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 | 2 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 , , | 5 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 , | 5 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 , , , | Leave a comment

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

Reality Check of California Water Fix Model results in a Critical Flow Year

by William Fleenor

The San Joaquin (left) and Sacramento (right) rivers meet near Antioch, an important location for X2 management during dry years. (Image credit: Carson Jeffres)

In 2008 a group from the Center for Watershed Sciences (including this author), joined by an economist from the Public Policy Institute, published findings that suggested that an alternative conveyance for Sacramento River water might improve ecological conditions in the Delta and improve reliability for Delta water exports [1, 2].

The original 2013 draft of the Bay Delta Conservation Plan (BDCP) (DEIR/EIS) included several alternatives using tunnels for Delta conveyance [3].  Long-term planning of this nature requires greatly simplified hydrodynamic models to simulate decades of data to estimate performance under a range of variable conditions.  These models also require manipulation to account for physical effects they don’t simulate (e.g., changes in habitat and sea-level rise conditions for which future management is unknown).

The manipulation involves simulating habitat changes and sea-level rise with other models that have far more physically accurate numerical computations, but which run too slowly to simulate details over many decades.  With results from the more accurate detailed models, a simple model can be calibrated to simulate a fuller range of conditions.

For the BDCP, the results of slow, more detailed 2- and 3-dimensional models (already imperfect) are incorporated into DWR DSM2, a faster 1-dimensional model, and run for a longer period, producing additional errors.  Results from DSM2 are then used to create an artificial neural network (ANN) for salinity intrusion used in the still-faster DWR CalSim II model to simulate the decades of planning for the DEIR/DEIS (more potential errors).  CalSim II is a monthly model that cannot resolve issues occurring on a shorter time scale (e.g., spring/neap tidal cycles, real-time flow changes, 14-day average compliance requirements, etc.).  Nearly all decisions made in the DEIR/DEIS were made using long-term averages of monthly averages of CalSim II results.

An earlier review of the DEIR/DEIS [4] pointed out this potential cascade of errors and recommended that the higher dimensional models be simulated for shorter periods of stressful conditions (e.g., drought) to corroborate the results.  The corroboration would help ensure that decisions made from the results were reasonable.

The final EIR/EIS [5] of the California Water Fix (FEIR/EIS) was released December, 2016 and still lacks such efforts to corroborate the results of the long-term simulations.

Here, I applied the 2-dimensional model, RMA2, to simulate Delta flows and salinity with and without the CWF for conditions of water year 2008, a dry year.  It is the same software used in CWF to provide input to modify DSM2 for habitat restoration.  It is the last year for which Clifton Court Forebay intake data have been made publicly available. (It would be easy to argue that not releasing Clifton Court Forebay operations data is a violation of California law (SB54).  These data are vital for detailed modeling of Delta flows and water quality.)

Figure 5-53 (Fig 1 below) in the FEIR/EIS summarizes results with a long-term average of ~3.5 MAF of water exported in dry and critical years with ~1 MAF of that through north Delta diversions (NDD).  Actual exports for water year 2008 were 3.43 MAF, which was similar to the long-term average and used for simulation with ~1 MAF taken from the new NDD intakes.

Figure 1 Figure 5-53 from the FEIR/EIS demonstrating exports in dry and critical water years

In the initial effort, I could not apply every operational restriction identified in the FERI/EIS, lacking time and money to re-write internal model code.  I honored first pulse constraints and sweeping velocity constraints past the NDD locations.  Beyond those, I applied the maximum volume of intake at the NDD locations to produce the maximum change throughout the Delta.  Using these criteria, the NDD volumes exceed 60% of total exports during the highest Sacramento River flows (6,000 of 11,000 cfs), but less than 30% during lower flow periods (Fig 2).

Figure 2. Modeled exports from NDD and south Delta pumps.

This modeling effort demonstrates that the work of the FEIR/EIS should hold true during low-flow drought periods, and I commend those involved with the modeling.  But I remain critical of their lack of providing detailed model corroboration.

One of the most watched Delta regulations is X2, the distance in kilometers from the Golden Gate Bridge of 2 psu (practical salinity unit) near the bottom along the path of the Sacramento River.  Since X2 is usually downstream of the confluence of the two rivers, and my analysis made no changes in net outflow, the only differences occur in fall and winter (Fig 3).  NDD exports only produced minor changes in X2 that could be easily managed.

Figure 3. Changes in X2 during water year 2008 by CWF and Base case

The key to salinity in Delta and export water is salinity in Franks Tract (FT).  Once salt gets into FT it is pulled to the pumps.  A graph of salinity changes in eastern FT helps explain when NDD affects Delta salinity (Fig 4), which includes the ratio of Total Exports to NDD.

Figure 4. Eastern Franks Tract EC changes along with Total Exports/NDD ratio.

Interestingly, salinity in Franks Tract falls during lower flow periods with CWF.  Only during the highest Sacramento River flows with NDD exports exceeding 50% of Total Exports does salinity in Franks Tract increase during CWF simulation.  The improvements during the lower flow periods result from a lower proportion of inflow into FT from False River and Dutch Slough, and a higher percentage of inflow from the Old River connection at the San Joaquin River (SJR) (supplied by water from the San Joaquin River and Sacramento River via the Delta cross channel).

The greater salinity near the end of January correlates with abrupt increases in the ratio of Total/NDD exports and the lack of Sacramento River water through the closed cross-channel gates.  However, for Total/NDD export ratios approaching 50% in May-June, salinity still falls with CWF.  A follow-up simulation capping the Total/NDD ratio to 50% shows that any increases in salinity can be managed.  Not shown is the simultaneous pulse of salinity up the San Joaquin River contributing to the January increase.  All these effects are manageable with proper insight and monitoring of the Delta.

For any given total export rate, any NDD export should reduce the negative net Old & Middle River flows (OMR) from through-delta pumping, and create more natural flow patterns through the Delta.  With proper monitoring and management, the negative OMR flows could likely be eliminated during critical times.  Creating a more natural flow pattern while reducing fish ‘salvage’ at the south Delta pumps and producing a system with improved reliability while maintaining Delta water quality goals would seem to benefit  all interests.

William Fleenor is an affiliate of the U.C. Davis Center for Watershed Sciences. His research focuses on the development and application of numerical hydrodynamic models for water management.

Further reading

[1] Lund, J., E. Hanak, Wm. E. Fleenor, R. Howitt, J. Mount, and P. Moyle, Comparing Futures for the Sacramento-San Joaquin Delta, Public Policy Institute of California, 2008, 241 pg

[2] Fleenor, W., E. Hanak, J. Lund, and J. Mount, “Delta Hydrodynamics and Water Quality with Future Conditions,” Appendix C to Comparing Futures for the Sacramento-San Joaquin Delta, Public Policy Institute of California, San Francisco, CA, July 2008.

[3] ICF International, 2013, Administrative Draft Environmental Impact Report/Environmental Impact Statement for the Bay Delta Conservation Plan, prepared for Califronia Department of Water Resources, U.S. Bureau of Reclamation, U.S. Fish and Wildlife Service, and National Marine Fisheries Service

[4] Mount, J., Wm. Fleenor, B. Gray, B. Herbold, and W. Kimmerer, 2013, Panel Review of the Draft Bay Delta Conservation Plan, prepared for The Nature Conservancy and American Rivers

[5] ICF International, 2016, Final Environmental Impact Report/Environmental Impact Statement for the Bay Delta Conservation Plan/California WaterFix, prepared for Califronia Department of Water Resources and U.S. Bureau of Reclamation

Posted in California Water, Delta | Tagged , | 3 Comments

Groundwater Recovery in California – Still Behind the Curve

by Thomas Harter and Bill Brewster

California has a unique and highly variable climate in which drought reoccurs periodically. California began this century in a dry period from 1999 to 2005, and experienced droughts from 2007 to 2009, and 2012 to 2016.  Such wet-dry cycles can be seen in Figure 1, which shows total rainfall amounts per water year (water years run from October 1 to September 30). These dry cycles greatly affect the state’s groundwater basins.

Figure 1: California statewide annual precipitation. Source: DWR 2017

Despite the current storms, the 2018 water year is well below average, and that pattern may continue. But from a groundwater perspective, it’s clear that dry is the new norm.

Why do groundwater basins continue to suffer the impacts of drought long after the rains have returned?  As explained last spring, a single wet winter after a dry period can replenish snowpack, soil moisture, and surface water reservoirs, but groundwater basins may take many years or even decades to recover.

An average or wet winter may make up for water level losses of one dry year, but often not much more.  Also, the amount and location of groundwater level recovery varies with other factors such as the local reliance on groundwater or chronic overdraft.

At the end of the most recent drought, the near average 2016 precipitation in Northern California helped stabilize groundwater levels, and some areas saw groundwater level recovery. The extremely wet winter in 2017 expanded groundwater recovery to most of California (Figure 2).

Throughout California, the wet winter of 2017 refilled groundwater storage leading to higher water levels in spring of 2017, when compared to spring 2016. Source: DWR 2017

In many areas with significant groundwater pumping, therefore, two average to wet years are not enough for groundwater to recover from several dry or drought years.  For example, the change in groundwater levels over the last 5 years (Figure 3) or the past 10 or 17 years (Figure 4) shows that groundwater aquifer conditions can have a long memory.

Figure 3: In most of California’s groundwater basins, the wet winter of 2017 did not refill groundwater storage to where it was before the 2012-2016 drought, in the spring of 2012. Source: DWR 2017

Figure 4: For most of California, 12 of the past 18 winters (and 7-8 of the past 11 winters) were below average or dry. As groundwater levels in most basins need one average or wet winter to recover from one below average or dry year, many areas are several average to wet years short of reaching water levels observed in spring 2000. Source: DWR.

The lack of groundwater level recovery is partly from persistent below-average precipitation in the past 20 years. This can be seen by comparing the long-term change in groundwater levels with the cumulative deviation from average (CDFM) statewide rainfall (Figure 5). The recent twenty-year sequence of more below-average years than average or wet years appears as a decline in the orange line in Figure 5. For comparison, DWR’s groundwater data and tools website includes groundwater level change maps of the difference in groundwater elevations over various time periods, with pie charts indicating the regional and statewide percent of wells increasing, decreasing, or staying relatively neutral (e.g., Figures 2 and 3). We can construct a groundwater level change index, for example, by subtracting the statewide percent of wells with increasing water levels from the statewide percent of wells with decreasing water levels over a period of time.  A positive number indicates more wells had increased water levels than decreased water levels, while a negative number means more wells have lower water levels than higher water levels.  For example, for Figure 2, the statewide groundwater level change index for 2016-2017 is computed as (30.7%+5.4%-1.0%-6.3%) = +28.8%.

The cumulative deviation from mean statewide precipitation (CDFM) since 1896 (blue line) shows that we reached peak surplus in 1983, 1998 and 2006. But by 2016, after a nearly steady ten-year decline, the deficit reached levels similar to the early 1990s. Note that the CDFM is, by definition, zero at the beginning and end of the averaging period.
Average and wet years can make up for groundwater decline in below-average years: The orange line indicates the difference between the total number of average to wet years to date and the number of below average to dry years to date. If an “average year” includes any year with at least 97% of average precipitation, then an equal number of years have been “average or above” years and “below average or dry” years since 1896 (difference = 0). For 1998 to 2017, five more years were “below average or dry” than “average or above”.

Figure 6 shows this groundwater level change index for 1, 3, 5, and 10 year periods preceding each year from 2012 through 2017. The long-term trends of all four indices – perhaps most so for the 10-year index – are similar to the precipitation trends– as precipitation deficit increases, the groundwater level change index becomes more negative (more and more wells with decreasing water levels). However, as the deficit decreases, fewer wells have decreasing water levels, and more wells have increasing water levels.  This very simple analysis doesn’t account for other factors that can affect long-term changes in groundwater levels, but shows the strong effect of the continued precipitation deficit, relative to 1998.

Figure 6: Comparison of the CDFM (blue) shown in the previous figure with a groundwater level change index that captures relative groundwater level change over the last 1 year, 3 years, 5 years, and 10 years prior to the year indicated at the bottom axis. The 10 year index most closely follows the precipitation CDFM.

What should well owners and operators expect for summer and fall of 2018 if it remains a below average to dry year? This would be like 2007 and 2012.  Both 2007 and 2012 followed wet years with surface reservoirs in good condition, like 2018.  Additionally, 2007 and 2012 had below average precipitation and a thin snowpack.

So, with a below average to dry 2018, groundwater levels would likely decline similarly to 2007 and 2012, but not as drastically as in 2014 or 2015 when additional groundwater pumping occurred from lack of available surface water for irrigation (Figure 7).

Figure 7: Unless April is exceptionally wet, expected water level changes between last fall and this coming fall will be of similar magnitude as between fall of 2011 (following a wet winter) and fall of 2012 (following a relatively dry winter, but with surface water storage carry-over from 2011 to support cities and agricultural irrigation). Source: DWR.

One thing is certain – California’s climate will continue to be variable.  And if the past 20 years are a guide, groundwater levels may have a difficult time recovering.  This reinforces the importance of drought contingency planning, especially for overdrafted groundwater basins and in basins with issues related to declining groundwater levels.

Thomas Harter is a Professor and Associate Director at the Center for Watershed Sciences. Bill Brewster is a Senior Engineering Geologist with the California Department of Water Resources.

 Further reading

CaliforniaWaterblog. Post-drought groundwater in California: Like the economy after a deep “recession,” recovery will be slow.

DWR Drought Page

Spring 2017 Groundwater Level Data Summary

USGS Runoff Estimates for California

DWR Groundwater Information Center Interactive Map Application

DWR Data and Tools Page

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