California’s Amazing Terminal Lakes

By Peter B. Moyle

Figure 1. Eagle Lake, Lassen Co.

When Californians talk of lakes, they usually mean reservoirs, the 1500 or so artificial bodies of water behind dams. Alternately, they may be referring to the 4,000 or so natural lakes in the Sierra Nevada or to one of the few large natural lakes in the state, such as Lake Tahoe or Clear Lake. But some of the most interesting lakes in the state draw our attention mainly when demand for water threatens to dry them up. These are terminal lakes, that mostly depend on seasonal rain or snow melt to maintain them as lakes. They are called terminal lakes because water flows into the basins through streams, but leaves mostly by evaporation or sinking into underground aquifers. Each lake has its own unique chemistry and other characteristics, although most are highly productive so are important to migratory waterfowl and invertebrates. They may or may not support endemic fish populations. This blog is a brief introduction to the largest of these fascinating lakes in California. All are in need of management to protect their distinctive features and biota.

Terminal Lakes are huge phenomena that are underappreciated for their importance in California. Most famously, they include Mono Lake, Salton Sea, and Lake Tulare. But the term also encompasses Goose, Alkali (3 lakes), Eagle, Honey, Owens, Walker, Carson, and Pyramid lakes. The latter three lakes are in Nevada but largely drain watersheds in California. All these lakes have unique characteristics and are important features of the landscapes in which they occur. Geologically, they are mostly in endorheic basins where water flows in but not out.

Terminal Lakes are fed by streams and typically require high flow events to maintain their water levels. For the most part, water enters from streams and leaves by evaporation or by seeping into the ground. However, after multiple wet years, some may spill over basin boundaries and into a river system. Not surprisingly, terminal lakes are mostly found in desert environments, where inflowing waters are coveted for irrigation and other uses; diversion greatly increases the likelihood these lakes will shrink or dry up, especially during periods of drought.

Table 1. Characteristics of ten terminal (endorheic) lakes of California (and Nevada). Area is surface area assumed to be typical before diversions prevented most inflow from reaching the lake. Historically, all varied in area and depth in relation t­o precipitation variations.

Terminal lakes were of major importance during the Pleistocene Period. Then, heavy rainfall resulted in much of the Great Basin being covered with enormous lakes, including Lake Lahontan in Nevada and California east of the Sierra Nevada. At times, much of the Central Valley must have been flooded as well. The lakes in Table 1 are mostly remnants of these ancient lakes, which during wet periods connected with other lakes.

Figure 2. Approximate Locations of major terminal lakes in California. Walker, Pyramid, and Carson lakes are in Nevada.

What follows is a brief introduction to each these lakes. Jay Lund (Lund 2023) and I (Moyle 2023) have already blogged about Lake Tulare, so it will not be treated further here.

Goose Lake is an immense lake (elevation 1433 m) that straddles the Oregon border; most of its watershed, and most of the water that historically flowed into the basin, is in Oregon. The lake goes dry naturally during periods of extreme drought, but the frequency of drying has increased presumably because of diversion of the water for agriculture (Heck et al. 2008). It has gone dry in 1851-2, 1926, 1929-34, 1992, 2002, 2013-15, and 2020 (Goose Lake Wikipedia).

Goose Lake has an endemic fish fauna (nine species) that find refugia in the inflowing streams and ponds in the basin when the lake dries up (Moyle, unpublished 1992). In 1989, I spent several days sampling the lake’s fish population during a wet period (since 1934!) with then graduate student Rollie White. Sampling was challenging because the lake was so shallow and strong winds came up every afternoon, which kept the lake turbid and unsafe for boating. We confined our boat sampling to nights and calm early mornings, using a variety of sampling gear. I was impressed with the abundance of fish, especially Goose Lake tui chubs. When we pulled in our gill nets, many of the tui chubs had small (10-12 inches) lampreys attached while others had round sores on the body where lampreys had been attached. The undescribed Goose Lake lamprey was a beautiful bronze color, that glowed in the sun. Also captured in abundance were tadpole fairy shrimp (Figure3), which are usually not found in waters containing fish.

Figure 3. (Upper Left) Goose Lake drying up, 1992 . (Upper Right) Goose Lake 1989 on a windy afternoon. Canada geese in foreground. (Lower Left) Tadpole fairy shrimp (Triops longicaudatus) from Goose Lake. (Lower Right) Goose Lake lamprey (Entosphenus sp.). Photos by P.B. Moyle.

A fish we did not catch was Goose Lake redband trout (see photo), which migrates up streams from the lake to spawn. Stream populations have been the focus of conservation, including Lassen and Willow creeks in California. Historically, this fish maintained fairly large populations in the lake and inflowing streams, which supported a lake fishery during wet years (Moyle et al. 2015). In 1992, USFWS proposed listing all Goose Lake fishes as ‘Threatened’ as the lake dried up (Moyle 1992). The proposal to list the species was withdrawn after local ranchers agreed to work with state and federal  agencies to allow assessment status on private lands.

Figure 4. Goose Lake redband trout, from a spawning fish in Willow Creek, from the lake. Photo by Jack Williams, March 29, 1988.                     

The Alkali Lakes are three connected lakes occupying the floor of Surprise Valley, California. The ‘lakes’ are mostly dry salty flats that can flood with shallow water in winter but typically dry out in summer, a pattern enhanced by diversion of inflowing streams to irrigate alfalfa fields. The lakes are one of the many remnants of Pleistocene Lake Lahontan. It is always a surprise to see the valley with its white alkaline (mostly dry) lakes and contrasting green fields of alfalfa, while crossing the Warner Mountain range. The aquatic fauna of the region is poorly characterized although inflowing streams contain apparently endemic fishes in Nevada.

Eagle Lake is second largest freshwater lake entirely within the boundaries of California. Once connected to Pleistocene Lake Lahontan, the lake today is supplied by water from Pine Creek and a few smaller creeks and springs.  The lake is at a high enough elevation (ca. 5100 ft) and is large and deep enough, to be characterized as a cool water ecosystem with a freshwater fauna. The water is nevertheless fairly alkaline (pH around 9); thus most ‘true’ freshwater fishes are excluded from it, including the alien species that are so abundant in most California lakes and reservoirs. Instead, the lake supports five endemic fishes that are specifically adapted to its unique chemistry. Four of the species have ancestors that inhabited Lake Lahontan, but the Eagle Lake rainbow trout has ancestors in the Sacramento system. This trout historically grew to large sizes because of abundant prey (tui chubs and invertebrates) and delayed maturity. The latter characteristic resulted in it giving rise to a hatchery strain that is widely planted in reservoirs around the state.  Eagle Lake also supports a substantial recreational fishery for Eagle Lake rainbows that is maintained by a hatchery rearing program. The high alkalinity of Eagle Lake also is an indication of its high productivity, with a food web that supports  breeding populations of waterbirds such as western grebes and osprey.

Figure 5. Eagle Lake as viewed from the now-defunct Eagle Lake field station.

Honey Lake is another Lake Lahontan remnant. It is the large expanse of alkali flat, sometimes partially flooded but usually dry, that is visible from Highway 395, south of Susanville. It is surrounded by marsh lands, important for migratory waterfowl. These marshes are fed by three major tributaries: Susan River, Long Valley Creek, and Willow Creek. During the Pleistocene, Eagle Lake apparently drained into Honey Lake, via Willow Creek. Recognition of this ancient connection led to an effort in the 1920s to hew a tunnel through lava rock in order to provide more water for agriculture in the Honey Lake basin. Bly Tunnel was completed, but the water added to Willow Creek was too little to make it to Honey Lake (Moyle et al. 1991). Native fishes include desert speckled dace, Tahoe sucker, tui chubs, and Lahontan redside.

Pyramid, Walker and Carson Lakes. These three terminal lakes are in Nevada but their water originates in California, flowing down the Truckee, Walker, and Carson rivers respectively. Pyramid Lake is the largest and most spectacular remnant of Lake Lahontan and has an endemic fish fauna, most famously Lahontan cutthroat trout and cui-ui, which support Indigenous and recreational fisheries. Lake levels dropped dramatically when the Truckee River was diverted to irrigate alfalfa in the early 1900s. The lake was ‘saved’ when the cutthroat trout and cui-ui were listed as endangered species, the Paiute tribe asserted its right to water to maintain the fishery, and other factors came into play. Walker Lake also suffered from irrigation diversions taking the inflowing water, becoming too low and too alkaline to support fish populations, except in wet years. On-going litigation is aimed at restoring the lake and its cutthroat trout fishery. Carson “Lake” is usually not regarded as a lake but as a ”sink” although it occasionally becomes a short-lived lake (e.g. 1987). Like the other two lakes, it is a remnant of Lake Lahontan and has suffered almost complete depletion of its water supply from agricultural diversion.

Mono Lake is the best known of California’s terminal lakes because of its stark beauty, unique ecology, and being center of a David vs. Goliath environmental battle (Hart 1996). The battle, to simplify, was between a volunteer Mono Lake Committee and huge Los Angeles Department of Water and Power. LADP was in the process of drying up the lake by diverting the water from inflowing streams, which MLC wanted to stop. Joined by major environmental groups, MLC was largely successful, not only saving the unique lake and restoring the streams, but setting legal precedents that have had consequences far beyond the lake (e.g., Public Trust Doctrine). The MLC continues in its role as guardian of the lake and its biota, with headquarters in Lee Vining (overlooking the lake) and activist staff and volunteers. Those who want to know more about this history and about the amazing natural history of the lake, should go to the MLC website ( and/or subscribe to their excellent newsletter.

Owens Lake. An important lesser-known story in the history of California is how developers in Los Angeles acquired, by nefarious means, the water flowing in streams of the Owens Valley and built an 223 mile long aqueduct to carry the water south. Starting in 1913, this diversion effectively dried up the streams, ending irrigated agriculture in the region. Less appreciated in this drama is that Owens Lake also dried up in the following years. This terminal lake had been a permanent body of brackish water, 25-50 feet deep, fed by the Owens River and was best known for its large populations of migratory and nesting waterfowl. Little is actually known about the ecology of the lake but the streams the fed it supported at least four endemic fishes, including Owens pupfish, which may have inhabited the lake as well.

An unexpected consequence of the drying of the lake was massive storms of toxic dust which spread over wide areas and were detrimental to human health. To control the dust, the City of Los Angeles was required to reflood much of the lake bed. Habitat for thousands of migratory birds re-developed, producing brine flies, brine shrimp and other fuel organisms for the migrating birds. The historic lake now exists as a shallow remnant, perhaps more similar to Mono Lake than to the original Owens Lake but dependent on pumping of water into the lake basin. However, in the snowy winter of 2023, there was more water than the LA aqueduct could handle, and large quantities flowed into the lake bed, at least temporarily resurrecting a less salty version of the lake.

Salton Sea is a salt water lake occupying the bed of long-dry Lake Cahuilla. The ‘sea’ was recreated in 1905 when the entire flow of the Colorado River, during a flood, burst through levees and flow into the Alamo Channel. Initially the ‘sea’ was a freshwater lake occupying the old lake bed. It became increasingly salty after the river was re-diverted into its ‘natural’ channel. Today the basin is a hypersaline drain for agricultural waste water, so is a toxic mess, with an uncertain future. There is a substantial literature on the Salton Sea, which has documented key changes to its ecosystem (e.g. Barnum et al. 2002) and the difficulties of finding a solution to its management, which must deal with the toxic water and also toxic dust.

Conclusions. Maintaining terminal lakes is an important conservation goal in California because each has its own distinctive chemistry and biota. Conservation mainly involves keeping them from drying up by reducing diversions of inflowing water. This management also reduces the severity of toxic dust storms, created by dry lake beds, that ultimately generate human health problems. The future of these lakes is uncertain given the predicted increase in long droughts from global warming. It is important to consider that future now, following the lead of the adherents of Mono Lake.

Peter B. Moyle is a Distinguished Professor Emeritus at the University of California, Davis and is Associate Director of the Center for Watershed Sciences.

Further Reading:

Barnum, D.A., Elder, J.F., Stephens, D. and Friend, M. eds., 2002. The Salton Sea. Hydrobiologia 473 (1-3):1-306.

Hart, J. 1996. Storm over Mono: The Mono Lake Battle and the California Water Future. Berkeley: University of California Press.

Lund, J. 2023. Tulare Basin and Lake – 2023 and their future, California WaterBlog, May 7, 2023

Moyle, P.B. 2023. Lake Tulare (and its fishes) shall rise again, California WaterBlog, April 16, 2023

Moyle, P.B. 1992, Biology and status of fishes of Goose Lake, California and Oregon. Unpublished report, written for the Goose Lake Fishes Working Group.

Moyle, P. B., T. Kennedy, D. Kuda, L. Martin, and G. Grant. 1991. Fishes of Bly Tunnel, Lassen County, California. Great Basin Naturalist 51:267-270.

Scheerer, P.D., Gunckel, S.L., Heck, M.P. and S.E. Jacobs. 2010. Status and Distribution of Native Fishes in the Goose Lake Basin, Oregon. Northwestern Naturalist 91(3):271-287.

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Schooling Fish: Behind the Scenes of Putah Creek Fish Sampling

By Christine A. Parisek, Peter B. Moyle, Joshua Porter, and Andrew L. Rypel

It’s a curious thing, teaching a classroom of future fish conservationists about revitalizing degraded ecosystems. Putah Creek was an unconventional place to teach ecology. After the creek turned bad, it stayed that way for decades – deteriorated habitat, nonexistent flow, garbage, rusted cars, even gravel mining. And while conditions have improved, many students, and even some scientists, still remain skeptical that this ecosystem could ever be anything but a spoilt ecosystem. Is it really possible to genuinely rehabilitate an ecosystem like that through improved management and community building? Those lessons work in other cases, for other ecosystems, but surely not this one. 

This blog explores the outcome of environmental stewardship over time, of patience and persistence that pays off, and of some extremely cool fishes you wouldn’t guess live in our local creek today. It’s a story that catches students, and even many members of the community, off guard. Those who have ties to the area, whether in growing up here or as UC Davis alumni, may vividly remember a time when the creek was a very different place.

Putah Creek Fish Sampling 

Professors Peter Moyle and Andrew Rypel introduce the Biology & Conservation of Fishes class to the start of a Putah Creek field trip. Photo by Christine Parisek.

On the crisp morning of November 4th, the UC Davis fish class (WFC 120) ventured on their annual field trip to Putah Creek, located just on the outskirts of campus. The most recent field trip expands a long-term student-generated dataset on Putah Creek spanning nearly 50 years. Students have spent most of this academic quarter learning about native and introduced fish species in California. A major goal of the course is cultivating an appreciation for the status of our fishes, and what we can do to protect them from extinction. Prior to this class, many of these students had never touched a fish before. The field trip is an opportunity to see local fish diversity up close, learn about our local watershed, and try a hand at different sampling methods. It is also a chance to tell the story of Putah Creek – a positive narrative about collaboration, team science, and diverse people uniting to successfully realize a shared vision.

Prickly sculpin (Cottus asper; Native). Left: Lateral view. Right: Dorsal view. Photo by Christine Parisek.
Sacramento sucker (Catostomus occidentalis; Native). Left: Ventral view showing the Sacramento sucker’s fleshy papillose suction-like lips. Right: Several Sacramento sucker in a well-aerated aquarium for the afternoon’s field trip demonstrations. Photo by Christine Parisek.

Class leaders and representatives from the East Bay Park District demonstrate a variety of active (shoreline seining, boat electrofishing, backpack electrofishing) and passive (gill nets, minnow traps, clover traps) sampling techniques for the students (under an approved Scientific Collection Permit and IACUC protocol). These data also support a reliable inventory of the fishes in the creek (e.g., Table 1). Some fishes are more or less likely to be captured via a particular method; thus we use a suite of tools for more robust data collection. Fishes caught during the trip are identified, counted, measured, and returned to the creek. A subset of unique fishes are kept in accessible well-aerated aquaria for students to observe up close during the day, and to use for practicing common measurements on fishes. In addition to the students, we often also get to chat with folks from the community passing by on their weekend jaunts. Another significant aspect of our collaboration with the East Bay Park District (EBPD) was that several of these collected fish, including many native fishes, went on to be incorporated into the EBPD Mobile Fish Exhibit and various visitor center aquariums in the East Bay; this has allowed EBPD to expand outreach and educate thousands of children (and adults) in the Bay area on the importance of native fish in California. We are especially grateful for the supportive and dedicated graduate students, research personnel, and East Bay Parks District representatives who help put on an experiential learning opportunity like this for the students every time – it truly takes a village!

Fish sampling in action during the Putah Creek field trip. Top left: Largemouth bass (Micropterus salmoides; Introduced). Top middle: Black crappie (Pomoxis nigromaculatus; Introduced). Top right: Sacramento sucker (Catostomus occidentalis; Native). Bottom left: Sacramento sucker (Catostomus occidentalis; Native). Bottom middle: Fall-run Chinook salmon  (Oncorhynchus tshawytscha; Native). Bottom right middle and bottom right: Class and community members gather to hold and learn about fish. Photos by Christine Parisek (top left, top middle, bottom right), Dave Ayers (bottom left, bottom middle, bottom right middle), John Durand (top right).
Passive and active fish sampling techniques in action. Top left: Seining. Bottom left: A group is boat electrofishing. Top right: Demonstrating a Sacramento sucker’s fleshy papillose lips. Middle right: A group gets ready to backpack electrofish. Bottom right: A group gathers around fish aquaria. Photos by Dave Ayers (top left), Christine Parisek (top and bottom right), and John Durand (bottom left, middle right).
Top left: Juvenile Sacramento pikeminnow (Ptychocheilus grandis; Native). Bottom left: Sacramento tule perch (Hysterocarpus traskii traskii; Native). Middle: Largemouth bass (Micropterus salmoides; Introduced). Top right: Black crappie (Pomoxis nigromaculatus; Introduced). Bottom right: Redear Sunfish (Lepomis microlophus; Introduced). Photos by Dave Ayers (bottom left) and Christine Parisek (others).

By now you may be thinking – Wait a minute, all these fishes can live Putah Creek? Salmon, too??!! I thought that place was a hole…

Ripple effects of reconciling ecosystems  

People are frequently shocked by the diversity of fishes in Putah Creek today. Yet in a landscape as heavily modified as California’s Central Valley, we often take for granted our ability to, with patience and persistence, improve the vibrancy of nature’s ecosystems. As the Tanzanian Proverb goes: “Little by little, a little becomes a lot.” 

For those that don’t know it – the Sacramento region historically had prolific salmon runs (Brown et al. 1994; Yoshiyama et al. 1998; Yoshiyama 1999). That is until dams, water diversions, and pollution significantly reduced habitat quality. In Putah Creek, humans ultimately desiccated the creek bed and, coupled with the construction of dams, quickly extirpated the anadromous fishes. Afterwards, the fish assemblage shifted to one dominated by invasive species. We often joke that even the cars couldn’t survive in the creek anymore (see below figure). Motivated by enforcement of California Fish and Game Code 5937, an Accord in 2000 prompted the creek be kept in better condition for fishes (see: Marchetti & Moyle 1995; Moyle et al. 1998). The Accord developed standards for minimum base flows, seasonal pulse flows, and a robust monitoring program in Putah Creek. With just 5% of flows returned to the creek, patience and persistence with nature, and stakeholder and community collaboration and commitment – rehabilitating the creek ecosystem transitioned from aspiration to reality. 

Putah Creek at 2 locations before and after the Accord. Photographs <2018 by Peter Moyle and ≥2018 by Emily Jacinto. Figure adapted from Jacinto et al. 2023.

Reconciled ecosystems like Putah Creek gain the ecological benefits from restoration interventions but also continue to support human needs (e.g., recreation, agriculture, cities). And there is no going back in time for Putah Creek. The creek is so deeply incised from years of poor land management that very little of the historical riparian ecosystem remains. It bears little resemblance to what it once did historically and it would be functionally impossible to engineer it back to that state. Yet through science-based management, we can approximate conditions that on the whole are good for native species. Managing in this general direction improves the ecosystem slowly, and over time, ecological processes begin to heal. The creek now has a regularly returning salmon run whose numbers appear to be growing, and improvements to the bird community are apparent too (See: Dybala et al 2018; Chapman et al. 2018; Rypel 2022; Jacinto et al. 2023b). 

Dr. Andrew Rypel holds an adult Chinook salmon (Oncorhynchus tshawytscha) that was making its way up Putah Creek during the 2023 fall field trip. Photo by Dave Ayers.

And this year marked the first time ever that an adult Chinook salmon Oncorhynchus tshawytscha was caught on the annual class field trip. The return of salmon to Putah Creek means a lot to the community, to cultural values, and to ecosystem services. The creek also means a lot to the UC Davis community. It is amazing that the university now has a run of Chinook salmon in its own backyard. Past decades of students from WFC 120 are noticing the change too, and it is heartening that we are all able to witness tangible evidence of the benefits of proactively managing this reconciled creek patiently and persistently. This is a tribute to a long list of concerned citizens, scientists, and managers who worked tirelessly for the creek over the years. 

Just imagine if there were more reconciled ecosystems managed and acting as natural labs like Putah Creek, scattered all over the state, each one once again serving its ecosystem function and in doing so reminding us all of the invaluable lesson that little by little, a little becomes a lot. Small changes that we have control over can make a big impact, and we shouldn’t take that for granted. Students from the class have gone off to become leaders in the California water and environmental communities. Others have become professors and scholars in other parts of the world. It is an important example for all of us to see in how to translate science into practice.

Christine A. Parisek is a Ph.D. candidate in the Graduate Group in Ecology at UC Davis and a science communications fellow at the Center for Watershed Sciences. Peter B. Moyle is an emeritus professor in the Center for Watershed Sciences, University of California, Davis. Joshua Porter is currently a Fisheries Biologist, focusing on angler education, with the Louisiana Department of Wildlife & Fisheries and was previously an Aquatic Exhibits & Fisheries Resource Analyst with the East Bay Parks District in California. Andrew L. Rypel is a professor of Wildlife, Fish, & Conservation Biology and Director of the Center for Watershed Sciences at the University of California, Davis.

Students from the 2023 fish class holding various fish during the field trip. Photo by Dave Ayers.
Class photo from the 2023 field trip to Putah Creek, California. Photo by Dave Ayers.
Left: Green sunfish (Lepomis cyanellus; Introduced.). Right: Bluegill sunfish (Lepomis macrochirus; Introduced).

Table 1. Fish species typically observed or collected during the Putah Creek class field trip. Take a look at their profiles on the UC-ANR California Fish website!

Native Fishes
Fall-run Central Valley Chinook Salmon (Oncorhynchus tshawytscha)
Central Valley Steelhead (Oncorhynchus mykiss); present in the system but not during the Fall field trip. 
Sacramento Tule Perch (Hysterocarpus traskii traskii)
Sacramento Sucker (Catostomus occidentalis occidentalis)
Sacramento Speckled Dace (Rhinichthys osculus subspecies)
Sacramento Pikeminnow (Ptychocheilus grandis)
Sacramento Perch (Archoplites interruptus)
Prickly Sculpin (Cottus asper subspecies)
Pacific Lamprey (Entosphenus tridentata)
Introduced Fishes
Spotted Bass (Micropterus punctulatus)
Largemouth Bass (Micropterus salmoides)
Smallmouth Bass (Micropterus dolomieu)
Mississippi Silverside (Menidia beryllina subspecies)
Mosquitofish (Gambusia affinis)
Goldfish (Carassius auratus)
Common Carp (Cyprinus carpio)
Green Sunfish (Lepomis cyanellus)
Bluegill Sunfish (Lepomis macrochirus)
Redear Sunfish (Lepomis microlophus)
Brown Bullhead Catfish (Ameiurus nebulosus)
Black Bullhead Catfish (Ameiurus melas)
Channel Catfish (Ictalurus punctatus)
White Crappie (Pomoxis annularis)
Black Crappie (Pomoxis nigromaculatus)
Bigscale Logperch (Percina macrolepida)
* The sampling methods described in this blog are under an approved Scientific Collection Permit and IACUC protocol. Fishes are identified, counted, measured, handled with love, and returned to the creek. Before you fish, it is always a good idea to check your local fishing regulations.

Further Reading – Understanding Putah Creek (Reverse Chronological Order)

Jacinto, E., Fangue, N.A., Cocherell, D.E., Kiernan, J.D., Moyle, P.B. and Rypel, A.L., 2023a. Increasing stability of a native freshwater fish assemblage following flow rehabilitation. Ecological Applications, p.e2868.

Jacinto, E., N.A. Fangue, D.E. Cocherall, J.D. Kiernan, P.B. Moyle, and A.L. Rypel. 2023b. Putah Creek’s rebirth: a model for reconciling other degraded streams? California WaterBlog. 

Rypel, A.L. 2023. Facing the Dragon: California’s Nasty Ecological Debts. California WaterBlog. 

Rabidoux, A., M. Stevenson, P.B. Moyle, M.C. Miner, L.G. Hitt, D.E. Cocherell, N.A. Fangue, and A.L. Rypel. 2022. The Putah Creek Fish Kill: Learning from a Local Disaster. California WaterBlog. 

Rypel, A.L. 2022. Being patient and persistent with nature. California WaterBlog. 

Rypel A.L., P.B. Moyle, and J. Lund. 2021. A Swiss Cheese Model for Fish Conservation in California. California WaterBlog.

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

Willmes M., A. Steel, L. Lewis, P.B. Moyle, and A.L. Rypel. 2020. New insights into Putah Creek salmon. California WaterBlog. 

Moyle, P.B. 2020. Crawdads: Naturalized Californians. California WaterBlog. 

Chapman, E., E. Jacinto, and P.B. Moyle. 2018. Habitat Restoration for Chinook Salmon in Putah Creek: A Success Story. California WaterBlog. 

Dybala, K.E., Engilis, A., Trochet, J.A., Engilis, I.E. and Truan, M.L., 2018. Evaluating riparian restoration success: long-term responses of the breeding bird community in California’s lower Putah Creek watershed. Ecological Restoration, 36(1), pp.76-85.

Moyle, P.B. 2017. What do stream fish do during flood flows? California WaterBlog. 

Tilcock, M. 2016. The Horror of a Salmon’s Wheel of Misfortune. California WaterBlog. 

Moyle, P.B. 2015. Salmon finding a home in my backyard – Could it be? California WaterBlog. 

Austin, C. 2014. Reconciling ecosystem and economy. California WaterBlog. 

Grantham, T., and P.B. Moyle. 2014. Flagging problem dams for fish survival. California WaterBlog. 

Börk, K.S.  J. F. Krovoza, J. V. Katz, and P. B. Moyle. 2012. The rebirth of California Fish & Game Code 5937: water for fish. University of California Davis Law Review 45: 809-913. 

Kiernan, J.D., Moyle, P.B. and Crain, P.K., 2012. Restoring native fish assemblages to a regulated California stream using the natural flow regime concept. Ecological Applications, 22(5), pp.1472-1482.

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

Marchetti, M. P., and P. B. Moyle. 2000Spatial and temporal ecology of native and introduced fish larvae in lower Putah Creek, California. Environmental Biology of Fishes 58:75-87.

Yoshiyama, R.M., 1999. A history of salmon and people in the Central Valley region of California. Reviews in Fisheries Science, 7(3-4), pp.197-239.

Yoshiyama, R.M., Fisher, F.W. and Moyle, P.B., 1998. Historical abundance and decline of chinook salmon in the Central Valley region of California. North American Journal of Fisheries Management, 18(3), pp.487-521.

Moyle, P.B., Marchetti, M.P., Baldrige, J. and Taylor, T.L., 1998. Fish health and diversity: justifying flows for a California stream. Fisheries, 23(7), pp.6-15.

Marchetti, M. and Moyle, P., 1995. The case of Putah Creek: Conflicting values complicate stream protection. California Agriculture, 49(6), pp.73-78.

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Crawdads: Naturalized Californians

Sandy, a 4+ year old red swamp crayfish, raised from a newly hatched egg by Marilyn Moyle.

By Peter Moyle

*this is a repost of a blog originally published in June 2020.

Crayfish, crawdads, crawfish: whatever you call them, they are everywhere in California’s waters and are as tasty as their lobster relatives. They are especially familiar to anglers who peer into the maw of a bass or pikeminnow or flush their stomachs to see what prey caused the bulging belly. Crawdads are familiar to kids wading in streams, who dare each other to catch one without being pinched. River otters love them as food too. I have watched otters dive in Putah Creek and repeatedly come up with one. With each capture, the otter rolls on its back and crunches the crayfish down. The otters appear to be smiling with satisfaction, smacking their lips.  People eating crayfish have the same general appearance.

Crayfish are so integrated into California’s aquatic ecosystems that they might be considered as native if you didn’t know their history. But most are the result of introductions as food for people or as forage or bait for game fish. And most California crayfish live in novel ecosystems. These ecosystems have a biota that is a mixture of native and non-native species living in habitats that are highly altered by the continuous actions of people. Crayfish therefore fit right in, feeding on organic matter, algae, dead fish or anything else they can process, and then being eaten themselves by native predators such as otters, herons and pikeminnows, or by non-native predators such as centrarchid (sunfish family) basses and bullfrogs. However, this integration comes at a cost, especially in less-altered waterways. Non-native crayfish, regardless of species, can (a) displace fish and native crayfish from cover, making them more vulnerable to predation, (b) reduce aquatic plant densities, making water clearer, (c) compete with fish for aquatic invertebrates as food, especially snails, and (d) displace native crayfish from their habitats. How much of all this they do in California ecosystems, however, is not well understood.

The situation with crayfish in California is actually complex because there are three native species and three non-native species. Their status ranges from extinct, to endangered, to being abundant enough to be sustainably harvested. Confusion is further generated by the tendency of many fish biologists (like me), when sampling aquatic habitats, to just refer to crayfish captured as “crayfish” with no reference to species.

California crayfish

Sooty crayfish. The extinct species is the sooty crayfish (Pacifastacus nigrescens) which was found only in a few streams in San Francisco. They disappeared after only a few specimens were collected in the 19th century, presumably victims of rapid urbanization. The story of sooty crayfish is a mystery because if these crayfish were present in the Bay area streams, why weren’t they found throughout streams of the Central Valley, as non-native species are today? But there is no evidence, archeological or otherwise, that crayfish were ever present in most areas that support non-native crayfish today.

Pilose crayfish. An apparent victim of poor field notes is the pilose crayfish (P. gambelii). The species was described from specimens collected in “California” (the complete locality information on the type specimen) by Charles Girard in 1852. While the pilose crayfish is widely distributed across western states, it is not found in California, indicating Girard made a mistake in noting the vague locality (Larson and Olden 2011).

Shasta crayfish. This crayfish (P. fortis) is native to cold, spring-fed streams and rivers of the Pit River system, including Fall River and Hat Creek in northeastern California.  When graduate students from my lab were studying this crayfish in the 1980s and 90s, I was impressed with how different they were in their behavior from other crayfish: they were not aggressive. If there was bucket of live Shasta crayfish being measured, I could stick my hand in the bucket to grab one without looking. Representatives of any other crayfish would grab my fingers or hand with a big claw and hold on until shaken off.  Shasta crayfish did not appear to have the well-developed defensive mechanism of waving their large front claws around while backing into cover. Unfortunately, this lack of aggression has made them an endangered species. Larger, much more aggressive signal crayfish have invaded their habitat. Shasta crayfish now persist only where signal crayfish have not invaded or have been removed.

Signal crayfish (left) vs Shasta crayfish. The more robust, aggressive signal crayfish causes extirpation of Shasta crayfish when it invades their spring habitats. Photo by P. Moyle.

Klamath signal crayfish. This crayfish (P. leniusculus klamathensis) is native to the Klamath River, where it is abundant and widespread. It is possible that crayfish in the Eel River also belong to this subspecies and are native (Riegal 1959). The Klamath signal crayfish is considered to be a subspecies because it can be distinguished by both morphology and genetics from the widespread Columbia signal crayfish. The subspecies itself was introduced into Lake Tahoe and the Truckee River in 1895 where it is thriving, although it has hybridized with non-native Colombia river signal crayfish, so is no longer a distinct taxon in the eastern Sierra Nevada. A 1970 study (Abrahamsson et al. 1970) estimated that Lake Tahoe supported over 5.5. million crayfish; a more recent estimate is over 220 million crayfish, which dominate benthic production and affect everything from water clarity to native fish abundance (S. Chandra, unpublished data). Because these crayfish are resistant to crayfish fungal plague (Aphanomyces astaci), which had destroyed the crayfish fisheries in Sweden, Sweden stocked many of their lakes with crayfish from Lake Tahoe. While crayfish fisheries have been tried in Lake Tahoe, they have not been sustained (S. Chandra, personal communication). It would be an interesting experiment to subsidize a fishery for 10-20 years to see if such a fishery could have a positive effect on the ecology of the lake, including native fish, fisheries, and water chemistry.

These crayfish are now integrated into the ecosystems of Sierra Nevada streams and lakes, for better or worse. Light (2003) found that populations of signal crayfish in Sierra Nevada streams were regulated in part by flow, similar to trout and native fish populations. However, presence of a downstream reservoir that served as a refuge was necessary for recolonization following extreme flow events. Light (2005) also investigated the effects of signal crayfish on the biology of native Paiute sculpin in a small Sierra Nevada stream. While she found some evidence of competition, effects were minor, demonstrating coexistence was possible; presumably flow was more important to regulating crayfish populations than other factors.

(Left) Signal crayfish. USGS photo. and (Right) Shasta crayfish. USFWS photo.  

Columbia signal crayfish. Wide-spread the huge Columbia River basin, this crayfish (P. l. lenuisculus) was introduced into California in the early 1900s by fisheries agencies. Generally, when biologists talk about the signal crayfish, this is the form they are referring to, assuming the two subspecies do not have any ecological differences. The signal crayfish was introduced into Europe as a large, edible crayfish. Unfortunately, the introduced crayfish carried crayfish plague, a disease that pretty much wiped out the native European crayfish (Astacus astacus). This meant that in countries like Sweden, where crayfish are a traditional winter holiday food, crayfish had to be imported. For a while (1970s and 80s), a fishery for signal crayfish in the Delta helped to satisfy the demand. At its peak, the fishery involved an average of 32 boats. But the fishery has apparently disappeared or become small, presumably because cheaper crayfish from other countries or from aquaculture operations have entered the market. However, it is likely environmental change also played a role. Today, signal crayfish appear to be uncommon in the Delta, replaced by red swamp crayfish. When the Delta fishery existed, the town of Iselton held an annual crawfish festival. When the fishery collapsed (for unknown reasons), the festival fell on hard times. For a while, the festival imported frozen crawfish from China  but but this apparently did not work well.  The revival of the festival in 2023 was possible because live red swamp crayfish were available in abundance from Louisiana, where it is raised  in rice paddies and other habitats.

Red swamp crayfish, Natural History of Orange County. Peter Bryant.

Red swamp crayfish. This crayfish (Procambarus clarki) is typically red and does inhabit swamps, where it burrows into the mud. This behavior can cause distress to farmers if the ‘swamp’ happens to be a rice paddy or its levee. On the other hand, farmers who harvest the crayfish consider them to be a bonus crop (Brady 2013). This crayfish is also very versatile, abundant in streams with warm to cool water, variable water quality, and mud to rocky bottoms. It is aggressive and has apparently displaced other crayfish, and an occasional swimmer, in many places where introduced. Introduced into California in the 1930s, it is now the most commonly encountered crayfish in the central and southern parts of the state and subject of a trap fishery in the Delta and Central Valley, mostly for bait.

Buciarelli et al. (2018) demonstrated how red swamp crayfish can change stream ecosystems that historically lacked crayfish. They preyed on or displaced dragonfly larvae in low gradient streams. The dragonfly larvae were more efficient predators on mosquito larvae than crayfish, so fewer dragonflies resulted in more mosquitoes. Red swamp crayfish have also been shown to be aggressive to other crayfish species and appear to have displaced signal crayfish from some streams in Oregon, as well as in Spain (Pearl et al. 2013). This may account for the observation that signal crayfish in California are often confined to cold headwater (trout) streams) when red swamp crayfish are present in the warm lower reaches of the streams.

Virile crayfish, Wikipedia commons.

Virile (Northern) crayfish (Faxonius virilis) are native to much of northeastern and midwestern USA and are one of the most widely introduced crayfish worldwide. They are best known as Orconectes virilis but were recently reclassified as Faxonius virilis by Crandall and de Grave (2017). They have been widely introduced around the western USA, including California, apparently because of their popularity as bait. The first records from the Central Valley were of crayfish in ponds near Chico State College, where they were kept for teaching purposes starting in the early 1940s (Riegel 1959). Today they seem to be common in southern California and abundant in the Central Valley. Virile crayfish, however, can live in a wide variety of habitats including flowing streams, preferring warm water. Like the red swamp crayfish, they create burrows into which they can find refuge as their habitat dries up. The fact their broad habitat requirements are similar to those of red swamp crayfish suggests the two species co-occur and perhaps compete for food and space at times.

General observations

Crayfish had an easy time invading California.  Here are some reasons.

  • People like to eat them or use them as bait for game fish.
  • They are hardy and easy to transport with minimal water.
  • A population can be established by a single ‘berried’ female carrying 100-300 fertilized eggs or newly hatched young. The young can mature in 1-2 years and live up to 5 years, longer in captivity.
  • They can live in a wide variety of streams, reservoirs, and other aquatic habitats, with signal crayfish doing well in cold waters (e.g. trout streams) and red swamp crayfish and virile crayfish widespread in warmer waters.
  • They quickly spread once introduced into a new area, making them nearly impossible to eradicate once established.
  • We have a poor understanding of how crayfish affect aquatic ecosystems and native aquatic species in California.

Because crayfish, especially non-native crayfish, are so widespread and abundant in California, they tend to be taken for granted. They are present in habitats from warmwater ditches to coldwater mountain lakes and appear to be thoroughly integrated into our aquatic ecosystems, even waters like Lake Tahoe. They do especially well in habitats thoroughly altered by people, such as reservoirs, regulated streams, and rice fields. But there is much we don’t know about them. Some potential research questions include:

  • What is the distribution of crayfish species in California today, native and non-native? Such information could allow us to see if they are useful indicators of habitat quality and change. Sampling e-DNA might be a useful approach to this question.
  • Do the species replace one another in different habitats?  Is the red swamp crayfish today the dominant crayfish in most habitats?
  • Are dominant crayfish suppressing invertebrates and plants in streams, lakes, and sloughs throughout California, changing the nature of the ecosystems? This seems to be true in Lake Tahoe.
  • Would removal of crayfish return a given aquatic ecosystem to its original state, favoring native species?
  • Are other crayfish species likely to invade California? For example, the rusty crayfish (Faxonius rusticus) is an ecosystem damaging, aggressive crayfish that is spreading across North America.

Further Reading

Abrahamsson, S.A. and Goldman, C.R., 1970. Distribution, density and production of the crayfish Pacifastacus leniusculus Dana in Lake Tahoe, California-Nevada. Oikos, 21(1): 83-91.

Agerberg, A. and Jansson, H., 1995. Allozymic comparisons between three subspecies of the freshwater crayfish Pacifastacus leniusculus (Dana), and between populations introduced to Sweden. Hereditas122(1): 33-39.

Brady, S. 2013. Incidental aquaculture in California’s rice paddies: red swamp crawfish. Geographical Review, 103(3): 336-354, DOI: 10.1111/j.1931-0846.2013.00002.x

Crandall, K.A. and  S. De Grave, An updated classification of the freshwater crayfishes (Decapoda: Astacidea) of the world, with a complete species list. Journal of Crustacean Biology, 37(5):615–653,

Larson, E.R. & J. D. Olden. 2011. The state of crayfish in the Pacific Northwest, Fisheries 36(2): 60-73.

Light, T., 2003. Success and failure in a lotic crayfish invasion: the roles of hydrologic variability and habitat alteration. Freshwater Biology 48(10): 1886-1897.

Light, T., 2005. Behavioral effects of invaders: alien crayfish and native sculpin in a California stream. Biological Invasions 7(3): 353-367.

McGriff D. 1983. The commercial fishery for Pacifastacus leniusculus (Dana) in the Sacramento-San Joaquin delta. Freshwater Crayfish 5(1): 403-417. DOI: 10.5869/fc.1983.v5.403

Pearl, C., B. McCreary, and M. Adams. 2011. Invasive crayfish of the Pacific Northwest. USGS Fact Sheet 2011-3132. USGS, Corvallis, Oregon.

Riegel, J.A.  1959.The systematics and distribution of crayfishes in California. California Fish and Game 45(1): 29-50.

Rogers, D.C. 2005. Identification Manual to the Freshwater Crustacea of the Western United States and Adjacent Areas Encountered during Bioassessment. EcoAnalysts, Inc. Technical Publication #1. 78 pp.

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Reallocating Environmental Risk

By Karrigan Bork & Keith Hirokawa

[X-posted from Environmental Law Prof Blog]

Up-close look at Chinook salmon at the Feather River Fish Hatchery fish ladder during the 2018 Oroville Salmon Festival. Photo Credit: California Department of Water Resources.

Living the good life has often meant finding ways to allow for growth and construction while ostensibly protecting the natural environment on which we depend. Want to build a housing development, but there’s a wetland in the way? Mitigate the harm by building a new one somewhere else. Want to dam a river, but there’s a salmon run in the way? Build fish passage around the dam. If that’s not feasible, build a hatchery instead. Want to log a forest, but worried about loss of downstream ecosystem services? Allow the harvest, with buffers and a few trees left behind to maintain essential services. Techno-optimism and overconfidence makes it easy to say yes and assume we can mitigate the impacts. Saying yes is much easier than saying no.

Unfortunately, these creative approaches often fail. Constructed wetlands fail to reproduce the essential hydrologic or biodiversity or other functions of natural wetlands. Fish passage fails to get enough fish up and down stream to keep populations viable. Hatcheries can’t sustain fisheries over the long term in the same way that habitat can. Even regulated logging can degrade downstream ecosystem services. As a result, our good environmental intentions have paved a path to widespread degradation.

Sometimes it is due to a lack of effort or an unwillingness to spend the necessary funds, but often mitigation fails despite the best intentions. It is difficult to predict how natural systems will respond to perturbation, and recreating systems is even harder. The uncertainty of these allow-but-mitigate decisions is critical: we depend on functional natural systems, and failed mitigation risks our future. But our current approach allocates the risk of bad decisions to the environment. That is, when mitigation fails, the environment and the public, not project proponents, pay the price. There are very few consequences to the parties responsible for mitigation if they get it wrong.

Successful mitigation requires that mitigation associated with a regulatory approval be designed to effectively neutralize the damage, rather than simply to ensure that permits are issued and construction commences. Embracing some form of the precautionary principle might help, but we seem unwilling to put off decisions or simply deny projects with uncertain impacts. Iterative adaptive management with long term monitoring might help, but this approach often stumbles due to the difficulty in refashioning policies. If we’re going to keep relying on engineering or policy fixes to soften the blow (and all evidence suggests that we will), we need a better way to allocate environmental risk.

Fortunately, we have faced this problem in other contexts, and policy makes have developed productive ways to manage uncertainty. Applying these approaches more broadly might reallocate environmental risk away from the environment and the public and place it on project proponents. Such a reallocation internalizes the risk for project proponents, leads to better environmental outcomes, and should lead to better environmental decision making.

For example, local governments often require developers who seek approval for new developments to provide needed public infrastructure improvements (e.g., roads, traffic control devices, sidewalks, water and sewer pipes, etc.) to reduce new congestion and defray the public costs of the new development. Because new development brings in higher use of public infrastructure, these improvements allow cities to ensure that developers pay more of the public costs of their developments. But if these improvements are poorly constructed or otherwise prone to failure, they can make the community worse off than before—more people, more expenses, and failed mitigation. This parallels the problems with failed environmental mitigation projects.

Local governments sometimes address this risk by requiring developers to post performance bonds. The developer purchases a performance bond from a third party, called the surety, a company that is “ensuring” the developer’s infrastructure work will meet relevant requirements. If the developer’s work fails to meet the requirements the government recovers funds from the surety which (ideally) are sufficient to bring the work up to par. Thus performance bonds allow developers to proceed with building their projects by guarding against the uncertainty of whether the required improvements will perform. The local government approving the project no longer bears the risk of the developer’s failure.

Financial assurances, in the form of bonds, insurance, or other mechanisms, could similarly play a more significant role in other areas of environmental law. New fish passage projects required for dams could carry insurance that would fund additional construction or even dam removal if functional fish passage proved impossible. Logging projects could require bonds that would pay for downstream remediation if efforts to mitigate impacts to the forest’s ecosystem services proved inadequate.

The idea of environmental performance bonds or other financial mechanisms to ensure performance is not new, but it has been vastly underutilized. For example, an assurance approach is also used in wetland mitigation and stream mitigation for Section 404 permitting under the Clean Water Act. Under regulations issued in 2008, 404 permits issued by the Corps of Engineers require financial assurance based on performance standards for newly constructed wetlands, which should ensure that the new wetlands adequately mitigate the wetlands lost through the permitted dredge and fill. The financial assurances, which may take the form of bonds, insurance, or other mechanisms, are generally only required for 5-10 years, however, a time frame too short to determine whether the new wetlands will actually achieve their mitigation requirements. Bonding for mine reclamation and financial assurances for hazardous waste treatment facility closure provide other examples, although such assurances are often insufficient to cover actual reclamation costs (sometimes by an order of magnitude).

We tend to assume success and proceed in face of uncertainty when other parties bear the risk of failure. We will also continue to get many mitigation decisions wrong. Thus, we need to reallocate the environmental risk away from the public and the environment. In this context, performance bonds or other financial assurances can reallocate the risk and increase the likelihood that mitigation will succeed, but this approach has been vastly underutilized to curb the current risk of loss in environmental permitting.

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. Keith H. Hirokawa is a Distinguished Professor of Law at Albany Law School.

The Klamath River. Photo credit: Brandon Swanson/OPB

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Dispatches From the Deep Pacific

By: Sophie R. Sanchez, Christine A. Parisek, Andrew L. Rypel

Background photo by Jeremy Bishop on Unsplash. Phylopics by Christopher Kenaley (Sternoptyx pseudobscura; CC0 1.0), Yan Wong (Malacosteus niger; CC0 1.0), C. Camilo Julián-Caballero (Chauliodus danae; CC BY 3.0), Erika Schumacher (Anoplogaster cornuta; CC BY-NC 3.0). Font by Charlie Samways (CC0 1.0). Text inspired by Game of Thrones, “Winter is Coming”.

Monsters are lurking…

Off the coast of California, down in the chilly depths of the Pacific Ocean, there lie the most unsettling denizens that appear summoned from the nightmares of Mira Grant. Here in the inky blackness, where nature spawned these most otherworldly configurations, inhabitants reign in pure darkness. Even the bravest of brave souls may not be able to suppress a shudder after reading this post. Prepare to endure a frightful encounter with some of nature’s most sinister and vile entities…

Fangtooth (Anoplogaster cornuta). Image credit: David Wrobel.

Fangtooth (Anoplogaster cornuta) – Adorned with malevolent fangs that provide its namesake, the fangtooth has a Dracula-esque bite and haunting charm which commands pure respect in “the midnight zone” of their oceanic abyss. The fangtooth’s ultra-black pigmented skin also absorbs light with 99.5% efficiency, practically providing this fish with a natural cloak of invisibility. As if that weren’t enough to give you the heebie-jeebies, these carnivores also have powerful musculature, enlarged heads, bulging eyes, and enormous gnashing jaws to help ambush and snatch unsuspecting prey. Indeed these primordial hunters are the quintessential model of predatory elegance, with a bioluminescent lure allowing them to play games, waiting patiently to execute the lethal strike. There are just two known species of fangtooth lurking in the world: common fangtooth (Anoplogaster cornuta) and, as if they could be any more formidable, shorthorn fangtooth (Anoplogaster brachycera). Great, just what it needed, an extra weapon.

Pacific viperfish (Chauliodus macouni). Image Credit: David Wrobel.

Viperfish (Chauliodus macouni) – Not to be confused with the Bulgarian punk rock band, the viperfish is one of the primary predators of the mesopelagic zone of the Pacific. Viperfish are quickly recognized by their massive fangs, resembling in many ways, a fishy vampire. These ghoulish creatures possess one of the largest teeth-to-head size ratios known on Earth. Amazingly, they can also unhinge their jaw to at least a 90° angle to take even bigger bites. Ultimately, these adaptations help ensure any prey captured by viperfish are most definitely consumed with no chance of escape. Meals are hard to come by in the deep sea, and viperfish therefore strike fear into the hearts of any planktivore also occupying our deep California coasts. Planktivorous and zooplanktivorous fishes make massive diel and crepuscular migrations up and down the water column, but viperfish lie and wait. Waiting for their chance to jump and kill. Its face and unsightly visage alone are enough to make one’s skin crawl, but imagine the heart-pounding reality of being confronted face-to-face with such a deadly creature.

Hatchetfish (Sternoptyx obscura). Image credit: Paul Caiger / Woods Hole Oceanographic Institution.

Hatchetfish (Sternoptyx obscura) – Shaped like the terrifying tool of choice by countless thriller antagonists (“heeeeeere’s Johnny”, anyone?), the hatchetfish lives up to its namesake. Cutting through a wide range of depths with its razor-thin body, this deep-sea fish bears a constant ghastly expression for all to shudder at. That is, if you ever see it at all. In a mystical feat of counterillumination, hatchetfish use light-producing organs called photophores along their underside to conjure up light nearly identical to the ambient environment. Now invisible to creatures viewing them from below, they eerily glide through the waters as phantoms of the sea. While you can’t see them, hatchetfish can definitely see you – bad news for us all. Their bulging eyes grasp even the slightest twinkle of light, and can focus on unassuming prey both near and afar. Protruding from the abyss, their nightmarish eyes are the last sights of luckless prey before they meet their fate…

Blackdragon (Idiacanthus antrostomus) – Blackdragon fish don’t just skulk in the dark; they are the dark. Female blackdragon are unnervingly ultra-black, absorbing 99.5% of light around them like their horrifying counterpart, the fangtooth. Their teeth, jagged and sharp, are similarly anti-reflective to prevent detection by prey. While the prospect of encountering this eel-like predator is enough to make anyone fear the dark, the light can’t be trusted either. Adorned with a long, wispy barbel dangling from their chin, blackdragon fishes use a light-producing organ found at the end of this barbel (chin) to attract unexpecting victims. The snap of their fangs proves an unpleasant surprise for countless crustaceans and fishes.

Even scarier? The fate of male blackdragon. Doomed to a life stunted in a larval-like phase, males completely lack a mouth and stomach. They live just long enough to mate before succumbing to their physiology. This sexual dimorphism, while an incredible adaptation to resource limitations and the need for genetic diversity, is terrifyingly polar: a mouth of violent teeth versus well, no mouth at all. We don’t know which is scarier.

Pacific Blackdragon (Idiacanthus antrostomus). Image Credit: K. Osbourn / Smithsonian National Museum of Natural History.


Lurking in the dark with their needle-like teeth, these deep-sea creatures seem like perfect candidates for the next JAWS film…but we won’t quite be needing a bigger boat.

Did we mention that all these fishes are actually super tiny and can fit in the palm of your hand? BOO!

Upper left: The common fangtooth (Anoplogaster cornuta) is actually only up to 6 inches (15.2 cm) in length. Their teeth are among the largest (in proportion to body size) of any fish in the ocean. Image Credit: NOAA Photo Library. Upper right: The Pacific viperfish (Chauliodus macouni) is actually only up to 12 inches (30 cm) in length and remains an excellent band name. Image credit: iNaturalist/hfb, Lower left: The Hatchetfish (Sternoptyx obscura) is actually only up to 3 inches (8 cm) in length. It remains a fearsome predator, but only to small crustaceans and plankton. Image credit: martychums / Instagram. Lower right: While female Pacific Blackdragon (Idiacanthus antrostomus) may reach 24 inches (61 cm), males reaching a whooping maximum of… 3 inches (8 cm). What they lack in stature they make up for in horror! Image credit: iNaturalist/stercorariidae.

Sophie R. Sanchez is a Junior Specialist at the Center for Watershed Sciences at the University of California, Davis. Christine A. Parisek is a Ph.D. Candidate in the Graduate Group in Ecology at UC Davis and a Science Communications Fellow at the Center for Watershed Sciences. Andrew L. Rypel is a professor of Wildlife, Fish, & Conservation Biology and Director of the Center for Watershed Sciences at the University of California, Davis.

Further Reading:

Fangtooth (Anoplogaster cornuta) –
-Monterey Bay Aquarium: Fangtooth,
-iNaturalist: Fangtooth,

Pacific Viperfish (Chauliodus macouni) –
-Monterey Bay Aquarium: Viperfish,

Hatchetfish (Sternoptyx obscura) –
-Monterey Bay Aquarium: Hatchetfish,
-Woods Hole Oceanographic Institution: Creature Feature: Hatchetfish

Pacific Blackdragon (Idiacanthus antrostomus) –
-Monterey Bay Aquarium: Pacific Blackdragon,
-Oceana: Pacific Blackdragon,

New York Times: How Ultra-Black Fish Disappear in the Deepest Seas –

Davis, A.L., Thomas, K.N., Goetz, F.E., Robison, B.H., Johnsen, S. and Osborn, K.J., 2020. Ultra-black camouflage in deep-sea fishes. Current Biology, 30(17), pp.3470-3476.

Monterey Bay Aquarium: Deep Sea Fishes, Habitat, Adaptations –

Freer, J.J. and Hobbs, L., 2020. DVM: the world’s biggest game of hide-and-seek. Frontiers for Young Minds, 8.

Learn about the Bulgarian progressive punk rock band, Viperfish:

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California Enacts Major Water Law Reform Legislation–But More Changes Are Needed

By Richard M. Frank

Note: this blog is a cross-post first published on Legal Planet.

The California Legislature has enacted and Governor Gavin Newsom recently signed into law SB 389, an important water law reform measure authored by State Senator Ben Allen.

California has one of the most antiquated and outdated water rights systems of any Western state. To put it bluntly, California currently faces a 21st century water supply crisis; relies on a 20th century water infrastructure system; and is burdened by a 19th century water rights legal regime. For a state that prides itself on innovative leadership in so many other areas of environmental and natural resources policymaking, California’s water rights law are sorely in need of modernization.

Compared to most other states, California has a fragmented and inefficient water rights system. Surface water claimed by those who divert water from state waterways to use on adjacent (“riparian”) lands don’t need to obtain prior approval from state water regulators to do so. Nor do users who divert water for shipment and application away from a waterway if they or their predecessors claim to have secured their “appropriative” water rights before 1914. Only those California appropriators who’ve perfected their water rights after 1914 are required to comply with the permit system administered by the State Water Resources Control Board.

As incredible as it may seem, this means that a large percentage of current California water users operate solely on the honor system, with no obligation to seek or obtain prior approval from the Water Board for their water diversions.  Indeed, many riparians and pre-1914 appropriators have taken the remarkable position that the Water Board–charged by the Legislature to oversee California’s entire water rights system–lacks authority to question, confirm or seek verification of their private water rights claims.

Senator Allen introduced SB 389 to address and put to rest any ambiguity regarding the Water Board’s power to require water users to verify their water rights claims–regardless of whether they’re subject to the Board’s permitting system. The newly-enacted legislation explicitly gives the Board the authority–which most observers believed it always had–to place that burden of proof squarely on private water users who assert those rights.

The new law also has teeth: it allows the Water Board, upon investigation of a water rights claim it ultimately finds to be undocumented or otherwise defective, to declare the offending water user’s continued diversion and use of state water to be an illegal trespass.

In sum, this new legislation explicitly places the burden of demonstrating the validity of a claimed water right on the private water user.  And that’s as it should be, considering that longstanding California water law also explicitly provides that the waters of California are a public resource incapable of private ownership.

SB 389 is actually part of a broader effort by the Legislature–and public interest groups–to reform and update California’s water laws.  Beginning in early 2021, the California Planning & Conservation League Foundation convened a diverse group of water law professors and other experts to formulate specific  recommendations for modernizing California water rights law.  The working group issued a report in February 2022 identifying 11 specific proposals to revise and improve state water law.

The Planning & Conservation League-sponsored report quickly drew the attention of the California Legislature: in its 2022 session, legislators approved and Governor Newsom signed into law bills codifying two of the working group’s recommended reforms.  AB 2108 (authored by current Assembly Speaker Robert Rivas) requires California’s State and Regional Water Boards to undertake “water justice” outreach efforts to Native American tribes and other underserved communities; those efforts include providing public funding to these groups in order to overcome existing barriers to their public participation in Board proceedings.  And SB 1205 (introduced by Senator Allen) explicitly directs the State Board to consider the effects of climate change when reviewing applications for new and modified water rights permits.

The political momentum for water law reform continued apace in 2023, as evidenced by the Legislature’s passage of SB 389 this year.  But that momentum did not stop there.  Prompted by several of the working group’s additional recommendations–and numerous, alarming press reports of water users diverting water without a legitimate water right, defying State Water Board drought response orders requiring curtailment of private water diversions, etc.–the Legislature took up additional, proposed reforms to California’s dysfunctional water rights system.  One bill, AB 460 (authored by Assemblymember Rebecca Bauer-Kahan) would grant the Board explicit authority to adopt and enforce “interim orders” designed to stop water scofflaws from thumbing their noses at state water conservation mandates and increases administrative penalties the Board can impose on those who exceed or disregard regulatory limits of their water rights.  Another 2023 bill, AB 1337 (introduced by Assemblymember Buffy Wicks), clarifies existing law that the Board has the authority to curtail all surface water rights when necessary to achieve water conservation goals in times of state drought.

Both AB 460 and AB 1337 were approved by the California State Assembly.  However, the 2023 legislative session ended before either bill could be fully considered by the State Senate.  Both now become “two-year bills” and will be revisited by the Senate in the 2024 legislative session.

In sum, newly-enacted SB 389 is an important and overdue revision to California’s water law system.  But it’s not the end of the road to water reform; rather, it’s a key step in a larger and longer water reform movement–one that has considerable political momentum behind it.  That effort should and will continue.

Let’s hope California’s water law system can be brought–kicking and screaming, if necessary–into the 21st century.

(Full disclosure: the author, along with Legal Planet colleague and Berkeley Law Professor Holly Doremus, is a member of the water law reform working group convened by the Planning & Conservation League Foundation and referenced in this post.)

Richard M. Frank is a Professor of Environmental Practice and Director of the California Environmental Law & Policy Center, School of Law, University of California Davis. He is also a faculty affiliate of the Center for Watershed Sciences.

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Strategic Decision Making for Dam Removal Planning

By Suman Jumani, Ted Grantham, Lucy Andrews, Jeanette Howard

California has a dam problem. Since the start of the 20th century, the state has built thousands of dams on its rivers and streams. Now, more than 75% of the largest dams (totaling over 900) are greater than 50 years old, and the mean age is close to 80 years old. This means that a significant proportion of the state’s dams are reaching – or have already reached – the end of their designed lifespan. Many are no longer performing their intended functions due to sediment build-up, lack of maintenance, or obsolescence. What do we do about these “deadbeat dams”? As discussed in an earlier post, given the poor condition of many of these dams, and the often devastating consequences of their failure, doing nothing is not a good option. So, the authors of that article suggest California take a proactive approach. In particular, they cite the need for a “structured assessment tool” to assess the risks of aging dams and help identify those whose time for removal has come.

In a paper, recently published in Environmental Challenges, we present a decision-support tool for dam-removal planning in California. It is designed as a multi-criteria evaluation framework that considers the broad suite of economic, environmental, and social factors that influence dam removal decisions. Expanding upon previous dam removal assessments in the state (e.g., Quiñones et al. 2015), the framework helps to identify dams for which removal would:

  1. Be opportunistically viable and improve safety without losing critical services (Tier 1),
  2. Result in improved riverine ecosystem integrity, function, and biodiversity (Tier 2), and
  3. Be beneficial or acceptable to local communities (Tier 3).

The first objective (or Tier 1) is achieved by identifying dams that are financially and opportunistically feasible to remove. These include relic dams that no longer provide beneficial functions, such as water supply or flood control. It also includes dams in poor physical condition that pose a safety liability. In addition, the screening process flags smaller dams, which may be less expensive or complex to remove than large dams, and those undergoing hydropower relicensing, which presents a formal opportunity to evaluate a dam decommissioning alternative.

River restoration is another compelling reason to remove dams. Tier 2 of our evaluation framework identifies dams whose removal would significantly improve river connectivity and restore more natural flow regimes to benefit a range of freshwater species, especially migratory fishes. In California, this means prioritizing dams whose removal would restore passage for salmon, steelhead, and other anadromous fish runs. Tier 2 evaluation criteria also favor dam removals in catchments that support high habitat diversity and are expected to be more resilient to climate change. Finally, this tier takes into account two potentially adverse environmental effects of dam removal: mobilizing reservoir sediments containing mercury and the potential for spreading invasive species either above or below dams. 

Overview of the dam removal decision-support framework. Steps outlined in solid lines (Tier 1 and Tier 2) can be computed through desktop analyses. Steps outlined in dashed lines require additional computational work and assessment of local, socio-cultural factors that may influence the feasibility of dam removal (Tier 3).

All criteria are assigned user-defined weights and aggregated as Tier 1 and Tier 2 scores for individual dams. When applied to a population of dams, it is possible to plot these scores independently to distinguish dams whose removal appears opportunistically feasible and ecologically beneficial (i.e., “good candidates”), from those which have relatively limited environmental benefits and/or are unlikely candidates for removal given the important services they provide (i.e., “poor candidates”). It is also possible to estimate the cost of dam removal based on the size and costs of removing similar dams in the past (Duda et al. 2023).

Biplot of Tier 1 and 2 scores of the 25 dams assessed for their removal potential. The size of each circle is proportional to its predicted cost of removal (standardized to 2020 US dollars). Higher scores along both axes (indicated by darker color gradients) imply greater benefits to be gained from removal.

Ultimately, dam removal decision-making lies within the social and political realms. Therefore, a set of additional (Tier 3) criteria are included in the framework to assess community perceptions and attitudes about dams of interest and to consider how dam removal could affect recreational, economic, and cultural values. Unlike the Tier 1 and Tier 2 assessment, this requires outreach to local communities, organizations, and governments to evaluate the feasibility of dam removal.

Overall, our approach can help identify ‘low-hanging fruit’ – especially deadbeat dams whose removal addresses public safety risks, provides environmental benefits, and has the support of local communities (for example, York Dam in Napa County). The framework is also intentionally flexible, allowing for the addition or exclusion of specific criteria, or weighting of specific objectives to reflect the values and priorities of those using the tool.

We envision this tool being applied to assess removal potential of dams within a watershed or a region. For instance, in our paper, we applied the framework as a ‘proof-of-concept’ to California’s North Coast region to assess the removal suitability of 25 large dams > 50 years old. We identified dams that could be opportunistically and ecologically beneficial to remove, including Cape Horn dam on the Eel River which is currently being proposed for removal by Native American tribes, non-profit organizations, and community groups. We did not examine Tier 3 criteria in depth, but suggest the dams flagged as “good candidates” be further analyzed for removal potential.  In our assessment, we also identified 10 “poor candidates”, several of which were associated with higher monetary costs of removal.

Looking Ahead

In developing and applying this framework, we encountered several notable data gaps. The most critical is the lack of a unified state dam database. Currently, California’s Division of Dam Safety and U.S. Army Corps of Engineers maintain a list of large dams in the state, but there are thousands of smaller dams (such as those reported in the Passage Assessment Database) that are not included in the state’s inventory. Furthermore, information about dam seismic safety risk, degree of reservoir sedimentation, contaminant levels, and presence of invasive species are not systematically reported or included in the state’s dam database. Given the widespread occurrence of aging dams in the state, there is a need for the state to invest resources in better characterizing dams to inform decisions over their future rehabilitation or removal. In the absence of such information, the risks of aging dams to people and the environment will continue to grow as prospects for a strategic and holistic approach to dam removal diminish.

Suman Jumani is a postdoctoral fellow at the Environmental Lab of the US Army Engineer Research and Development Center. Ted Grantham is an Associate Professor of Cooperative Extension in the Environmental Science, Policy, and Management Department at UC Berkeley. Lucy Andrews is a PhD candidate at UC Berkeley. Jeanette Howard is the director of science for The Nature Conservancy’s California land science team.

Further Reading

Duda, J. J., Jumani, S., Wieferich, D. J., Tullos, D., McKay, S. K., Randall, T. J., Jansen, A. (2023). Patterns, drivers, and a predictive model of dam removal cost in the United States. Frontiers in Ecology and Evolution, 11, 1215471.

Jumani, S., Andrews, L., Grantham, T. E., McKay, S. K., Duda, J., & Howard, J. (2023). A decision‐support framework for dam removal planning and its application in northern California. Environmental Challenges, 12, 100731.

Manahan, M. D., & Verville, S. A. (2004). FERC and dam decommissioning. Nat. Resources & Env’t., 19, 45.

Manfree, A., Moyle, P., & Grantham, T. (2020). Small Dam, Big Deal: York Dam Removed in Napa Valley. California WaterBlog.

Pejchar, L., & Warner, K. (2001). A river might run through it again: criteria for consideration of dam removal and interim lessons from California. Environmental Management, 28, 561-575.

Perera, D., Smakhtin, V., Williams, S., North, T., & Curry, A. (2021). Ageing water storage infrastructure: An emerging global risk. UNU-INWEH Report Series, 11, 25.

Pohl, M. M. (2002). Bringing down our dams: Trends in American dam removal rationales 1. JAWRA Journal of the American Water Resources Association, 38(6), 1511-1519.

Quinones, R. M., Grantham, T. E., Harvey, B. N., Kiernan, J. D., Klasson, M., Wintzer, A. P., & Moyle, P. B. (2015). Dam removal and anadromous salmonid (Oncorhynchus spp.) conservation in California. Reviews in Fish Biology and Fisheries, 25, 195-215.

Rypel, A.L., Parisek, C.A., Lund, J., Willis, A., Moyle, P.B., Yarnell, S., Börk, K. (2023) What’s the dam problem with deadbeat dams? California WaterBlog

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Happy New Water Year 2024!  – from 2023’s wild ride to the wilderness of 2024

by Jay Lund

October 1 marked the beginning of the new Water Year in California. Water years here run from October 1 until September 30 of the next calendar year, and are named for the calendar year of the bulk of the water year (January-October).  It is a good time to reflect on the last year and make largely futile predictions of precipitation for the coming 12 months.


The main lesson from the wild 2023 water year in California was the reminder that California’s hydrology is highly variable and rarely knows its average.  Following 2021, one of the driest years of record and another dry year in 2022, 2023 was one of the wettest years of record.  An earlier reminder of this occurred from 2014-2015 (two of California’s driest years) to 2017 (the wettest year in California’s official records).  Figure 1 shows a histogram of the Sacramento Valley’s annual water year runoff over 116 years. It is not a normal distribution.

Figure 1. California’s runoff is not normal – Histogram of Annual Sacramento Valley Water Year Unimpaired Runoff, 1906-2022, bin ranges in million acre-feet (maf) (Average = 17.7 maf/year)

What will happen in 2024?

Nobody really knows, but you can expect endless speculation from now until March.  Only by March (and sometimes late March) is it late enough in California’s mercurial wet season that we have seen most of the water year’s precipitation. 

Statistically, there is almost no correlation of unimpaired runoff in northern California from one year to the next, as seen in Figure 2.

Figure 2. Last year’s Sacramento Valley precipitation has no correlation with next year’s precipitation (DWR data, CDEC)

Similarly, there is almost no correlation between El Niño conditions and runoff from northern California, as seen in Figure 2. However, these correlations are a bit stronger in southern California.

Figure 3. Classical El Niño estimates don’t help much in predicting northern California’s annual runoff.

Sometimes in life, and always with California water, all we can do is to prudently prepare for contingencies and surprises, while we wait for the future.

California’s current water storage – Good short-term news

Current surface storage in California is generally in very fine shape.  Most reservoirs are well above average storage for this time of year.  Interesting exceptions are the large Trinity Reservoir in far northern California at 85% of average and Millerton Reservoir on the San Joaquin River at 80%.  This great surface water storage insulates the state somewhat if this year is dry, but could become a liability if this coming year has early floods.

Most water storage in California is underground and 2023 brought a lot of water for managed and incidental groundwater recharge.  For the Tulare basin, which averages about 2 million acre-ft (maf) of groundwater overdraft (with as much as 6 maf of additional overdraft in past drought years), the immense water availability in 2023 brought in only enough additional water for about two years of average groundwater overdraft, and not even one year of severe drought.  Even with major (even excessive) investments, wet year groundwater recharge will be far from sufficient to solve the southern San Joaquin Valley’s groundwater overdraft problems (but it will help some).

On the whole, we enter 2024 with less worry about drought and more worry for floods.  But we should worry about both, reasonably.

Strategic changes and climate handwringing

Many aspects of California water are eternal from our human perspective – a Mediterranean climate with large seasonal and interannual variability, a tendency to be dry, great internal geographic variability in hydrology and water demands, large structural changes in water uses and demands driven by technological changes and global markets, and recurrent introductions of non-native species.  California water management has always had to deal with large changes (both variability and structural changes).

Today’s climate (and more) is changing.  It is important to prepare for multiple interacting changes altogether. 

Fortunately, California’s ever-restructuring economy continues to become less dependent on abundant supplies of water.  This is especially true for cities, where more than 90% of the state’s population and economy are now largely (but not entirely) decoupled from water issues.  Even in irrigation-dependent agriculture, shifts to more profitable permanent crops (when accompanied by groundwater management) make rural economies less vulnerable to climate. 

California’s native ecosystems are becoming more vulnerable to changes in climate, the stresses of water and habitat reduction, fragmentation, and disruption combined with invasive species introductions promise continued declines.  There seems to be no plausible scenario where California’s future ecosystems will be like its past ecosystems.  Yet we have barely begun discussing realistic futures for managing California’s forest and aquatic ecosystems.

We need to think about and discuss how to adapt to these changes more strategically.  These discussions will be hard, but should be exciting if they open broad opportunities for more sustainably and resiliently achieving human and ecosystem objectives.

What to do?

Every year, water managers and users must be prepared for both flood and drought.  It has always been thus, and it is becoming more like this with a warmer climate. These trends indicate that water managers need to be serious about planning.

Californians should pay serious attention to water and its likely changes from climate change. But without complacency or panic over our remarkably effective yet substantially flawed water management system and institutions.  Complacency and panic are rhetorically convenient, but expensive and potentially life-threatening reactions to situations that deserve serious thought, analysis, and deliberations.

Our deliberations and analyses remain relics of the history of water infrastructure and allocation for agricultural and urban growth.  They are not without value, but need improvements to help us adapt to a changing climate, ecosystems, economy, and social concerns.  This requires more serious and difficult discussions than our distracting fixations on the state of El Niño and the latest now-banal climate projections.

Think hard and discuss these challenges soberly with others, especially those outside your current advocacy identity.  These are not conversations we should seek to control from a short-term perspective.

Now, go have a drink (of water) to celebrate surviving another surprising and enlightening water year that should help us prepare for future surprising water years.

Further reading

Sacramento Valley historical unimpaired runoff data.

Moyle, P. (2023), “Future Ancestors of Freshwater Fishes in California,”, September 17.

Lund, J. “Happy New Water Year 2023!“ October 2, 2022.

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The myth of normal river flow: Drought, floods, and management of California’s rivers

By Julie Zimmerman, Jennifer Carah, Kirk Klausmeyer, Bronwen Stanford, Monty Schmitt, Mia Van Docto, Mary Ann King, and Matt Clifford

Is California still experiencing drought? Even after a winter of record rainfall and snowpack, followed by a tropical storm, this is still an important question. And if you read the headlines, the answer is…yes and no. Although drought has been declared officially over, unsustainable groundwater pumping and overallocation of surface water leads to water deficits that persist, stressing rural communities, urban water supplies, and ecosystems. So even in this year of abundant rainfall and snowpack, water managers and river ecologists are still thinking about drought. In fact, drought conditions can be thought of as the base case, or the more common of two extremes that tend to drive management action in California. As climate change increases frequency and severity of both drought and flood in California (Swain et al. 2018), water managers must continuously plan for both very dry and very wet conditions.

What makes water management in California so challenging?

California’s patterns of rainfall and river flow are defined by variability and extreme events. Precipitation and streamflow in California are more variable from year-to-year and within a year than any other part of the U.S. (Dettinger 2011). The dry season can last for 6 months or more in many parts of California, with many rivers relying on groundwater to keep flowing, and species relying on the ability to migrate from drying rivers to survive. Freshwater species are adapted to natural variability in river flow, but not to the alterations in flow caused by people – including water extraction, river regulation from dams, and climate change. The vast majority of rivers in California experience altered flow conditions (Zimmerman et al. 2018) and human water use, management, and habitat loss have worsened drought conditions (AghaKouchak et al. 2015). Human activities have at least doubled the probability of occurrence of extreme drought compared to natural conditions (He et al. 2017). This pattern would only intensify if climate change were included in the analysis.

A result is that freshwater biodiversity is in crisis, in California and around the world. Declines in biodiversity in freshwater habitats are happening faster than any other habitat type. Freshwater covers less than 1% of the earth’s surface, but holds 10% of the earth’s species, including one-third of all vertebrates (Tickner et al. 2020). The Living Planet Index ( indicates population declines for freshwater species of 81% between 1970 and 2012, the greatest decline over all habitat types, with the main threats including habitat loss and degradation from dams and unsustainable water use. Freshwater biodiversity loss in California follows – or even leads – the global trend. In 2021, 73% of California’s freshwater fishes were extinct, listed under the Endangered Species Act, or considered species of special concern (Leidy and Moyle 2021). Beyond fishes, nearly half of California’s freshwater species are threatened with extinction, and that number is far higher – 90% for species found only in California and nowhere else on earth (Howard et al. 2015).

When are California rivers experiencing drought, and when is it a problem?

Here’s what we know: drought conditions are occurring with more frequency, greater severity, and longer duration. Human water use compounds the effects of drought, further stressing the state’s ecosystems and impacting farms, rural communities, and urban water supplies. Water use and management in California has become unsustainable in many watersheds, contributing to the drastic loss of freshwater biodiversity, decimating California’s iconic rivers, and triggering legal battles over a limited public resource with far too many demands. The problems are complex and overwhelming.

Where do we begin? One of our most critical needs is the ability to identify where drought conditions are likely, so that planning and action can occur in advance of the driest months and years. The U.S. Drought Monitor produces weekly maps of drought status based on precipitation, soil moisture, and other factors, as a way to determine drought impacts across the country – influencing agriculture, water supply, and terrestrial ecosystems. However, the U.S. Drought Monitor does not assess drought status in rivers and streams or potential drought effects on freshwater ecosystems. To fill this need, the Salmon and Steelhead Coalition, comprising The Nature Conservancy, Trout Unlimited, and California Trout, developed a Drought Flows Monitor web tool ( that identifies watersheds likely experiencing critically dry conditions. This tool can be used as a trigger to act quickly and efficiently to mitigate the effects of drought on freshwater species, regionally as well as in crucial watersheds. The Drought Flows Monitor can help guide decisions by identifying California watersheds with historically low natural flows where ecological risk from human water use is very high.

How does it work?

The Drought Flows Monitor relies on data in the Natural Flows Database (NFD) that can be accessed at The NFD models a range of natural stream flows for every stream reach in California at the monthly time step for 1950 to the present and is extended monthly. The most downstream reach of the largest river in each large watershed was selected to summarize statewide drought effects. Mean monthly natural flow predictions were downloaded from the NFD for each reach, and the likely presence of drought was assessed by comparing that monthly flow to the historical range of flows for that month and location. Drought severity was then characterized using U.S. Drought Monitor categories (

Categories include exceptional drought (lowest monthly flow for the model period); extreme drought (monthly flow in the 2-5th percentile of the range for the model period); severe drought (6-10th percentile); moderate drought (11-20th percentile); abnormally dry (21st-30th percentile) and average/ wet (31st-100th percentile). Figure 1 illustrates how the flow predictions for a given month and watershed are assigned to these categories.

Figure 1: Estimated unimpaired flow for July from 1950 to 2023 for Butte Creek. The lowest predicted flows are assigned a drought category and colored based on the percentile rank.

The tool can be used to look at historical and current drought conditions in California’s watersheds. Figure 2 shows drought status of California’s watersheds for the wettest (2017) and driest (1977) years from 1950 to 2022, according to the Northern Sierra 8 station index. One pattern is that drought conditions in 1977 were widespread and severe, but tended to be more widespread and severe in March and April than in August. This doesn’t mean conditions weren’t dry in August – streams were going dry and water was scarce – but three important insights can be gleaned from this pattern.

First, drought effects are not synonymous with dry streams. Abnormally low flows during the wet season are common during drought and can have big impacts even if a river doesn’t go dry. A river that might have 2,000 cfs in March of a wet year might only have 200 cfs in March of a drought year. That difference can have vast ecological consequences for species that rely on high flows to inundate rearing habitat and support migration in March.

Second, drought effects often appear in late winter and early spring and will likely persist until the start of the following year’s wet season. The reduction in August drought severity in 1977 shown in Figure 2 is likely because many streams have very low or no flows in August in most years, rather than because drought severity has lessened. Surface flow assessments can’t distinguish an average year from a drought year when flow is zero in both cases, even if impacts on riparian species and groundwater levels might be quite different. We know this because few areas of California are likely to get significant rain after April, and during dry years the end of significant storms often happens earlier, in March. Longer dry seasons are likely to become more common with climate change (Swain et al. 2018). We don’t have to wait until summer to start thinking about changing water management. We can confidently begin drought management actions much earlier, evaluating any rare late-season storms that may improve conditions.

Third, human and ecological experiences of a drought are based on observed flow – or what actually occurs in a river – rather than natural flow. These maps don’t include the effects of dams, diversions, or discharges. Streams often go dry during a drought because of the interaction of natural drought effects and human use – which is why human water use should be managed during drought years to avoid exacerbating drought effects that further degrade or dry up perennial streams and rivers.

Figure 2: Drought Flows Monitor results for the wettest and driest years during the 1950-2022 period according to the Northern Sierra 8 station index.

How can the Drought Flows Monitor improve water management decisions?

The Drought Flows Monitor captures current and historical drought conditions that occurred throughout California. Drought conditions can be detected for any month, but patterns of two or more months of drought by March or April result in drought conditions likely to persist until the start of the next wet season. This means we can tell fairly early in a year if water will get scarce during drier and hotter months.

At least two types of management decisions can be made using this information: 1) immediate water conservation efforts for priority streams and rivers as a watershed enters drought conditions, according to natural flow estimates, and 2) planning for longer-term drought actions over the dry season, once a watershed has been in drought conditions for two or more months by April. The drought categories in the Drought Flows Monitor provide a useful framework for tailoring drought actions as drought severity increases, potentially beginning with voluntary water conservation efforts in the abnormally dry category, and progressing to water restrictions or curtailments as watersheds enter severe, extreme, and exceptional drought. Advanced drought planning is lacking for most of California’s watersheds, but this tool provides data helpful in closing that gap, providing advance notice, and addressing water scarcity before it becomes an emergency.

What about human water use?

The Drought Flows Monitor only considers natural flow conditions, as an indicator of natural drought stress. It is not a comprehensive indicator of drought conditions experienced by freshwater species as it does not account for additional human modifications to flow and habitat. In some locations with long-term gages, results from the Drought Flows Monitor can be compared to gage data to confirm observed flow conditions are indeed critically dry, and identify locations where human water use is likely further stressing freshwater species. The Monitor includes links to USGS gages and visualizations of current flow observations compared with historical discharge to help users assess whether drought categories based on natural flows are consistent with observed data. But because gage locations are very limited, other approaches to assess actual flows and ecological stress are still needed. To help fill these data gaps, The Nature Conservancy is currently working with collaborators to model actual flows in all stream reaches in California, to provide a dataset of flows that include human modifications and can be compared with natural flow conditions and enable alteration assessments, even where gages are not present. You can learn about our work on actual flows modeling on the California Water Blog:

The Drought Flows Monitor can be used to trigger drought actions directly, and as a tool to identify watersheds to verify instream conditions and stress to freshwater species through site visits or collection of field data. Collection of site-specific data is resource-intensive and cannot be applied across large spatial scales; so, a hierarchical approach of identifying priority watersheds using the Drought Flows Monitor that are further assessed using site-specific empirical methods can help protect rivers across large areas. Used together, statewide assessment of drought severity using the Drought Flows Monitor, combined with empirical observations at targeted watersheds, can help guide decisions to protect freshwater species in the rivers and streams with the highest ecological risk of water use. That said, knowing actual flows is not necessary for action when drought conditions are expected. When a watershed experiences drought, any additional decrease in flow risks harm to freshwater species, and drought actions are warranted. The Drought Flow Monitor is a tool for developing more comprehensive management that is responsive to changing conditions, fast to implement, and widespread – the type of approach needed to protect freshwater biodiversity in a changing climate.

Julie Zimmerman is the Director of Freshwater Science for The Nature Conservancy’s California Chapter. Jennifer Carah is a Senior Scientist for The Nature Conservancy’s California Chapter. Kirk Klausmeyer is the Director of Data Science for The Nature Conservancy’s California Chapter. Bronwen Stanford is Lead River Scientist for The Nature Conservancy’s California Chapter. Monty Schmitt is a Senior Project Director for The Nature Conservancy’s California Chapter. Mia Van Docto is a Conservation Hydrologist for Trout Unlimited. Mary Ann King is the California Water Project Director for Trout Unlimited. Matt Clifford is the California Director of Law and Policy at Trout Unlimited.


The Drought Flows Monitor was developed by members of the Salmon and Steelhead Coalition Drought Science Workgroup, including: The Nature Conservancy (Julie Zimmerman, Jennifer Carah, Kirk Klausmeyer, Monty Schmitt, Jeanette Howard, Bronwen Stanford), Trout Unlimited (Matt Clifford, Mia van Docto), and California Trout (Gabe Rossi – also with UC Berkeley, and Charlie Schneider). The Coalition coordinated the development of this tool with the California Department of Fish and Wildlife Instream Flow Program.

Further Reading:

AghaKouchak, A., D. Feldman, M. Hoerling, T. Huxman, and J. Lund. 2015. Water and climate: Recognize anthropogenic drought. Nature 524: 409–411.

Dettinger, M. 2011. Climate change, atmospheric rivers and floods in California—a multimodel analysis of storm frequency and magnitude changes. Journal of the American Water Resources Association 47: 514–523.

He, X., Y. Wada, N. Wanders, and J. Sheffield. 2017. Intensification of hydrological drought in California by human water management. Geophysical Research Letters 44: 2016GL071665.

Howard, J. K., K. R. Klausmeyer, K. A. Fesenmyer, J. Furnish, T. Gardali, T. Grantham, J. V. E. Katz, S. Kupferberg, P. McIntyre, P. B. Moyle, P. R. Ode, R. Peek, R. M. Quiñones, A. C. Rehn, N. Santos, S. Schoenig, L. Serpa, J. D. Shedd, J. Slusark, J. H. Viers, A. Wright, and S. A. Morrison. 2015. Patterns of freshwater species richness, endemism, and vulnerability in California. PloS ONE 10: e0130710.

Leidy, R. A., and P. B. Moyle. 2021. Keeping up with the status of freshwater fishes: A California (USA) perspective. Conservation Science and Practice 3: e474.

Swain, D. L., B. Langenbrunner, and J. D. Neelin. 2018. Increasing precipitation volatility in twenty-first-century California. Nature Climate Change 8: 427–433.

Tickner, D., J. J. Opperman, R. Abell, M. Acreman, A. H. Arthington, S. E. Bunn, S. J. Cooke, J. Dalton, W. Darwall, G. Edwards, I. Harrison, K. Hughes, T. Jones, D. Leclère, A. J. Lynch, P. Leonard, M. E. McClain, D. Muruven, J. D. Olden, S. J. Ormerod, J. Robinson, R. E. Tharme, M. Thieme, K. Tockner, M. Wright, and L. Young. 2020. Bending the Curve of Global Freshwater Biodiversity Loss: An Emergency Recovery Plan. Bioscience 70: 330–342.

Zimmerman, J. K. H., D. M. Carlisle, J. T. May, K. R. Klausmeyer, T. E. Grantham, L. R. Brown, and J. K. Howard. 2018. Patterns and magnitude of flow alteration in California, USA. Freshwater Biology 63: 859–873.

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Evolution of Drought Response and Resilience in California’s Cities

By Erik Porse

Drought is a regular event in California. In recent decades, California has experienced five prolonged drought periods (1976-77, 1987-1992, 2007-09, 2011-16, 2020-22). Urban water agencies have responded with investments in supply and demand management measures, which have made California’s cities more resilient to drought effects. What motivated these investments?

Our current habits of water use in California’s cities are shaped by past policies and habits. Prior to 1976, urban water management in California was dominated by actions to increase supplies during the state’s Hydraulic Era (Hanak et al., 2011). In the early 1900’s, California’s developing cities built large infrastructure systems to transport water across long distances. San Francisco’s Hetch Hetchy Aqueduct (1913) and the Los Angeles Aqueduct (1914) were early projects. Later, in 1939, the Metropolitan Water District of Southern California completed the Colorado River Aqueduct. Importing water to increase local supplies remained the dominant approach through the 1970s with the completion of California’s State Water Project in 1972. These infrastructure projects grew metropolitan economies and allowed for high rates of water use in cities, which set a bar for perceptions of future efficiency (Cahill & Lund, 2013; Gleick et al., 2003).

By the late 1970s, the era of large engineering projects faded. Drought and land use changes in California instigated broader planning approaches. New sources of water were fewer. The severe drought of 1976–1977 in California spurred statewide actions to reduce demand and diversify supplies (DWR, 1978; Mitchell et al., 2017).[1] By 1977, an estimated 150 communities had implemented mandatory water conservation actions, especially in the San Francisco Bay Area and Sierra Foothills. Communities handed out water conservation kits, and some instituted fines (Agras et al., 1980; Morgan, 1982). Conservation was a public response to drought (DWR, 1978). Monthly water use reporting by agencies to the Department of Water Resources (DWR) through Bulletin 166, which started in 1960, was an important tool that evolved into the Public Water System Statistics (PWSS) after 1980 (it would take until 2013 for regular reporting of urban water use to again became widely and publicly available). In 1978, the California Energy Commission adopted efficiency regulations for toilets and faucets (Vickers, 2010). The regulations were early actions in what became decades of state and federal water efficiency measures (Diringer et al., 2018). After the drought subsided, studies evaluated economic impacts and effects on wastewater systems, while interest grew to understand how utilities could decrease demand (Berk et al., 1993; DeZellar & Maier, 1980; Koyasako, 1980).

Images of DWR’s Bulletin 166, which reported total and per capita urban water use for an example city (Sacramento) within the 1975 (left) and 1994 (right) updates to Bulletin 166 and the California Water Plan

California experienced another severe and prolonged drought from 1987-1992. By 1991, many urban water agencies had instituted conservation measures through water use restrictions, price surcharges, prohibitions on wasting water, public education programs, messaging, water use efficiency rebates, and giveaway programs, coupled by supply augmentation through trading (Dixon & Pint, 1996; Moore et al., 1993). Interest grew in recognizing and mitigating economic impacts of drought, spurred by a recession in 1990–1991 (Dixon & Pint, 1996). The drought solidified the types of activities that make up many of today’s utility conservation programs. In 1991, urban water agencies joined with advocacy groups to sign a joint Memorandum of Understanding (MOU) Regarding Urban Water Conservation in California and established the California Urban Water Conservation Council (CUWCC). CUWCC developed a suite of Best Management Practices (BMPs) that became a template for water conservation across the state (CUWCC, 1991). Shortly after, new federal requirements through the Energy Policy Act of 1992 increased efficiency for faucets, showerheads, and toilets (Diringer et al., 2018). Later, in 2007, the BMPs were adopted as a requirement to receive state funding (AWWA, 2017; Mitchell et al., 2017).

Changes in daily per capita demand for indoor water fixtures associated with year of installation. Sources: Compiled by OWP at Sacramento State (2022) based on studies from the Pacific Institute (Diringer et al., 2018), the Residential End-Uses of Water Study and the California Single-Family Water Use Efficiency Study (DeOreo et al., 2011, 2016), the Alliance for Water Efficiency (AWE, 2020), and the Handbook of Water Use Conservation (Vickers, 2010).

California endured another drought from 2007–2009. Many urban areas had limited effects, but broader water policy issues regarding water quality and pumping restrictions from the Southern Sacramento–San Joaquin Delta instigated statewide actions for urban water conservation (Mitchell et al., 2017). Senate Bill (SB) x7-7, the Water Conservation Act of  2009, required DWR to develop water use efficiency targets for agencies to achieve 20 percent savings by 2020 (DWR, 2010). Each agency was given a per capita target and had to submit data on recent demand. The targets established a contemporary baseline for future urban water use efficiency regulations. Requirements for submitting Urban Water Management Plans to DWR created new, openly available data. The SB x7-7 regulations also expanded consideration of Commercial, Industrial, and Institutional properties in conservation programs (DWR and CII Task Force, 2013). Yet, regular reporting of data on consumption remained intermittent and ceased after 2011.

Most Californians living in the state today experienced the 2012–2016 statewide drought. It was severe by comparison to the historical record (Griffin & Anchukaitis, 2014; Lund et al., 2018). The drought brought new policy approaches and, afterwards, a recognition of the potential severity of future conditions. Many urban areas relied on past investments and experienced limited effects in the first several years of drought (Lund et al., 2018). By 2014, California Governor Brown issued a voluntary water use reduction requirement of 20% across all urban areas through Executive Order B-17-2014. Water agencies implemented drought shortage contingency plans, which targeted savings of up to 20%, but through 2014, the Governor’s requested targets were only achieved in a few communities experiencing the most severe effects. In May 2015, with limited snowpack, agricultural fallowing, and drying wells in some small rural communities, the Governor signed Executive Order B-37-16, which required urban areas to reduce demand by 25%. The policy was later implemented with a sliding scale of conservation targets ranging from 4–36%, depending on past conservation actions taken by water agencies (SWB, 2015).

The mandatory restrictions were highly controversial. State regulatory agencies elicited input from water supply agencies, nonprofits, industry organizations, and researchers, which all shaped ultimate implementation of the executive order requirements (DWR, 2016; Mitchell et al., 2017; Talbot, 2019). By 2016, across the state, urban areas were meeting the statewide conservation target. They achieved this by boosting drought messaging and funding rebates to replace turf and indoor fixtures (Mitchell et al., 2017; Pincetl et al., 2019; Quesnel & Ajami, 2017). Municipalities and government agencies also reduced irrigation in public spaces. After the drought proclamation was lifted in 2017, water use increased but did not return to pre-2013 levels. The drought instigated significant legislation for urban water use, including SB 555 to require leak loss reduction programs and AB 1668-SB 606 to set supplier-specific urban water use targets for urban areas throughout the state.

After only a few years, drought conditions returned in 2020-2022. By Summer 2021, Governor Newsom urged urban residents to reduce water use by 15% through voluntary, but not mandatory requirements. California residents responded by reducing water use by 7%. Data collection and standardization efforts for urban water use reporting since 2013 made it easier to track savings. Most urban areas experienced limited effects, drawing on past investments in supply and efficiency measures. Yet, more widespread restrictions were looming if drought continued. For instance, in Spring 2022, parts of urban Los Angeles areas were under severe restrictions. While drought conditions eased in Winter 2022 and restrictions were lifted, without precipitation, the restrictions were set to expand. Widespread simultaneous drought across both California and the greater Colorado River Basin showed the vulnerability of California’s urban areas to severe 21st Century climate conditions. Significant policy changes from the 2020-22 drought are still emerging. For example, legislation to prohibit using potable water for irrigating ornamental (“non-functional”) turf in commercial, industrial, institutional, and multifamily properties may be enacted this year if signed by the Governor (AB 1572). The legislation was supported by major water agencies and emerged from drought response policies.

California’s cities today are better prepared to manage drought. This is the result of regulations, investments, collaboration, technology, and changes in our habits of water use. A severe and prolonged drought could still significantly impact urban areas, but most drought effects in cities today are slow to emerge and hard to evaluate (Lund et al., 2018). Wildfires amplified by drought disrupted urban life and imposed health risks in 2017-2020. Within cities, aging urban tree canopies, dominated by imported species with high water use needs, have suffered. Climate change adaptation for urban water management will increase costs for residents and businesses in California. Urban water agencies will need to improve outreach programs to support urban heat mitigation given changes in landscape irrigation. Finally, as cities have grown more efficient in how they use water, short-term options for future drought mitigation have reduced. Urban water agencies face significant challenges to support livable communities and contribute to climate change goals in California. The next chapter of drought response and resilience for California’s urban water sector is yet to be written.

Erik Porse is the Director of the California Institute for Water Resources and an Associate Cooperative Extension Specialist in the University of California Division of Agriculture and Natural Resources (UC ANR).

Further Reading

Agras, W. S., Jacob, R. G., & Lebedeck, M. (1980). The California drought: A quasi-experimental analysis of social policy. Journal of Applied Behavior Analysis, 13(4), 561–570.

AWE. (2020). AWE Conservation Tracking Tool, Version 3, Standard North American Edition. Developed by M-Cubed, for the Alliance for Water Efficiency (AWE).

AWWA. (2017). Errata to AWWA Manual M52, Water Conservation Programs—A Planning Manual , 2nd ed. (December 2017). American Water Works Association.

Berk, R. A., Schulman, D., McKeever, M., & Freeman, H. E. (1993). Measuring the impact of water conservation campaigns in California. Climatic Change, 24(3), 233–248.

Cahill, R., & Lund, J. (2013). Residential Water Conservation in Australia and California. Journal of Water Resources Planning and Management, 139(1), 117–121.

CUWCC. (1991). Memorandum of Understanding Regarding Urban Water Conservation in California. Amended January 4, 2016. California Urban Water Conservation Council.

DeOreo, W., Mayer, P., Martien, L., Hayden, M., Funk, A., Kramer-Duffield, M., Davis, R., Gleick, P., Heberger, M., Henderson, J., & Raucher, B. (2011). California Single-Family Water Use Efficiency Study. Aquacraft, Inc.

DeOreo, W., Mayer, P. W., Dziegielewski, B., & Kiefer, J. (2016). Residential end uses of water, version 2. Water Research Foundation.

DeZellar, J. T., & Maier, W. J. (1980). Effects of Water Conservation on Sanitary Sewers and Wastewater Treatment Plants. Journal (Water Pollution Control Federation), 52(1), Article 1. JSTOR.

Diringer, S., Cooley, H., Heberger, M., Phurisamban, R., Donnelly, K., Turner, A., McKibbin, J., & Dickinson, M. A. (2018). Integrating Water Efficiency into Long‐Term Demand Forecasting (4495). Water Reserach Foundation, Prepared by the Pacific Institute, the Institute for Sustainable Futures (University of Technology, Sydney), and the Alliance for Water Efficiency.

Dixon, L., & Pint, E. M. (1996). Drought Management Policies and Economic Effects on Urban Areas of California: 1987-1992 (Vol 813). RAND Corporation.

DWR. (1978). The 1976-1977 California Drought – A Review. California Department of Water Resources.

DWR. (2010). 20×2020 Water Conservation Plan. California Department of Water Resources.

DWR. (2016). Making Water Conservation a California Way of Life: Implementing Executive Order B-37-16. California Department of Water Resources, State Water Resources Control Board, California Public Utilities Commission, California Department of Food and Agriculture, and California Energy Commission.

DWR and CII Task Force. (2013). Commercial, Industrial, and Institutional Task Force Water Use Best Management Practices. Report to the Legislature. (Volume I: A Summary). California Department of Water Resources.

Gleick, P. H., Haasz, D., Henges-Jeck, C., Srinivasan, V., & Wolff, G. (2003). The Potential for Urban Water Conservation in California. 176.

Griffin, D., & Anchukaitis, K. J. (2014). How unusual is the 2012-2014 California drought? Geophysical Research Letters, 41(24), 9017–9023.

Hanak, E., Lund, J., Dinar, A., Gray, B., Howitt, R., Mount, J., Moyle, P., & Thompson, B. “Buzz.” (2011). Managing California’s water: From conflict to reconciliation. Public Policy Institute of California.

Kam, J., Stowers, K., & Kim, S. (2019). Monitoring of Drought Awareness from Google Trends: A Case Study of the 2011–17 California Drought. Weather, Climate, and Society, 11(2), 419–429.

Koyasako. (1980). Effects of Conservation on Wastewater Flow Reduction: A Perspective (EPA-600/2-80-137; p. 154 pages). U.S. Environmental Protection Agency Municipal Environmental Research Laboratory.

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

Mitchell, D., Hanak, E., Baerenklau, K., Escriva-Bou, A., McCann, H., Perez-Urdiales, M., & Schwabe, K. (2017). Building Drought Resilience in California’s Cities and Suburbs. Public Policy Institute of California.

Moore, N. Y., Pint, E. M., & Dixon, L. S. (1993). Assessment of the economic impacts of California’s drought on urban areas: A research agenda. Rand.

Morgan, W. D. (1982). Water Conservation Kits: A Time Series Analysis of a Conservation Policy. Journal of the American Water Resources Association, 18(6), 1039–1042.

OWP at Sacramento State. (2022). Environmental and Economic Effects of Water Conservation Regulations in California: Evaluating effects of urban water use efficiency standards (AB 1668-SB 606) on urban retail water suppliers, wastewater management agencies, and urban landscapes. Prepared by the Office of Water Programs at Sacramento State, the University of California Los Angeles, the University of California Davis, and California Polytechnic University Humboldt.

Pincetl, S., Gillespie, T. W., Pataki, D. E., Porse, E., Jia, S., Kidera, E., Nobles, N., Rodriguez, J., & Choi, D. (2019). Evaluating the effects of turf-replacement programs in Los Angeles. Landscape and Urban Planning, 185, 210–221.

Quesnel, K. J., & Ajami, N. K. (2017). Changes in water consumption linked to heavy news media coverage of extreme climatic events. Science Advances, 3(10), e1700784.

SWB. (2015). State Water Board Adopts 25 Percent Mandatory Water Conservation Regulation. California State Water Resources Control Board.

Talbot, A. (2019). Urban Water Conservation in the Sacramento,California Region during the 2014-2016 Drought. University of California, Davis.

Vickers, A. (2010). Handbook of water use and conservation: [Homes, landscapes, businesses, industries, farms. Amy Vickers & Associates, Inc.

[1] Meteorological analysis identifies slightly different timeframes for several recent drought periods. See, for example, Kam (2019) that describes drought periods from 1975–1978 and from 1987–1994.

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