermine our adaptive plans, plans which are assuredly more embellished and highly dimensioned than Monet’s bridge. In sum, we cannot simply create a bridge over uncertainty, no matter how alluring it may be. – Wyatt Arnold

Further Reading

Klemes, V (1982), “Empirical and Causal Models in Hydrology,” Scientific basis of water resource management, National Academy Press, Washington, DC.

Wilby, R.L.  and S. Dessai (2010) “Robust adaptation to climate change,” Weather, Vol. 65, No. 7, July.

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California’s continued drought

By Andrew L. Rypel

As California’s drought deepens, it is worth checking in on the status of water supplies and what might be in store for the rest of the summer, and beyond.

What started with the promise of a wet water year, ended up dry, again. In January, the 8-Station Index showed precipitation totals keeping pace with the wettest year on record. Then it got dry and accumulated totals flat-lined. The final result is a below average water year, although not one of the driest years on record. To be precise, we are 13.3 cumulative inches below the long-term average for the northern Sierras.

Fig. 1. Accumulated precipitation for northern California during the current water year. Graph from the California Department of Water Resources, California Data Exchange Center https://cdec.water.ca.gov/cgi-progs/products/PLOT_ESI.pdf

Current conditions in reservoirs are a mixed bag. Shasta Reservoir remains low at only 40% of capacity, and 49% of the historical average. On this same date in 2021, Shasta was 41% of capacity and 51% of long-term average. Thus conditions in Shasta are very similar to those observed last year. So holding coldwater to support eggs and juvenile winter-run Chinook salmon in the Sacramento River will again be a major challenge this summer. On the heels of a mostly failed year class of winter-run Chinook salmon in 2021, the run is now at perilous risk of extinction. After all, these salmon operate on just a three year life-cycle. Perhaps because of this, efforts have accelerated to move adult winter-run Chinook salmon into coldwater habitats above Shasta Reservoir and into upper Battle Creek. Juvenile outmigrants would have to be trapped and moved around structures on their way out (‘two-way trap and haul’), or fishways re-operated for the specific benefit of salmon (‘one-way trap and haul’). Neither management approaches have been attempted at scale before in these systems. Two-way trap and haul is notoriously expensive and managers have reluctantly avoided it in the past (Lusardi and Moyle 2017).

Comparison of California reservoir levels in 2021 (left) to the same date in 2022 (right). Figures and data from the California Department of Water Resources, California Data Exchange Center https://cdec.water.ca.gov/resapp/RescondMain

Other reservoirs are faring better than one might expect. Oroville is at 53% of capacity and 67% of the historical average. For comparison, at this same point in 2021, Oroville was at 36% capacity and 46% of the historical average. Folsom Reservoir stands at a whopping 88% capacity and 111% of the long-term average – quite good for this point in the drought. This also compares favorably to only 34% of capacity and 43% of the long-term average for Folsom at the same date in 2021.

One potentially interesting observation is that many locally-operated reservoirs appear to be doing particularly well. New Bullard’s Bar and Don Pedro sport 102% and 82% of long-term average, respectively. These reservoirs were also decently full during 2021. Yet, the architecture of these reservoirs may partially explain this dynamic. For example, New Bullard’s Bar is a large capacity reservoir (969,600 acre-foot) but drains a watershed that is comparatively small; the entire Yuba River watershed is 857,600 acres. Similarly, Don Pedro has a capacity of 2,030,000 acre-foot and the entire Tuolumne River drains a watershed of 1,253,120 acres. In this sense, reservoirs with a high capacity:watershed ratio reservoirs may be more slowly impacted, and thus more durable over longer drought. Grantham et al. 2014 ranked all major dams in California based on their degree of regulation (DOR). Both of these reservoirs had DOR values well >1, which was a threshold identified in the study for strong hydrologic regulation. 

It is likely that high air and water temperatures will occur again this summer, as temperatures have been high for recent years. This will have specific and diffuse socioecological impacts. During the last drought, increased temperatures led to parched soils and stressed trees, and ultimately major forest mortality events (Keen et al. 2022). Obviously, drought also increases frequency and severity of wildfires. The top seven largest wildfires in California history all occurred within the last 4 years. Last summer, the Dixie Fire was the largest of the 2021 wildfires, burning close to 1M acres in Butte, Plumas, Shasta, Tehama, and Lassen Counties. As of writing, there are already seven active wildfires burning. How many major wildfires will accumulate during 2022?

Groundwater is taking a major hit. Water right curtailment orders will occur again this growing season. Growers that have planted annual crops will likely rely on groundwater in an attempt to finish. Tree growers with young crops may be forced to use groundwater or purchase water at high prices to try to keep trees alive. California produces ~80% of the world’s almonds and acreage planted has been growing, despite drought risk. Declining groundwater stores will stress rural wells that will run dry or become contaminated by nitrates. Land subsidence from reduced groundwater will impact the capacity for canals to operate properly. Finally, overdraft of groundwater supplies from this year (and previous years, such as 2021) will make SGMA objectives even more difficult to obtain, and require repayment of aquifers for additional drought pumping in future years for many basins.

The Delta ecosystem continues its sad decline. The delta smelt is virtually extinct from the wild, and although releases of hatchery smelt have been initiated, the habitat issues that historically plagued smelt remain unaddressed. To a large extent they have gotten worse. Water temperatures continue to increase, and increased temperatures are a major factor in recruitment failures of smelt (Komorosky et al. 2015). Longfin smelt are declining behind delta smelt (Eakin 2021). Warmer temperatures and clearer waters (due to effects of non-native clams) have intensified the rate of spread of invasive aquatic plants. The switch of fish habitats from cold turbid waters to warm, clear and plant filled habitats has shifted the ecological regime in the Delta to favor non-native fishes such as black basses. These species in turn, compete and predate on native fishes, which cause further declines in Sacramento Valley and Delta endemics.

Castaic Reservoir as seen at 46% capacity during the 2014 drought. Photo from Planet Labs Inc, and downloaded from https://commons.wikimedia.org

Other drought-related impacts are emergent. Water prices are increasing across the board. San Diego County Water Authority will be charging close to $2,000 per acre foot for untreated water in 2023. Many growers that have elected to sell water rather than grow have received record sale prices. These effects are being further compounded by macroeconomic inflation. Urban water restrictions have already been put in place in much of the state. The economic fallout of agricultural water shortages will result in rising unemployment and financial stress to agricultural communities and various irrigation districts. Amidst drought conditions, an interesting plan emerged earlier this month that involved the state potentially purchasing senior water rights. The details and fate of this plan remain murky. As water becomes more expensive and scarce, there may be less interest and prioritization of environmental programs, even though drought is the time when these programs might be most needed by wildlife.

Andrew L. Rypel is a professor of Wildlife, Fish & Conservation Biology and Co-Director of the Center for Watershed Sciences at the University of California, Davis.

Further reading

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

Börk, K., A.L. Rypel, and P. Moyle. 2020. New science or just spin: science charade in the Delta, https://californiawaterblog.com/2020/03/15/new-science-or-just-spin-science-charade-in-the-delta/

Eakin, M. 2021. Assessing the distribution and abundance of larval longfin smelt: what can a larval monitoring program tell us about the distribution of a rare species? California Fish and Wildlife Special CESA Issue: 189-202.

Grantham, T.E., J.H. Viers, and P.B. Moyle. 2014. Systematic screening of dams for environmental flow assessment and implementation. Bioscience 64: 1006-1018.

Keen, R.M., S.L. Voelker, S.Y.S. Wang, B.J. Bentz, M.L. Gouldon, C.R. Dangerfield, C.C. Reed, S.M. Hood, A.Z. Csank, T.E. Dawson, A.G. Merschel, and C.J. Still. 2022. Changes in tree drought sensitivity provided early warning signals to the California drought and forest mortality event. Global Change Biology 28: 1119-1132. 

Jessoe, K., J. Medellin-Azuara, P. Moyle, J. Durand, and A. Willis. 2021. A few lessons for California’s new drought. California Waterblog https://californiawaterblog.com/2021/05/16/a-few-lessons-for-californias-new-drought/

Komoroske, L.M., R.E. Connon, K.M. Jeffries, and N.A. Fangue. 2015. Linking transcriptional responses to organismal tolerance reveals mechanisms of thermal sensitivity in a mesothermal endangered fish. Molecular Ecology 24: 4960-4981.

Lund, J., T. Harter, R. Gailey, R. Frank, G. Fogg. 2015. The Earth is falling! – land subsidence and water management in California. California Waterblog https://californiawaterblog.com/2015/12/27/the-earth-is-falling-land-subsidence-and-water-management-in-california/

Lusardi, R.A., and P.B. Moyle. 2017. Two-way trap and haul as a conservation strategy for anadromous Salmonids. Fisheries 42: 478-487.

Moyle, P., K. Börk, J. Durand, T.C. Hung, and A.L. Rypel. 2021. 2021: Is this the year that wild delta smelt become extinct? https://californiawaterblog.com/2021/01/10/2021-is-this-the-year-that-wild-delta-smelt-become-extinct/

Rypel, A.L. 2021. Do largemouth bass like droughts? https://californiawaterblog.com/2021/05/02/do-largemouth-bass-like-droughts/







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Considerations for Developing An Environmental Water Right in California

By Karrigan Börk, Andrew L. Rypel, Sarah Yarnell, Ann Willis, Peter B. Moyle, Josué Medellín-Azuara, Jay Lund, and Robert Lusardi

Tuolumne River Northwest of Tuolumne Meadows, Yosemite National Park. Photo by Dick Witt, downloaded from wikicommons.org

This week, news emerged of a State Senate plan that would spend upwards of $1.5B to purchase senior water rights from California growers. Under California’s first-in-time, first-in-right water allocation system, senior water rights are filled first, before more junior right holders get their water. The proposal is ostensibly promising. Because of widespread diversions, the aquatic biodiversity of California has been effectively exposed to chronic drought every year, and additional flows may help native species. If purchases can quickly add additional water to rivers in the right places and at the right times, they could benefit ecosystems and endangered species, like Chinook salmon and delta smelt (Moyle et al. 2019, Obester et al. 2020). But it could also easily become a payoff for wealthy water holders with marginal benefit for ecosystems, species, and people. The potential for abuse is particularly troubling when the State is using public funds to buy water, which technically belongs to the people of the state and which the State can already regulate to achieve the same aims. As the old saying goes, the devil is in the details. 

This blog highlights some important considerations for decision makers on making effective environmental water right purchases. Below are several questions and themes for a successful water purchasing program.

Does purchasing water rights actually result in more water for ecosystems?

Water rights in California are complicated, and there are many ways a water right purchase could not add appreciable water for ecosystems. 

First, many water rights exist only on paper. Some right holders only use a portion of their water right in most years and can only use the full right occasionally, e.g., in very wet years. The state of the data and reporting system in California, especially for senior water rights, makes it challenging to know how much water senior right holders are entitled to and how much water they actually use. And we’re most interested in their consumptive use – the share of water use that becomes available and legal to sell under California law – a quantity that’s even harder to pin down. Established legal and regulatory process exist to dedicate real water rights to the environment. California Water Code Section 1707 provides a mechanism to transfer water rights to instream use, and it, combined with other water code sections on water transfers, does a fair job of making sure that what’s being transferred is real water that will actually increase flows and be protected from other users. Practitioners have already developed practical guidelines for successfully completing the 1707 process. The State must take care to purchase real wet water rights that will result in enforceable instream flows. 

Second, water transferred to instream use needs to stay instream. On many rivers, the full flow of the river is already spoken for through existing rights, often many times over; California has allocated up to 1000% of natural surface water flow, with most of these water rights issued in the Sacramento and San Joaquin rivers. If purchased rights are simply retired or not otherwise protected for ecosystem purposes, then holders of other existing water rights can (and often will) simply take the water. 

Third, even with an effective mechanism for selecting real water rights and protecting them instream, improvements to monitoring and enforcement are essential to ensure true increases in instream flows. Many diversions are only roughly monitored, such that neither the water user nor the State knows exactly how much water is being used. Many river stretches lack flow gages, so it is difficult to quantify how much water remains instream (though SB 19 is attempting to address the limited network of stream gages in California). And the Water Board lacks adequate resources to enforce existing limits on water rights. The State needs open and reproducible data on diversions and flows, along with a meaningful enforcement threat to ensure any water set aside for environmental benefit remains in the ecosystem.

Finally, these water rights should be “new” water. The Water Board, through its Bay Delta Water Quality Control Plan, is already reducing water rights to protect public trust uses and water quality in the Bay Delta watershed. Water users are negotiating over Voluntary Agreements that could be a part of that Plan. In addition, many growers will need to fallow some fields to meet the mandates of SGMA. Many state and federal laws already circumscribe many water rights to protect instream water uses. Purchases with public funds should be focused on water rights that right holders would otherwise use, so the funds don’t go to pay for water that would have remained instream anyway.

What price should California pay?

The Water Board already has the power to reduce water rights to protect the public trust or to ensure water is used reasonably so as not to destroy public resources, and it has previously exercised that power. They consistently win the resulting lawsuits. California could legally and constitutionally acquire much of this water through other mechanisms, without paying for it. So what exactly is the State paying for here? 

In a nutshell, the state would pay for acquiring water quickly, with less political resistance and bureaucratic wrangling, and with less political ill-will and fewer messy and protracted lawsuits. That might make sense; we’re in a climate crisis, and salmon and many of California’s imperiled species don’t have time to waste. But it also means the State should not be paying full price. Water use reductions to support instream flows could occur through other government actions, without a State buyback. A water right that is sometimes curtailed by the state during drought due to endangered species or public trust concerns simply isn’t worth as much as a water right that doesn’t face such regulation. The question is whether water right holders get paid something now for their right or lose some of this water right with no payment after a protracted and expensive fight into a rapidly changing future. Prolonged litigation isn’t as advantageous to current water rights holders as they might seem. Longer and deeper curtailments are possible given the trajectory of California’s climate, meaning the right could become worth even less in the future.

The best approach to pricing might be something like the reverse auctions that The Nature Conservancy is already using to generate migratory bird habitat. Under this approach, water right holders bid to sell their water to the state, and the lowest bids would be more favored, provided that they are real wet rights, as discussed above. This should be coupled with continued pressure from the Water Board to exercise their existing powers to reduce water available to right holders, as they did in the last drought, to generate conditions that would encourage water right holders to sell. And, as we’ll discuss in further detail, another complexity is that it’s not just the cheapest water the state should buy, but the cheapest real water in the right place at the right time for the ecosystem (see point 3 below). Paying full price for water rights could amount to a giveaway to wealthy water right holders, but the reverse auction model can avoid this pitfall.

Paying public money for a publicly-owned and regulated resource will strike some advocates as morally wrong. They might argue it sets a dangerous precedent of buying out those who oppose regulation or treating water rights as a more concrete form of property than they actually are. Legislators should be aware of this philosophical opposition and must carefully craft the purchase program to ensure it provides enough water and ecological benefits to merit the actual and political costs. Because California water already belongs to all Californians, and water rights are subject to continuing State supervision, the State should make sure the funds they dedicate go as far as possible.

What water, when, and where?

What are the precise goals of these purchases? The plan may become the beginnings of an ‘environmental water right’. This would be a positive step. 83% of California’s endemic fish species are declining (Moyle et al. 2011). Furthermore, outmigration survival of juvenile Chinook salmon is strongly linked in a threshold manner to river flows (Michel et al. 2021). Thus additional flows could benefit endangered species, especially if deployed strategically. However, if additional flows are simply gobbled up by other water users downriver or deployed in the wrong places and times, the environmental benefit to people and ecosystems could be nil. Water budget and accounting mechanisms are needed to ensure water is getting where and when it is most needed.

“When” matters.

The ecological value of water changes over time; both between seasons and across years. For example, additional flows during drought may yield more ecological return on investment than increased flows in wet years. As one heuristic, average annual runoff in California is 71M acre-feet. Thus a total of 200,000 acre-feet of additional water (the figure provided in the linked article above) is only 0.3% of the average water budget. However, runoff in drought years is much lower. Runoff during the 1977 drought year was only 15M acre-feet; so 200,000 acre-feet is 1.3% of the water budget in such dry years. An accounting or water budget that details when additional flows would be available is needed to accurately track the availability of surplus water.

The value of water for economic uses also changes over time. Opportunity costs of water in the irrigation season of dry years are particularly high. Thus creating a buffer in wet years might be more cost effective than buying out agricultural water use during dry years. A buyback program that considers a baseline amount plus dry-year option may reduce uncertainties for both farming and ecosystem needs.

Monticello Dam provides flows tailored to help native fishes in lower Putah Creek, photo from Bureau of Reclamation

“Where” matters.

There are better and worse places for additional water. Adding high quality water is valuable, so water rights in spring-fed streams and groundwater-dominated rivers have high potential for adding higher value than simply additional flow volume due to their unique water quality. Spring-fed and groundwater-dominated streams are more resilient to climate change than strictly surface runoff-dominated streams, and, as a result, they support robust ecosystems

Adding significant amounts of water to tributaries can make a significant difference, in part because less water is needed to enhance these habitats. Similarly, adding water to coastal rivers, which may be less complicated and easier to monitor, could result in significant gains.

On maintem rivers, giving juvenile salmon and other native fishes better access to productive riparian and floodplain areas could support aquatic biota. Data from a host of studies demonstrate that salmon grow better when exposed to floodplain habitats (e.g., Katz et al. 2017, Holmes et al. 2021), and new studies are testing potential survival benefits for floodplain-reared salmon. But this may not require purchases of water rights; permanent easement arrangements, long-term conservation easements and/or NRCS programs could provide similar benefits at less cost and with more impact than just adding water to maintem rivers. Strategic tributary investments are likely to often provide greater and more sustainable ecosystem value compared to large mainstem purchases, where many other users, especially in the Central Valley, bid up water prices and the marginal proportions of flow improvements are smaller.

Equity and Social Justice.

In 2021, the California Water Board released Resolution No. 2021-0050, titled “Condemning Racism, Xenophobia, Bigotry, and Racial Injustice and Strengthening Commitement to Racial Equity, Diversity, Inclusion, Access, and Anti-racism.” This remarkable document acknowledged that the “Water Boards’ programs were established over a structural framework that perpetuated inequities based on race,” and it provides extensive background on the systematic exclusion of many groups from the water right acquisition process. The most senior water rights in California, those targeted by this purchase program, were acquired during a period when racism was the norm, when women often lacked independent legal identity, and when Asian people were unable to become citizens, even though citizenship was open to most other races. Indigenous peoples were still subject to state-sponsored genocide and systematically disenfranchised of their land and water rights. As a result, most minorities and many women were excluded from acquiring water rights or land with appurtenant water rights. Most senior water rights were originally claimed by white men, and that disparity has continued. Buying out water rights now, as opposed to rationally regulating them, risks perpetuating that tradition. Because of the State’s continuing ownership and regulatory interest in water rights, the State still has opportunity to redress past injustices, as the Water Board resolution acknowledges. Early drafts of the legislation for the purchase program appear to recognize this history and attempt to mitigate some of the lasting harm through funding for increased access to drinking water for disadvantaged communities. Without intentional engagement to address these past injustices, the broader purchase program might result in better public control of water, but at the cost of extending inequities. 


The State Senate proposal offers the promise of real change in California water. It might help to move past a decades-long stalemate, protect important tributary and coastal rivers, and ensure the survival of imperiled species. It offers quick action that could create long-sought environmental water rights. But the details matter. This proposal could just as easily result in a very minor increase in mainstem flows that does little to benefit ecosystems, or even pay for water rights that aren’t worth the paper they’re written on. A decade from now, this might be seen as a turning point or just another expensive water scheme. 

At some point, transdisciplinary water and ecosystem experts need to be brought into the room. Scientists can assist policy makers to identify the locations, times, and dynamics of flows that can have the most environmental benefit (e.g., California Environmental Flow Framework). Further, transparent cost benefit analysis, water balance modeling, or ecological optimization provide important insight on when and how (e.g., functional flows) to best use additional water for the environment.

Although engaging with experts can be challenging and can occasionally stymie progress, scientists also deliver data-driven frameworks for optimizing investments and learning the most from an experiment. This knowledge works to ensure that decisions are ultimately based on sound science while also looking at economic and distributional effects in water reallocations. Management plans/processes that are transparent, reproducible and science-based often help. Indeed, some states have adopted democratic boards with a science-based mission to oversee management of natural resources within the context of the public trust. A similar model may be useful here.

Strong legal and scientific oversight will be essential to maximize the ecological benefits of purchases. We hope these suggestions provide encouragement and guidance for decision makers as they further consider water right purchases for the environment.

Yuba River near Bridgeport, California. Photo by Michael Nevins, United States Army Corps of Engineers, downloaded from wikicommons.org

Karrigan Börk is an Acting Professor of Law at the UC Davis School of Law and an Associate Director at the Center for Watershed Sciences. Andrew L. Rypel is a professor of Wildlife, Fish & Conservation Biology and Co-Director of the Center for Watershed Sciences at the University of California, Davis. Sarah Yarnell is a Research Hydrologist at the Center for Watershed Sciences. Ann Willis is a Research Engineer at the Center for Watershed Sciences. Peter B. Moyle is a Distinguished Professor Emeritus at the University of California, Davis and is Associate Director of the Center for Watershed Sciences. Josué Medellín-Azuara is an Associate Professor at the University of California, Merced. Robert Lusardi is an Assistant Adjunct Professor and Research Ecologist in the Department of Wildlife, Fish & Conservation Biology and the Center for Watershed Sciences at UC Davis. 

Further Reading

Bellido-Leiva, F.J., Lusardi, R.A. and Lund, J.R., 2021. Modeling the effect of habitat availability and quality on endangered winter-run Chinook salmon (Oncorhynchus tshawytscha) production in the Sacramento Valley. Ecological Modelling, 447, p.109511.

Börk, K., and A.L. Rypel. 2020. Improving infrastructure for wildlife. Natural Resources & Environment.

Börk, K., A.L. Rypel, and P. Moyle. 2020. New science or just spin: science charade in the Delta, https://californiawaterblog.com/2020/03/15/new-science-or-just-spin-science-charade-in-the-delta/

Grantham, T.E., and Viers, J.H. (2014). 100 years of California’s water rights system: patterns, trends and uncertainty. Environmental Research Letters 9(8), 084012.

Grantham, T.E. and Viers, J.H. (2014). California water rights: You can’t manage what you don’t measure. California Waterblog.

Holmes, E.J., P. Saffarinia, A.L. Rypel, M.N. Bell-Tilcock, J.V. Katz, and C.A. Jeffres. 2021. Reconciling fish and farms: Methods for managing California rice fields as salmon habitat. PLoS ONE 16(2): e0237686.

Hollinshead, S.P. and J.R. Lund, “Optimization of Environmental Water Account Purchases with Uncertainty,” Water Resources Research, Vol. 42, No. 8, W08403, August, 2006.

Katz, J.V.E., C. Jeffres, J.L. Conrad, T.R. Sommer, J. Martinez, S. Brumbaugh, N. Corline, and P.B. Moyle. 2017. Floodplain farm fields provide novel rearing habitat for Chinook salmon. PLoS ONE 12(6): e0177409.

Lusardi, R.A., Nichols, A.L., Willis, A.D., Jeffres, C.A., Kiers, A.H., Van Nieuwenhuyse, E.E., et al. (2021). Not All Rivers Are Created Equal: The Importance of Spring-Fed Rivers under a Changing Climate. Water 13(12), 1652.

Medellín-Azuara, J., Paw U, K.T., Jin, Y. Jankowski, J., Bell, A.M., Kent, E., Clay, J., Wong, A., Alexander, N., Santos, N., Badillo, J., Hart, Q., Leinfelder-Miles, M., Merz, J., Lund, J.R., Anderson, A., Anderson, M., Chen, Y., Edgar, D., Eching, S., Freiberg, S., Gong, R., Guzmán, A., Howes, D., Johnson, L., Kadir, T., Lambert, J.J., Liang, L., Little, C., Melton, F., Metz, M., Morandé, J.A., Orang, M., Pyles, R.D., Post, K., Rosevelt, C., Sarreshteh, S., Snyder, R.L., Trezza, R., Temegsen, B., Viers, J.H. (2018). A Comparative Study for Estimating Crop Evapotranspiration in the Sacramento-San Joaquin Delta. Center for Watershed Sciences, University of California Davis. https://watershed.ucdavis.edu/project/delta-et

Michel, C.J., J.J. Notch, F. Cordoleani, A.J. Ammann, and E.M. Danner. 2021. Nonlinear survival of imperiled fish informs managed flows in a highly modified river. Ecosphere 12: e03498.

Middleton Manning, BR. 2018. Upstream: Trust Lands and Power on the Feather River. Tucson: University of Arizona Press. 256 pp.

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

Moyle, P., K. Börk, J. Durand, T. Hung, A.L. Rypel. 2019. Futures for Delta Smelt, https://californiawaterblog.com/2019/12/15/futures-for-delta-smelt/

Moyle, P.B. 2021. Drought makes conditions worse for California’s declining native fishes. https://californiawaterblog.com/2021/06/27/drought-makes-conditions-worse-for-californias-declining-native-fishes/

Rypel, A.L. 2022. Nature has solutions…What are they? And why do they matter? https://californiawaterblog.com/2022/03/

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! https://californiawaterblog.com/2022/02/13/rice-salmon-what-a-match/

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

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

Yarnell, S.M., Petts, G.E., Schmidt, J.C., Whipple, A.A., Beller, E.E., Dahm, C.N., Goodwin, P. and Viers, J.H., 2015. Functional flows in modified riverscapes: hydrographs, habitats and opportunities. BioScience, 65(10), pp.963-972.


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Demystifying mist as a source of water supply

Source: Wikicommons
Fog envelopes the Golden Gate Bridge. Source: Wikimedia Commons

By Jay Lund

(originally posted in 2015)

In some of the world’s driest places, atmospheric moisture is a major source of water for native ecosystems. Some algae, plants and insects in the Israeli and Namibian deserts get much of their water from fog, dew and humidity. The spines of some cacti species have evolved to collect fog droplets. California’s redwood forests derive a significant amount of their moisture from fog.

Some drought-minded California residents along the coast, perhaps yearning for a clear ocean view, have suggested harvesting fog as a water supply.

Globally, few places get drinking water from coastal fog. They are mostly rural areas with abundant fog but little other available water. Communities along the parched northern coast of Chile have captured fog for some of its water supply by erecting large fences of synthetic fiber cross-wise to the coastal wind. The condensate on the netting is channelled for collection and use.

A fog fence or catcher supplies water to poor residents of Lima, Peru. Source: Wikimedia Commons

Fog harvesting yields from 1 quart to 3 gallons of water daily per square yard of fog mesh [1].

What would this mean for a typical coastal household?

A household of three that uses 300 gallons a day would need 1,030 to 12,300 square feet of fog mesh [2]. To fit on a typical single-family lot,  the length of the fog fence would be limited to about 50 feet. That means the fence would need to stand 21 to 250 feet tall, about the height of the State Capitol dome.

To fit on a typical single-family lot, the length of the fog fence would be limited to about 50 feet. That means the fence would need to stand 21 to 250 feet tall, about the height of the State Capitol dome. Illustration by Stephanie Pi, UC Davis.
To fit on a typical single-family lot, the length of the fog fence would be limited to about 50 feet. That means the fence would need to stand 21 to 250 feet tall, about the height of the State Capitol dome. Illustration by Stephanie Pi, UC Davis.

Building such a fence would cost a household thousands of dollars and require cleaning (algae tends to grow on the mesh) and repair (the mesh becomes a big sail in a storm). Homeowners probably also would want a sizable water tank to fill for periods of clear weather.

For virtually all homeowners, a fog water supply would almost always be costly and inconvenient. Some households might use fog as a supplemental supply, but it usually will be at a steep additional cost.

If these numbers were scaled up for San Francisco, population 800,000, the fog fence would need to cover 10 to 120 square miles, or 20 percent to 2.5 times the area of the city (47 square miles). Fog will unlikely be a major water supply for California.

But this is only for atmospheric fog. More petty forms of fog frequently blur discussions of water in California. If we could demistify some of this haze, we might condense our discussions and diminish our droughts.

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

May 2016 update:

Oddly enough, apparently a SF Bay Area vodka maker is experimenting using fog-collected water in its distilling: $125 per bottle.  At that price, I expect it is economical.


[1] The density of liquid water is 1,000 kg per cubic meter. The density of water in fog might range from 0.05 to 0.5 grams per cubic meter. If the fog mesh can wring 10 to 50 percent of the water from a coastal breeze blowing 2 miles per hour for half the day, then 1 cubic meter of fog mesh would produce roughly 1 cup to 2.5 gallons of water a day. Not a bad agreement between theory and practice.

[2] To meet a daily water demand of 300 gallons, the coastal household would need a giant square fog mesh of 32 to 111 feet on each side for a total area of 1,030 to 12,300 square feet, which is larger than most California houses.

Further reading

Dawson, T. E. (1998), “Fog in the California redwood forest: ecosystem inputs and use by plants,” Oecologia, Volume 117, Issue 4, December, pp 476-485

Estrela, M.J., J.A. Valiente, D. Corell, M.M. Millán. 2008. “Fog collection in the western Mediterranean basin (Valencia region, Spain)”. Atmospheric Research, Volume 87, pp. 324–337

Friedmann, I., Y. Lipkin, and R. Ocampo-Paus. 1967. “Desert Algae of the Negev (Israel)”. Phycologia, 6:4, 185-200

Goodman, J. 1985. “The collection of fog drip”. Water Resources Research, Vol. 21, No. 3, pp. 392-394. A very small field experiment on coastal Montara Mountain south of San Francisco, Calif.

Henschel, J.R. and M.K. Seely. 2008. “Ecophysiology of atmospheric moisture in the Namib Desert”. Atmospheric Research, Volume 87, Issues 3–4, March 2008, Pages 362–368

Ju, J., H. Bai, Y. Zheng, T. Zhao, R. Fang, and L. Jiang. 2012. “A multi-structural and multi-functional integrated fog collection system in cactus”. Nature Communications, 4 Dec. 2012

Klemm, O. et al. 2012. “Fog as a Fresh-Water Resource: Overview and Perspectives”. Ambio. Mar 2012; 41(3): 221–234

Snyder, R.L. 1992. “Fog contribution to crop water use”. Drought tips, No. 92-40, UC Davis

Victoria, M. and M. Jaen. 2002. “Fog water collection in a rural park in the Canary Islands (Spain)”. Atmospheric Research, Volume 64, pp. 239–250


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The Failed Recovery Plan for the Delta and Delta Smelt

By Peter Moyle

Few native species are as controversial as Delta Smelt. It is a 3-4 inch translucent fish that lives only in the California Delta, where the Sacramento and San Joaquin rivers meet. This place also happens to be the heart of California’s complex water supply system which provides fresh drinking water to 35-million Californian’s and supports a multi-billion dollar agricultural industry. As water demand increased over the years, the smelt declined, approaching extinction. This blog probes into lessons we can learn from the failure of efforts to protect the smelt, laid out in the 1990s.

Delta Smelt

In 1993, the Delta Smelt was listed as a threatened species, under the Federal Endangered Species Act of 1973 (ESA). Once listed, actions were initiated to “recover” the species under the powerful, no-nonsense provisions of the ESA. On December 19, 1994, critical habitat for the smelt was defined as essentially the entire Delta, plus the dynamic extent of the low salinity zone (technically, the location of the 2 ppt isohaline or X2), to make sure responses of different life history stages to variability in freshwater outflow were included. On November 11, 1996, the US Fish and Wildlife Service adopted the recovery plan (the Plan) discussed here. The ultimate goal of this Plan was to improve habitat conditions for Delta Smelt so it could be removed from the ESA list once it was no longer threatened with extinction. Twenty-five smelt generations later, this goal has not been achieved, and Delta Smelt populations have declined further.

Today Delta Smelt exist mainly as hatchery fish that are raised, from egg to adult, at two locations. This year, over 55 thousand hatchery Delta Smelt were released into their historical habitat areas and there is now some early evidence of their survival and spawning. But the question remains: can we really expect a self-sustaining population of smelt to re-develop in habitat which has failed to support them in the past?

Recovery Plan

Delta Smelt. Photo credit: Renee Reyes. USBR.

In this blog, I focus on the recovery plan to obtain insight into why recovery efforts have failed, despite a large body of research findings on what smelt populations need for survival. I have a personal interest in the recovery plan because in 1995 I was appointed Team Leader to prepare (officially, to assist), for the USFWS, The Recovery Plan for the Sacramento/San Joaquin Delta Native Fishes (the Plan). The Team consisted of 10 scientists with knowledge of the Delta and its fishes, representing academia, state and federal agencies, and water agencies[1]. Given the perceived urgency of our task we met frequently with a high level of participation from all members, finishing the Plan in about a year.

Early in process, the Team proposed broadening our efforts to include other native fishes that were in decline from poor habitat conditions in the Delta. Our argument was basically that recovering multiple species together fit well under Section 2 of the ESA which says that a primary purpose of the ESA is to provide a means for the conservation of ecosystems on which endangered and threatened species depend. To my surprise, the proposal was accepted by USFWS. “Accordingly, the purpose and scope of this recovery plan is to outline a strategy for the conservation and restoration of the Sacramento-San Joaquin Delta that currently supports or has the potential to support Delta native fishes (USFWS 1996, p.1)”

To create a multi-species plan, we established five criteria for adding additional species to the Plan and chose seven species: Delta Smelt, Longfin Smelt, Sacramento Splittail, Green Sturgeon, Sacramento Late Fall-run Chinook Salmon, Spring-run Chinook Salmon, and San Joaquin Fall-run Chinook Salmon. We did not include Sacramento Winter-run Chinook salmon because it had been listed previously and had its own recovery plan. Sacramento Perch were added by the USFWS after the initial draft of the Plan was completed, even though it was extirpated from the Delta.

A Naïve Approach

In retrospect, this idealistic approach was naïve. Only the Delta Smelt had legal clout, so other species could be largely ignored by managers, at least until Longfin Smelt, Spring-run Chinook, and Green Sturgeon also became listed under the ESA. Sacramento Splittail were listed for a short period but became delisted as more and better information on their biology developed (Moyle et al. 2004). An ecosystem-based approach to management of the Delta also emerged from the signing of the Bay-Delta Accord on December 15, 1994, which was supposed to restrict exports and set salinity standards that restricted outflow, to an extent. Yet the Accord (as CALFED Bay-Delta program) failed in its mission, at least as far as native fishes are concerned, despite the development of the Strategic Plan for the Ecosystem Restoration Program (ERP, issued in 1998). For Delta Smelt and other listed fishes, the goals of the recovery Plan were incorporated the ERP. The expectations were that other native fishes would have increasing or stable populations in 25 years (i.e. by 2023). The evidence is clear that this has not happened [2]. So, the rest of this blog focuses in on why the Plan also failed to recover the Delta Smelt and Delta fish habitats.

I reread the Plan after a long absence and the first thing that struck me was how little we knew about Delta Smelt at the time. We relied heavily on a few older published studies, agency reports where smelt were incidental catches, anecdotal and unpublished reports, and the life history study by Moyle et al. (1992). For quantitative assessment of distribution and abundance, such as it was, the Team relied on data from the Fall Midwater Trawl Survey of CDFW, which we thought had the best representation of both adult smelt numbers and distribution. This sampling program was established to monitor the abundance of Striped Bass, not smelt, but was regarded as generally useful for monitoring all pelagic fishes in the upper estuary and Delta.

Causes of Smelt Decline

The Team generally agreed Delta Smelt had declined to a small fraction of their historical population size, which was assumed to be represented by base-lined data from 1967-1981. The reduced populations in 1982-1992 were used for comparison, although 1987-92 were drought years. After the initial decline, most smelt seemed to be confined to the Sacramento River channel between Collinsville and Rio Vista. The Team outlined several plausible explanations for the decline. In the Plan, the causes of decline were stated to be “multiple and synergistic but seemed to be in the following order of importance (p. 19):”

1. Reduction in outflow

2. Entrainment losses to water diversions

3. High outflows

4. Changes in food

5. Toxic substances

6. Disease, competition, and predation.

Reduction in inflow to the Delta, the result of decades of dam construction and diversions, was considered to be a logical cause, because subsequent outflow from the Delta was seemingly insufficient to carry juvenile smelt to their most productive rearing area, Suisun Bay, as outflow. However, Delta Smelt numbers showed a positive relationship with outflow (X2) before 1981-82 and negative relationship after that (Kimmerer 2002). In contrast, other pelagic fishes such as Striped Bass, Longfin Smelt and American Shad showed a fairly strong positive relationship between numbers and outflow in all years.

Estimates of fish entrainment in water diversions, especially in the big state and federal pumping plants in the south Delta, were largely based on analyses of CDFG (now CDFW) that entrainment of juvenile Striped Bass was a major cause of bass decline. This justified a hatchery program for rearing Striped Bass and a program for taking young-of-year bass from the salvage operations and rearing them in cages, to increase survivorship. For Delta Smelt, Kimmerer (2008) was the first to demonstrate potential large effects of the pumping plants on their survival.

High outflows were included as a possible cause of decline because the period of decline included both years with low outflow (1987-91) and years with exceptionally high outflows (1982, 1986). It was speculated that high outflow years could “flush” Delta Smelt, and their planktonic food supply, to unfavorable habitats downstream. The Team speculated that the combination of both exceptionally high and low outflows during the evaluation period created unfavorable conditions for smelt.

Changes in food reflected a general recognition that zooplankton seemed less abundant in Delta Smelt rearing habitat than they once were. Three lines of evidence were presented: the shift in copepod species from native to non-native species, blooms of the diatom Melosira, which was regarded as low quality food for zooplankton, and the invasion of the overbite clam, Corbula amurensis, which by 1986-87, was demonstrably depleting zooplankton populations in Suisun Bay. The first two causes of change were largely dismissed, but it was quickly accepted that the overbite clam invasion was likely depleting plankton populations (Kimmerer et al. 1994). The problem from a Delta Smelt perspective is that the invasion occurred after the major smelt decline had taken place. So, the clam might be preventing recovery but was regarded as an unlikely cause for the initial decline.

Toxic substances (contaminants), especially agricultural pesticides, were listed as a potential threat but unstudied. Subsequent laboratory studies indicated contaminants of various sorts were potentially a problem, but impacts of individual toxins were hard to pin down. Delta waters at times seemed a soup of contaminants, unhealthy for fish.

The Plan found “no evidence that disease, competition, or predation has caused Delta Smelt populations to decline, despite the abundance of introduced species in the estuary (p.22-23).” It was implied, however, that further study might show that species such as Striped Bass and Mississippi Silversides were having a negative impact. It was noted that CDFW stopped planting Striped Bass in the estuary in 1992 because of potential predation on endangered species.

The loss of genetic integrity due to hybridization of Delta Smelt with non-native Wakasagi had no published support. Later studies indicated this was not a problem.


The Plan and scientific thinking in the 1980s and 90s revealed no ‘smoking gun’ causes of decline of Delta Smelt. But the Team agreed the key to recovery of smelt was habitat restoration for each major life stage: spawning, larval and juvenile transport, rearing, and adult migration. This meant having adequate outflows for each life stage, each living in a food-rich environment that was relatively free of toxins and had low entrainment in diversions. The Plan indicated the smelt population would be considered restored “when its population dynamics and distribution pattern within the estuary are similar to those that existed in the 1967-1981 period.” The distribution requirement was particularly important because recovery of endangered fish species is usually focused on population size, not distribution. The Team developed very specific criteria for distribution, because before the decline Delta Smelt were widely distributed in the Delta, including the south and central Delta. The temporary resurgence of a smelt population in the 1990s almost met the abundance and distributional requirements for delisting. Rapid changes after that made recovery no longer possible.

Figuring out how to make recovery possible required a major research program, which was quickly instituted. Generous funding for research was important for producing the insights into smelt biology that were gained. Meanwhile, the decline continued, to the point that the natural population has largely disappeared, and hatchery smelt have been planted in ‘vacant’ Delta habitat. But the total amount of suitable habitat for Delta Smelt has further diminished by invasions of aquatic plants, especially Egeria densa. These plants now line Delta channels, slowing outflow and tidal flows, filtering out sediment and organic matter and making the water clearer and warmer. Habitat in the south and central Delta is now largely free of Delta Smelt and most other open-water fishes. Instead, it is lake-like habitat that supports common non-native species such as Largemouth Bass, Bluegill, and Black Bullhead. Elsewhere, Asian and overbite clams suppress zooplankton populations while fishes such as Mississippi Silverside prey on larval smelt and other fishes. Clearly, habitat for Delta Smelt has not recovered, nor has it for other species in the Delta Native Fishes Recovery Plan, with the possible exception of Sacramento Splittail (but see https://californiawaterblog.com/?s=splittail )

Failure of the Plan

The causes of decline and suppression of Delta Smelt and other native fishes continue to be multiple and are covered elsewhere (e.g., Moyle et al. 2018. Hobbs et al. 2017) so are beyond the scope of this blog. But it is clear that habitat for native fishes has worsened dramatically since the 1996 Plan was adopted. This trend continues with sea level rise, climate change, new invaders, and other factors. The questions then become: “How much habitat remains available for native fishes? Is it possible to create sufficient habitat through restoration?” Can we work with rapid environmental change in ways that favor native fishes or do we just ‘roll with the punches’? The discussion of alternative responses to climate-related changes in Suisun Marsh (Moyle et al. 2014) provides some ideas of how to respond.

In short, developing the Recovery Plan for the Sacramento/San Joaquin Delta Native Fishes was basically a good idea because it amounted to a Delta native fish habitat recovery plan. It failed in part because it was never instituted on a large enough scale under a coherent plan of shared governance among state and federal agencies. Providing water to agriculture has almost always trumped providing significant water for the Delta ecosystem and its fishes. This inequity is increasingly being recognized as a violation of the Public Trust, which has a particularly long history in relation to sharing water and has been undergoing a revival in recent years in California litigation. (e.g., D. Des Jardins. 2022, https://cah2oresearch.com/2022/05/23/california-senate-proposes-2-billion-program-to-balance-water-supply-and-water-rights/).

But the Plan also failed because the governance structure for Delta water and fishes has not been prepared for unanticipated changes to Delta habitats, especially those related to climate change and invasive species. Even the scientific community has been surprised by the rate of change, if not the trajectory. A grand experiment is underway to see if current Delta habitat can support a re-established, self-sustaining population of Delta Smelt. Regardless, the severe decline of Delta Smelt is a major indicator of the Plan’s failure and of the failure of more recent management efforts (Börk et al. 2020). Unless large-scale action is taken to make Delta habitats more favorable to native freshwater fishes, the other native fishes in the Plan (and outside the Plan) will likely follow the trajectory of Delta Smelt, if on longer time scales.


An ecosystem-based approach is needed to allow native aquatic species and their ecosystems to persist (Mount et al. 2019). As the recovery Plan and the CalFed strategic plan show, using this approach has attractive features, but so far the approach has failed to protect native fishes. One option is to develop biological goals for the Delta and then use multiple linked species models to define habitat conditions needed to reach those goals (Dahm et al. 2019). Then, all it takes is strong cooperative leadership, especially from state and federal fish and water agencies, to develop and use an ecosystem-based approach and to acquire the resources to implement it. Can these agencies actually work together, along with NGOs and diverse groups with interests in the Delta, to create conditions favorable for recovery of desirable species? In particular, can sufficient water be provided for the environment under the Public Trust or other laws? Or is it too late to ‘restore’ appropriate habitats? If the latter is the case, we need to decide what the Delta ecosystem of the future should look like and what species we want living there. Otherwise, nature will decide for us.

Peter B. Moyle is a Distinguished Professor Emeritus at the University of California, Davis and is Associate Director of the Center for Watershed Sciences. This blog is originally posting on Dr. Moyle’s birthday. Happy birthday Dr. Moyle!!! 🙂

Further Reading

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

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. https://www.deltacouncil.ca.gov/pdf/science-program/biological-goals/2019-09-18-April-2019-biological-goals-final-report.pdf

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).

Kimmerer, W.J. 2002. Effects of freshwater flow on abundance of estuarine organisms: physical effects or trophic linkages? Marine Ecology Progress Series 243:39-55.

Kimmerer WJ. 2008. Losses of Sacramento River Chinook salmon and Delta smelt to entrainment in water diversions in the Sacramento-San Joaquin Delta. San Francisco Estuary Watershed Science 6(2).

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. https://www.ppic.org/wp-content/uploads/a-path-forward-for-californias-freshwater-ecosystems.pdf

Moyle, P.B., R. D. Baxter, T. Sommer, T. C. Foin, and S. A. Matern. 2004. Biology and population dynamics of Sacramento splittail (Pogonichthys macrolepidotus) in the San Francisco Estuary: a review. San Francisco Estuary and Watershed Science [online serial] 2(2):1-47.http://repositories.cdlib.org/jmie/sfews/

Moyle, P.B., J. Durand, and C. Jeffres. 2018. Making the Delta a Better Place for Native Fishes. White Paper, Orange County Coastkeeper and Center for Watershed Sciences, University of California. 63 pp.[available from author]

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., A. D. Manfree, and P. L. Fiedler. 2014. Suisun Marsh: Ecological History and Possible Futures. Berkeley: University of California Press.

Moyle, P.B., R. M. Quiñones, J.V.E. Katz, and J. Weaver. 2015. Fish Species of Special Concern in California. 3rd edition. 842 pp. Sacramento: California Department of Fish and Wildlife. https://www.wildlife.ca.gov/Conservation/Fishes/Special-Concern

[1] I apologize for giving the ERP Strategic Plan such short shrift. It has many good features including taking an adaptive management approach and basing management recommendations on conceptual models (full disclosure: I was a member of the Core Team that produced the document).

[2] Team members were Peter Moyle, Robert Pine (Executive Secretary, USFWS), Larry R. Brown (USGS), C.H. Hanson (Hanson Environmental), Bruce Herbold (USEPA), Kenneth M. Lenz (USBR), Lesa Meng (USFWS), Jerry J. Smith (San Jose State University), Dale Sweetnam (CDFG), and Leo Winternitz (CDWR).

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A conservation bill you’ve never heard of may be the most important in a generation

by Andrew L. Rypel

This blog is a short introduction to a lesser known federal bill that is one of the most significant pieces of fish and wildlife legislation in decades. In Spring of 2021, Rep. Debbie Dingell (D-Mich.) and Rep. Jeff Fortenberry (R-Neb.) introduced the Recovering America’s Wildlife Act. During July 2021, a separate adaptation of the act was also introduced in the Senate (S.2372) by Sen. Martin Heinrich (D-NM) and Sen. Roy Blunt (R-MO). At its core, the bipartisan bill seeks to provide $1.39B in annual funding for state and tribal fish and wildlife agencies to protect and conserve declining species.

Fig. 1. Status of native fishes in California. Figure adapted from data in Moyle et al. 2011.

Of course, Californians are keenly aware of the jeopardy facing native biodiversity. 83% of our highly endemic fish fauna is declining. Many native fishes not currently listed under the US Endangered Species Act will be listed in the future as populations continue to collapse. A bevy of plant and animal communities are also struggling, which provided motivation for California’s Biodiversity Initiative and the 30×30 Partnership. Outside the existential threat to biodiversity, species declines create a regulatory environment filled with uncertainty – this is bad for businesses of all stripes. Conservation solutions with tangible benefits for ecosystems, species, and people provide win-win opportunities that will be increasingly needed in the future. 

Insufficient funds for conservation have plagued the vast majority of declining species. For example, State Wildlife Action Plans or SWAPs are a common mechanism for state fish and wildlife agencies to prioritize species conservation needs. Sometimes, these funds are used for grants to assist with such work – often termed ‘state wildlife grants’ or SWGs. Yet in most states funds allocated for SWAPs and SWGs are minuscule compared to need. Thus most actions just don’t get done. That may seem odd to many in the public because they see lots of other things happening at the agencies. 

How are most state fish and wildlife agencies funded?

For better or for worse, most state wildlife agencies operate under a “customer-driven” funding model. The bulk of funding for conservation is from purchases of hunting and fishing licenses. A smaller fraction of agency budgets is from federal excise taxes. On the fisheries side, the Dingell Johnson Act (AKA Sportfish Restoration) is a federal excise tax on recreational fishing and boating expenditures, and also a portion of boat gas. On the wildlife side, Pittman-Robertson Federal Aid in Wildlife Restoration Act (or ‘PR’ funds) derives funding from a federal excise tax on firearms and ammunition. But even these funds are held in trust by the USFWS and redistributed back to state agencies using an algorithm partly based on license sale statistics. Combined, license sale revenues and excise tax funds have been the primary engines for growth in American fisheries and wildlife management over the last ~80 years. It therefore also means that hunters and anglers have traditionally paid for most fish and wildlife conservation programs. And because they paid the bill, they more or less drove policy conversations during this time. One result of this system is that a lot of outstanding science and management actually got done, it’s just that it focused disproportionately on ‘game species’. Meanwhile, there was little funding and work for countless other native fishes that weren’t valued by the majority customer block (Rypel et al. 2021). Redressing inequities and funding biases requires dealing with this funding issue in a straightforward way.

Fig. 2. Long-term decline of fishing license sales in California expressed either as an absolute total (left) or on a per capita basis (right). Data from US Fish and Wildlife Service National Fishing License Reports.

Another major problem with the customer-driven funding model is that sometimes customer blocks shrink and disappear. Fishing and hunting license sales have actually been declining for some time (Fig. 2). The many potential reasons for such trends warrant their own blog, but their effects on conservation budgets are tangible. In California, the decline has been blunted by a growing human population over this time frame. Yet as the state’s population recently plateaued near 40M, participation rates have continued to decline and we are starting to see the downstream funding impacts. For almost 30 years (1958-1988), roughly 10% of California’s population would buy a fishing license annually, peaking in 1988 (Fig. 2, right). Today, only ~4% buy a license. So funds for traditional fish conservation programs have taken a major hit. Some of this budgetary gap has likely been made up by bond measures (e.g., Prop 1). Yet, many species have life cycles that rely on essential habitats not targeted by bonds. Further, most funding for fish work in California is concentrated on threatened and endangered species. Thus a stunning diversity of species can fall through these conservation funding cracks. In the fisheries realm, I think of species like golden trout (our state fish) or coastal cutthroat trout. It gets worse for fishes like California roach, California hitch, California speckled dace or even Sacramento perch.

California has a recent State Wildlife Action plan with a wide range of priorities that would benefit from funding. It is estimated that the Recovering America’s Wildlife Act would provide funding to implement 75% of every state’s action plan. I went through the CA SWAP document this week and was impressed at the detail and comprehensive nature of California’s current SWAP. Here are some goals from the SWAP I found personally interesting/admirable on what could get done if the Recovering America’s Wildlife Act were to pass. This list is not exhaustive or ordered in any specific way but provides insight into the type of work that could be done in California should the act pass:

  • In North Coast and Klamath Province, by 2025, miles of streams with target amphibian population are increased by at least 5% from 2015 miles.
  • In Bay Delta and Central Coast lagoons, by 2025, acres/miles with desired channel pattern (connected floodplains) are increased by at least 5% from 2015 acres/miles.
  • In the San Joaquin River, by 2025, miles of river where native species are dominant are increased by at least 5% from 2015 miles.
  • In the Deserts, by 2025, acres/miles with desired inches of groundwater are increased by at least 5% from 2015 acres/miles.
  • By 2025, population of Eagle Lake Rainbow Trout is increased by at least 5% from the 2015 population size.
  • In the South Coast, translocate species to increase current distribution; specifically, translocate Santa Ana sucker, Santa Ana speckled dace, and UTS into suitable habitat in the Big Tujunga, San Gabriel, and Santa Clara watersheds.
  • Develop or update and implement grazing BMPs in the Sierra Nevada.
  • Remove introduced brook trout in the context of recovery of listed Lahontan cutthroat trout.
  • By 2025, acres of wet mountain meadow habitat increased by at least 5% from 2015 acres.
  • Evaluate current condition and estuarine needs for coho salmon, eulachon, Pacific lamprey, and longfin smelt in key estuaries (i.e., Smith, Klamath, and Eel rivers and Humboldt Bay).

Current Status of Recovering America’s Wildlife Act

After years of working its way through Congress. The Recovering America’s Wildlife Act has now been approved by both chambers of Congress, meaning it can receive floor votes soon. The bill is notable for its bipartisan support, especially in such hyper-polarized times. The Senate bill received 32 cosponsors – including 16 Republicans. Many leading conservation organizations support the act, including The American Fisheries Society and The Wildlife Society.

The act still faces obstacles in both chambers though. There remains debate over how to pay for it and what features in the draft act will be included in the final act. As it stands, the act would:

  1. Provide ~$1.39B in funding annually to state fish and wildlife agencies to implement their SWAPs.
  2. Almost $100M in funding annually to assist tribal agencies in recovery with declining species.
  3. 10% of the funds would become available for an annual grants competition program to enhance multi-state cooperation on conservation.

Other benefits of implementing the act include leveraging existing funds with other agencies and institutions, providing greater regulatory certainty to industry, and empowering fisheries and wildlife professionals to successfully conserve natural resources for future generations.  

Passage of the Recovering America’s Wildlife Act would be a major milestone in the management of America’s natural resources. It would signal a shift away from the entrenched customer-based model of conservation, to a degree. And it is a much needed example for how conservation activities can occur in a bipartisan way. Even if folks can’t agree on everything, sometimes, they can agree on something – why not conservation of our fragile biodiversity?

Golden trout caught from the Golden Trout Wilderness, California in 2014. Photo by DaveWiz84 downloaded from wikicommons.org.

Andrew L. Rypel is a professor of Wildlife, Fish, and Conservation Biology and Co-Director of the Center for Watershed Sciences at the University of California, Davis.

Further Reading

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

Rypel, A.L., P. Saffarinia, C.C. Vaughn, L. Nesper, K. O’Reilly, C.A. Parisek, M.L. Miller, P.B. Moyle, N.A. Fangue, M. Bell-Tilcock, D. Ayers, and S.R. David. 2021. Goodbye to “rough fish”: paradigm shift in the conservation of native fishes. Fisheries 46 605-616.

Rypel, A.L. 2022. Nature has solutions…What are they? And why do they matter? California WaterBlog https://californiawaterblog.com/2022/03/27/nature-has-solutions-what-are-they-and-why-do-they-matter/




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How engineers see the water glass in California

Engineering a water glass at 50 percent. Source: xkcd.com

This is another dry year.  How do California’s engineers see a partially-full water glass?  Mostly the same as they did in the original 2012 version of this post, but we’ve added a few more perspectives.

by Jay R. Lund

Depending on your outlook, the proverbial glass of water is either half full or half empty. Not so for engineers in California.

Civil engineer (and George Carlin): The glass is twice as big as it needs to be.

Flood control engineer: The glass should be 50 percent bigger.

Army Corps levee engineer: The glass should be 50 percent thicker.

Mexicali Valley water engineer: Your leaky glass is my water supply.

Delta levee engineer: Why is water rising on the outside of my glass?

Dutch levee engineer: This water should be kept in a pitcher.

Southern California water engineer: Can we get another pitcher?

Northern California water engineer: Who took half my water?

Lower Colorado River water engineer (outside of California): California took half my water.

Lower Colorado River water engineer (inside California): Sorry for shortages in other states.

Tulare Basin water engineer: I’m saving that empty storage to capture floods for recharge.

California Water Commission engineer: Would a bigger glass provide public benefits?

USBR CVP or NOAA engineer: Is that water cold?

Consulting engineer: How much water would you like?

Environmental engineer: I wouldn’t drink that.

Water reuse engineer: Someone else drank from this glass.

Groundwater engineer: Can I get a longer straw?

Google engineer: Stereo view disabled on device.

Academic engineer: I don’t have a glass or any water, but I’ll tell you what to do with yours.

Lawyers, NGOs, managers, regulators, and elected officials also seem to have different views of glasses at 50% of their capacity.  We can start a collection of these perspectives.

Quote Investigator has a more scholarly view of the subject. https://quoteinvestigator.com/2022/04/08/wrong-size/

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

Further reading

Munroe, Randall. Glass Half Empty. xkcd.com

Quote Investigator (2022),” Optimist: The Glass Is Half Full. Pessimist: The Glass Is Half Empty. Comedian: The Glass Is the Wrong Size,” https://quoteinvestigator.com/2022/04/08/wrong-size/

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Five “F”unctions of the Central Valley Floodplain

by Francheska Torres, Miranda Tilcock, Alexandra Chu, and Sarah Yarnell

The Yolo Bypass is one of two large flood bypasses in California’s Central Valley that are examples of multi-benefit floodplain projects (Figure 1; Serra-Llobet et al., 2022). Originally constructed in the early 20th century for flood control, up to 75% of the Sacramento River’s flood flow can be diverted through a system of weirs into the Yolo Bypass and away from nearby communities (Figure 2; Salcido, 2012; Sommer et al., 2001). During the dry season, floodplain soils in the bypass support farming of seasonal crops (mostly rice). Today, the bypass is also widely recognized for its ecological benefits. In 1994, much of the bypass was designated as a Wildlife Area by the Fish and Game Commission, with the goal of reestablishing wetland habitat for waterbirds along with other wildlife (Yolo Bypass Wildlife Land Management Plan, 2008). The Yolo Bypass is one potential representation of harmony that can be achieved between floods, farming, fish, and feathers (Salcido, 2012).

The Yolo Bypass supports a range of broad multi-benefits to ecosystems and society:

Figure 1: Conceptual diagram of the role of multi-benefit projects in the context of social-ecological systems (Serra-Llobet et al., 2022).

Flood functions

Figure 2. Yolo Bypass, California. (A) Location Map (B) Regional Map (C) Yolo Bypass (Serra-Llobet et al., 2022).

During winter when high runoff fills rivers, the bypass provides space for floodwaters to spread and travel downstream to the Delta without damaging homes or communities. During high precipitation events, excess water enters the Yolo Bypass at Fremont Weir when Sacramento River flows exceed ~55,000 cubic feet per second (Sommer et al., 2001). When the Sacramento River reaches 27.5 feet at Sacramento’s I Street Bridge, the Sacramento Weir can be opened manually for additional water to drain into the Yolo Bypass, and eventually into the bypass’ Toe Drain near Rio Vista. During storms, you can check if flows over-top the Fremont Weir, using the California Data Exchange Center (CDEC) at https://cdec.water.ca.gov/guidance_plots/FRE_gp.html

Farm functions

In dry months (late spring and summer), the Yolo Bypass supports farming of seasonal crops including rice, safflower, processing tomatoes, corn, and sunflower. Wild rice has a tolerance to colder weather and is one of the types of rice grown in the bypass (Sommer et al., 2011). In winter (Dec-Mar), the existing field infrastructure can extend the duration of water inundation to facilitate development of invertebrate biomass (Corline et al., 2017), growing food to help struggling fish populations. Leftover crop residue from harvested lands supports fish and wildlife as a foraging area.

Fish functions

During winter when flooding occurs, the Yolo Bypass becomes a food-rich habitat for many fish species, including Chinook Salmon. Floodplains are important nursery habitats for juvenile salmon in California, providing growth opportunities from a highly productive food web (Jeffres et al., 2020). Juvenile salmon rearing on the floodplain can grow up to 1mm a day (Corline et al., 2017; Katz et al., 2017; Rypel et al., 2022)! For small salmon, growth rates provide huge benefits for their journey to the ocean and later survival. 

Feather functions

The Yolo Bypass is part of the Pacific Flyway, one of four primary migration routes through North America for birds, particularly waterfowl (Bird et al., 2000; Eadie et al., 2008; Sommer et al., 2011). Each year, many bird species migrate through the Yolo Bypass or use this area for nesting. The Yolo Bypass Wildlife Area (YBWA), in particular, is a success story for shorebird habitat and productive waterfowl (Salcido, 2012). The Swainson’s hawk, a threatened species, frequents YBWA, with up to 70 individuals observed foraging on the floodplain at once (Sommer et al., 2011). YBWA also provides recreational (bird watching and hunting) and educational opportunities.

Filter functions

Floodwaters spread across the bypass, seep into the subsurface recharging groundwater, and fill local shallow aquifers. Nitrogen and phosphorus are also delivered and infiltrate floodplain soils subsequently assisting plant growth. Groundwater provides a key water source during dry summers and times of drought, with roughly 85% of Californians relying on groundwater as a source of drinking water (Harter, 2008). In California approximately 40% of water demand is met by groundwater (Figure 3).

Figure 3: California’s Statewide Water Supply and Percent Total Supply Met by Groundwater, by Hydrologic Region (2005-2010) (Department of Water Resources, 2013).


Management goals for the Yolo Bypass have expanded from flood management and agriculture to include habitat management and restoration for birds and fishes (Serra-Llobet et al., 2022). This current, multipurpose, version of the Yolo Bypass is a model of an increasingly well-managed multi-benefit social-ecological system with public-private partnerships that allows wildlife, flood risk reduction, and agriculture to co-exist adjacent to a major urban region. Its potential to provide greater inundated floodplain habitat with more natural patterns of inundation is widely recognized, with expanding benefits for nature and humans. Documentation of the remarkable ecological value of the inundated bypass has helped to shepherd a new emphasis on floodplain restoration throughout the Sacramento-San Joaquin Valley (Johnson, 2017).

Franceska Torres is a Junior Specialist at the Center for Watershed Sciences studying otoliths and what they can tell us about salmon migration, their age and their growth. She got her bachelor’s degree in Marine and Coastal Science with an emphasis in Marine Ecology and Organismal Biology from the University of California, Davis. Miranda Bell Tilcock is an Assistant Specialist at the Center for Watershed Sciences. Alexandra Chu is a Junior Specialist at the Center for Watershed Science. She works on the Eyes and Ears Project, peeling eye lenses from Chinook Salmon for stable isotope analysis to reconstruct their life history and identify critical rearing habitats. Sarah Yarnell is an Associate Professional Researcher at the Center for Watershed Sciences. Her studies focus on integrating the traditional fields of hydrology, ecology and geomorphology in the river environment.

Further Reading

Bird, J. A., Pettygrove, G. S., & Eadie, J. M. (2000). The impact of waterfowl foraging on the decomposition of rice straw: mutual benefits for rice growers and waterfowl. Journal of Applied Ecology, 37(5), 728–741. https://doi.org/https://doi.org/10.1046/j.1365-2664.2000.00539.x

Corline, N. J., Sommer, T., Jeffres, C. A., & Katz, J. (2017). Zooplankton ecology and trophic resources for rearing native fish on an agricultural floodplain in the Yolo Bypass California, USA. Wetlands Ecology and Management, 25(5), 533–545. https://doi.org/10.1007/s11273-017-9534-2

Department of Water Resources. (2013). California Water Plan. Department of Water Resources. https://data.cnra.ca.gov/dataset/california-water-plan-groundwater-update-2013

Eadie, J. M., Elphick, C. S., Reinecke, K. J., & Miller, M. R. (2008). Wildlife values of North American ricelands. In S. W. Manley (Ed.), Conservation in ricelands of North America (pp. 7–90). The Rice Foundation. http://pubs.er.usgs.gov/publication/5211451

Harter, T. (2008). Watersheds, Groundwater and Drinking Water: A Practical Guide (L. Rollins (Ed.)). University of California Agriculture and Natural Resources. https://books.google.com/books?id=AmKl8C7zVoAC

Jeffres, C. A., Holmes, E. J., Sommer, T. R., & Katz, J. V. E. (2020). Detrital food web contributes to aquatic ecosystem productivity and rapid salmon growth in a managed floodplain. PLOS ONE, 15(9), e0216019. https://doi.org/10.1371/journal.pone.0216019.

Johnson, M. (2017). Cosumnes River Provides Model for Floodplain Restoration. The New Humanitarian. https://deeply.thenewhumanitarian.org/water/articles/2017/04/19/cosumnes-river-provides-model-for-floodplain-restoration-in-california

Katz, J. V. E., Jeffres, C., Conrad, J. L., Sommer, T. R., Martinez, J., Brumbaugh, S., Corline, N., & Moyle, P. B. (2017). Floodplain farm fields provide novel rearing habitat for Chinook salmon. PLOS ONE, 12(6), e0177409. https://doi.org/10.1371/journal.pone.0177409

Rypel, A. L., Alcott, D. J., Buttner, P., Wampler, A., Colby, J., Saffarinia, P., Fangue, N., & Jeffres, C. A. (n.d.). Rice & salmon, what a match! | California WaterBlog. Retrieved May 5, 2022, from https://californiawaterblog.com/2022/02/13/rice-salmon-what-a-match/

Salcido, R. E. (2012). The success and continued challenges of the Yolo bypass wildlife area: A grassroots restoration. In Ecology Law Quarterly (Vol. 39, Issue 4). https://doi.org/10.15779/Z38B541

Serra-Llobet, A., Jähnig, S. C., Geist, J., Kondolf, G. M., Damm, C., Scholz, M., Lund, J., Opperman, J. J., Yarnell, S. M., Pawley, A., Shader, E., Cain, J., Zingraff-Hamed, A., Grantham, T. E., Eisenstein, W., & Schmitt, R. (2022). Restoring Rivers and Floodplains for Habitat and Flood Risk Reduction: Experiences in Multi-Benefit Floodplain Management From California and Germany. Frontiers in Environmental Science, 9. https://doi.org/10.3389/fenvs.2021.778568

Sommer, T.R., Harrell, B., Nobriga, M., Brown, R., Moyle, P., Kimmerer, W., & Schemel, L. (2011). California’s Yolo Bypass: Evidence that flood control Can Be compatible with fisheries, wetlands, wildlife, and agriculture. Fisheries, 26(8), 6–16. https://doi.org/10.1577/1548-8446(2001)026<0006:cyb>2.0.co;2

Sommer, T. R., Nobriga, M. L., Harrell, W. C., Batham, W., & Kimmerer, W. J. (2001). Floodplain rearing of juvenile chinook salmon: Evidence of enhanced growth and survival. Canadian Journal of Fisheries and Aquatic Sciences, 58(2), 325–333. https://doi.org/10.1139/f00-245

Yolo Bypass Wildlife Land Management Plan. (2008). https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=84924&inline

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Government Spending on Stormwater Management in California

By Erik Porse, Maureen Kerner, Brian Currier, David Babchanik, Danielle Salt, and Julie Mansisidor

Stormwater infrastructure in cities is highly visible and serves to mitigate flooding and reduce pollution that reaches local waterbodies. Being so visible, it might be reasonable to assume that stormwater is adequately funded both in infrastructure and water quality management. Yet, stormwater infrastructure and water quality improvement are notoriously difficult to fund. Paying for stormwater quality improvements in California has been a multi-decade challenge due to the industry’s relatively recent emergence during a time of fiscal constraints on local governments.

US funding needs for stormwater grew significantly after 1987. Amendments to the Clean Water Act (CWA) required municipalities to reduce pollutants such as sediment, oil and greases, and bacteria in stormwater. Through the CWA, regulatory agencies develop targets for pollution reductions, which municipalities must meet to obtain a discharge permit through the National Pollutant Discharge and Elimination System (NPDES) administered by the US Environmental Protection Agency (EPA) and state agencies. This new duty required localities to reconsider stormwater systems as more than just pipes and gutters to manage flooding.

Responsibility for most stormwater management, including funding, lies with city and county governments. This creates challenges in funding stormwater programs and projects. Municipal stormwater programs were established more recently than other water sector programs and often lack dedicated funding sources. In California, many stormwater programs were developed in recent decades when local taxation powers were already constrained by proposition ballot measures.[i] Without dedicated funding streams, municipal stormwater programs compete against other essential municipal services.

Amid fiscal challenges for local governments, diverse and integrated approaches to stormwater infrastructure design have emerged. Traditional stormwater designs relied on centralized “grey” infrastructure such as pipes, channels, and gutters, which conveyed water quickly from urban streets. In recent years, distributed designs, sometimes called green infrastructure or low-impact development (LID), have grown increasingly popular. These approaches offer opportunities to connect stormwater management goals with other planning sectors. Well-designed distributed green infrastructure can support urban and water planning needs such as street beautification, multi-modal transit, water conservation, and groundwater recharge. In California, green infrastructure typically includes native and drought-tolerant vegetation. Cities view these opportunities as “win-wins” that offer cost savings and support holistic approaches to broader community goals.

While cities recognize the benefits of these planning innovations, the adequacy of local stormwater spending in California has been a contentious policy issue for decades. In the early 2000s, state regulators developing municipal NPDES permits contended with claims of high costs for permit compliance. Local governments lacked standardized rubrics for tracking comparable spending. In 2018, similar issues arose as the California State Auditor reviewed local watershed studies in Southern California, the San Francisco Bay Area, and the Central Valley, which identified large stormwater investment needs. Today across California, stormwater funding efforts are growing, but they require years of planning. More cities and counties are developing funding through popular ballot measures such as Measure W in Los Angeles County that funded its regional Safe, Clean Water Program. SB 231 in 2017 resolved a long legal debate by clarifying that stormwater systems were not subject to Proposition 218 requirements, but many localities continue to seek popular approval for new or updated local stormwater fees. Examples exist for both successful and unsuccessful public measures.

During this time, very few state or national studies estimated what communities actually spend on stormwater. America’s Infrastructure Report Card, a national benchmark of infrastructure spending, addressed stormwater for the first time in 2019 and estimated a national funding gap of at least $7.5 billion (ASCE 2021). In California, a 2005 study by the Office of Water Programs (OWP) at Sacramento State surveyed six municipalities to estimate costs for compliance with permit requirements, finding that communities spent between $18 and $46 per household on permit compliance activities (Currier et al. 2005). In 2014, the Public Policy Institute of California estimated statewide annual stormwater funding needs in the range of $1 to $1.5 billion across the state, while current funding was only $500 to $800 million based on extrapolations from a few communities (Hanak et al. 2014).

In the context of the continued policy debates and local funding challenges for stormwater, in 2018, OWP sought to quantify existing stormwater funding and update its 2005 study (Babchanik et al 2022, Currier et al 2005). We explored if questions of municipal stormwater spending could be answered with data that already existed, but was only available in static, disaggregated, and difficult-to-use sources. This occurs in many sectors of water management in California.

After surveying possible sources, we identified spending and budget data for stormwater management in over 160 local governments in California through publicly available annual reports (discoverable through public sources). We extracted the data and developed standardized rubrics for classifying costs. The level of detail varied widely, with some localities reporting many years of data in a report, broken down by categories, and others only reporting a single year’s aggregated totals. Activities identified in NPDES permits provided a template for categorizing costs, including public education, pollution prevention, and illicit discharge detection and elimination. We standardized all data to 2018-dollar values.

Once categorized and standardized, we aggregated the totals and examined trends. Stormwater duties are dispersed across cities, counties, and flood control districts. The publicly-available reporting identified over $700 million in annual spending on stormwater management. However, this is an underestimate, as it only covered about half of the state’s urban and suburban populations. The availability of data varied across regions and depended on local municipal or regional board practices regarding publication of annual reports. Some local governments also posted annual reports on their websites. The composite database is available for future use.

Spending varied widely across the state. Annual expenditures for cities ranged from $48,000 to $88 million (median=$890,000), while annual county expenditures ranged from $400,000 to $51 million (median=$13 million). Counties and flood control districts budgeted on average more per entity than cities ($18 million/year vs. $3 million/year), but in aggregate, cities spent more than counties ($520 million/year vs. $170 million/year).

We also examined trends in per capita spending by cities. Reported data indicates that 50% of cities spent $14/person or less annually on stormwater management. A few small- or medium-sized cities had large reported per capita spending on stormwater (over $300/person-year). Average and median per capita spending values were $35/person-year and $14/person-year, respectively. Quantifying per capita spending was possible for cities but not counties, because county programs do not have identifiable populations. Many regions have overlapping city and county stormwater programs, with counties taking on some region-wide duties that make it difficult to compare values across regions.

We also examined spending trends by categories of activities. Many municipalities categorized costs based on broad categories from federal Phase 2 NPDES permits. The lumped category of “Pollution Prevention” had the most spending, followed by “Operations and Maintenance” and “Capital Costs.” While these categories offer an easy rubric for standardizing costs, they provide limited insight into the outcomes of spending. Some municipalities reported more detailed data with activities such as “Street Sweeping”, “Pesticide and Fertilizer Management”, and “Hazardous Household Waste Collection”. In developing standardized cost-reporting requirements, both regulatory agencies and local governments would benefit from a coherent list of detailed activities. This would enhance opportunities to evaluate the beneficial outcomes of local stormwater management investments.  

Overall, the analysis validated the approach of estimating stormwater spending trends by collecting and standardizing annual budget and expenditure reporting from municipalities. The analysis also demonstrated that aggregating such data can address difficult and long-standing policy questions. However, the available data was not formatted for easy analysis and was only available for some of the state.

California regulators and municipalities will continue efforts to fund stormwater management and quantify funding gaps in future years. In California’s federated system of government that spans local and state agencies, quantifying trends can be challenging. Yet, data often already exists to answer some large policy questions. If the data become available in better formats for analysis, the information can help localities and state agencies develop funding plans to address California’s integrated sustainability and resilience goals. Stormwater management programs have the potential to help achieve diverse climate and equity goals, from groundwater recharge to urban beautification to sanitation and housing. Addressing these critical challenges will require a renewed understanding of the value of well-funded public services and infrastructure, including stormwater.

Erik Porse is a Research Engineer at OWP at Sacramento State, and an Assistant Adjunct Professor at UCLA’s Institute of the Environment and Sustainability. Maureen Kerner is a Research Engineer at OWP at Sacramento State and Associate Director of the Environmental Finance Center at Sacramento State. Brian Currier is a Research Engineer at OWP at Sacramento State. David Babchanik is a Civil Engineering student at Sacramento State and lead author of the associated research study. Danielle Salt is a Research Engineer at OWP at Sacramento State. Julie Mansisidor is the Publications Manager at OWP at Sacramento State.

Further Reading:

Babchanik, D., Salt, D., Kerner, M., Currier, B., and Porse, E. (2022). Municipal Stormwater Management Spending in California: Data Extraction, Compilation, and Analysis. Environmental Management, 1-13.

Currier, B., Jones, J.M., and Moeller, G. (2005) NPDES Stormwater Cost Survey: Final Report. Office of Water Programs at Sacramento State. Prepared for the California State Water Resources Control Board, Sacramento, CA

EFC at Sacramento State. (2020). Evaluating Benefits and Costs for Stormwater Management. Part 2: Evaluating Municipal Spending in California. EPA Region 9 Environmental Finance Center at Sacramento State University.

33 U.S.C. 1251 – 1376; Chapter 758; Amended February 4 (1987) Federal Water Pollution Control Act (Clean Water Act). Washington, D.C.

ASCE (2021) Report Card for America’s Infrastructure. American Society of Civil Engineers.

Campbell, C. W., Dymond, R., Key, K., and Dritschel, A. (2018). Western Kentucky University Stormwater Utility Survey 2018. Western Kentucky University.

CASQA and SCI Consulting. (2017). “Stormwater Funding Barriers and Opportunities.” California Stormwater Quality Association (CASQA).

Hanak, E., Gray, B., Lund, J., et al. (2014) Paying for Water in California. Public Policy Institute of California, San Francisco, CA.

Kea, K., Dymond, R., and Campbell, W. (2016). An Analysis of Patterns and Trends in United States Stormwater Utility Systems. JAWRA Journal of the American Water Resources Association, 52(6), 1433–1449. https://doi.org/10.1111/1752-1688.12462

US EPA. (1999) Economic Analysis of the Phase II Storm Water Rule. Chapter 4: Potential Costs, Pollutant Load Reductions, and Cost Effectiveness.

[i] Proposition 13 in 1972 constrained local property tax growth and Proposition 218 in 1986 required majority popular or landowner votes for new taxes and fees by local governments.

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The Putah Creek Fish Kill: Learning from a Local Disaster

By Alex Rabidoux, Max Stevenson, Peter B. Moyle, Mackenzie C. Miner, Lauren G. Hitt, Dennis E. Cocherell, Nann A. Fangue, and Andrew L. Rypel

Putah Creek is a small stream located in the Central Valley that has been extensively modified to suit urban and agricultural water needs. Following ratification of the Putah Creek Accord in 2000, however, the creek has also been proactively managed for restoration of native fishes, including fall-run Chinook salmon. The Accord stipulates that pulse flows be supplied to the lower creek during fall and spring to mimic a natural flow regime. A result from these environmental flows has been salmon spawning in the creek since 2003 (Yolo Bypass Wildlife Area Land Management Plan, 2008). Unfortunately, the future of  Putah Creek salmon is not yet secure.

In November 2021, salmon entering Putah Creek were part of a large fish kill in the lower creek. The event took everyone familiar with the creek by surprise and prevented successful migration of the creek’s fall salmon. Only 4 or 5 adult Chinook salmon made it upstream to suitable spawning habitat. The result was particularly tragic as it followed on the heels of the restoration of a salmon run in the creek, as well as habitat for other fishes. Salmon spawning in the creek has produced 10s of thousands of out-migrating juveniles. The return of salmon is an important, highly visible symbol for why Putah Creek is often regarded as a role model for effective water management and environmental stewardship (Davis Enterprise, 5/24/2020).

In this blog, we describe the conditions that led to the fish kill in lower Putah Creek and the response to the kill by scientists and others monitoring the creek. Although the kill was a disaster for salmon and other fishes in the creek, it also demonstrated how representatives of diverse agencies could work together, without finger pointing, to find out what happened in order to prevent it from happening again. The response showed how the Putah Creek Accord is still working. The authors of this blog combined their collective experiences to conduct an autopsy, and in doing so, paint a detailed picture here of what happened.

Salmon in the creek

The fall of 2021 started well for the creek, as the creek was prepared to receive its annual salmon run. In early October, the Solano County Water Agency (SCWA) and soon to retire Putah Creek Streamkeeper, Rich Marovich, celebrated the removal of a longstanding low dam that caused formation of undesirable habitat upstream in what might otherwise have been spawning grounds for salmon. After years of failed negotiation and lack of regulatory enforcement, a unique relationship was formed with the help of UC Davis’s Dr. Peter Moyle, Water Audit, and SCWA that resulted in removal of the debris dam in the cool-water region of Putah Creek (Figure 1). This allowed for subsequent restoration activity to revitalize the stream bed in the area for salmon spawning. Similar restoration activities have been performed throughout the creek since 2016.

In early October, UC Davis researchers were gearing up for the annual sampling of fall-run Chinook salmon carcasses in the creek. As part of this effort, crews from UC Davis and SCWA canoed and inspected all 26-miles of Lower Putah Creek. The survey examined possible impediments to fish passage that could prevent upstream movement of adult salmon. This routine sampling has been in place since 2016 and salmon have been observed returning to spawn successfully in Putah Creek every year over this time frame.

The success of spawning is most evident in the spring when their juvenile salmon (smolts) begin out-migrating in droves, headed for the ocean. In 2018, over 30,000 juvenile salmon were captured and released from a rotary screw trap, highlighting the productive capacity and potential of the system. Researchers and agency staff alike had high expectations that 2021 would bring another large return of salmon. 2021 might also mark one of the first years in which natal-origin Putah Creek salmon (some of those 30,000 juveniles from 2018) could return to spawn in Putah Creek. With salmon populations struggling throughout the Central Valley, Putah Creek represents one of few locations where numbers are on the rise (California Water Blog, 5/13/2018).

In the months leading up to the annual adult salmon migration, SCWA worked closely with a multitude of regional partners including the Putah Creek Council, UC Davis, California Department of Fish & Wildlife (CDFW), and Los Rios Farms on timing of fall pulse flows and removal of the check dam at the base of the creek. The fall pulse flows have the intended purpose of attracting salmon to Putah Creek, but timing of the pulse is a balancing act of salmon migration patterns, flooding of waterfowl habitat, mosquito risks and water availability in the Yolo Bypass. Therefore, after close coordination with the regional partners, the fall pulse flow was scheduled to begin on November 2.

Atmospheric river rain event

On October 24, one-week before the scheduled pulse flow, a large atmospheric river event dropped 6-8 inches of rain on the Putah Creek and Cache Creek watersheds. The event was atypically early, providing 25-30% of the region’s annual average rainfall in just 24 hours. The large rainfall, in conjunction with the burn scar from the 2020 LNU Fire (which burnt over 90% of the Interdam Reach of Putah Creek), prevented most of the rainwater from soaking into the ground, and instead inundated Putah Creek with nutrient rich runoff. The rain event was so large, >1,500-cfs of creek water was released through the Putah Creek Diversion Dam for several hours during evening and early morning hours after the storm event. While the event was a natural pulse flow for salmon, several fish passage barriers were still in place, preventing salmon from migrating into Putah Creek on the coattails of the rain-driven pulse. These barriers include an earthen road crossing (Rd 106A, Figure 2, left picture) and an agricultural impoundment dam (the Los Rios check dam, Figure 2, middle and right pictures). In a typical year, both structures are removed to permit upstream passage of adult salmon and timed to coincide with the pulse flow.

The fish kill

Following the storm, on November 1, the two remaining fish passage barriers, the road 106A crossing and the Los Rios check dam, were removed.  At Los Rios Check Dam, several salmon were observed swimming upstream after the flashboards were removed. Presumably, salmon had moved up the Toe Drain and into the very lowest reaches of Putah Creek following the pulse from the storm. SCWA’s consulting wildlife biologist, Ken Davis, noticed a total of 6 moribund salmon, a prelude of what was to come. 

On November 2, the scheduled salmon attraction flows began (November 3rd through the 8th ).  At that time, UC Davis researchers observed a large-scale fish kill in Putah Creek near the Los Rios check dam. The kill included not only salmon, but Sacramento sucker, a variety of sunfishes, striped bass, largemouth bass, common carp, and mosquitofish; these fishes represented a wide range of sizes and diverse ecological niches. All dead fish were found within one mile of the check dam. 

During the field investigation, UC Davis researchers observed black, nutrient-rich water, entering Putah Creek just upstream of the Los Rios check dam.  The researchers then noted that water with low dissolved oxygen (DO) concentrations was being pumped from the Toe Drain into the CDFW Wildlife Refuge. They also noted and that water draining from the refuge ponds was re-entering Putah Creek, causing a DO sag near the check dam. UC Davis researchers notified SCWA, CDFW, and DWR of their findings, and asphyxiation was noted as the cause of death of fish in Lower Putah Creek.

Despite being tolerant of low oxygen for short periods of time, adult Chinook salmon are very large fish, which have greater oxygen requirements than smaller fish, so adult salmon were likely among the first individuals to perish. But also killed, were much smaller fish, such as sunfish and mosquitofish, which are more capable of surviving low-oxygen conditions. Unfortunately, dissolved oxygen concentrations as low as 1-2 mg/L were reported in the Toe Drain, the typical threshold for sufficiently oxygenated water for salmon is approximately 7mg/L. The sag in dissolved oxygen observed in late October through early November is the largest dissolved oxygen dip recorded in the past several years. All female salmon examined perished before spawning, as indicated by presence of fully-developed eggs still in their ovaries (Figure 3).


Figure 5: Net tidal flow and DO at Lisbon Weir at the Toe Drain (3-miles downstream of Putah Creek).  Notice the large flow corresponding to the 10/24 storm event and corresponding DO sag during and after the storm.

UC Davis researchers continued to conduct weekly surveys of Putah Creek through January, to monitor any upstream movement of salmon. Based upon their initial findings, SCWA began to work closely with the CDFW Wildlife Refuge to identify specific fields and drains impacting Putah Creek. In short order, CDFW and their operating partners from Los Rios Farms, were able to eliminate any further tailwater leakage into Putah Creek by modifying a single culvert. SCWA staff then began periodic water quality sampling of lower Putah Creek within the Yolo Bypass, as well as the confluence with the Toe Drain. Water quality sampling was extended to encompass over 17-miles of the Toe Drain from northern Liberty Island in the Delta, down to the Sacramento Weir just north of Interstate 80.  Results of sampling, as well as data from the Department of Water Resources’ (DWR) real-time water quality stations, showed over 13-miles of water with critically low DO in the Toe Drain both upstream and downstream of the Putah Creek confluence. SCWA staff quickly realized that the DO issue and corresponding fish-kill were far beyond the capability of SCWA to monitor alone. And Putah Creek alone was not the only part of the system at risk. Additional partners and creative solutions would be needed to resolve extent and cause of the poor water quality.

On December 8, 2021, reports from UC Davis and SCWA were shared with key stakeholders in the Yolo Bypass, including DWR, CDFW, State Water Contractors, Reclamation District (RD) 108, and the Northern California Water Association. In subsequent discussions with RD 108 and DWR, there appeared to be a novel capacity to convey either agricultural drainage water from the Colusa Basin Drain or Sacramento River water from the Knights Landing Outfall Gates to potentially flush the Yolo Bypass Toe Drain and push out remaining low DO water in favor of replenishing it with less affected water. 

Figure 6. Mean daily dissolved oxygen at Lisbon Weir in the Yolo Bypass from 1 October to 1 February in each year, 2017-2021. All water quality data collected from: https://cdec.water.ca.gov/dynamicapp/wsSensorData. Dashed line indicates 7mg/L threshold, solid vertical line is peak daily carcass count in each year.

Based on water quality and fish concerns by CDFW and DWR staff, SCWA staff removed debris that had accumulated north of the I-80 in the Yolo Bypass to further facilitate fish passage and water conveyance. SCWA also continued water quality monitoring in the Colusa Basin Drain. One week later the region again received a series of atmospheric storm events that subsequently flushed the Toe Drain and restored DO to more suitable levels. Unfortunately, the low DO conditions had persisted for too long, and no additional salmon were observed migrating into Putah Creek. In total, UC Davis researchers identified 81 Chinook salmon carcasses within the last 2.25 kilometers of Lower Putah Creek, and 1 live salmon in the upstream reaches of Putah Creek, although a few (4-5) additional salmon apparently made it up to the Diversion Dam (observations of staff). Recent snorkeling surveys below diversion dam detected juvenile salmon, indicating successful spawning by the survivors of the fish kill (T. Salamunovich, April 2022).

Lessons learned

While the event was tragic, it provided several key lessons for the Lower Putah Creek and Yolo Bypass community:

  • Organic matter and low DO are on-going problems. Initial findings by the USGS (Stumpner, 12/15/2021) and others, indicate that the large DO sag in the Toe Drain and associated parts of the Delta was largely due to a rapid increase in flow (precipitation and run off) following the large rain event at the end of October. This flow pushed out accumulated organic matter in the creek and ditches, presumably from deposition of dead aquatic vegetation. In the Yolo Bypass, the Toe Drain, and related water conveyance canals, invasive aquatic vegetation is pervasive. The last 2-miles of Putah Creek (within the Yolo Bypass and DFW Wildlife Refuge) also support an abundance of aquatic vegetation throughout the main channel. When widespread in such quantities, decaying aquatic vegetation can lead to diminished dissolved oxygen concentrations.
  • Climate change requires building more resilent systems.  Large atypical storms, such as the one that occurred on October 24 may become more common, and will require planning outside of previous bounds of environmental variability, in order to build management systems capable of adapting to changing conditions quickly.
  • Regional partnerships are increasingly important. The event emphasized the importance of regional partners, including resource agencies (CDFW, DWR), local public agencies (SCWA, RD 108), scientific experts (UC Davis), and local landowners. Most of the lands in Yolo Bypass and along lower Putah Creek watershed are privately owned, so cooperation among landowners is truly essential.
  • Scientific support is essential. Ongoing long-term research conducted by UC Davis continues to provide pivotal and timely data helping to protect and restore Putah Creek. Without the observations of UC Davis scientists in November, the Water Agency and other stakeholders would not have been aware of the magnitude and causation of the fish kill on Putah Creek, until much later. Scientists are also collaborating directly with managers in near real time to improve conservation; thus Putah Creek represents a critical example of real time resource management in California and the Delta.
  • Fish passage barriers need to be modified or removed. Modification of existing fish passage barriers in Putah Creek and in the Yolo Bypass, including the Road 106A Crossing, Los Rios Check Dam and the Lisbon Weir, should be high priority for resource agencies. DWR and CDFW oversee most of these facilities.

Alex Rabidoux is a Principal Water Resources Engineer with Solano County Water Agency. Max Stevenson is a Streamkeeper with Solano County Water Agency. Peter B. Moyle is a Distinguished Professor Emeritus at the University of California, Davis and is Associate Director of the Center for Watershed Sciences. Mackenzie C. Miner is a MS student at the University of California, Davis. Lauren G. Hitt is a PhD student at the University of California, Davis. Dennis E. Cocherell is a Lab Manager and Staff Research Associate in Wildlife, Fish, and Conservation Biology at the University of California, Davis. Nann Fangue is a professor and Chair of the Department of Wildlife, Fish & Conservation Biology at University of California, Davis. Andrew L. Rypel is a professor of Wildlife, Fish, and Conservation Biology and Co-Director of the Center for Watershed Sciences at the University of California, Davis.

Further Reading:


USGS (unpublished).  Stumpner, Elizabeth. BGC UPDATE: Low Dissolved Oxygen and High Nitrate Following Storm Events

Chapman, E., E. Jacinto, and P. Moyle. Habitat restoration for Chinook salmon in Putah Creek: a success story. https://californiawaterblog.com/2018/05/13/habitat-restoration-for-chinook-salmon-in-putah-creek-a-success-story/

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. 1995. The case of Putah Creek: conflicting values complicate stream protection. California Agriculture 49: 73-78.

McManus, J. 2022. It’s time to restore habitat for salmon runs, before it’s too late. CalMatters https://calmatters.org/commentary/2022/03/its-time-to-restore-habitat-for-salmon-runs-before-its-too-late/

U.S. Geological Survey, 2022. USGS water data for the Nation: U.S. Geological Survey National Water Information System database, accessed November 17, 2021  http://dx.doi.org/10.5066/F7P55KJN

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.

Willmes, A. Steel, L. Lewis, P.B. Moyle, and A.L. Rypel. 2020. New insights into Putah Creek salmon. https://californiawaterblog.com/2020/10/18/new-insights-into-putah-creek-salmon/

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