Environmental Flows in California

By Alyssa Obester, Sarah Yarnell, and Ted Grantham

The California Environmental Flow Framework was recently highlighted in the 2020 Water Resilience Portfolio to address the seemingly impossible task of establishing of how much water our rivers and streams need to support healthy ecosystems. While many methods for setting environmental water needs exist, the Framework provides a unique and flexible approach that is applicable statewide.

What is the California Environmental Flows Framework? Developed by a workgroup of researchers and agency staff from across the state, the Framework is a guidance document for developing ecological flow criteria, which describe the timing and magnitude of streamflow required throughout the year to support native species and their habitat. These criteria are defined according to the natural range of hydrologic conditions under which native species have evolved, but can be refined under the Framework to prioritize specific ecosystem management goals (e.g., endangered species needs) or to accommodate novel ecosystem conditions. The Framework also describes desirable practices for making decisions on how to balance ecological flow needs with human water uses.

Unlike other environmental flow assessment methods, the Framework offers an approach that:

  • Considers all aspects of the annual hydrograph, focusing on flow components linked to ecological function in streams (functional flows);
  • May be applied across a broad diversity of geographic and water management settings and desired ecosystem goals;
  • Provides tools and guidance for developing ecological flow regimes;
  • Provides guidance for balancing multiple management objectives; and
  • Provides recommendations for, and examples of monitoring and adaptive management programs.
Fig. 1. Streams in California with existing instream flow requirements, data provided by the State Water Resources Control Board’s Cannabis Policy Program’s mapping tool.

Protecting stream flow is essential to the persistence of native species and health of our freshwater ecosystems. To date, however, few streams in California have legally recognized environmental flow protections (Fig. 1), where regulators have set the amount and timing of water to be left instream to support fish, wildlife, and habitat maintenance and creation. Where environmental flow protections do exist, they are limited typically in geographic scope and generally are focused on the needs of a few endangered species and fail to consider ecosystem needs holistically.

A key action recommended in the Governor’s Water Resilience Portfolio is protecting and enhancing natural systems. To do so requires a broad understanding of the flows needed to support aquatic and riparian species and tools to translate this knowledge into management practice. The California Environmental Flows Framework provides a means of doing so. A draft of the Framework will be available for public review in early summer 2020. Further information about this effort can be found at CEFF.ucdavis.edu.

Further Reading

California Environmental Flows Framework Technical Team. (2018). The California Environmental Flows Framework website. http://ceff.ucdavis.edu.

California Natural Resources Agency, California Environmental Protection Agency and Department of Food and Agriculture. (2020). Draft Water Resilience Portfolio.

Yarnell, S.M., Stein, E.D., Webb, J.A., Grantham, T., Lusardi, R.A., Zimmerman, J., Peek, R.A., Lane, B.A., Howard, J., and Sandoval-Solis, S. A functional flows approach to selecting ecologically relevant flow metrics for environmental flow applications. River Res Applic. 2020; 1– 7. https://doi.org/10.1002/rra.3575

Yarnell, S., Obester, A., Grantham, T., Stein, E., Lane, B., Lusardi, R., Zimmerman, J., Howard, J., Sandoval-Solis, S., Henery, R., and Bray, E. (2018). Functional flows for developing ecological flow recommendations. California Water Blog.

Alyssa Obester is a researcher at the UC Davis Center for Watershed Sciences. Sarah Yarnell is a senior researcher at the Center for Watershed Sciences. Ted Grantham is faculty at the University of California, Berkeley and an affiliate of the Center for Watershed Sciences. Alyssa, Sarah, and Ted are part of a larger technical group that is continuing to work on implementing a functional flows approach across California via the Environmental Flows Workgroup, a sub-group of the California Water Quality Monitoring Council. Technical group members include individuals from UC Berkeley, UC Davis, Utah State University, UC Agriculture and Natural Resources, Southern California Coastal Water Research Project, The Nature Conservancy, California Trout, California Department of Fish and Wildlife, and the State Water Board.

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New science or just spin: science charade in the Delta

By Karrigan Bork, Andrew L. Rypel, and Peter Moyle

Fig. 1. Aerial view of the Harvey O. Banks Delta Pumping Plant, the first major plant designed and constructed within the California State Water Project. Photo Credit: California Department of Water Resources.

Science-based decision making is key to improved conservation management and a legal mandate in the US Endangered Species Act.  Thus supporters of federal efforts to increase water exports from the Central Valley Project (CVP) and State Water Project (SWP) have claimed that these efforts are based on new science. Yet unpacking those claims requires some legal analysis, a basic understanding of science, and more than a little nuanced reading.

First, some background. For a review of federal efforts to increase Delta exports, and the recent biological opinions (BiOps) released by the U.S. Fish and Wildlife Service (FWS) and the National Marine Fisheries Service (NMFS) approving those efforts, please see this earlier blog post. California has elected to sue the federal government over the recent BiOps, and, at the same time, California is proceeding with its own analysis of plans to change the operation of the SWP. Finally, the State Water Resources Control Board (SWRCB) is updating the state’s Bay Delta Plan, which addresses water quality and quantity in the Delta. The SWRCB has adopted a new plan for the San Joaquin River watershed, and is in the process of adopting a plan for the Sacramento River watershed. However, adoption and implementation efforts appear to be on hold while the Newsom Administration attempts to negotiate voluntary agreements with water users and environmental groups. The voluntary agreements might ultimately replace (or be integrated into) a comprehensive Bay Delta Plan update. There are many moving parts, but one thing tying all these efforts together is the proponents’ claim that their approach is mandated by the best science.

Supporters of the federal plan in particular seek to wrap the effort in the mantle of science. On the media call for the roll out of the new BiOps, Paul Souza, Regional Director for US Fish and Wildlife Service cited “tremendous new science now that we didn’t have a decade ago.” On the same call, Ernest Conant, Regional Director of the Mid-Pacific Region of the Bureau of Reclamation, argued that the new approach was “infused with new scientific information.” U.S. Rep. Kevin McCarthy, R-Bakersfield, told Fox News “this president has worked greatly using science, not based on politics but on science, to allow to have more of that water stay with the Californians and America.” Finally, during his remarks to Rural Stakeholders on California Water Accessibility in Bakersfield, CA, President Trump argued that the old plan was based on “old science, obsolete studies, and overbearing regulations that had not been updated in many, many years, and sometimes for decades,” promising that the new federal plans “use the latest science and most advanced technology.” The science drumbeat has played a central role in this media blitz.

The rationale for this approach is easy to understand. Policy makers frequently cloak political decisions in a scientific framework; in policy circles, this is known as the science charade (Adler 2017; Wagner 1995). The science charade lets political leaders avoid responsibility for unpopular decisions – they’re just following the science, not making hard decisions based on their own ethical considerations (Doremus 1997). The science charade also lets decision makers minimize public input on policy decisions – why should the uninformed public have a say in technical decisions (Adler 2017)? Scientists themselves sometimes embrace this approach because it affords them a measure of control over policy decisions (Adler 2017). The courts only reinforce the science charade – they are very reticent to overturn federal agency decisions that claim to be based on science, rather than policy preferences (Clark 2009).

This approach is not limited to supporters of the federal plans; everyone claims that science is on their side. But the current federal roll out is uniquely focused on claiming that new science justifies increased water exports from the Delta. Moreover, NMFS brought in new scientists to rewrite their draft BiOp last summer, after the first draft concluded the federal pumping plan was likely to drive species to extinction. This suggests some skepticism about NMFS’s claims to rely on “new science.”

Natural resource sciences are unique compared to many fields (e.g., physics). For example, the best natural resource science normally involves understanding not only the organisms of interest, but also the dynamics of their complicated ecosystems, which in turn are typically controlled by people. Indeed, most scientists are trained to view natural resource management quite broadly, e.g., as the intersection of organisms, habitat and people (Nielson 1999). Each aspect is critical and affects the other two, and managing with all three in mind presents opportunities for enhancing natural resources overall. However, management frequently goes awry when a disproportionate focus is placed on only one aspect of the problem (Sass et al. 2017). The science charade preys on the misconception that these spheres should be disconnected, suggesting we can somehow separate organisms and ecosystems from the decisions people make.

The US Endangered Species Act explicitly requires that federal decisions consider the best available science. For example, 16 U.S. Code § 1536(a)(2) requires that “each agency shall use the best scientific and commercial data available” when preparing biological opinions under the Act.  This is, objectively, the right approach. Bad science leads to bad decisions. But this mandate also encourages the cloaking of policy preferences as scientific mandates (Adler 2017). Consider three aspects of the current political struggle over Delta water.

Fig. 2. Dissection of Delta smelt as part of a study to monitor the effects of introducing hatchery smelt into the wild. Photo Credit: California Department of Water Resources.

First, the roll out for the new biological opinions treats existing science as old and obsolete, claiming it is no longer the best available science. But science is not milk. It doesn’t just go bad. New science can illuminate, and the state of the art sometimes changes over time, but older science is not inherently wrong or less valuable. Science grows by building on existing ideas and knowledge, not by rejecting it outright. As Isaac Newton famously wrote, “If I have seen a little further, it is by standing on the shoulders of giants.” For example, the 2010 report “Development of Flow Criteria for the Sacramento-San Joaquin Delta Ecosystem” found that flow standards aimed solely at protecting fish populations in the Delta would require 75% of the unimpaired flow in the Sacramento and San Joaquin watersheds. Certainly, other water needs mean that the Delta will not get these flows, but simply dismissing this report as old science is inherently flawed.

Second, to the extent that new science requires new approaches in the Delta, existing new science indicates that restoration of the Delta will require more water to be left in the Delta, not less. The 2017 Scientific Basis Report for the SWRCB Bay Delta Plan effort noted that additional flows into the Delta, and decreased exports of water from the Delta, always benefits native biota, provided that temperature, timing, and quality targets were met. Zero new science shows that native fishes and most other native organisms in the Delta can survive on less water.  Keep in mind that the Delta is one of the best studied estuarine ecosystems in the world, with continuous major research producing new and improved understanding of the ecosystem (i.e. science).

Third and finally, the new science claims in the biological opinions seem to focus on emerging approaches that might reconcile water use with ecosystem needs based on real time monitoring and habitat improvements. But immediate claims that this new science allows greater water exports from the Delta hides key policy decisions on acceptable extinction risks.

Fig. 3. John E. Skinner Delta Fish Protective Facility, located two miles upstream of the Banks Pumping Plant. Photo Credit: California Department of Water Resources

For example, the real time “Enhanced Delta Smelt Monitoring (EDSM)” program is supposed to allow managers to reduce pumping from the Delta when monitoring detects smelt in the area around the pumps, thus keeping smelt from being sucked into the pumps. But smelt populations are currently too low to detect, and a January 2018 independent scientific review concluded, “it is difficult to see how the EDSM currently can be used to inform water operations in near real time.” The review encouraged FWS to attempt to validate this approach, but the BiOps offer no such validation. Using this approach without showing that it works places all risk of failure on the Delta Smelt, and ultimately risks their extinction. This is a policy decision, not new science standing alone.

Similarly, the BiOps indicate habitat improvements will reduce the need for water in the Delta. As prior blog posts here have noted, better habitat improves salmon growth, which may improve salmon survivorship. Better habitat also may allow managers to reconcile human uses of the landscape with ecosystem needs. Could this approach allow managers to achieve ecosystem and species recovery targets with less water? It seems unlikely, but the BiOps depend on habitat improvement to make up for increased water exports. Even if this approach could work, it would require that suitable habitat improvements be in place before water exports increase. But most improvements mandated in the last round of BiOps are merely proposed, not complete, and most ongoing improvement projects remain unfinished and untested.

The increased pumping anticipated in the BiOps would begin well before any improvements in species numbers would result from habitat improvement. This approach assumes that additional unspecified habitat will compensate for decreased water in the short term. Success would depend entirely on protected species being lucky enough to persist under current conditions but with less water. Suggesting that the decisions expressed in the BiOps are based solely on science masks this central policy calculus, which is never explicitly revealed. However, the benefits of such an approach to Delta water users are well-documented: there is less political accountability, less public input, and more deferential court review.

Fig. 4. Release of tagged Chinook salmon into the Sacramento River. Photo Credit: California Department of Water Resources.

What’s the solution? There’s no magic bullet to stop the science charade, but using properly vetted (i.e., peer-reviewed) science literature and independent science reviews of new rulemakings can go a long way toward ensuring true science-based policies. California’s Delta Science Program, for example, relies on an independent review panel to provide objective feedback to policymakers. Adaptive management approaches that would increase ecosystem protections if new approaches fail would better allocate risk in uncertain situations. The science community itself must also watch and safeguard how policy makers use its work. It is not enough to simply conduct and publish scientific articles – not anymore. And courts asked to review decisions that touch on science must distinguish between scientific conclusions and policy decisions that are cloaked as science.

In the near term, California agencies may soon face this challenge head on. First, as noted above, the California Department of Water Resources (DWR) is preparing an environmental analysis of its own plans to change the operation of the Delta pumps. DWR has proposed a plan that embraces some of the same approaches to science used by the federal plan. Comments from the California Department of Fish and Wildlife (CDFW) and the SWRCB to DWR have raised these concerns, but it is not yet clear how the DWR will respond and whether CDFW will ultimately grant DWR the permits it needs to proceed on the terms DWR has proposed.

Second, the SWRCB will have to approve any voluntary agreements that are developed for the Delta. The Newsom Administration is pushing hard for a suite of voluntary agreements to benefit the Delta ecosystem while also meeting water user needs. The benefits of successful voluntary agreements are tantalizing: an infusion of private funding, improved habitat, improved ecosystems, and continued availability of needed water, all done faster and with fewer lawsuits. But any agreements must ultimately comply with state environmental law, and the SWRCB will make the first determination as to whether the science supports whatever voluntary agreements the Administration can develop. The voluntary agreements appear to rely on the same habitat-for-water hopes that undergird the BiOps, and the agreements would lock in the water withdrawals before regulators know if the habitat improvements actually work. A safer approach would be to improve the habitat, and then conduct scientific studies to see if listed species actually benefit before withdrawing additional water. Failing that, the agreements should at least provide for water use reductions as a fail safe if species declines continue despite the new habitats. The best available science recognizes that nature is sometimes unpredictable and science is sometimes misread or just wrong. It requires contingency plans.

If the Administration succeeds in developing a set of voluntary agreements, and as DWR concludes its environmental analysis, look for the media blitz to emphasize that science supports their approach. It will fall to the state regulatory agencies to determine whether they are truly supported by science, or merely by a science charade. 

Further Reading

Jonathan H. Adler, The Science Charade in Species Conservation, 24 Sup. Ct. Econ. Rev. 109, 116 (2017).

Sara. A. Clark, Taking a Hard Look at Agency Science: Can the Courts Ever Succeed?, 36 Ecol.L.Q., 317 (2009).

Holly Doremus, Listing Decisions Under the Endangered Species Act: Why Better Science Isn’t Always Better Policy, 75 Wash. U. L.Q. 1029, 1038 (1997)

Carson Jeffres, Frolicking fat floodplain fish feeding furiously, June 2, 2011.

Peter Moyle, Jeff Opperman, Amber Manfree, Eric Larson, and Joan Florshiem, Floodplains in California’s Future, Sept. 10, 2017.

Peter Moyle, Karrigan Bork, John Durand, Tien-Chieh Hung, and Andrew Rypel, Futures for Delta Smelt, Dec. 15, 2019.

Larry A. Nielsen, History of Inland Fisheries Management in North America in Inland Fisheries Management, 2nd Ed. 3 (Christopher C. Kohler and Wayne A. Hubert eds., 1999).

Greg G. Sass, Andrew L. Rypel, and Joshua D. Stafford, Inland Fisheries Habitat Management: Lessons Learned from Wildlife Ecology and a Proposal For Change, 42 Fisheries 197 (2017).

Wendy Wagner, The Science Charade in Toxic Risk Regulation, 95 Colum. L. Rev. 1613 (1995).

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Contemplating the Carp

By Kim Luke and Brian Williamson

The UC Davis Arboretum is a defining feature of the campus. Students, faculty, and ducks alike all enjoy the waterway that was once a part of Putah Creek. Many organisms call the Arboretum “home”, but one of recent interest is the non-native Common Carp (Cyprinus carpio). Originally native to Eurasia, Common Carp were widely introduced to aquatic environments throughout the USA as a potential sport- and food-fish. Yet sportfishing interest for Common Carp in the USA never took full flight, and while stockings quickly ceased, the species quickly become one of the most invasive animals in the world. Abundant and easy to spot, you may have seen this Arboretum dweller with its beautifully large scales perusing the waters on campus. While It’s easy to see these invasive fish on campus, some people can’t see eye-to-eye on whether their presence is welcome or not. The following excerpts are from two student researchers at the Center for Watershed Sciences, providing two separate viewpoints on the Carp.


I transferred to UC Davis in the fall of 2018, and while my time on campus has been brief, the Arboretum has quickly become my favorite place. It’s the perfect spot to visit when I need a break from studying and homework. Aside from a place for relaxation, the Arboretum also became an outdoor classroom during my laboratory course on “Biology & Conservation of Birds”. I grew to appreciate the Arboretum even more once I learned about the surprising diversity of birds that inhabit this ecosystem. So far, I’ve been able to call the Arboretum my quiet place, my classroom, and now I also get to call it the research site of my senior thesis.

Fig. 1. Carp-DEUM Project setting up nets for sampling in the Arboretum.

This past fall I began the Carp-Dependent Ecosystem Urgent Management (Carp-DEUM) Project. The Arboretum is a beautiful place, but the water turns an opaque pea-green color during summer. Warm temperatures combined with high nutrient concentrations, especially phosphorus, conspire to produce massive and prolonged algae blooms throughout the waterway. In addition to being unsightly, algal blooms can have negative ecological and health impacts. Harmful algal blooms, or HAB’s, induce sickness and even death for humans, animals, and pets. The blooms have caused such concern on campus that signs were created warning people not to enter the Arboretum water. HAB’s also can trigger mass mortality events, such as fish kills, further complicating socioecological systems. But what does this have to do with Carp?

Carp are ecosystem engineers and can have a dominating influence over water quality when biomass is high. Carp spend most of their time swimming along benthic habitats, and by doing so accomplish two things: 1) they kick up extra nutrients from the substrate into the water column, and 2) they uproot submerged and emergent aquatic vegetation. Previous research in Minnesota lakes reveals that plant cover in aquatic ecosystems exhibits a threshold response to Carp biomass, where past a certain biomass of Carp, the amount of vegetation changes rapidly (Fig. 2). When plant coverage is reduced, and Carp biomass high, large algal blooms are often observed. My Carp-DEUM Project will estimate Carp biomass in the Arboretum waterway and evaluate whether reducing the Carp population within the Arboretum could help to mitigate HAB’s.

Fig. 2. Relationship between macrophyte cover in the shallow (i.e., littoral) areas of lakes and Carp biomass within those lakes, source: https://www.maisrc.umn.edu/sites/maisrc.umn.edu/files/a_decade_of_common_carp_management.pdf

Because legacy phosphorus concentrations in sediments throughout the waterway likely remain high, there is a strong possibility that should Carp be removed, aquatic plant coverage would quickly expand. These changes are predicted to be coincident with increases in water clarity overall.

I want the Arboretum to be a hospitable and safe ecosystem for humans and other species, but the invasive Carp complicates management towards these goals. The project is ambitious, and I often feel overwhelmed by all I have to manage. But more than that, I’m excited for an opportunity to conduct this research and learn all I can about Carp and their ecological importance in the Arboretum!


Fig. 3. Brian with an Arboretum Carp. Photo by Jasmine Shen.

The Arboretum played a substantial role in my choice to attend UC Davis. The idea of having a piece of “nature” – although very obviously constructed and managed – that could be a haven from the stress of school was very alluring. When I moved to Davis the Arboretum became important to me, and I have visited often to ponder, learn, recreate, and feel at ease. I noticed the foot-long fish cruising the murky water soon after arriving in Davis. A decade ago, I marched down to the concrete-lined bank of the Arboretum waterway, rolled a piece of white bread into a ball between my palms, stuck the bread ball on a hook, and cast my line into the water. After an hour of fishing I got my first bite and became acquainted with the power and resolve of the Common Carp. Thus began one of the most intimate relationships I’ve had with another species. After hooking that first beauty, I devoted much of my spare time to the pursuit of Carp. After becoming proficient at capture with rod and reel, I resigned to taking every lunch break to simply observe their behavior. I took many friends on angling expeditions to the Arboretum, several of whom caught their first fish along those concrete banks. Those friends not only gained the opportunity to come into contact with and gain the knowledge necessary to capture Carp, but also to learn about the unique ecosystem that they entered while stalking the fish – a turbid body of water  in the center of a human-dominated landscape.

Much of California’s Central Valley was historically a large flooded-wetland with murky water. Heavy alterations to Central Valley waterways and invasive animals have led to the decline of turbid water and rise of submersed vegetation in California. Carp clearly bioturbate substrates, stirring up sediment and nutrients as they go. A goal of potentially removing Carp from the Arboretum would be to create clearer water in which submersed vegetation can thrive. However, with turbid water disappearing in the state, I believe we should cherish the green, muddy, and vegetation-free waters of the Arboretum.

Blooms of algae, presumably facilitated by Carp, can lead to low dissolved oxygen events. Because of this, the only fish species found in the Arboretum are those that can tolerate very low dissolved oxygen concentrations. The suite of species inhabiting the Arboretum is quite unique. If low dissolved oxygen events no longer occurred, new fish species could establish and displace current species.

Fig. 4. Sacramento Blackfish. Photo by Matthew Young

Among these unique species is the native Sacramento Blackfish (Orthodon microlepidotus). Blackfish are a filter-feeding minnow that rely on plankton as a food source, and are currently quite abundant in the Arboretum waterway. The nutrients that Carp release into the water may be critical for production of food for these fish. Blackfish are in decline throughout their native range, potentially because of decreased planktonic food resources. The facilitation of Blackfish by Carp might be treasured and taken into consideration.

The Arboretum and its waterway provide a beautiful sanctuary for students, visitors, and the Davis community. Its importance to me is tied to the Carp that inhabit it.  The reduction of toxin-producing algae in the Arboretum is important, but because Carp may facilitate a valuable type of habitat and unique assemblage of fishes that is rapidly disappearing from the state, other methods of algae control might also be explored.


There is no question that harmful algal blooms are occurring in the Arboretum waterway. It is important to identify the factor or combination of factors causing algal blooms to inform best management strategies to control toxin-producing algae. Carp may cause HABs, and the current study will produce useful information on this question. If Carp are identified as a major problem, then all options for management, including fish removal, might be considered. Yet a future vision of the Arboretum and valued features must be clearly defined with input from all who are invested in the waterway.

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Is the Sacramento Splittail an Endangered Species?

by Peter Moyle, Dylan Stompe, and John Durand

The Sacramento splittail is a lovely, silvery-white fish that lives primarily in Suisun Marsh, the north Delta and other parts of the San Francisco Estuary (SFE; Moyle et al. 2004). The name comes from its unusual tail, in which the upper lobe is larger than the lower lobe. It is a distinctive endemic species that for decades has fascinated those of us who work in Suisun Marsh.  Splittail are consistently among the most abundant fishes in our samples, despite being uncommon or absent elsewhere. Historically, splittail were distributed from Tulare Lake in the southern Central Valley to roughly the present site of Redding in the north.

 Splittail have a number of attributes that make them special:

  1. Although a member of the minnow family (Cyprinidae), splittail can reach over 40 cm (16 in) in length and live 7-9 years.
  2. They thrive in brackish water (up to 29 ppt salinity), with a preference for low to moderate salinities. Most other minnow species are confined to fresh water.
  3. They are a hardy species with a tolerance for warm temperatures (up to 33 degrees C) and low dissolved oxygen levels (<2 ppt).
  4. They are obligate floodplain spawners. Adults migrate to places such as the Yolo Bypass and Cosumnes River floodplains to spawn during winter flood events. Juveniles leave the floodplain as the water drops and then move downstream to rearing areas such as Suisun Marsh.
  5. Females produce large numbers of eggs, so even a few successful spawners in a low-flow year can maintain populations.
  6. They feed on the bottom. About half their gut contents is detrital organic matter and the other half is invertebrates. Before the invasion of the overbite clam, the main invertebrate prey was opossum shrimp (Neomysis). After the invasion, they added the clams as major part of their diet.
  7. There are apparently two populations, one in the Delta and Suisun Marsh and a much smaller one in the estuaries of Petaluma and Napa rivers (Baerwald et al. 2006).
  8. The Clear Lake splittail, a distinct species derived from the Sacramento splittail, became extinct in the 1960s or 70s.
  9. They support a small fishery both as a food fish and as bait favored by striped bass anglers.

From the information above, you can deduce that splittail should be well adapted to the difficult and often changing conditions in the upper SFE. However, in 1999 splittail were listed by the US Fish and Wildlife Service as a threatened species.  They were taken off the threatened species list in 2003. So, what is going on with splittail populations?

Splittail became confined to the SFE, rather than occupying the entire Central Valley, only in fairly recent times, concurrent with the launch of multiple fisheries studies in the estuary that were designed to track populations of Chinook salmon, striped bass, and Delta smelt.  These programs provide a good basis for evaluating overall population trends. The best data on trends comes from the UC Davis Suisun Marsh monthly sampling program (otter trawls), which started in 1980 and which has kept track of abundance of young-of-year (YOY) fish, yearlings, and adults (Figure 1).

Splittail numbers (trawl catches) were high at the beginning of the Suisun study and then declined, despite three good spawning years (1980, ‘82, and ‘86). Numbers then became extremely low through 1994, coinciding with the drought of 1987-92.   As a result, the species was petitioned for listing under the Endangered Species Act in 1992. Recruitment increased slightly in 1995, followed by another poor spawning year in 1996. Overall numbers stayed fairly low through 1999, after which all age classes experienced a generally upward trend to the present. The dramatic increase in abundance after 1999 led to delisting in 2003. The delisting was supported by more research on life history, environmental tolerances, and population dynamics (Moyle et al. 2004).  A life history model also showed that population trends were strongly driven by wet years in which large numbers of juveniles were produced by adults spawning on the floodplains. However, even in drought years enough spawning can take place to maintain a small population. Increased resilience of splittail to drought may be the result of improved access to floodplain habitat since the 1990s, when the Cosumnes River Preserve and the Yolo Bypass were developed for wildlife. Presumably, this meant that even during dry years, short high-flow events provided splittail with opportunities for successful spawning.

Figure 1. Trends in yearly splittail catches in the UC Davis otter trawl sampling program, 1980-2018. Annual numbers are based on catches from monthly sampling at 17-21 stations. Note that fluctuations in catch are largely driven by recruitment of young-of-year (blue) to the population, although population persistence is largely driven by the abundance of adult splittail (grey).

The next question becomes, do other fish surveys in the estuary reflect what is going on in Suisun Marsh in terms of population trends? The California Department of Fish and Wildlife (CDFW) Fall Midwater Trawl Survey shows continued decline (Figure 2), but it is a pelagic (open water) survey that does a poor job of capturing bottom-oriented species like splittail. The Bay Study Otter and Midwater Trawl surveys (not shown) have catches similar to the CDFW Fall Midwater Trawl, with small catches of splittail. The U.S. Fish and Wildlife Service (USFWS) Beach Seine Survey (Figure 2,3), in contrast, shows trends similar to the Suisun Marsh Study, reflecting that it samples inshore areas where young splittail occur as they leave floodplains. .

The salvage data from the south Delta water export pumps (State Water Project, Federal Central Valley Project) show large numbers of young splittail during years when numbers are also high in the Suisun Marsh Study (Figure 2). The pumping plants appear to take large numbers of splittail only during wet years, when juveniles are moving downstream en masse to rearing areas.  Splittail numbers peak in the USFWS Beach Seine Survey in the same years, reflecting their bias towards collecting young moving downstream from spawning areas.

It is worth noting the response of splittail to drought in the surveys that catch them in the greatest numbers (Figure 2). Early in the Suisun Marsh Study, splittail catches showed dramatic declines, apparently because reproduction was minimal during extended drought. In wet years following droughts, there was typically a surge in recruitment of young fish. The drought response was muted in later surveys apparently because enough older fish were in the population to sustain the population until better spawning conditions returned. This was well demonstrated by the splittail response to the 2012-16 drought, during which numbers rose to record levels.

Figure 2. Standardized catches of splittail in five fish surveys. Note the extremely low catches of the fall midwater trawl survey compared to other surveys (y-axis scaling). Periods of drought are represented by shaded areas and dashed vertical red line represents the invasion of the SFE by the Asian clam. Details of standardization and each trawl survey can be found in Stompe et al. (in review, 2020).


There are several lessons that can be drawn from this story.  First, the splittail is a resilient species that can thrive in a limited part of upper SFE (the North Delta Habitat Arc, Moyle et al. 2016) that includes the Yolo Bypass and Cosumnes River floodplain for spawning, the Sacramento River for dispersing the young, and Suisun Marsh as a nursery area. The splittail is not in danger of immediate extinction although its status needs to be carefully monitored, especially during long periods of drought, given its limited distribution. In the short run (10-20 years) it can be regarded as a management success because favorable flows and restored floodplains appear to have worked. It is also possible that splittail have benefitted from operation of the Salinity Control Gates on Montezuma Slough that has kept Suisun Marsh salinities at favorable levels throughout the summer months, even in dry years. However, more studies are needed to nail down exactly what factors are limiting their abundance and to find ways to expand their range.

A second lesson is that for each species some surveys are better than others for determining trends for splittail and other species (e.g. Suisun Marsh Otter Trawl vs. Fall Midwater Trawl).

A third lesson is that research pays.  A number of diverse studies on splittail were conducted after it was listed, contributing to its being delisted. However, further study of splittail is still needed to prevent decline in a rapidly changing estuary. There are other species in the region that could also benefit from study before they get listed, to find out if listing is necessary.

The Sacramento splittail has demonstrated resilience that keeps it from being regarded once again as threatened or endangered, despite its limited range. Recent changes in federal water policy that allow more fresh water to be exported from the Delta may cause additional stress to splittail populations, resulting in a need to return it to the long list of threatened and endangered fishes in California.

Further Reading

Baerwald, M., V. Bien, F. Feyrer, and B. May. 2006. Microsatellite analysis reveals two genetically distinct splittail (Pogonichthys macrolepidotus) populations in the San Francisco Estuary. Conservation Genetics. DOI: 10.1007/s10592-006-9157-2.

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., J. Durand, A. Manfree. 2016. The North Delta habitat arc: an ecosystem strategy for saving fish. UCD Center for Watershed Sciences, California WaterBlog. November 6. 2016.

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

Stompe, D. K., P.B. Moyle, A. Kruger, and J.R. Durand (in review). Integrating use of fish surveys in the San Francisco Estuary.  San Francisco Estuary and Watershed Science.

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California’s Driest February and Coming Drought?


Feb 2020 precip

Source: DWR CDEC


By Jay Lund

February has been amazingly dry in California, if anyone hasn’t noticed.  No precipitation at all in February, a dry forecast, about 51% of seasonal Sacramento Valley precipitation (a bit less for the San Joaquin and Tulare basins), and only about half (45-57%) of normal snowpack for this time of year.  Unless March is wet, this dry year seems likely to advance the onset of the fire season and threaten forest health this year.

Reservoir levels are still not bad for this time of year.  Many are fuller than average, perhaps reflecting some snowpack loss.  Some other reservoirs are a bit low.  This is inherent in the first year of a drought, low precipitation and snowpack, but mostly ok reservoirs.

Groundwater has recovered somewhat from the previous 2012-2016 drought, better in the north, but less in the state’s more overdraft-prone areas in the San Joaquin and Tulare basins.

USBR recently released a sobering contract allocation:  100% north of the Delta and 100% for San Joaquin Valley settlement contractors, but only 15% for Westlands and 20% for more reliable Class 1 Friant water contracts (zero for Class 2).   These folks, and others in the San Joaquin and Tulare basins, will be looking to buy water and are likely to pump more groundwater.  In the height of the 2012-2016 drought, these areas pumped about 6 million acre feet (maf)/year or more, on top of an average annual overdraft of almost 2 maf in these regions.

Several dry years will be tougher, again, on farming, and deepen groundwater depletion, making it tougher to comply with SGMA’s call for recovering 2014 groundwater levels by 2040.  This will increase interest in Delta and upstream diversions, with implications for Delta and environmental flow discussions and policies.

What is the likelihood of 2020 being a drought year (below normal, dry, or critically dry)?  This seems quite likely. The plot below has Annual precipitation vs. Precipitation before March 1 for 101 water years.  Given how unusually dry February and the rest of the year has been, March and April are unlikely to save us from some form of dry year.  (Still, in the 4th year of drought, 1991 had a “miracle March”, with three times average March precipitation, but this is unlikely).

Feb vs annual precip

Is 2020 is the start of a multi-year drought?  This is much less likely, but more likely than we’d like.  The dryness of subsequent years in California have pretty low correlations, overall.  By definition half of years have less than the median runoff.  Of 112 years of Sacramento Valley runoff records, 56 years had less than median runoff, 30 times had adjacent 2 years with both less than median, 18 times had 3 sequential below-median years, 10 times of 4 sequential below-median years, 4 times of 5 sequential below-median years, and 2 times of 6 sequential below-median years.  This understates correlation a bit because longer droughts can have rosier years interspersed, but it makes the point that multi-year droughts are far from certain after one dry year, and that drought-year correlations are not terribly high on the scale of a few years.  Recent apparent changes in climate make historical statistics less firm, of course, but are likely better than a blind guess.

Is 2020 a continuation of a longer drought, from 2012 or even 2007?  Given the diverse aspects of California’s water system, this is undoubtedly true for some areas and in some aspects.  Lovers of drought statistics will revel in this question, some of which will be interesting and even useful.  From a surface reservoir perspective, no, because essentially all reservoirs have refilled.  From a groundwater perspective, one can argue we are in more than a century of drought, without refill, in some areas.  (When tortured enough, drought statistics can confess almost anything.)

What to do now?  Hope for the best and prepare for the worst, as should be done every year in managing water in California’s highly variable hydrology.

Given the high likelihood of a drier year and the likelihood of a drought, it is not a bad time for state, federal, and local agencies to prepare and digest some lessons from the last drought, and maybe prepare some drought exercises (“dry runs”, so to speak) to local, state, and federal agencies get better acquainted.  Many agency water leaders retired (or fled) at the end of the 2012-2016 drought (who can blame ’em).  It may already be time, after 4 wetter years, for the next generation of water managers to cut their teeth on drought management.

Whether 2020 is a drought year of not, California will be seeing another major drought.  Given the difficulty and centrality of Delta operations during drought, now might be a good time for the state to develop a multi-agency Delta drought plan.

Don’t panic, and don’t be complacent.  Prepare carefully.

Further reading

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

The banality of California’s ‘1,200-year’ drought, September 23, 2015, Jay Lund

Jay Lund is in absentia Director of UC Davis’ Center for Watershed Sciences.  Currently, he has fled California on sabbatical, only to find drought and viral uncertainty in Eurasia, as well as cool old aqueducts and great water experts even outside of California. 


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Field courses help young people see the real world

by Andrew L. Rypel

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Further reading

UC Davis Center for Watershed Sciences education webpage, https://watershed.ucdavis.edu/education/classes/

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

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

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

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

By Bill Fleenor, Amber Manfree, and Megan Nguyen

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

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

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

The main points are:

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

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

Further Reading

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

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

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

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

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Realty Meets Climate Reality

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

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

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

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

Man beside river

He was wrong.

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

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

Expert advice

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

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

Pinter: [Grimace]

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

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

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

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

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

Mapping risk

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

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

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

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

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

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


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

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

live oak view from below, looking up

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

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

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

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Striped Bass: An Important Indicator Species in the Delta

Peter and an inconvenienced bass

by Peter Moyle

The striped bass is a favorite sport fish in the San Francisco Estuary (SFE), especially the Delta, because of its large size, sporting qualities, and tasty flesh. Historically, it supported major commercial and sport fisheries but the commercial fishery was shut down long ago and the sport fishery is in long-term decline. The decline of adult fish is reflected in decline of juvenile striped bass as well. Juvenile abundance in the major fish surveys of the SFE track the decline of delta and longfin smelt well. These declines are a good indication that major changes have taken place in the pelagic (open water) environment in the upper SFE, creating problems for pelagic fishes in general.  Nevertheless, adult striped bass, which are voracious predators, have been accused of causing the declines through predation, although there is little evidence for this (see https://californiawaterblog.com/2011/01/31/striped-bass-control-the-cure-worse-than-the-disease/ and https://californiawaterblog.com/2016/05/22/6206/)

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

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

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

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

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

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

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

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

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

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

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

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

Further reading.

Dahm, C., W. Kimmerer, J. Korman, P. B. Moyle, G. T. Ruggerone, and C.A.Simenstad. 2019. Developing Biological Goals for the Bay-Delta Plan: Concepts and Ideas from an Independent Scientific Advisory Panel. A final report to the Delta Science Program. Sacramento: Delta Stewardship Council. Report, http://www.deltacouncil.ca.gov/pdf/science-program/biological-goals/2019-09-18-April-2019-biological-goals-final-report.pdf\

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

Mount, J., B. Gray, K. Bork, J. E. Cloern, F. W. Davis, T. Grantham, L. Grenier, J. Harder, Y. Kuwayama, P. Moyle, M. W. Schwartz, A.Whipple, and S.Yarnell. 2019.  A Path Forward for California’s Freshwater Ecosystems.  San Francisco: Public Policy Institute of California. 32 pp. https://www.ppic.org/publication/a-path-forward-for-californias-freshwater-ecosystems/

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

Moyle, P.B.  and W.A. Bennett, 2011. Striped bass control: cure worse than disease? California WaterBlog, January 31. https://californiawaterblog.com/2011/01/31/striped-bass-control-the-cure-worse-than-the-disease/

Moyle, P.  A. Sih, A. Steel, C. Jeffres, and W. Bennett. 2016.  Understanding predation impacts on Delta native fishes. UC Davis Center for Watershed Sciences California WaterBlog. May 22. https://californiawaterblog.com/2016/05/22/6206/

Stompe, D. and P. Moyle, 2018. Striped bass in the San Francisco Estuary: insight into a forgotten past.  California WaterBlog, November 18, https://californiawaterblog.com/?s=striped+bass

O’Rear, T. and P. Moyle 2019. Remarkable Suisun Marsh: a bright spot for fish in the San Francisco Estuary. https://californiawaterblog.com/2019/08/25/remarkable-suisun-marsh-a-bright-spot-for-fish-in-the-san-francisco-estuary/

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

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A Change of Plans

1957 Water Plan map

Development map from the 1957 California Water Plan

by Jay Lund

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

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

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

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

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

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

Further Readings

California Department of Water Resources, California Water Plan, 1957.  Now buried on the DWR web site at: https://water.ca.gov/LegacyFiles/waterplan/docs/previous/californiawaterp03cali.pdf

California Department of Water Resources, Central Valley Flood Protection Plan, 2012.  A very useful recent state plan now buried on the DWR web site at: https://water.ca.gov/LegacyFiles/cvfmp/docs/CVFPPAttVol4_20120307.pdf

California Resources Agency, California Water Action Plan, 2014.

California Resources Agency, Draft Water Resilience Portfolio, 2020.

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

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

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