Killing Native Fishes for Fun and Predator Control

by Teejay A. O’Rear, John R. Durand, and Peter B. Moyle

A hardhead on the North Fork American River.

A recent posting of a short film on a 2017 fishing derby (FISHBIO 2018a) is disturbing to those of us interested in conserving our native fishes.  The film glorifies killing Sacramento pikeminnow and hardhead for reducing predation on juvenile Chinook salmon and for attracting more people to sport-fishing.  The idea is for anglers, from senior citizens to kids, to catch and kill as many pikeminnow and hardhead as possible for prizes.  On derby day in 2017, 638 fish were killed, some appearing to weigh more than four pounds.  The big fish were likely 15-20 years old.

Supposedly, removing these fish as predators will increase the number of adult salmon returning to spawn a few years later. In fact, little scientific evidence exists to support the notion that hardhead and pikeminnow affect numbers of returning adult salmon.

The sponsor referenced the bounty program instituted on the Columbia River for northern pikeminnow (a related but different species than Sacramento pikeminnow), implying that a similar program may have similar benefits in the Sacramento-San Joaquin Watershed.  The Columbia River consists of a series of hydropower dams along the mainstem river and major tributaries, creating a series of slow-flowing reservoirs through which salmon have to migrate and within which most predation of northern pikeminnow on salmon is concentrated (Vigg et al. 1991).  These Columbia River reservoirs differ considerably from tailwater rivers where Sacramento pikeminnow and hardhead in the video were targeted.

The Columbia River bounty program is notable because it was instituted after considerable research (e.g., Poe et al. 1991, Vigg et al. 1991) that examined metabolic rates of predators, predator diets, predator abundances, habitat types, and daily/seasonal predation rates.  The research suggested that reducing northern pikeminnow numbers could improve salmon survival.  No such research has been performed for Sacramento pikeminnow or hardhead in the Sacramento-San Joaquin Watershed.

The lower American River is one area where hardhead and pikeminnow reside.

Hardhead have jaws deep in the throat with big, flat teeth (like human molars) used for grinding up hard-shelled prey such as crayfish.   While pikeminnow may feed on naïve hatchery-released salmon until full, their slow digestive rate (Vondracek 1987) indicates the population effect is likely small, even when hundreds of pikeminnow are present.   The account of the derby states Sacramento pikeminnow are known for “disturbing salmon redds to scavenge for eggs.”  In fact, the pikeminnow mainly consume eggs that failed to get buried, eggs doomed in any case. Of course, steelhead/rainbow trout do the same thing (e.g., Johnston 2018) but they are not castigated for such “bad behavior,” being game fishes.

Various studies demonstrate the futility of Sacramento pikeminnow and hardhead control.  Females of both species, even relatively small ones, produce thousands of eggs, so a few individuals can restore a population quickly.  In the 1980s, a UC Davis team evaluated an effort to eradicate pikeminnows, hardhead, suckers, and other native fishes from the North Fork Feather River, which were thought to compete with trout.  The California Department of Fish and Game (as it was then) killed 99.9% of the fish with a poison, an effort repeated previously at about 10-year intervals. Examination of the ages of the dead fish showed that most large individuals were spawned a year or two after the previous poisoning operation (Moyle et al. 1983).

Clearly, the few fish that survived the operation had banner reproduction in the following years.  A saying goes that “Nature abhors a vacuum,” which this illustrates well.  Likewise, in a reach of the Mokelumne River, all predatory fish were removed by electroshocking, but predator numbers tripled after two weeks due to new predators moving into the vacant space (Cavallo et al. 2013, Grossman 2016).  In the Columbia River, the northern pikeminnow removal co-occurred with increased numbers of Caspian Terns, Double-crested Cormorants, and marine mammals, all of which consume high numbers of salmon (Carey et al. 2012).

The lower Yuba River, another area where pikeminnow reside.

As discussed in a previous blog about striped bass predation (Moyle et al. 2016), top predators such as Sacramento pikeminnows can potentially help salmon populations by consuming other predators and competitors, including their own young (Brown and Moyle 1981).  Ironically, the derby sponsor’s website contains an earlier report (FISHBIO 2018b) on attempts to control numbers of the invasive green crab, which resulted in an increase in the population.  Control was focused on removing large adult crabs, to reduce reproduction. However, the major factor limiting survival of juvenile crabs was abundance of adults, which were highly cannibalistic. Simplistic solutions to complex problems rarely work!

The website claims the derby educates people about the harm done by predatory fish to salmon.  However, the main area in the Sacramento Valley where pikeminnow predation has been seriously considered a problem was at the Red Bluff Diversion Dam, which created near-optimal conditions fish and bird predation on salmon (Vondracek et al. 1991). The problem was largely resolved once the diversion dam’s gates were left open during salmon emigration (Moyle 2002). Many other studies, such as Sabal et al. (2016), have also noted that artificial structures enhance predation.

Predation is a two-partner relationship.  Salmon and steelhead in the Central Valley are largely hatchery-supported, with little genetic difference between wild and hatchery-produced fish (Pearse and Garza 2015, Satterthwaite and Carlson 2015).  Effects of hatcheries on genes can be profound, and one of the most common effects of hatcheries is reduction of predator-avoidance behaviors (Berejikian 1995).   Hatcheries also create naïve fish by spraying food pellets onto the water surface of concrete-lined raceways crowded with fish. When released into rivers, these domesticated juveniles become easy prey as they encounter myriad water-diversion structures that concentrate and disorient them on their way to the ocean. Minimizing hatchery influences and redesigning water-control structures would better improve juvenile survival. Using predation as an excuse to indiscriminately kill native fishes and not take other major actions is shameful.

The foothill yellow-legged frog, a Species of Special Concern, commonly occur with hardhead as part of the native community.

The goal of killing large numbers of Sacramento pikeminnow and hardhead implies that these fishes are of little value.  But Sacramento pikeminnow and hardhead are native fishes restricted to northern and central California, part of the native biotic community that California Department of Fish and Wildlife’s (CDFW) Ecosystem Restoration Program (CDFW 2018) seeks to restore.  Further, hardhead are a California Species of Special Concern because of their long-term decline in numbers (Moyle et al. 2015).  Hardhead and large pikeminnow are good game fish, and anglers who catch them when fishing for other species are often surprised at their sporting qualities.  Properly prepared, both species can be good eating as well; scaling, filleting, scoring the fillets to cut through the intermuscular bones, then breading and frying gives tasty fish nuggets (Buffler and Dickson 1990).

The website states that one of the derby’s goals was to get more people fishing – sport-fishing – because fewer people are sport-fishing in California these days.  Implicit in the definition of sport-fishing is fair chase and restraint from killing unnecessarily.  With no evidence of Sacramento pikeminnow or hardhead harming salmon or steelhead populations in the Central Valley, coupled with hardhead’s conservation status, the killing of hardhead and pikeminnow in their native watershed appears to be highly antithetical to the spirit of sport-fishing.

We – anglers and conservationists – find the justifications for the derby lacking in evidence, overly selective and simplistic, and degrading to the spirit of sport-fishing.  Rather than killing any species found with a few salmon in their guts, a more productive approach is to create a better ecosystem for salmon.  Such a holistic approach – for example, using rice fields and duck ponds for growing fish food, increasing winter and spring river flows, restoring tides to Delta islands – promises benefits to not only salmon but also other native species, including hardhead and Sacramento pikeminnow. As remnants of wild, native California, a much better place for hardhead and Sacramento pikeminnow is swimming freely in their home rivers, rather than in a dog-food bowl or flowerbed.

Teejay O’Rear is a fish ecologist at the Center for Watershed Sciences and lab supervisor for Dr. Peter Moyle. His research interests include the application of the reconciliation-ecology concept in the Sacramento-San Joaquin Watershed, with a particular focus on non-mainstem and/or generally ignored habitats (e.g., managed wetlands, water-supply reservoirs, agricultural ditches, and dead-end sloughs) that may benefit both native and desirable non-native species – including people. John Durand is a researcher specializing in estuarine ecology and restoration at the Center for Watershed Sciences. Peter B. Moyle is a UC Davis Professor Emeritus of fish biology and an associate director of the Center for Watershed Sciences.


Berejikian, B. A.  1995.  The effects of hatchery and wild ancestry and experience on the relative ability of steelhead trout fry (Oncorhynchus mykiss) to avoid a predator.  Canadian Journal of Fisheries and Aquatic Sciences 52(11):2476-2482.

Brown, L.R. and P. B. Moyle. 1981. The impact of squawfish on salmonid populations: a review. North American Journal of Fisheries Management 1:104-111

Buffler, R., and T. Dickson.  1990.  Fishing for Buffalo.  Minneapolis: University of Minnesota Press.

Carey, M.P., B. L. Sanderson., K. A. Barnas, and J. D. Olden. 2012. Native invaders–challenges for science, management, policy, and society. Frontiers in Ecology and the Environment 10: 373-381.

Cavallo, B., J. Merz, and J. Setka, 2013. Effects of predator and flow manipulation on Chinook salmon (Oncorhynchus tshawytscha) survival in an imperiled estuary. Environmental Biology of Fishes 96: 393-403.

CDFW.  2018.  Ecosystem Restoration Program.  CDFW.  July 25, 2018.

FISHBIO.  2018aFishing for pikeminnow: a native predator removal derby.  The Fish Report. July 10, 2018.

FISHBIO.  2018bCrab wars: the invasive European green crab.  The Fish Report. July 22, 2018.

Grossman, G.D. 2016. Predation on fishes in the Sacramento–San Joaquin Delta: current knowledge and future directions. San Francisco Estuary and Watershed Science 14(2).

Johnston, R.  2018.  Rivers: the lower Sacramento River and the Feather River.  RJ’s Fly Trips.  July 31, 2018.

Moyle, P.B. 2002. Inland Fishes of California. Berkeley: UC Press.

Moyle, P.B., R. M. Quiñones, J.V.E. Katz, and J. Weaver. 2015.  Fish Species of Special Concern in California.  3rd edition.  Sacramento: California Department of Fish and Wildlife.

Moyle, P., A. Sih, A. Steel, C. Jeffres, and W. Bennett.  2016.  Understanding predation impacts on Delta native fishes.  California WaterBlog.  July 25, 2018.

Moyle, P. B., B. Vondracek, and G. D. Grossman.  1983.  Responses of fish populations in the North Fork of the Feather River, California, to treatments with fish toxicants.  North American Journal of Fisheries Management 3:48-60.

Pearse, D. E., and J. C. Garza.  2015.  You can’t unscramble an egg: population genetic structure of Oncorhynchus mykiss in the California Central Valley inferred from combined microsatellite and single nucleotide polymorphism data.  San Francisco Estuary and Watershed Science: 13 (4).

Poe, T.P., H. C. Hansel, S. Vigg, D. E. Palmer, and L.A. Prendergast. 1991. Feeding of predaceous fishes on out‐migrating juvenile salmonids in John Day Reservoir, Columbia River. Transactions of the American Fisheries Society 120: 405-420

Sabal, M., S. Hayes, J. Merz, and J. Setka. 2016. Habitat alterations and a nonnative predator, the Striped Bass, increase native Chinook Salmon mortality in the Central Valley, California. North American Journal of Fisheries Management 36: 309-320.

Satterthwaite, W. H., and S. M. Carlson.  2015.  Weakening portfolio effect strength in a hatchery-supplemented Chinook salmon population complex.  Canadian Journal of Fisheries and Aquatic Sciences 72: 1860-1875.

Vigg, S., T. P. Poe, L. A. Prendergast, and H. C. Hansel. 1991. Rates of consumption of juvenile salmonids and alternative prey fish by northern squawfish, walleyes, smallmouth bass, and channel catfish in John Day Reservoir, Columbia River. Transactions of the American Fisheries Society 120:421-438.

Vondracek, B. 1987. Digestion rates and gastric evacuation times in relation to temperature of the Sacramento squawfish, Ptychocheilus grandis. Fishery Bulletin 85(1):159-63.

Vondracek B, S. R. Hanson, and P. B. Moyle. 1991. Sacramento squawfish predation on Chinook salmon below a diversion dam on the Sacramento River. Unpublished manuscript files.

Posted in Conservation, Fish, Sacramento-San Joaquin Delta | Tagged , , , | 10 Comments

Groundwater exchange pools in Los Angeles: An innovative example of adaptive management

by Erik Porse, Kathryn Mika, Stephanie Pincetl, Mark Gold, and William Blomquist

Major groundwater basins in metropolitan Los Angeles. Most of the groundwater basins are adjudicated.

Across California, Groundwater Sustainability Agencies (GSAs) are devising plans to reduce long-term overdraft. As part of the 2014 Sustainable Groundwater Management Act, GSAs will submit plans in 2020-2022, which detail strategies to bring groundwater use into balance by 2040. Planning processes must assemble stakeholders and estimate sustainable yields of groundwater, quantify existing pumping, describe future options to limit overdraft, and identify funding. GSAs are actively searching for ways to stretch limited supplies and sustainably use the underground storage space created by decades of overdraft, drawing on lessons of previous regional agreements.

In one part of Los Angeles County (a region whose groundwater basins are mostly adjudicated, in contrast with most other parts of the state), an innovative approach has established a community exchange pool where parties can store and purchase water. The arrangement, which allows pumpers such as water districts and municipal utilities to newly store water in the emptied aquifers, was incorporated into a 2013 re-adjudication of the groundwater management agreement, now managed by the Water Replenishment District of Southern California. The new arrangement presents intriguing questions. For instance, what is the potential for groundwater storage and exchange pools to help meet regional goals of water supply planning in L.A.?

The Central and West Coast Basin territories managed by WRD, where an exchange pool was instituted by the 2013 re-adjudication (Source: WRD)

In a recently-published study, we modeled potential operations of groundwater exchange pools across the L.A. County metro area and its adjudicated basins and sub-basins. Results indicated that, if used, storage and exchange pools have significant potential to promote long-term water supply reliability, including mitigating potential effects of water scarcity from reduced imports. Combined with water conservation, exchanging groundwater among retailers could reduce water shortages by as much as 80%. To accomplish this, pumpers with excess water store it for later use, or transfer it to other parties with supply shortfalls. Storage pool operations were seasonal, with more groundwater banking taking place during winter months and more extractions occurring in late summer.

The rules that organize such arrangements are critical. Accessibility to exchange pools is an important driver of their success. L.A.’s regional groundwater adjudications specify pumping rights among parties. These allocations occurred decades ago, and not all communities and agencies have pumping rights. This inhibits capacity to deal with water scarcity and reduces economic incentives for building enhanced stormwater capture infrastructure that augments groundwater supplies, which is a useful economic benefit to quantify in paying for new infrastructure. Opening up access to groundwater basins, and exchange pool arrangements, by adjusting pumping rights and/or making storage and transfers more widely available could enhance reliability across retailers.

Additionally, a distinction exists between rights to pump groundwater vs rights to store groundwater. Groundwater is one type of Common Pool Resource (CPR) and L.A. basins were seminal examples in the development of contemporary theories of CPR management. In California today, groundwater management agreements might treat the Common Pool Resources of groundwater supply and groundwater storage as either separate or joint. For instance, if only existing pumpers in a basin can access the storage capacity, storage and supply are managed jointly. Alternatively, if other parties without pumping rights in a basin could access its storage capacity, the CPRs would be managed separately.

Modeling results showed that this distinction is important. Managing access pumping and storage to exchange pools separately allows for greater reductions in regional shortages as compared to allotting rights for pumping and storage in exchange pools to only existing pumpers. This occurs because communities and agencies without current access to groundwater rights are more vulnerable to imported water cutbacks. Broadening access to storage facilitates broader reliability.

The modeling included a few assumptions for the storage pool operations. For instance, it assumed water retailers would meet demand reduction targets before offering water to exchanges, and also allowed pumpers to extract more than their regular allocations.  We also did not account for how water would be recharged into the groundwater basins, or the economic costs of implementing the exchange pools.  Clearly all of those issues would have to be addressed for exchange pools to be established broadly across a groundwater management area, but the modeling results were sufficient to suggest that such institutional reforms are worth taking seriously.

The organization of exchange pools also involves both philosophical and policy debates. Generally, exchanges of groundwater can occur as bilateral transfers between two parties, regulated contributions to storage pools based on allotted rights, market-driven exchanges where parties buy and sell water, or other schemes. Market-driven exchanges can effectively move water from areas of excess to areas of economic demand. But, markets do not necessarily address issues of equity and access. For instance, small, undercapitalized retailers in L.A. that would benefit from additional sources of water supply may not actually have funds or authority to participate in exchange pools, let alone fix their existing systems. Moreover, bilateral transfers may not adequately protect other important groundwater basin interests and values – where and how water is stored, and when and how it is withdrawn, can impact other basin users and the overlying lands and structures. As a critical resource supporting health and safety needs, groundwater basins must also be managed to incorporate state policies for water as a human right.  These should all be complimentary goals in organizing flexible groundwater management agreements.  For these and other reasons, relying on just one design for exchange pools will likely fail to achieve regional water supply reliability and equity goals.  What can be said with confidence is that for groundwater exchange pools to realize their potential, “storage management” will have to become an essential element in groundwater management.

As California groundwater users develop groundwater sustainability plans, flexible and adaptive agreements will be critical. Regional agencies are poised to be innovators. The groundwater basin adjudications of L.A. are unique historic, but evolving, examples of court-approved pacts that lay out the conditions for adaptive management, both between years and over time. Exchange pools can be a useful contribution in promoting management flexibility.

Erik Porse is a Research Engineer in the Office of Water Programs at CSU-Sacramento and a Visiting Assistant Researcher at UCLA. Bill Blomquist is a Professor of Political Science at Indiana University-Purdue University Indianapolis (IUPUI) in Indianapolis, Indiana.  His areas of research are water resource management, institutions, and the policy making process. Stephanie Pincetl is the Director of the California Center for Sustainable Communities and a Professor-in-Residence at the UCLA Institute of the Environment and Sustainability. Katie Mika was a postdoctoral scholar at the UCLA Institute of the Environment and Sustainability and authored reports for the LA Sustainable Water Project. Mark Gold is associate vice chancellor for Environment and Sustainability at UCLA and heads UCLA’s Sustainable LA Grand Challenge.

Further Reading

Blomquist, William A. 1992. Dividing the Waters : Governing Groundwater in Southern California. San Francisco, Calif.; Lanham, Md.: ICS Press.

Central Basin/West Coast Basin Amended Judgment. 2013. Central and West Basin Water Replenishment District v. Charles E. Adams et al: Third Amended Judgment. Superior Court of the State of California, Los Angeles County.

Kiparsky, Michael, Andrew T. Fisher, W. Michael Hanemann, John Bowie, Rose Kantor, Chris Coburn, and Brian Lockwood. “Recharge Net Metering To Enhance Groundwater Sustainability.” (2018).

Langridge, Ruth. Evaluating California’s Adjudicated Groundwater Basins in the SGMA Era. California Water Blog. October 23, 2016.

Langridge, Ruth, Abagail Brown, Kirsten Rudestam, and Esther Conrad. 2015. An Evaluatoin of California’s Adjudicated Groundwater Basins. University of California, Santa Cruz.

Ostrom, Elinor. 1965. “Public Entrepreneurship: A Case Study in Ground Water Basin Management.” Ph.D. Dissertation, Los Angeles, CA: University of California, Los Angeles.

Ostrom, Elinor. 1990. Governing the Commons : The Evolution of Institutions for Collective Action. Cambridge: Cambridge University Press.

Porse, Erik, Madelyn Glickfeld, Keith Mertan, and Stephanie Pincetl. 2015. “Pumping for the Masses: Evolution of Groundwater Management in Metropolitan Los Angeles.” GeoJournal, August.

Porse, Erik, Kathryn B. Mika, Mark Gold, Stephanie Pincetl, and William A Blomquist. 2018. “Groundwater Exchange Pools and Urban Water Supply Sustainability.” Journal of Water Resources Planning and Management 144 (3).

Schlager, Edella, William Blomquist, and Shui Yan Tang. 1994. “Mobile Flows, Storage, and Self-Organized Institutions for Governing Common-Pool Resources.” Land Economics 70 (3): 294.

Water Replenishment District of Southern California. 2015. Groundwater Basins Master Plan: Draft Program Environmental Impact Report. ESA/120192. Los Angeles, CA.

Posted in California Water, Groundwater, urban water | Tagged , | 1 Comment

Indirect Environmental Benefits of Cannabis Cultivation Regulation

by Kathleen Stone

Marijuana plants for harvest inside a growing room. (Mel Melcon / Los Angeles Times)

The external pressures for cannabis cultivation and the immediate need for water use regulation may provide opportunities for broader, long-sought environmental objectives in California. Specifically, legislation and state programs regulating water use for cannabis cultivation could produce collateral benefits for environmental instream flow and water quality management in general.

The Medical Cannabis Regulation and Safety Act included several state laws from 2015 and 2016. Of these, Assembly Bill 243 (AB 243) and Senate Bill (SB 837), passed in October 2015 and June 2016, respectively, include several provisions for regulating water use for cannabis cultivation (CDFA 2016).

AB 243 established responsibilities for state agencies to regulate the impact of medical marijuana cultivation on the environment (CA State Legislature 2015). The bill called for several agencies, including the California Department of Fish and Wildlife (CDFW) and the California State Water Resources Control Board (SWRCB), to reduce the effects of cultivation on the environment and required the SWRCB to regulate marijuana cultivation water use and waste discharge (CA State Legislature 2015). The bill also has the California Department of Food and Agriculture (CDFA) administer a cultivation licensing system (CA State Legislature 2015). These state agencies would coordinate with local agencies to enforce environmental cultivation regulations (CA State Legislature 2015). SB 837 required the CDFW and SWRCB to further develop water diversion and use standards for cannabis cultivation (CA State Legislature 2016). The bill also requires that cultivators specify water diversion sources and report diversion amounts to the SWRCB at least annually.

This previous legislation was adopted into the Medicinal and Adult-Use Cannabis Regulation and Safety Act, enacted as Senate Bill 94 (SB 94) in June 2017 (CA State Legislature 2017). This bill increased regulatory authority for state agencies in permitting and required cultivators to report additional cultivation specifications.

With these laws, several state agencies were tasked with developing programs and policies to regulate and enforce cultivation water use. Table 1 summarizes the main state agencies involved in developing regulation and the primary purpose of each policy and program.

Table 1. State Agencies Involved in Regulating Cannabis Water Use

The SWRCB, working with the CDFA and CDFW, developed the Cannabis Cultivation Policy: Principles and Guidelines for Cannabis Cultivation, released in October 2017 (SWRCB 2017). This policy outlines regulatory jurisdictions for state agencies regarding water quality, waste discharge, groundwater use, instream flow, monitoring, licensing, and enforcement requirements for cannabis cultivation (Carah et al. 2018; SWRCB 2017). An exemption from the California Environmental Quality Act (CEQA) allowed timely development of statewide instream flow requirements (Carah et al. 2018; SWRCB 2017). The policy establishes fourteen regional boundaries for cultivation water use regulation and identifies nine priority regions with sensitive salmon migration habitats, shown in Figure 1 (SWRCB 2017).

Figure 1. Cannabis Cultivation Regulation Regional Boundaries (SWRCB 2017)

The immediate need for cultivation regulation and the development of these state agency programs, which call for environmentally focused regulations of water quality and flows, has provided an opportunity to expedite long-sought environmental objectives and flow regulations for streams affected by cannabis production, and perhaps environmental flow management in general. Progress on environmental flow management often seems slow or stalemated in California. External pressures for cannabis cultivation and its regulation could bring broader progress and precedence on instream flow and water quality management.

Water policy often moves in mysterious ways. External forces sometimes are needed to innovate over the status quo. Just as a drought was needed to finally bring groundwater management to California, perhaps marijuana is needed to bring more effective environmental management to California’s streams.

Kathleen Stone is a M.S. graduate student in Civil and Environmental Engineering at the University of California, Davis. Her research focuses on quantifying the economic tradeoffs of groundwater policy alternatives.

Further Reading

Bauer, Scott, et al. 2015. Impacts of Surface Water Diversions for Marijuana Cultivation on Aquatic Habitat in Four Northwestern California Watersheds.

Butsic, Van, and Patrick Murphy. 2016. Regulating Marijuana as a Crop

California Department of Fish and Wildlife. 2018a. Watershed Enforcement Program (WEP)

California Department of Fish and Wildlife. 2018b. Cannabis Restoration Grant Program

California Department of Food and Agriculture. 2018. CalCannabis Cultivation Licensing Fact Sheet

California Department of Food and Agriculture. 2017. CalCannabis Cultivation Licensing: Final Program Environmental Impact Report.

California Department of Food and Agriculture. 2016. Comprehensive Medical Cannabis Regulation and Safety Act 2016

California State, Legislature. 2015. Assembly Bill 243

California State, Legislature. 2016. Senate Bill 837

California State, Legislature. 2017. Senate Bill 94

California State Water Resources Control Board. 2017. Cannabis Cultivation Policy – Principles and Guidelines for Cannabis Cultivation

Carah, J., Clifford, M., Grantham, T., & Schultz, D. 2018. Environmental Flows Seminar: Cannabis Regulation and Impacts

Chappelle, Caitrin, and Lori Pottinger. 2015. California Streams Going to Pot from Marijuana Boom

Posted in Uncategorized | Tagged , | 3 Comments

SGMA struggles to overcome marginalization of disadvantaged communities

by Kristin Dobbin

Small Disadvantaged Communities (DACs), or DACs with less than 10,000 people, have long been disproportionately affected by California’s water management woes such as groundwater overdraft and pollution. Now, new research from the UC Davis Center for Environmental Policy and Behavior shows that the majority of small DACs are not participating in the Groundwater Sustainability Agencies (GSAs) formed to address them.

In 2014, California passed the Sustainable Groundwater Management Act (SGMA). Under SGMA, 127 high- and medium-priority groundwater basins were required to form Groundwater Sustainability Agencies (GSAs) by June 30, 2017. Now, GSAs have until January 2020 or 2022, depending on their basin condition, to develop Groundwater Sustainability Plans (GSPs). Throughout the process, GSAs have a responsibility to “consider the interests of beneficial uses and users,” specifically including DACs, which California defines as communities where the average Median Household Income is less than 80% of the state’s average.

How or if this will happen, however, is an important policy and research consideration extending beyond just SGMA. SGMA’s closest cousin in the state, the Integrated Regional Watershed Management (IRWM) program, has been criticized for not meeting the needs of small DACs. As a result, under Proposition 84 (2006), the state invested more than $2.5 million in DAC pilot studies; Proposition 1 (2014) includes $51 million in funding for DAC involvement in the IRWM program.

A spatial analysis identified small DACs intersecting one or more exclusive GSAs. GSA formation documents from the Department of Water Resources’ (DWR) SGMA portal were then used to analyze how small DACs are integrated into governance. Our analysis reveals three key findings.

First, the SGMA process will impact many of the state’s small DACs. 45% (243 of 545) of small DACs in the state intersect one or more GSAs. Moreover, a similar percentage of GSAs, 41% (109 of 269), intersect one or more small DAC. For example, the Tulare Lake hydrologic region has 81 small DACs intersecting 26 different exclusive GSAs, more than any other hydrologic region (Figure 1).

Figure 1. Small DACs and exclusive GSAs in the Tulare Lake Basin.

Second, the prevalence of small DACs was not well accounted for in the initial interested parties lists submitted to DWR despite the requirement of Water Code Section 10723.8 to include them. Overall, only 55% of the small DACs intersecting exclusive GSAs were identified anywhere in interested parties lists submitted. Only 51% of GSAs correctly identified all the small DACs in their boundaries. 23% identified none of the small DACs in their boundaries. Figure 2 provides an example of an interested parties list submitted to DWR. While the GSA’s list claims that there are no DACs known at this time, according to DWR’s publicly available DAC mapping tool, this particular GSA contains eight small DACs.

Figure 2. A screenshot of the interested parties list from an exclusive GSA’s notification.

Third, the vast majority of small DACs are not formally participating in GSA governance. 25% (27 of 109) of GSAs with small DACs have small DAC members and 28% (30 of 109) have small DAC board members. Figure 3 shows how participation varies by hydrologic region. Participation rates also vary by the incorporation status of the community. While 47% (15 of 32) incorporated small DACs are members of their GSA and 53% (17 of 32) are board members, only 10% (22 of 211) of unincorporated small DACs are members of their GSAs and only 12% (25 of 211) are board members.

Figure 3. GSAs with small DACs, small DAC members and small DAC board members by hydrologic region.

While GSA and board membership are not the only ways that DACs can or do participate in SGMA, these numbers, taken together with the 45% of small DACs that were not listed anywhere on their respective interested parties lists, calls into question the participatory and inclusive nature of the SGMA process thus far. SGMA, like IRWM before it, poses challenges in representing these already marginalized groundwater users. Understanding these challenges, and what can and should be done about them, are important areas for future research as GSAs dive head first into writing their GSPs.

 Kristin Dobbin is a PhD student in Ecology at UC Davis studying regional water management and drinking water disparities in California. Many thanks to Mark Lubell and Amanda Fencl for their review and edits.

Further Reading

Balazs, C., & M. Lubell. 2014. Social learning in an environmental justice context: a case study of integrated regional water management. Water Policy, 16(S2), 97-120.

Disadvantaged Communities Visioning Workshop December 3-5, 2014. Recommendations. 2015.

Dobbin, K. Research Brief: Small Disadvantaged Community Participation in Groundwater Sustainability Agencies. 2018. (English / Spanish).

Dobbin, K., J. Clary, L. Firestone and J. Christian-Smith. 2015. Collaborating for Success: Stakeholder engagement for Sustainable Groundwater Management Act implementation.

Feinstein L, Phurisamban R, Ford A, Tyler C and Crawford A (2017) Drought and Equity in California, Pacific Institute, Oakland, CA

Posted in California Water, Drinking water, Drought, Groundwater | Tagged , , | 7 Comments

Guest Species – What about the nonnative species we like?

by Karrigan Bork, JD, PhD

Striped bass – One of California’s guest species.

Conservationists worry about a host of nonnative species, and with good reason. Nonnative species cause north of $120 billion per year in damages in North America alone, and they present the primary extinction risk for roughly half of the threatened or endangered species in the United States.

The worst offenders are well known – aquatic species like zebra mussels and Asian carp, and terrestrial species like kudzu, yellow star thistle, and myriad rat species. But there’s another category of nonnative species, species that we celebrate and enjoy.

“Guest species” describes naturalized nonnative species that humans have introduced, intentionally or accidentally, and which we actively conserve because we benefit from having them in the wild. This isn’t just semantics; the terms we use to describe a species play a central role in determining how we think about that species.

Pheasants are another guest species in the United States that have acquired iconic status.

Guest species include intercontinental introductions like honey bees, earth worms, pheasant, wild horses, and brown trout; and many other species that we’ve moved around (directly or via habitat modification) within North America, like striped bass, largemouth bass, turkey, and deer. These species are well-loved, culturally significant, and may play important roles in their new ecosystems.

But they also create significant conflicts for aquatic ecosystem management, and these conflicts often crop up as part of our most heated debates about how we manage our natural resources. My recent paper on guest species undertook case studies of several of these conflicts, including management of striped bass in California’s Delta and rainbow trout in Utah’s Green River. These two case studies highlighted several common themes in dealing with guest species that help to explain why they breed so much conflict. Top themes include:

  1. federal oversight of state wildlife management breeds conflict;
  2. people love their guest species, which increases conflicts;
  3. guest species can eventually become part of the local ecosystem; and
  4. guest species may be better adapted for the current environment than native species.

Guest species are particularly prevalent among aquatic species, which makes this a central issue for watershed scientists. Introduced fish species make up anywhere from 10% of the total species in eastern areas up to 30–60% of fish species in the west, and most of these transplanted species were introduced as game species or forage for game species.

UC Davis fish ecologist Carson Jeffres with a Delta striped bass. Photo by Martin Koening

Striped bass came to California via railroad in 1870, brought by Livingston Stone at the suggestion of the California State Board of Fish Commissioners. Striped bass populations exploded, and the population supported a commercial fishery for many years. Striped bass remain among the most popular California game fish, and 81% of fisherman near striped bass fish for them, with an average expenditure of $146.91 per day.

In 2008, the Coalition for a Sustainable Delta filed suit against the California Department of Fish and Wildlife, arguing that the state’s fishing regulations for striped bass amounted to a violation of the federal Endangered Species Act (ESA). The Coalition, a group of agricultural water users, seeks to “to better the conditions of those engaged in agricultural pursuits in the San Joaquin Valley by ensuring a sustainable and reliable water supply.”

The Coalition argued that the lawsuit was a way to improve the numbers of listed species in the Delta, which would in turn allow the coalition members to divert more water from the Delta. However, the lawsuit looks more like an effort to separate striped bass fishermen from the rest of the sportfishing community, which would reduce the community’s strong opposition to many Coalition positions. Regardless, the lawsuit was a bombshell for wildlife managers in California and across the country.

The Coalition’s theory of the case goes like this: the ESA bars any killing of any endangered species of fish or wildlife without a permit; the state catch and size limits increased the number of striped bass in the Delta; increased numbers of striped bass eat increased numbers of threatened and endangered species; therefore, the state regulations protecting striped bass amounted to state actions that kill endangered species in violation of the ESA. This line of reasoning was successful in a similar case in Hawaii.

But if courts generally accept this line of reasoning, virtually any management of game species could amount to a violation of the ESA, which carries serious monetary penalties and potential jail time. This could include management of native species as well – the law does not distinguish between native and nonnative species in this kind of conflict.

The Coalition’s lawsuit over striped bass ultimately failed. After the judge in the case signaled that the science on striped bass was too convoluted for easy resolution without trial, the parties settled the lawsuit in February 2011. Per the settlement agreement, CDFW recommended that the California Fish and Game Commission (an independent body which writes the sport fishing regulations in California) “modify the striped bass sport fishing regulation to reduce striped bass predation on the listed species.” See Coal. for a Sustainable Delta v. McCamman, No. 1:08-CV-00397 OWW GSA, 2011 WL 1332196, at *5 (E.D. Cal. Apr. 6, 2011). The Commission unanimously rejected the proposed change in February 2012, and although the court dismissed the case, the broader dispute remains unresolved.

This dispute highlights several of the aforementioned themes:

First, federal oversight of state wildlife management breeds conflict. Under the traditional North American model of wildlife management, state agencies, funded by hunting and angling licenses and special taxes, manage wildlife at the state level. This inherently creates some preference for game species at the state level.

When the federal government intrudes in the game management space, most often through the ESA, longstanding tensions between the state and federal governments can make the disputes worse. With striped bass, California once had an ESA permit allowing them to enhance striped bass populations via stocking, but abandoned that effort. Anglers at the state level, who had funded that effort with a special striped bass fee, blamed federal regulators for intruding on their fishery. This conflict is unlikely to go away and could easily spread to encompass other guest species. The Fish and Wildlife Service and the National Marine Fisheries Service should act now to clarify how the ESA applies to state management of game species and should, if necessary, work with state agencies to permit (and mitigate for) these activities.

Second, people love their guest species, which increases conflicts. As with the striped bass, many aquatic guest species were introduced into new ecosystems as game species for our fishing pleasure, and this effort has been a success. Introduced game fish are well loved, with strong interest groups lobbying at the state and federal level on their behalf. The striped bass fan club in California includes the Sportfishing Conservancy, the California Sportfishing League, the Coastside Fishing Club, the California Striped Bass Association, and the California Sportfishing Protection Alliance, all of which lobby on the fish’s behalf.

Wild horses: another guest species of the American West with iconic status. Image source: Wyoming Public Media

This isn’t limited to aquatic species – Wyoming put the wild horse, a guest species, on its state quarter.

Because people love these guest species, efforts to reduce their populations or eliminate them entirely often run into stiff opposition, ranging from lawsuits to direct action, i.e. sabotage of removal efforts or reintroduction of the species. The flip side is that this same love of guest species brings people closer to their environments and can result in increased environmental activism, as seen by the sportfishing groups’ broader involvement in protecting the Delta ecosystem from pollution and water withdrawals. Guest species are a, and perhaps the, motivating factor for many casual conservationists today. Without these species, conservationists lose much of their public support.

Third, guest species can eventually become part of the local ecosystem. This is true in two ways – both in terms of the bass’s role in the ecosystem, and in broader philosophical terms. Scientists have a very difficult time predicting what would happen in the Delta ecosystem if striped bass were functionally removed. Although striped bass eat some listed species, they also eat predators on listed species, and so ecologists can’t accurately predict how striped bass removal would affect the populations of listed species. Ecosystems like the Delta “are so highly altered that attempting to restore them to an earlier condition or stable state is largely not possible.”

More broadly, striped bass have been in California for almost 150 years. Based on research on transplanted salmon populations, the California striped bass are likely adapted to the West Coast ecosystems and are likely genetically differentiated from their East Coast kin. These fish have adapted to their new habitats, and they have thrived in the current Delta, which offers habitat far different than historic conditions. The Delta today is a novel ecosystem, an ecosystem which lacks a historic analog.

If we think about native species as species that evolved in a given habitat, then it’s hard to say what’s native to a novel ecosystem like the Delta. Today’s Delta isn’t the Delta where Delta smelt evolved or where winter run Chinook salmon evolved, and these species are not well adapted to today’s Delta. Within this framework, guest species like the striped bass are as native to a novel ecosystem as anything else. This is not to devalue the biodiversity offered by native species–it must be protected as well. But it does mean that we shouldn’t devalue guest species in novel ecosystems just because they were not a part of the historic ecosystem.

This brings up the fourth and final theme: guest species may be better adapted for the current environment than native species. In places like the Delta, the habitat has been changed so much that species evolved for the historic Delta cannot survive without intense and ongoing human intervention. This is only going to get worse under climate change. A recent study of California fishes found that, under project climate scenarios, “[m]ost native fishes will suffer population declines and become more restricted in their distributions; some will likely be driven to extinction. . . . In contrast, most alien fishes will thrive, with some species increasing in abundance and range.”

This means we must think long and hard about removing guest species. If these species are the most likely to survive our future climate, removing them now in a bid for historical ecosystem re-creation is misguided and shortsighted. We could end up with nothing left to protect.

Karrigan Bork is a Visiting Assistant Professor with a joint appointment at the McGeorge School of Law and the Dept. of Geological & Environmental Sciences, both part of the University of the Pacific. He is also a visiting researcher at the UC Davis Center for Watershed Sciences. His research interests include environmental law, natural resources law, international law, and administrative law, focusing on the interplay of science and law. For more information visit his SSRN page.

Further reading

Karrigan Börk, Guest Species: Rethinking Our Approach to Biodiversity in the Anthropocene, 2018 Utah L. Rev. 169 (2018).

Moyle, PB, Jeffres CA, and Durand J. 2018. Resurrecting the Delta for desirable fishes. California WaterBlog.

Moyle PB et al. 2016. Understanding predation impacts on Delta native fishes. California WaterBlog.

Moyle PB and Bennett WA, 2011.  Striped Bass: the cure worse than the disease. California WaterBlog.

Posted in Conservation, Fish, Stressors | Tagged , | 4 Comments

Managing Domestic Well Impacts from Overdraft and Balancing Stakeholder Interests

by Robert M. Gailey and Jay R. Lund

The historic drought in California from 2012 through 2016 brought unprecedented groundwater level declines and reports of dry domestic supply wells.  This was particularly true in the Central Valley.

New research on conditions in Tulare County during the drought provides insight regarding tradeoffs in interests between domestic well owners and agricultural pumpers, as well as suggests an approach for addressing the needs of both stakeholder groups.  These results can be useful for groundwater management policy and implementing the Sustainable Groundwater Management Act (SGMA).

Groundwater often buffers water supplies against drought.  The benefits from increased well pumping are greatest during long droughts when statewide groundwater use can rise from about 30 to 60 percent of human water demand.  Up to 80 percent of this use is for crop irrigation.

Agriculture is willing to incur higher costs from additional groundwater pumping during drought because it is profitable to do so.  Moreover, investments in trees and vines hardens agricultural water demands and creates need for the constant water supply provided by pumping groundwater.  (Domestic water demands also are hardening with water conservation, but are much smaller – particularly in rural areas.)

Other costs often result from groundwater use and affect neighbors who might not benefit from sustaining economic production by pumping more during drought.  Increased pumping decreases the volume of water stored in groundwater systems and water levels fall.  This groundwater drawdown can spread from deep, high-capacity wells – sometimes for thousands of feet.

In regions where there are many production wells, areas of water-level depression from individual wells can merge into broader regions of impact.  The decreased water levels can cause problems for shallower wells.  Pumps are no longer properly submerged, cavitation occurs and pumps stop working unless they are moved lower in the wells.  Some wells are too shallow to allow further pump lowering and must be shut down or replaced with deeper wells.

These are expensive actions and service providers are in high demand during drought.  Domestic wells are generally more susceptible to going dry and incurring additional costs because they are mostly shallower than the larger and deeper agricultural wells that draw down water levels the most.  These domestic well impacts are a classic case of economic externality – when one party is affected by another’s actions.

Domestic wells are common in rural areas that lack municipal and community water supplies.  Rural wells often supply economically disadvantaged households and communities already struggling with water quality problems from nitrate and arsenic.  Domestic well owners usually cannot compete financially with larger pumpers to employ the skilled labor needed to fix wells.

Figures 1 a and b show the distribution and density of domestic and agricultural supply wells in California (approximately 235,000 domestic and 34,000 agricultural wells statewide).  Although drought problems for domestic wells are more likely in sub-basins designated as Critically Overdrafted and High Priority by the California Department of Water Resources under SGMA, differences in stakeholder interests likely also occur in other areas. Potential impacts of agricultural groundwater pumping on shallow domestic wells should be considered when groundwater management plans are developed.

Figure 1. Numbers of wells in California: a domestic wells (Dom) and b irrigation wells (Ag). Gray shaded area is the portion of Tulare County located on floor of the Central Valley (study area). Data source: CADWR Well completion report map application

Available data do not provide a precise count of domestic supply well impacts in Tulare County during the 2012-2016 drought; however, our analysis suggests that the part of the county on the valley floor experienced approximately 1,100 well outages.  The cost to maintain uninterrupted supply from these wells is estimated at $10.3 million.  Because agricultural revenue during this same period was significantly higher (approximately $35 billion), reducing groundwater pumping for agricultural supplies would likely have cost far more than the estimated additional costs to maintain domestic wells.

Institutions in the southern Central Valley and elsewhere in California are beginning to plan for compliance with SGMA.  The new regulations require including a range of stakeholder concerns in planning.  Balancing agricultural pumping with domestic supply reliability will likely be an important consideration.  A funding mechanism to prepare shallow domestic and community wells for decreased groundwater levels (lowering pumps and replacing wells) might allow agriculture to maintain operational flexibility to meet their water demand during drought.

Figures 2 a and b show how information on agricultural profits and domestic well impacts could be used to develop a management policy that considers both stakeholders’ interests.  Using the historic groundwater level record (Figure 2a), three policies regarding maximum allowable depth to groundwater are considered for the recent drought.  Policy 1 limits the decrease in groundwater level to the previous lowest point (which occurred in 2010).  Policy 2 specifies a limit halfway between the previous low and the lowest point during the recent drought.  The Unregulated policy entails no regulation and allows groundwater levels to drop as low as needed to meet all pumping demands (as happened in 2017).  For policies 1 and 2, groundwater levels reaching the regulatory limit would trigger significant curtailment of pumping so that no additional decline occurred and groundwater levels would rebound more quickly after the drought when pumping lessened.

Figure 2: Example groundwater management policy analysis: a potential policies and resulting groundwater hydrographs and b depth and compensation trade off curves. Groundwater depth data source: Well 362539N1193051W001 CADWR Water Data Library. Ag is agricultural. Opp is opportunity. Dom is domestic well. Ops is operations. Prof is profit. Black and colored dots on Fig. 2b correspond to groundwater depths at 1 m intervals. Red dot is 36 m and blue dot is 50 m.

The hypothetical policies can be evaluated based on principles of economics using the estimated costs for domestic wells and agricultural financial data.  The end result is a plot of agricultural opportunity costs (lost profit resulting from limited water supply) against domestic well costs (Figure 2b), which demonstrates the trade-off in costs between stakeholders for the different policies discussed above (indicated as colored dots).  This curve presents the spectrum of potential policies from a perspective of neutral economic efficiency.  Moving from one potential policy to another results in gains for one party and losses for the other.

Maximizing economic benefits to all stakeholders results in a specific maximum groundwater depth policy (dashed green line on Figure 2a and green diamond on policy trade off curve on Figure 2b).  The water depth for this policy is near the historic low during the recent drought because the agricultural opportunity cost is so much greater than the domestic well cost.  This disparity in costs affects the economic calculations that drive policy selection.  Although maximizing the overall economic benefits would do little to ease impacts to domestic wells, future water level declines would be limited (blue dotted line on Figure 2a could not dip below green dashed line).

This total economic welfare approach does not address 1) the distribution of cost among stakeholders relative to benefits received, 2) ability of each stakeholder to absorb costs and 3) impacts on human subsistence (need for drinking water versus need for additional production).  These considerations may lead to more stringent policies that lessen the burden on domestic wells (left shift along depth policy tradeoff curve from green diamond).

An alternative approach might be for agriculture to provide some compensation for well costs.  The green dotted line on Figure 2b indicates a constant level of maximum economic welfare (and a single maximum water depth policy) but varies from no compensation (green diamond) to full compensation (red diamond).  It is a compensation trade-off curve that represents a negotiated, or regulated, shifting of the externality from well owners back to agricultural producers.

The amount of compensation (location along green dotted line on Figure 2b) might depend on considerations such as whether some of the groundwater level decline occurs from pumping farther away rather than from nearby agricultural pumpers.  The compensation approach is obviously preferable for domestic well owners and would also be preferable for agricultural producers if it reduced costs relative to a more stringent policy.

This analysis assumes the maximum groundwater depth policy only addresses costs to domestic wells from agricultural pumping that are related to supply quantity.  Other considerations, such as maximum depth limits related to land subsidence, also could be incorporated.  The approach presented here would supplement balancing the groundwater budget as required by SGMA.  Groundwater systems should be managed to an agreed upon set of metrics that includes water depth thresholds.  Achieving agreement on the specific metrics could be made easier using some economic analysis.

More details on the research summarized here will be presented at noon on May 22, 2018 at the Center for Watershed Sciences, UC Davis.

Rob Gailey recently earned a PhD in Civil and Environmental Engineering at the University of California, Davis and is a practicing hydrogeologist in California.  Jay Lund is a Professor of Civil and Environmental Engineering at the University of California, Davis, where he is also Director for its Center for Watershed Sciences.

Further Reading

Gailey R.M. (2018) Approaches for Groundwater Management in Times of Depletion and Regulatory Change.  PhD Dissertation, University of California – Davis.

CADWR (2014) California water plan update 2013. California Department of Water Resources. California Department of Water Resources.

CADWR (2015) California’s most significant droughts: comparing historical and recent conditions. California Department of Water Resources.

County of Tulare (2017) Drought effects status updates.

Feinstein L, Phurisamban R, Ford A, Tyler C and Crawford A (2017) Drought and Equity in California, Pacific Institute, Oakland, CA Last accessed 28 September 2017

Hanak E, Lund J, Arnold B, Escriva-Bou A, Gray B, Green S, Harter H, Howitt R, MacEwan D, Medellín-Azuara, Moyle P and Seavey N (2017) Water stress and a changing San Joaquin Valley, Public Policy Institute of California, March 2017.

State of California (2017) Household water supply shortage reporting system.

Tulare County Agricultural Commissioner (2017) Tulare County crop and livestock report, 2016.

Posted in Groundwater | Tagged , | 7 Comments

Habitat Restoration for Chinook Salmon in Putah Creek: A Success Story

by Eric Chapman, Emily Jacinto, and Peter Moyle

2017 was another good year for Chinook salmon in Putah Creek.

Putah Creek is just a small stream flowing through Yolo and Solano counties, fed by releases of water from Lake Berryessa. For decades, Chinook salmon were rare in the creek.

Yet, now, with salmon populations struggling throughout the Central Valley, Putah Creek numbers are on the rise. Over the past five years the estimated number of adult spawners has increased from eight in 2013 to over 500 in each of the past three years (200-500 in 2014, 500-700 in 2015, 1500-1700 in 2016, and 700 in 2017).

When much of California was in the historic drought of 2012-2016, hatcheries resorted to trucking juvenile Chinook salmon far downstream to the Delta. The intent was to increase the number of juveniles reaching the ocean because survival is poor in the rivers during low water years (Michel et al. 2013, Michel et al. 2015). While trucking can sustain adult populations, it increases the rate of adult straying into other watersheds upon return from the ocean, rather than homing to their natal watershed (Johnson 1990, Lasko 2012).

However, ongoing restoration and management efforts in Putah Creek have made conditions favorable for attracting salmon. Flashboards blocking access to the creek at the Los Rios Check Dam in the Yolo Bypass are removed every year in November and salmon attraction flows are released for five consecutive days from the Putah Diversion Dam in Winters, CA.

Map of Putah Creek from the Putah Diversion Dam (PDD) to the Toe Drain (yellow star). Salmon migrate through the yellow area to and from the spawning grounds in red. Number of adult carcasses sampled (blue circles and numbers) in different sections (black circles) of the spawning grounds. The location of the rotary screw trap is above Winters, CA (yellow star).

Minimum flows were established to enhance rearing habitat for juvenile salmon and to facilitate outmigration (Kiernan et al. 2012). During summer and fall, the Solano County Water Agency has also been using heavy equipment to scarify (turn over) the bottom of selected reaches of the creek; this process exposes spawning gravel that has been buried by years of siltation and compaction.

Over the past two years, salmon spawning has been observed on nearly every patch of gravel from the Putah Diversion Dam to Davis, a distance of ~25 kilometers. Fish were observed spawning on the newly exposed areas and on sites from previous scarification efforts. Use by salmon seems to keep the sites from becoming cemented in again.

In Winters, people watched salmon spawning below the pedestrian bridge. This reach was site of a major restoration project that removed a concrete dam and recreated a meandering stream, greatly improving salmon habitat.

Where did these fish come from and are they spawning successfully? Are juveniles making it out of Putah Creek to the ocean and are any of them returning as adults to spawn? UC Davis and the Solano County Water Agency set out to answer these questions by sampling both adult and juvenile life stages.

Adult Sampling

In 2016, researchers from the UC Davis Department of Wildlife Fish and Conservation Biology began conducting carcass surveys throughout the creek. Surveys did not begin until December in 2016, but in 2017 they coincided with the arrival of adults in the creek. The researchers poled canoes from the Putah Diversion Dam to Davis at least once during every week of the run. This allowed them to estimate the number of fish throughout the creek from week to week.

Colby Hause, a researcher at UC Davis, poles a canoe during carcass surveys. (photo: Eric Chapman)

The 2017 estimate of 700 fish is likely within ± 20%.  In the future, we hope to employ other methods as well to estimate abundance, such as use of special cameras to record passing fish.

During the two years of carcass surveys, otoliths (ear bones) were collected in order to determine the origin and age of salmon spawning in Putah Creek. Genetic samples were also collected, and tiny, coded wire tags (CWTs) were extracted from fish missing their adipose fin. The missing fin indicates they were of hatchery origin.

Results from 23 CWT fish from 2016 found that 20 were from the Mokelumne River Hatchery, two were from the Nimbus Hatchery on the American River, and one from the Feather River Hatchery. All of the tagged fish were fall-run Chinook salmon that had been trucked downstream to be released closer to the ocean during the drought.

Two otoliths collected from a carcass and location of coded wire tags (CWT). Note that the head of this fish is pointing upwards (photo: Eric Chapman)

These 23 fish were a subsample of the 126 carcasses recovered on the creek. Otolith microchemistry from the 91 fish with an intact adipose fin was determined at the University of California Davis Interdisciplinary Center for Plasma Mass Spectrometry, focusing on Strontium (Sr) isotope ratios (87Sr/86Sr). These isotope ratios vary among rivers in the Central Valley of California. The strontium isotopes are incorporated into each otolith on a daily basis, allowing for assignment of natal origin of individual fish by measuring the isotope ratios at the core of the otolith.

The microchemistry of the otolith center reflects where the fish was hatched and reared. Unfortunately, considerable overlap exists among the strontium signatures of possible natal sources, including between rivers and hatcheries, making some results difficult to interpret. For example, the strontium signature of Chinook salmon from Putah Creek overlaps with that of the wild Feather River fish but not with those in fish produced in the Feather River Hatchery.

Gabriel Singer with a large male sampled during carcass surveys. (photo: Eric Chapman)

The otolith microchemistry showed that there were at least five stocks of fish in Putah Creek in 2016. One fish was sampled that could have been of Putah Creek origin but it could have also been a naturally produced Feather River fish. To determine the difference between Putah Creek and the Feather River, it will be necessary to incorporate other trace elements or isotope systems in the future.

Juvenile Sampling

In the spring of 2017, a rotary screw trap (RST) was deployed to determine spawning success and to describe emigration timing of the juveniles. This was an extremely high water year, with Lake Berryessa overflowing during much of late winter. Because of the hazards of running a trap at high flows, the trap wasn’t operated until May 1st when the water subsided. On May 2nd there were nine juvenile fall run Chinook salmon in the trap; juveniles were captured daily until May 20th,with a peak of over 30 fish on May 10th.

The screw trap used to sample juvenile Chinook in Putah Creek. Photo credit: Ken Davis

The 215 juvenile salmon sampled into June 2017 were large, averaging 97 millimeters in length and 11.4 grams in weight. This indicates that high flows did not push them out of Putah Creek, rather it provided rearing conditions that enabled them to thrive prior to migration. These conditions were likely found on the edges of the creek and outside of the banks where floodplain conditions exist.

Daily catch summary of juveniles sampled in Putah Creek during 2017.

The jury is still out on successful spawning and rearing in 2018. The RST has been deployed again in 2018, and hundreds of small outmigrating  juveniles were captured as of January-March.  One hundred of the largest fish will receive an acoustic transmitter that will be surgically implanted to track their survival and migratory behavior. Receivers that detect the transmitters will be situated at the base of the creek, enabling the researchers to determine emigration survival from Putah Creek. An array of receivers collaboratively deployed by UCD and fisheries agencies outside the creek will enable modelling of survival through the Delta and San Francisco Estuary all the way to the Golden Gate, which has the last line of receivers prior to the Pacific Ocean.

Typical juvenile salmon caught in the RST during 2017 spring sampling (photo: Eric Chapman)

Putah Creek is a success story for salmon because water releases from a dam and habitat restoration projects have worked together to attract salmon and to allow them to spawn and rear successfully. It is likely that at least some adult salmon that returned to spawn were themselves spawned in Putah Creek. It seems possible that in the future a run could develop that is not dependent on hatchery strays, but is made up of natal fish from the creek.

Otoliths and genetics help us understand what happens when a creek is reborn and made available to fish. Spawner surveys and juveniles caught in the rotary screw trap confirm that restoration actions are working and that Putah Creek offers habitat that is suitable for producing fall-run Chinook salmon on an annual basis. Putah Creek is already regarded as model for restoration of habitat for native fishes and other plants and animals. To add wild salmon to this trajectory of success requires continued management of the creek to benefit salmon, including expansion of habitat restoration projects.


We thank the Solano County Water Agency for funding this project and for all of their help throughout the project. We would also thank Malte Willmes and James Hobbs for processing the otoliths in the mass spectrometer. Finally we thank all of the members of the UCD Biotelemetry Laboratory (Gabriel Singer, Colby Hause, Tommy Agosta, Christopher Bolte, and Patrick Doughty), volunteers, and students for their help during field work.

Eric Chapman, the lead researcher, works in Peter Moyle’s fisheries laboratory in the Center for Watershed Sciences. Emily Jacinto is a lab assistant at UC Davis. Peter Moyle is professor emeritus at the University of California, Davis, and Associate Director of the Center for Watershed Sciences. 

Further reading

Johnson, S.L., Solazzi, M.F. and Nickelson, T.E., 1990. Effects on survival and homing of trucking hatchery yearling coho salmon to release sitesNorth American Journal of Fisheries Management10(4), pp.427-433.

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

Lasko, G.R. 2012. Straying of late-Fall-run Chinook salmon from the Coleman National Fish Hatchery into the lower American River, California. Masters thesis, California State University, Sacramento.

Michel, C.J., Ammann, A.J., Chapman, E.D., Sandstrom, P.T., Fish, H.E., Thomas, M.J., Singer, G.P., Lindley, S.T., Klimley, A.P. and MacFarlane, R.B., 2013. The effects of environmental factors on the migratory movement patterns of Sacramento River yearling late-fall run Chinook salmon (Oncorhynchus tshawytscha). Environmental biology of fishes96(2-3), pp.257-271.

Michel, C.J., Ammann, A.J., Lindley, S.T., Sandstrom, P.T., Chapman, E.D., Thomas, M.J., Singer, G.P., Klimley, A.P. and MacFarlane, R.B., 2015. Chinook salmon outmigration survival in wet and dry years in California’s Sacramento River. Canadian Journal of Fisheries and Aquatic Sciences72(11), pp.1749-1759.

Posted in Biology, Fish, Restoration, Salmon | Tagged , , , | 3 Comments

Improving Urban Water Conservation in California

by Erik Porse

The relatively dry 2017-18 winter in California resurfaced recent memories of drought conservation mandates. From 2013-16, urban water utilities complied with voluntary, then mandatory, water use limits as part of Executive Order B-37-16. Urban water utilities met a statewide 25% conservation target (24.9%), helping the state weather severe drought. Winter rains in 2016-17 led to a reprieve from mandatory conservation. Freed from statewide requirements, urban water agencies ended mandatory cutbacks by meeting “stress tests” that included several years of secured water supplies.

A useful outcome of the 2013-17 drought period was long-needed reporting data on monthly urban water use and conservation. This reporting has continued, creating a growing repository for measuring trends. The data helps understand how much water California cities actually use, including trends over time, across geography, and seasonal differences.

But, importantly, can it help understand how much water California cities should use? Some analysis of the water conservation reporting data, coupled with recent research, lends a few clues to this more complex question.

Seasonal and Geographic Differences in Water Use

Recent water use totals through the end of 2017 show that cities in many parts of the state continue to use less water compared to 2013, but not as efficiently as during drought. There were a few exceptions, including the South Coast where 59% of utilities reported increases compared to the similar period in 2013.

But examining trends over time and space is instructive. Some localities continued high, even ostentatious, rates of water use. In addition, seasonal differences are evident. Drier months see much higher per capita water use due to outdoor irrigation, as shown in graphics via the Pacific Institute’s water use webmap. But winter irrigation can be just as important. Moving towards urban landscapes with no winter irrigation requirements can be as effective as limiting summer irrigation.

Summer and winter water use across Los Angeles urban retailers (source: Pacific Institute, downloaded November 2017)

Benchmarking Per Capita Consumption

Many cities in California have higher rates of water use than counterparts in other countries. But what does a target of 100 gallons per person per day (total use) actually mean for urban life?

The 2016 Executive Order sought to address this question in part by requiring state agencies to develop water use budgets based on specified targets of indoor use, commercial and industrial needs, and outdoor irrigation. This effort is continuing. But water use budgets themselves do not reveal the implications of various per capita targets, especially for outdoor needs.

Could a city in coastal Southern California, for instance, exist with 80 gallons per capita per day of total use? What would this mean for its plants, trees, and landscapes? How would the effects change in the San Francisco Bay Area or the Central Valley? Urban ecology research demonstrates that plants and trees often show distinct and varying physiological characteristics and water use trends in cities, owing to irrigation habits, climate, and other factors. Such emerging knowledge must help inform practice.

In Los Angeles, for example, research used experimental data for species-specific tree and lawn water use to estimate outdoor water use budgets and associated effects of conservation on trees and plants. Across metropolitan LA, an estimated target of 80-100 gallons per capita per day could support trees and low water landscapes, along with current residential and commercial needs, while also allowing for significant cutbacks in imported water. More aggressive conservation at the lower end of that range would require long-term conversion of the existing tree canopy to low-water and drought tolerant species.

Urban Yards as a Resource

Well-designed urban yards can support important plant and animal species, but residents need better tools, information, and guidelines on soil and irrigation practices. Outdoor landscapes constitute 50% of total urban water use in many areas. Water utilities increasingly fund replacement of lawns as a way to promote long-term conservation. But most programs do not require resultant landscapes with ecological diversity and native plants.

Research from Los Angeles indicates that, even in the absence of such requirements, turf replacement can yield more diverse landscapes. Urban utilities with ecologists on staff can better ensure turf replacement that supports biodiversity, native vegetation, and trees. Some examples, such as the City of Long Beach’s turf replacement program, offer useful guidance for residents. Resources such as the Calflora database of native California plants and Cal-Poly’s Urban Forest Ecosystem Institute tree selection guide are excellent statewide resources. But improving native and drought-tolerant plant selections in California’s urban nurseries would allow residents to translate such information into practice.

Water Use in an Era of Big Data

Urban water use trends are usefully understood when consumption data is linked with other data sets, including US Census data, county property tax records, and climate trends. This allows for high-resolution analysis that informs investments and rate-setting procedures. Some examples of innovative data initiatives exist, including the California Data Collaborative. Such tools have cascading benefits for planning.

Statewide efforts around water data are ramping up, but the state’s fragmented system of water governance inhibits broader analysis. Moreover, high-detail water use data is difficult to obtain. More accessible data across residential, commercial, industrial, and institutional properties is essential for improving management. Linking and publishing this data is an important step for promoting 21st Century, data-driven urban water polices in California.

Responsibility at Many Levels

Both water utilities and residents are essential participants in continued conservation. Utilities must retool finances to stabilize revenues given long-term conservation. Additionally, they must better engage residents and community organizations in promoting culture change. But residents also have responsibilities. Building social capital is key. Community-based organizations help engage residents in this task. For example, The River Project with its Water LA program engages residents in remaking landscapes for dual goals drought-tolerance and stormwater management. The Sacramento Tree Foundation and TreePeople are additional examples of community-based groups effectively bridging gaps between residents and utilities. Water agencies that meaningfully engage community groups will be better positioned to promote long-term conservation.

Given the popularity and continued growth of California’s cities, along with the inevitability of drought, urban water conservation will need to continue. Implementing policies to promote equitable conservation, which also supports cities where we want to live, is a challenge that an innovative California is capable of tackling.

Erik Porse is a Research Engineer in the Office of Water Programs at
CSU-Sacramento and a Visiting Assistant Researcher at UCLA.

Further Reading

Cahill, R., & Lund, J. (2012). Residential water conservation in Australia and CaliforniaJournal of Water Resources Planning and Management139(1), 117-121.

Gleick, P. H., et al. (2003). Waste not, want not: The potential for urban water conservation in California. Oakland, CA: Pacific Institute for Studies in Development, Environment, and Security.

Hanak, E., & Davis, M. (2006). Lawns and water demand in CaliforniaPPIC Research Reports.

Litvak, E., Bijoor, N. S., & Pataki, D. E. (2013). Adding trees to irrigated turfgrass lawns may be a water‐saving measure in semi‐arid environmentsEcohydrology7(5), 1314-1330.

Litvak, E., Manago, K. F., Hogue, T. S., & Pataki, D. E. (2017). Evapotranspiration of urban landscapes in Los Angeles, California at the municipal scaleWater Resources Research53(5), 4236-4252.

Mini, C., Hogue, T. S., & Pincetl, S. (2014). Estimation of residential outdoor water use in Los Angeles, CaliforniaLandscape and Urban Planning127, 124-135.

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

Pataki, D. E., McCarthy, H. R., Litvak, E., & Pincetl, S. (2011). Transpiration of urban forests in the Los Angeles metropolitan areaEcological Applications21(3), 661-677.

Pincetl, Stephanie, Thomas W. Gillespie, Diane Pataki, Erik Porse, Shenyue Jia, Erika Kidera, Nick Nobles, Janet Rodriguez, and Dong-ha Choi. (2017) “Evaluating the Effects of Turf-Replacement Programs in Los Angeles County.”

Porse, Erik, Kathryn B. Mika, Elizaveta Litvak, Kimberly F. Manago, Kartiki Naik, Madelyn Glickfeld, Terri S. Hogue, Mark Gold, Diane E. Pataki, and Stephanie Pincetl. “Systems Analysis and Optimization of Local Water Supplies in Los Angeles.” Journal of Water Resources Planning and Management 143, no. 9 (2017): 04017049.

Posted in California Water, Conservation, Drought, urban water | Tagged | 3 Comments

Resurrecting the Delta for Desirable Fishes

by Peter Moyle, Carson Jeffres, John Durand

Cache Slough sunrise. Photo by Matt Young

The Delta is described in many ways.  When extolling the Delta as a tourist destination, it is described as a place of bucolic beauty; islands of productive farmland are threaded by meandering channels of sparkling water, a place to boat, fish, view wildlife, and grow cherries and pears.

But when its future is discussed, especially in relation to big water projects, this heavenly place is often portrayed as being on its way to an aquatic Hellscape.

The Sacramento Bee recently (April 8, 2008) published a reasonable editorial advocating a holistic approach to solving Delta problems.  But the editors chose language to describe the Delta such as:  it is “dying as the planet warms” and it is on the verge of “ecosystem collapse.” This language tracks that of groups that want to “save the Delta,” especially from proposed changes to its human-dominated plumbing system.

At the risk being labeled heretics, we say the Delta is not dying, and its ecosystem is not on the verge of collapse, but that it is changing.

The last time California faced real collapse of aquatic ecosystems was before the passage of the state and federal clean water acts in the 1970s, which eliminated or greatly reduced the dumping of huge volumes of toxic material into the estuary.  The present Delta, as measured by total fish populations, species diversity, navigability, migratory waterfowl abundance, and other measures, even water quality, is a ‘healthy’ ecosystem in many ways.

The most likely future Delta, even after widespread levee failure, will not feature a collapsed ecosystem (whatever that may be) or even a particularly unhealthy Delta ecosystem.  No matter what happens, there will still be fish and fisheries in the Delta, as well as boating, abundant wildlife, complex food webs and prosperous farms. But the future ecosystem may not have many of the species we find desirable today, especially endangered species such as delta smelt and winter-run Chinook salmon. Current land use patterns are also likely to change, away from urbanization and low-value agriculture.

If present trends continue, native fishes in the Delta will be replaced largely by alien species such as wakasagi smelt, Mississippi silversides, and largemouth bass. Deeply  subsided islands will be transformed via levee collapses to large open areas of tidal brackish water. These habitats will favor salt-tolerant species such as striped bass, starry flounder, crangon shrimp, splittail and various species of Japanese gobies.  In short, at least in the water, the fishes tell us that, no matter what happens, there will be thriving novel ecosystems that will support many of the same functions as today. The present ecosystem is already quite different from earlier manifestations of the ecosystem, especially the original historic ecosystem. Native species disappear while non-native species increase.

But we don’t have to accept whatever Delta ecosystem comes our way. To some extent, we can choose the species making up the future Delta ecosystem as well as many of its physical features, if we make some tough management decisions and accept that ecosystem changes will continue, some beyond our control.  Today’s somewhat foggy general vision of the Delta’s future seems to be that it will remain in its present configuration forever, with levees and channels maintained despite continual land subsidence, bigger storms, higher tides, and changing habitats and economies.  This Delta is assumed to continue as a freshwater system, thanks to large pulses of water from dams.  Despite these pulses, native fishes will gradually disappear, although fall-run Chinook salmon runs may continue due to hatcheries and trucking operations.  Delta smelt and longfin smelt will likely be extinct; they will no longer drive water decisions unless maintained by artificial propagation, like salmon. Fisheries for largemouth bass and other warm-water fishes will expand, dominating the system even more than today.

This vision does not have to prevail in all of the Delta.  We recently wrote a report that provides an alternative vision (Moyle et al. 2018, Making the Delta a Better Place for Native Fishes (   The vision we present is a modified version of some earlier thoughts (Moyle et al. 2013, and other references listed below).  The key to this vision is that management for native species and related values focuses on the North Delta Arc, a string of habitats connected by the Sacramento River.  The  Arc starts in the Yolo Bypass, continues through the Cache Slough region, then down the river past Rio Vista and into Suisun Marsh.  It also includes the Cosumnes-Mokelumne river corridor, to the Sacramento River.

Under this vision, the central and south Delta are treated as habitat that is, in fact, inhospitable for native fishes.  Indeed, native fishes may need to be excluded from these parts of the Delta, especially in summer.  The main issue for the central and south Delta is creation of a corridor for safe passage of adult and juvenile salmon and steelhead between San Francisco Bay and the San Joaquin, Tuolumne, Merced, and Stanislaus rivers.  This division of the Delta into two ecosystems is tacitly recognized already by most restoration projects (e.g., EcoRestore) as being located in the Arc.  This area provides the best opportunities because of habitat diversity and the fact that the Sacramento River connects these diverse habitats. The river also serves as the major migration corridor for fishes.

Our paper recommends 17 actions, listed below. Collectively, these actions could significantly improve habitat for native fishes, either directly or indirectly through stressor reduction and through development of new approaches via research. They at least will slow the ecosystem shift now occurring in favor of native species, floodplains, and wetlands.


  1. Four Easy Fixes (Fremont Weir, McCormick –Williams Tract, Delta smelt beaches, Putah Creek restoration).
  2. Expand Monitoring for Estuarine Health
  3. Provide a Water Right for the Environment
  4. Develop a Functional Flow Regime for the Delta
  5. Expedite Permitting and Implementation of Habitat Restoration Projects


  1. Expand EcoRestore and Learn from First 30,000 Acres
  2. Expand Restoration Projects in the North Delta Habitat Arc
  3. Establish Suisun Marsh as a Horizontal Levee
  4. Eliminate Predation Problems at Clifton Court Forebay
  5. Improve Delta Passage for Juvenile Salmon from the San Joaquin River and Tributaries.


  1. Reversing Subsidence in the Delta
  2. Accommodating Climate Change
  3. Reducing Impacts of Invasive species
  4. Reducing Impacts of Pesticides, Micro-contaminants, and Other Toxic Materials


  1. Experimenting with Island Flooding
  2. Evaluating Restoration Projects
  3. Developing a Stable Source of Innovative Research Funding.

As the report states: “The alternative to taking these and other actions is to continue on our present path, which is leading to the extinction of native fishes and the loss of significant fisheries for Chinook salmon, steelhead, striped bass and other fishes. It is important to remember that the Delta will always support a complex ecosystem. But whether that ecosystem is one that is desirable and consistent with our needs is up to us.”

The vision expressed by our report accepts that changes to the Delta ecosystem are inevitable but that, optimistically, we can collectively direct some of the change towards a more desirable state than will exist without high levels of additional activity. This vision can encompass actions favored by those who want to “save” the Delta, as well as those who envision a managed ecosystem that includes most of the remaining native fish fauna, as well as many other desirable elements, native and non-native.  It is not a vision that supports the rhetoric of a dying Delta or the Delta as a collapsed ecosystem, a rhetoric which does not lead to plausible actions to improve reality.

Peter B. Moyle is a UC Davis Professor Emeritus of fish biology and an associate director of the Center for Watershed Sciences. John Durand is a researcher specializing in estuarine ecology and restoration at the Center for Watershed Sciences.  Carson Jeffres is a researcher specializing in fish ecology at the Center for Watershed Sciences.

Further reading

Durand, J., P. Moyle, and A. Manfree. 2017. Reconciling conservation and human use in the Delta. UCD California Water Blog, February 12, 2017.

Hanak, E., J. Lund, J. Durand, W. Fleenor, B. Gray, J. Medellín-Azuara, J. Mount, P. Moyle, C. Phillips, and B. Thompson. 2013. Stress Relief: Prescriptions for a Healthier Delta Ecosystem. San Francisco: Public Policy Institute of California. Available at

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

Lund, J., E. Hanak, W. Fleenor, W. Bennett, R. Howitt, J. Mount, and P. B. Moyle.  2010. Comparing futures for the Sacramento-San Joaquin Delta. Berkeley University of California Press. 230 pp.

Moyle. P.B. W. Bennett, J. Durand, W. Fleenor, J. Lund, J. Mount, E. Hanak, and B. Gray. 2012. Reconciling wild things with tamed species- a future for native fish species in the Delta. California Water Blog. Center for Watershed Sciences, June 15, 2012.

Moyle, P. B., W. Bennett, J. Durand, W. Fleenor, B. Gray, E. Hanak, J. Lund, J. Mount. 2012. Where the wild things aren’t: making the Delta a better place for native species. San Francisco: Public Policy Institute of California. 53 pages.

Moyle, P. B., W. A. Bennett, W. E. Fleenor, and Jay R. Lund. 2010. Habitat variability and complexity in the upper San Francisco Estuary. San Francisco Estuary and Watershed Science  8(3): 1-24.

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

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

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

Moyle, P.B., C. Jeffres, and J. Durand. 2018, Making the Delta a Better Place for Native Fishes (

Opperman, J.J, P.B. Moyle, E.W. Larsen, J.L. Florsheim, and A.D. Manfree. 2017 Floodplains: Processes, Ecosystems, and Services in Temperate Regions. Berkeley: University of California Press.


Posted in Delta, Fish, Restoration, Sacramento-San Joaquin Delta, Uncategorized | Tagged , , | 10 Comments

Modeling, Measuring, and Comparing Crop Evapotranspiration in the Delta

by Jesse Jankowski

Crop evapotranspiration (ET) is the biggest managed loss of water in California, accounting for roughly 80% of human net water use, and includes crop water applications transpired from plants and evaporated from soil. Methods to estimate ET have been developed based on a robust scientific understanding of its physics and data collected in the field or remotely by aircraft or satellites. Irrigation decisions often incorporate approximations of ET to help meet crop water demands, aided by field data from a state-supported network of weather stations.

For water managers, accurate ET estimation is important in large-scale accounting to calculate water available for multiple uses. In the Sacramento-San Joaquin Delta, consumptive water use informs project operations and affects the availability of environmental flows for fish habitat and salinity management. Water rights transfers and impacts of land fallowing also can be quantified by comparing ET from specific crops and bare soil. States like Idaho, with simpler agricultural systems, rely on ET models with remotely-sensed data to administer water rights.

As local parties work to implement the Sustainable Groundwater Management Act (SGMA) in California, ET measurements and estimates will be particularly important in modeling surface and groundwater availability and interactions.

At the request of the State Water Resources Control Board Office of the Delta Watermaster, UC Davis’ Center for Watershed Sciences convened seven modeling teams and one field team from the UC Davis Department of Land, Air and Water Resources to measure and estimate ET from agricultural lands in the Delta during the 2015 and 2016 water years (October 2014 through September 2016). Participating modeling teams included the Department of Water Resources (CalSIMETAW and DETAW models), the USDA Agricultural Research Service (DisALEXI model), the Irrigation Training & Research Center at Cal Poly (ITRC-METRIC model), NASA’s Ames Research Center (SIMS model), and UC Davis (UCD-METRIC and UCD-PT models).

Field stations were deployed to five fallow fields in 2015 and 14 fields of the dominant land uses, alfalfa, corn, and pasture, in 2016. These sites provided ground-based data for comparison to the modeled ET estimates. Land use surveys for each year were used to analyze ET estimates and gauge trends for specific land uses; 26 crop categories were selected to compute total agricultural ET within the Delta.

The estimates vary but give a sense of the total annual ET in the Delta, show trends for major crops in the area, and help quantify uncertainties for different land covers and times of year. The comparative study also provided policy insights for the use of model and field data in water resource management and to help improve estimation of ET in California.

Delta Service Area, ET model estimates, and field stations deployed for this study.

A 2016 Interim Report included a “blind comparison” of the models for the 2015 water year only. The Final Report contains results which benefited from group learning, standardized input datasets, and access to the UC Davis field data for the 2015 and 2016 water years. The seven models estimated about 1.4 million acre-feet of annual consumptive water use in the Delta; each model was within 11% of this average. Most ET occurs during the summer growing season (March through September) from five major land uses: alfalfa, corn, fallow lands, pasture, tomatoes, and vineyards.

Estimated annual ET, in thousand acre-feet, from crops in the Delta in 2015 and 2016.      *Information about specific models is provided in technical appendices to the Final Report.

The most common crops in the Delta in both years were alfalfa, corn, and pasture, which made up about 40% of Delta agricultural land and nearly 60% of its annual crop ET. Fallow lands increased to about 17% of the Delta’s agricultural lands and crop ET in 2016, though the 20 days of field measurements over bare soil in 2015 suggested that evaporation could be lower than predicted by the models. The largest differences between models occurred late in the growing season for almonds, corn, and potatoes, and relative variations between estimates were larger in the non-growing season when lands are typically fallow and ET is low due to colder temperatures and cloudy skies.

Detailed comparisons between models suggest that model assumptions, alternate input datasets, and interpolation between satellite images contributed to most differences and uncertainties among ET estimates. Although estimates could be improved with further calibration, ET models will also differ due to their human components: even when automated with computers, the expertise of a modeler is required to develop, run, and use them.

Estimated total monthly ET, in thousand acre-feet, from major crops in the Delta in 2016.

Several policy insights and recommendations arise from this work:

  • Land use surveys such as the ones done for 2015 and 2016 in this study are valuable for water planning. Years of data shows trends in land use, like the increased fallowing in the Delta in 2016 which might show preparation for permanent tree or vine crops. When combined with other input data from satellites, field stations, or models, land use surveys also can help estimate ET from specific locations and areas. Support for land use surveys and additional information on irrigation methods, winter crops, and native versus invasive vegetation will be important for a variety of water management and policy decisions.
  • Remote sensing-based water use estimates are less labor-intensive, offer better coverage, and provide more standardized estimation than diversion reports from individual water users. Even if such estimates are sometimes less accurate, they are more consistent through space and time. The results of the seven different models in this study help quantify when and where these uncertainties might be larger, as even small errors represent water with potentially high economic value, particularly during droughts.
  • More accurate and understandable evapotranspiration data can support better water planning at regional scales with full-coverage information. Farm-scale irrigation management can be improved with high-resolution estimates, and water trading is aided by quantifying the water saved from crop shifts or land fallowing. Better ET estimates also improve the accuracy of water balances, for Delta water operations and for groundwater balances in critical basins across California implementing the Sustainable Groundwater Management Act.
  • Meteorology data collected in the field can be used to estimate ET on much finer scales. Microclimates like the “Delta Breeze” and other temperature and humidity variations may cause ET to be lower than expected by models, and specific irrigation and crop maintenance practices will have their own impacts. Additional field data is needed for ET from fallow lands, particularly on Delta islands below sea level. A new field study is underway for the 2018 growing season. More comparisons and cooperation across field measurements and model estimates will be especially useful for unique regions like the Delta.
  • Although this study focused on crop ET, about 12% of the Delta is natural vegetation such as woodlands, riparian zones, and floating plants. Another 18% is open water or urban areas. Some non-agricultural lands may have higher ET than crops, so habitat restoration efforts could increase regional consumptive water use. Because most estimation methods are tailored towards agricultural ET, further model refinements and more field data from both upland and riparian vegetation are needed.
  • Having the State of California establish a collaborative group of agencies, research centers, academic institutions, and consultants to continue the study of evapotranspiration in the Delta and elsewhere would help improve ET estimates and increase the effectiveness of state and local investments in ET estimation. The exchange of common datasets and standards enhances transparency, access to technical information, public knowledge, and reduces overall costs. The large amounts of data made publicly available through this project alone are a great opportunity for further research.

The Final Report for the project and full model and field datasets can be viewed at the project website.

Jesse Jankowski ( is a graduate student in Civil Engineering at UC Davis and a research assistant at the Center for Watershed Sciences.

Further Reading

Allen, R.G., Pereira, L.S., Raes, D. and Smith, M. Crop evapotranspiration- Guidelines for computing crop water requirements. Food and Agriculture Organization of the United Nations irrigation and drainage paper 56, 1998.

California Department of Water Resources. California Irrigation Management Information System- Resources. 2018.

California Department of Water Resources. Land Use Viewer. 2018.

Idaho Department of Water Resources. Mapping Evapotranspiration. 2018.

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

Mount, J., Chappelle, C., Gray, B., Hanak, E., Lund, J., Cloern, J., Fleenor, W., Kimmerer, W., and Moyle, P. California’s Water: The Sacramento-San Joaquin Delta. Public Policy Institute of California, 2016.

Posted in Agriculture, California Water, Delta, Planning and Management, Tools | Tagged , | 1 Comment