California isn’t running out of water; it’s running out of cheap water

by Wyatt Arnold

A California water myth which becomes especially pernicious in droughts is that California is “running out of water” (Hanak et al. 2009). Viewing California’s supply and demand pressures in terms of fixed water requirements perpetuates this myth and invariably places undue attention on building additional supply infrastructure. Instead, managing water as a scarce resource suggests a balanced portfolio of water trading, investments in conveyance, smart groundwater replenishment, and demand management. With such a balanced portfolio, 1) California’s water supply situation is not broadly dire, and 2) California’s vast and interconnected water infrastructure and groundwater resources can minimize most problems from the state’s highly variable climate.

An economics-driven model of California’s water system, the California Value Integrated Network (CALVIN), has provided such insight from several perspectives, including climate change, groundwater, water markets, and reservoir operations. But in many of these studies, authors lamented an unrealized potential to capture the impact of hydrologic variability more realistically. With perfect foresight, CALVIN was run with complete foreknowledge of 82-years of hydrology – giving exactly optimal solutions to managing reservoir over-year (“carryover”) storage through multi-year droughts, for example. Now, with access to high performance computing resources, a limited foresight carryover storage value function (COSVF) method (Draper 2001) has been applied to California’s entire system – more than 26 surface reservoirs and over 30 groundwater basins (Arnold 2021, Khadem 2018).  These model runs are the most comprehensive and realistic analyses of the potential for broad integrated portfolios of actions across water agencies to address California’s water supply problems.

So, what do these new limited foresight CALVIN results tell us about California’s water supply? Here are three things to get started:

  • From the standpoint of long-term average marginal economic value of water, perfect and limited foresight closely agree; however, limited foresight is more relevant for the risk averse, who prefer to minimize larger but rarer shortages at the cost of average performance.
  • Limited foresight results also suggest that, in general, increasing the storage capacity of reservoirs in California has a very low marginal economic benefit relative to other infrastructure investments like conveyance and groundwater pumping capacities.
  • A large range of carryover storage and conjunctive use operations yield similar statewide economic performance (summing water operation and scarcity costs statewide over 82 years of wet and dry conditions). Consideration of a broad portfolio of conjunctive use, trading, water conservation, and local infrastructure options may not significantly change major surface reservoir operations.

Economics of Carryover Storage

Many reservoirs in California have been drawn down to near record low levels in the current drought. People are alarmed that reservoir storages are so low after only two dry years and are speculating whether prudent decisions were made about storage management. Climate change is making these decisions riskier, yet modeling the historical record remains important as a frame of reference.

Here, I focus on Shasta, Oroville, and off-stream San Luis carryover operations suggested by the new limited foresight optimization results and compare with carryover storage simulated by two versions of the State’s reservoir system model, CalSim-II, to shed light on how and why the system’s carryover storage is so volatile.

Figure 1 shows the time series of carryover operations modeled through two of California’s notorious droughts. The first thing to notice is that total carryover storage varies a lot from year to year for all models. Second, all models tend to quickly draw down carryover storage in dry years – only perfect foresight CALVIN, knowing the exact length and depth of drought in advance, maintains and draws down carryover storage in the final year of drought. Third, CalSim-II simulated carryover storage – both the Water Storage Investment Program run and the recent Delivery Capability Report 2019 run – lie just above the sampled range of limited foresight runs, suggesting near-optimal operations (blue shaded region) during dry years and droughts.

Without a crystal ball, it is not economical to maintain too much carryover or drought surface water storage. The probability of refilling the following year is high, both due to the volume of carryover storage capacity relative to annual runoff and the low year-to-year correlation of annual runoff. Lower carryover storage raises groundwater pumping in the latter year(s) of drought, but also reduces average groundwater use and pumping costs and helps reduce groundwater overdraft (see Figure 2). Also, higher reservoir releases tend to reduce shortages where access to groundwater is limited, which lowers average shortage costs. Sustaining higher carryover volumes (upper end of the limited foresight range and CalSim-II alike) provides more surface supply in the latter year(s) of a drought, which reduces maximum shortage costs; however, the more risk-averse operation raises long-term average costs and the marginal value of groundwater that would eliminate overdraft. Limited foresight modeling (both optimization and CalSim-II) tends to use more groundwater in drier years (Figure 2), which points to groundwater’s importance as a buffer against hydrologic uncertainty.

Figure 1. Total carryover storage (ending September) of Shasta, Oroville, and San Luis as modeled by perfect and limited foresight CALVIN and CalSim-II Delivery Capability Report 2019 (CS-II DCR 2019) and Water Storage Investment Program (CS-II WSIP) historical runs. Drought periods of 1976-77 and 1987-92 are shaded in light tan. The limited foresight range is based on 26 near-optimal statewide solutions.
Figure 2. Total groundwater pumping volume in the Central Valley as modeled by CALVIN for perfect foresight, limited foresight, and with reservoir carryover storage fixed to CalSim-II Water Storage Investment Program historical run outputs.

Other Considerations for Carryover Storage

Water supply is not the sole objective of carryover storage operations. Federal and State operators of Shasta and Oroville reservoirs seek to maintain storage reserves for environmental requirements. For example, Shasta’s carryover storage objectives include maintenance of a cold-water pool to support Salmon habitat in the Sacramento River. Other economic objectives include recreation and hydropower. CalSim-II’s higher carryover storage relative to limited foresight CALVIN are partially attributable to these objectives in addition to Federal and State contractual water supply obligations to Sacramento and Feather River water rights holders. While CALVIN incorporates minimum environmental flow constraints, more complex environmental requirements such as cold-water pool management and some Delta operational constraints are less well represented. Nevertheless, the limited foresight CALVIN results provide a more realistic representation of the economic value of carryover storage in California’s multi-reservoir conjunctive use system.

Concluding Thoughts

Aggressive use of carryover water storage in California’s major reservoirs is economically prudent and reduces overall groundwater reliance. Water supply risks of lower carryover storage are further mitigated through greater system integration such as increased water trading, groundwater banking, and drought water use reductions. The higher risks of having low carryover storage, although not quantified here, appear to fall on California’s stressed ecosystems. A warming climate, expected to continue through at least mid-century even with aggressive global greenhouse gas mitigation, is changing runoff timing, magnitude, and frequency in ways that will make managing carryover storage more challenging. Future work should focus on this aspect and incorporate alternative hydrologic traces reflecting expected climate changes.

Further Reading

Arnold, Wyatt. 2021. The Economic Value of Carryover Storage in California’s Water Supply System with Limited Hydrologic Foresight. [MS, UC Davis]. Available at: https://watershed.ucdavis.edu/shed/lund/students/WyattArnoldThesis2021.pdf

Draper, A. J. 2001. Implicit Stochastic Optimization with Limited Foresight for Reservoir Systems. [PhD, UC Davis]. https://watershed.ucdavis.edu/shed/lund/students/DraperDissertation.pdf

Hanak, Ellen, Jay Lund, Ariel Dinar, Brian Gray, Richard Howitt, Jeffrey Mount, Peter Moyle, et al. 2009. “California Water Myths.” Public Policy Institute of California.

Khadem, M., C. Rougé, J. J. Harou, K. M. Hansen, J. Medellin‐Azuara, and J. R. Lund. 2018. Estimating the Economic Value of Interannual Reservoir Storage in Water Resource Systems.” Water Resources Research 54 (11): 8890–8908.

Wyatt Arnold recently completed a master’s degree in Civil and Environmental Engineering at the University of California – Davis.  He currently works for the California Department of Water Resources in the Climate Adaptation Program.

Data from CalSim-II runs are available on the California Natural Resources Agency OpenData site: 1) Water Storage Investment Program model (1995 Historical Detrended run) available at https://data.cnra.ca.gov/dataset/climate-change-projections-wsip-2030-2070, 2) Delivery Capability Report 2019 run available at: https://data.cnra.ca.gov/dataset/state-water-project-delivery-capability-report-dcr-2019 

Posted in Uncategorized | 6 Comments

California isn’t running out of water; it’s running out of cheap water

by Wyatt Arnold

A California water myth which becomes especially pernicious in droughts is that California is “running out of water” (Hanak et al. 2009). Viewing California’s supply and demand pressures in terms of fixed water requirements perpetuates this myth and invariably places undue attention on building additional supply infrastructure. Instead, managing water as a scarce resource suggests a balanced portfolio of water trading, investments in conveyance, smart groundwater replenishment, and demand management. With such a balanced portfolio, 1) California’s water supply situation is not broadly dire, and 2) California’s vast and interconnected water infrastructure and groundwater resources can minimize most problems from the state’s highly variable climate.

An economics-driven model of California’s water system, the California Value Integrated Network (CALVIN), has provided such insight from several perspectives, including climate change, groundwater, water markets, and reservoir operations. But in many of these studies, authors lamented an unrealized potential to capture the impact of hydrologic variability more realistically. With perfect foresight, CALVIN was run with complete foreknowledge of 82-years of hydrology – giving exactly optimal solutions to managing reservoir over-year (“carryover”) storage through multi-year droughts, for example. Now, with access to high performance computing resources, a limited foresight carryover storage value function (COSVF) method (Draper 2001) has been applied to California’s entire system – more than 26 surface reservoirs and over 30 groundwater basins (Arnold 2021, Khadem 2018).  These model runs are the most comprehensive and realistic analyses of the potential for broad integrated portfolios of actions across water agencies to address California’s water supply problems.

So, what do these new limited foresight CALVIN results tell us about California’s water supply? Here are three things to get started:

  • From the standpoint of long-term average marginal economic value of water, perfect and limited foresight closely agree; however, limited foresight is more relevant for the risk averse, who prefer to minimize larger but rarer shortages at the cost of average performance.
  • Limited foresight results also suggest that, in general, increasing the storage capacity of reservoirs in California has a very low marginal economic benefit relative to other infrastructure investments like conveyance and groundwater pumping capacities.
  • A large range of carryover storage and conjunctive use operations yield similar statewide economic performance (summing water operation and scarcity costs statewide over 82 years of wet and dry conditions). Consideration of a broad portfolio of conjunctive use, trading, water conservation, and local infrastructure options may not significantly change major surface reservoir operations.

Economics of Carryover Storage

Many reservoirs in California have been drawn down to near record low levels in the current drought. People are alarmed that reservoir storages are so low after only two dry years and are speculating whether prudent decisions were made about storage management. Climate change is making these decisions riskier, yet modeling the historical record remains important as a frame of reference.

Here, I focus on Shasta, Oroville, and off-stream San Luis carryover operations suggested by the new limited foresight optimization results and compare with carryover storage simulated by two versions of the State’s reservoir system model, CalSim-II, to shed light on how and why the system’s carryover storage is so volatile.

Figure 1 shows the time series of carryover operations modeled through two of California’s notorious droughts. The first thing to notice is that total carryover storage varies a lot from year to year for all models. Second, all models tend to quickly draw down carryover storage in dry years – only perfect foresight CALVIN, knowing the exact length and depth of drought in advance, maintains and draws down carryover storage in the final year of drought. Third, CalSim-II simulated carryover storage – both the Water Storage Investment Program run and the recent Delivery Capability Report 2019 run – lie just above the sampled range of limited foresight runs, suggesting near-optimal operations (blue shaded region) during dry years and droughts.

Without a crystal ball, it is not economical to maintain too much carryover or drought surface water storage. The probability of refilling the following year is high, both due to the volume of carryover storage capacity relative to annual runoff and the low year-to-year correlation of annual runoff. Lower carryover storage raises groundwater pumping in the latter year(s) of drought, but also reduces average groundwater use and pumping costs and helps reduce groundwater overdraft (see Figure 2). Also, higher reservoir releases tend to reduce shortages where access to groundwater is limited, which lowers average shortage costs. Sustaining higher carryover volumes (upper end of the limited foresight range and CalSim-II alike) provides more surface supply in the latter year(s) of a drought, which reduces maximum shortage costs; however, the more risk-averse operation raises long-term average costs and the marginal value of groundwater that would eliminate overdraft. Limited foresight modeling (both optimization and CalSim-II) tends to use more groundwater in drier years (Figure 2), which points to groundwater’s importance as a buffer against hydrologic uncertainty.

Figure 1. Total carryover storage (ending September) of Shasta, Oroville, and San Luis as modeled by perfect and limited foresight CALVIN and CalSim-II Delivery Capability Report 2019 (CS-II DCR 2019) and Water Storage Investment Program (CS-II WSIP) historical runs. Drought periods of 1976-77 and 1987-92 are shaded in light tan. The limited foresight range is based on 26 near-optimal statewide solutions.
Figure 2. Total groundwater pumping volume in the Central Valley as modeled by CALVIN for perfect foresight, limited foresight, and with reservoir carryover storage fixed to CalSim-II Water Storage Investment Program historical run outputs.

Other Considerations for Carryover Storage

Water supply is not the sole objective of carryover storage operations. Federal and State operators of Shasta and Oroville reservoirs seek to maintain storage reserves for environmental requirements. For example, Shasta’s carryover storage objectives include maintenance of a cold-water pool to support Salmon habitat in the Sacramento River. Other economic objectives include recreation and hydropower. CalSim-II’s higher carryover storage relative to limited foresight CALVIN are partially attributable to these objectives in addition to Federal and State contractual water supply obligations to Sacramento and Feather River water rights holders. While CALVIN incorporates minimum environmental flow constraints, more complex environmental requirements such as cold-water pool management and some Delta operational constraints are less well represented. Nevertheless, the limited foresight CALVIN results provide a more realistic representation of the economic value of carryover storage in California’s multi-reservoir conjunctive use system.

Concluding Thoughts

Aggressive use of carryover water storage in California’s major reservoirs is economically prudent and reduces overall groundwater reliance. Water supply risks of lower carryover storage are further mitigated through greater system integration such as increased water trading, groundwater banking, and drought water use reductions. The higher risks of having low carryover storage, although not quantified here, appear to fall on California’s stressed ecosystems. A warming climate, expected to continue through at least mid-century even with aggressive global greenhouse gas mitigation, is changing runoff timing, magnitude, and frequency in ways that will make managing carryover storage more challenging. Future work should focus on this aspect and incorporate alternative hydrologic traces reflecting expected climate changes.

Further Reading

Arnold, Wyatt. 2021. The Economic Value of Carryover Storage in California’s Water Supply System with Limited Hydrologic Foresight. [MS, UC Davis]. Available at: https://watershed.ucdavis.edu/shed/lund/students/WyattArnoldThesis2021.pdf

Draper, A. J. 2001. Implicit Stochastic Optimization with Limited Foresight for Reservoir Systems. [PhD, UC Davis]. https://watershed.ucdavis.edu/shed/lund/students/DraperDissertation.pdf

Hanak, Ellen, Jay Lund, Ariel Dinar, Brian Gray, Richard Howitt, Jeffrey Mount, Peter Moyle, et al. 2009. “California Water Myths.” Public Policy Institute of California.

Khadem, M., C. Rougé, J. J. Harou, K. M. Hansen, J. Medellin‐Azuara, and J. R. Lund. 2018. Estimating the Economic Value of Interannual Reservoir Storage in Water Resource Systems.” Water Resources Research 54 (11): 8890–8908.

Wyatt Arnold recently completed a master’s degree in Civil and Environmental Engineering at the University of California – Davis.  He currently works for the California Department of Water Resources in the Climate Adaptation Program.

Data from CalSim-II runs are available on the California Natural Resources Agency OpenData site: 1) Water Storage Investment Program model (1995 Historical Detrended run) available at https://data.cnra.ca.gov/dataset/climate-change-projections-wsip-2030-2070, 2) Delivery Capability Report 2019 run available at: https://data.cnra.ca.gov/dataset/state-water-project-delivery-capability-report-dcr-2019 

Posted in Uncategorized | 3 Comments

Home is where the habitat is

 by Dylan Stompe, Teejay O’Rear, John Durand, and Peter Moyle

            The San Francisco Estuary (estuary) is sometimes called the most invaded estuary in the world, and for good reason. Through many avenues, hundreds, if not thousands, of species have been introduced to San Francisco Bay, the Delta, and their rivers. Some introductions were byproducts of human activity and include organisms that “hitchhiked” on the bottom of boats or as stowaways in ballast water carried by international shipping vessels. Others were deliberate and undertaken either legally by the government or illicitly by individuals for biocontrol, fisheries, or disposal of unwanted pets.

            The U.S. Fish and Wildlife Service (USFWS) defines aquatic invasive species as “aquatic organisms that invade ecosystems beyond their natural, historic range.” Under this definition, any species brought into the estuary and establishes a self-sustaining population would be considered an aquatic invasive. However, we challenge that assertion given the current state of much of the estuary. If we focus on the historic range of an organism strictly as a function of geography, then the organisms introduced by people to the estuary are invasive aquatic organisms under the USFWS definition. If, however, if we interpret the natural range to encompass the habitats to which species are native, then many non-native species would be considered right at home in the estuary.

            For example, much of the Delta is made up of waterways that resemble southeastern lakes (such as Lake Okeechobee) much more so than they resemble the historic Delta habitat of sloughs and marshes. These new habitats are largely constrained by levees, eliminating the vast marshes and floodplains that once existed. Compounding these landscape changes are highly altered flow regimes. Upstream reservoirs capture water and control its release, dampening winter floods and increasing summer flows. The flatter hydrograph and modified landscape have made the Delta much more suitable habitat for many introduced species. These species are well-adapted to the low flows, increased water clarity, higher temperatures, large beds of aquatic weeds, and other features of the modern Delta. 

             Sadly, some native species, such as Delta smelt, are actually strangers to these altered habitats. While they are geographically native, the traits that once made them so abundant in the Delta are maladaptive in these new habitat conditions. Much like we would not expect Delta smelt to succeed if introduced to Lake Okeechobee, it should not be surprising that they are no longer successful in the warm, clear, and highly vegetated waters of the Delta.

            Take a breath! Contrary to what you may be thinking right now, we are not proposing to give up on species such as the Delta smelt. We are suggesting that trying to reestablish this species in poorly suitable habitats is extremely difficult. While there is a legal and moral obligation to help sustain Delta smelt and other critically endangered species, the Delta will require radical restoration for Delta smelt to persist in their native geographic range. State and federal agencies, as well as some private groups, have begun implementing a number of measures, including habitat restoration and hatchery supplementation, but these are slow to implement and unlikely to reverse the immediate extinction spiral (Börk et al. 2020). Rather than wait for better Delta solutions to emerge, creative solutions to sustain wild Delta smelt outside of the hatchery setting should be explored.

            One potential solution is to establish self-sustaining, non-hatchery-supplemented Delta smelt refuge populations in reservoirs with suitable conditions. A proof-of-concept has already been established by the Delta smelt’s cousin wakasagi (Hypomesus nipponensis), which was planted and is currently thriving in several Sierra reservoirs, such as Oroville, Rollins, and Almanor. Habitat requirements for these species are similar, and many reservoirs are cool, dark at depth, and have abundant zooplankton – conditions Delta smelt need. Wakasagi and Delta smelt will hybridize, so Delta smelt cannot be stocked into reservoirs that already contain wakasagi. But many reservoirs similar to Oroville and Almanor exist where wakasagi are absent: Mountain Meadows, Union Valley, Davis, Frenchman, and Britton, to name a few.

Figure 1. Lake Davis at sunset. “Lake Davis” by seabamirum is licensed with CC BY 2.0. To view a copy of this license, visit https://creativecommons.org/licenses/by/2.0/

This form of “assisted migration” has worked for another Delta fish that recently became extinct in its “natural, historic range”: Sacramento perch. Sacramento perch was once so abundant in the Delta that it supported a commercial fishery, but it is no longer found in its historic waters. It has avoided extinction, however, by its successful introduction to farm ponds and reservoirs across the American West. While these populations of perch are not strictly “native,” they have saved the species from extinction and preserve some of their cultural, ecological, and recreational value.

            Sometimes we daydream about what our estuary once looked like and the epic amounts of salmon, smelt, and other native species that once swam in its waters. Unfortunately, it’s wishful thinking to believe that the daydream will be anything more than that given the magnitude of change in the estuary. The Delta smelt inhabits a novel ecosystem that contains very little habitat that could be considered natural for it. Additionally, some invasive species, such as the overbite clam (Potamocorbula amurensis) and Brazilian waterweed (Egeria densa), have caused habitat shifts that are nearly irreversible and these species are going nowhere.  Further, they’re no doubt going to be joined by new species that will further alter the Delta from its historic state, such as the recently introduced alligatorweed (Alternanthera philoxeroides; Walden et al. 2019). Therefore, novel management strategies must be used to keep species such as Delta smelt from going extinct. So, this begs the question – if we have thousands of Delta smelt in a hatchery, why not take a page out of the Sacramento perch playbook and plant them in some reservoirs while we still have smelt to plant?

            Do the best you can with what you’ve got – the Delta is currently not the best we’ve got for Delta smelt. The best we got – it’s the reservoirs.

Dylan Stompe is a fisheries researcher and graduate student at the Center for Watershed Sciences. Teejay O’Rear is a fish ecologist at the Center for Watershed Sciences and lab supervisor for Dr. John Durand. Peter Moyle is Distinguished Professor Emeritus at the University of California, Davis 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.

Further Reading

Börk, K., Moyle, P., Durand, J., Hung, T., Rypel, A. L. 2020. Small populations in jeopardy: delta smelt case study. Environmental Law Reporter, 50(9), 10714-10722

Cohen, A.N., Carlton, J.T. 1998. Accelerating invasion rate in a highly invaded estuary. Science, 279(5350), 555-558.

Crain, P.K., Moyle, P.B. 2011. Biology, history, status and conservation of Sacramento perch, Archoplites interruptus. San Francisco Estuary and Watershed Science, 9(1).

Moyle, P.B. 2021. Can Japanese Smelt Replace Delta Smelt? California Water Blog. https://californiawaterblog.com/2021/02/07/can-japanese-smelt-replace-delta-smelt/

O’Rear, T., Moyle, P.B., Durand, J.R. 2018. Delta Smelt and Salmon Habitats Beyond the Estuary. Presentation. https://watershed.ucdavis.edu/library/delta-smeltand-salmon-habitats-beyond-estuary.

Walden, G. K., G. M. S. Darin, B. Grewell, D. Kratville, J. Mauldin, J. O’Brien, T. O’Rear, A. Ougzin, J. V. Susteren, P. W. Woods.  2019.  Noteworthy collections, California (Alternanthera philoxeroides). Madrono 66(1): 4-7.

Posted in Uncategorized | 2 Comments

Drought Makes Conditions Worse for California’s Declining Native Fishes

Long Valley speckled dace and Whitmore Marsh, its last natural native habitat in the Owens Valley. Other habitats have been heavily modified by poor landuse and mostly dried up.  Photos by J. Katz and P. Moyle.

by Peter Moyle and Andrew Rypel

California is home to 131 kinds of native fishes that require freshwater for some or all of their life-cycle. Most of these fishes are found only in California and most (81%) are in decline (Moyle et al. 2015, 2020). Thirty-two (24%) are already listed as threatened or endangered by state and/or federal governments. Declines are usually the result of fishes losing the competition with humans for California’s water and habitat (Leidy and Moyle 2021). This competition is heightened by the ongoing severe drought.  Thus, there is a petition circulating to declare the delta smelt extinct to make supposedly large amounts of water available to farmers, even though the smelt is not extinct and the amount of water devoted to delta smelt is small (Börk et al. 2020). Winter-run Chinook are being vilified because they require cold-water releases from Shasta Reservoir even though the lack of cold water mostly results from poor management of the reservoir’s pool of water. In the Klamath River Basin, farmers are angry because they are not being provided with water from Upper Klamath Lake, blaming the demands of endangered suckers and salmon, even though juvenile salmon in the river are already dying in this extraordinary drought.

One response to these ongoing problems is federal and state financial relief for farmers.  For example, California politicians have proposed state and federal funding to improve canals that deliver water to farmers in the San Joaquin Valley. Yet deterioration of the canals was created by over-drafting ground water, causing land and canals to subside. Some $800 million in government funds is proposed to subsidize this infrastructure repair, that will mostly go to improving the ability of farmers to take water away from fish. An equivalent bill to improve access of native fishes to water or improve their habitats does not seem to be in the works.

              If native fishes are going to persist through this extended drought (there is no end in sight), a statewide program of monitoring, emergency, and preparatory actions is needed. This program needs to check on the condition of all native fishes annually, with the capacity to take action if key habitats are drying up or are otherwise becoming unsuitable.  Here are some examples that reflect the diversity of actions that are ongoing or needed to keep California’s native fishes viable despite the combined immediate threats of competition for water with people and loss of habitat by drought. In general, species listed under the federal Endangered Species Act (ESA) are more likely to have resources devoted to their recovery than are species that are not listed. More complete information on these example species can be found in Moyle et al. 2015, 2017.

              The central coast Coho salmon is listed as endangered under federal and state ESAs  because of loss of habitat combined with reductions in stream flows, often drought related. This fish has been brought back from the brink of extinction by a combination of intensive management of Lagunitas Creek (Marin County) and an innovative captive breeding program at the Dry Creek Hatchery. Coho have the advantage of being charismatic, as sleek sea-run fish that are highly visible when they spawn, reminding people that California coho once supported extensive sport and commercial fisheries.

              The Sacramento splittail once lived throughout the Central Valley and upper San Francisco Estuary.  The only population remaining today spawns on flooded vegetation especially in the Yolo Bypass. After spawning the fish return to their main rearing area, Suisun Marsh, followed by the juveniles a few months later.  They were listed as a federally threatened species for a short time but the designation was rescinded when studies revealed their remarkable resilience, even during short droughts. But their total distribution is increasingly restricted and persistence through long droughts will be increasingly difficult, without help, such as providing more reliable floodplain habitat for spawning.

              The northern California roach is a small minnow largely confined to springs and isolated small streams in the upper Pit River watershed in California and Oregon. Its original description as a distinct species in 1908 was largely ignored by subsequent workers. Baumsteiger and Moyle (2017), however, using genomic techniques, validated the species distinctiveness. Its current status, especially in California, is poorly known but most of its known habitats are degraded by poor land management (e.g., livestock grazing) and other factors, exacerbated by drought. This species may easily disappear unnoticed from California if steps not taken to protect it and its habitats.

              The Long Valley speckled dace is another small minnow headed for extinction because it had not been seen as unique. An unpublished genomics study reveals that it is quite different from other dace and has been isolated for thousands of years in the streams and marshes of the Owens Valley region. These habitats are disappearing as the water disappears.  Its last natural refuge is Whitmore Marsh, which is watered by a hot spring, now converted to a swimming pool.  The only other population is in a small pond monitored by CDFW at the White Mountain Research Station. Neither population can be regarded as secure.

              Green sturgeon are ancient survivors, reaching 2-3 m in length and living 50-75 years or more. Like salmon, they are anadromous, spending most of their time in the ocean.  Unlike salmon however, they spawn many times throughout their long lives. There are two distinct populations recognized, the southern green sturgeon and the northern green sturgeon. The former consists of small population that spawns in the Sacramento River, while the latter spawns in north coast streams, principally the Klamath River and the Rogue River (Oregon). The southern population is listed as a threatened species and is likely further threatened by drought-reduced flows in the Sacramento River. Thanks to its being ESA-listed, however, considerable resources have been devoted to it, so managers can take advantage of new knowledge of its life history requirements. The northern population in the Klamath River supports a small tribal fishery which is threatened by reduced flows and temperatures. The 2002 fish kill in the lower Klamath, caused by low flows in combination with disease, is famous for killing thousands of adult salmon and also killed a few green sturgeon.

              Clear Lake Hitch is a native fish that is found exclusively in Clear Lake, Lake County, where it was once an abundant food for the indigenous Pomo people.  Formerly, it ascended tributary streams by the thousands to spawn in the spring. Hitch numbers are greatly reduced due to alteration and diversion of its spawning streams and to predation by non-native fishes in the lake. Reductions in flows are particularly a problem in drought years. Furthermore, Clear Lake struggles with blue-green algae blooms, especially during hot summers, which functionally limits the oxythermal habitat of fishes like the Clear Lake hitch, and can also can fish kills (Till et al. 2019). Importantly, Clear Lake also has a history of native fish extinctions; the Clear Lake Spilttail (another species only found in Clear Lake) has not been captured since 1970 and is presumed extinct. Local people monitor the hitch populations but funding for habitat restoration and other actions is limited, so the future of these fish is far from secure, despite being listed as Threatened under the state ESA and despite its importance to Pomo culture.

Each of California’s native fishes have a similar story, even species not threatened with extinction. But the most threatened species need special attention. The more obscure species need be protected by champions who watch out for their welfare, such as the CDFW biologist who checks up on Red Hills roach in their tiny streams, ready to mount a rescue operation if needed. Ultimately, each species needs protection in their special habitats, preferably as a statewide system of managed watersheds that protect more than just threatened fish (Howard et al 2018). We discussed many of these issues at length in a recent blog post.

Winter-run Chinook salmon and Delta smelt are examples of species that have been saved from extinction so far by extraordinary measures, as prescribed under the state and federal ESAs. These acts have managed to prevent extinction of most listed California fishes so far, but drought, combined with threats from activities by people, is pushing ESA protections to the breaking point.

Further reading

Baumsteiger, J. and P.B. Moyle 2017. Assessing extinction.  Bioscience 67: 357-366. doi:10.1093/biosci/bix001

Baumsteiger, J. and P. B. Moyle. 2019.A reappraisal of the California Roach/Hitch (Cypriniformes, Cyprinidae, Hesperoleucus/Lavinia) species complex. Zootaxa 4543 (2): 2221-240. https://www.mapress.com/j/zt/article/view/zootaxa.4543.2.3  (available as open-access download)

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

Howard, J.K, K. A. Fesenmyer, T. E. Grantham, J. H. Viers, P. R. Ode, P. B. Moyle, S. J. Kupferburg, J. L. Furnish, A. Rehn, J. Slusark, R. D. Mazor, N. R. Santos, R. A. Peek, and A. N. Wright. 2018. A freshwater conservation blueprint for California: prioritizing watersheds for freshwater biodiversity.  Freshwater Science 37(2):417-431. https://doi.org/10.1086/697996

Leidy, R. A. and P. B. Moyle. 2021. Keeping up with the status of freshwater fishes: a California (USA) perspective.  Conservation Science and Practice. 2021;e474. https// doi.org/ 10.1111/csp2.474. 10 pages. Open Access.

Lennox R.J., D.A. Crook, P. B.  Moyle, D. P. Struthers, and S. J. Cooke 2019. Toward a better understanding of freshwater fish responses to an increasingly drought-stricken world. Reviews in Fish Biology and Fisheries 29:71-92  https://doi.org/10.1007/s11160-018-09545-9.  Open Access.

Moyle, P., J. Howard, and T. Grantham, 2020. Protecting California’s Aquatic Biodiversity in a Time of Crisis. California Water Blog. https://californiawaterblog.com/2020/05/03/protecting-aquatic-biodiversity-in-california/

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

Moyle, P., R. Lusardi, P. Samuel, and J. Katz. 2017. State of the Salmonids: Status of California’s Emblematic Fishes 2017.  Center for Watershed Sciences, University of California, Davis and California Trout, San Francisco, CA. 579 pp. https://watershed.ucdavis.edu/files/content/news/SOS%20II_Final.pdf

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

Moyle, P.B., D. Stompe, and J. Durand. 2020. Is the Sacramento splittail an endangered species?  https://californiawaterblog.com/2020/03/03/is-the-sacramento-splittail-an-endangered-species/

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

Till, A., A.L. Rypel, A. Bray, and S.B. Fey. 2019. Fish die-offs are concurrent with thermal extremes in north temperate lakes. Nature Climate Change 9: 637-641.

Peter Moyle is Distinguished Professor Emeritus at the University of California, Davis and is Associate Director of the Center for Watershed Sciences. Andrew Rypel is a professor of Wildlife, Fish, and Conservation Biology and Co-Director of the Center for Watershed Sciences at the University of California, Davis.

Posted in Uncategorized | 19 Comments

Mitigating Domestic Well Failure for SGMA and Drought in the San Joaquin Valley

by Rob Gailey and Jay Lund

Domestic wells serve sizable potable water demands in California and much of the world. These wells tend to degrade and fail with declining regional groundwater levels. In areas of irrigated agriculture, impacts to shallower domestic wells may occur from ongoing groundwater use and worsen during drought when agricultural pumping increases to compensate for diminished surface water supplies. Impacts on domestic wells include increased pumping lift, pump cavitation, well screen clogging, and wells running dry.  Our recent work examines the potential for managing these impacts in part of the San Joaquin Valley (shown in Figure 1) where groundwater sustainability plans were completed in 2020 as required by the Sustainable Groundwater Management Act.

Figure 1. Study area. Blue outlined area is the Central Valley. Dark orange filled area in the southern Central Valley is the San Joaquin Valley. Light orange filled areas with outlines are critically-overdrafted groundwater subbasins in the San Joaquin Valley. Only a portion of the area covered by these subbasins is considered based on limited data. Gray shaded areas indicate the portion of critically overdrafted subbasins considered in this work.
Chart, line chart

Description automatically generated
Figure 2. Domestic well mitigation cost as a function of retirement age for the groundwater management parameters. MO is Measurable Objective, MT is Minimum Threshold,and DF is drought factor (relative to groundwater level declines during 2012-2016 drought).

As groundwater levels decline during drought, we consider mitigation actions and costs for additional pumping energy, lowering pumps, cleaning well screens, and replacing dry wells with deeper wells.  These actions allow continued domestic well use. Our analysis estimates: 1) the range and magnitude of mitigation actions, 2) their likely costs, 3) where and when impacts are likely to occur, and 4) labor and time needed to resolve problems for those who depend on domestic wells for drinking water. These actions and costs are driven by how drought declines in groundwater are likely to affect existing domestic wells of varying depths.

Estimated total mitigation cost for groundwater level declines to planned management targets (Measurable Objectives defined under the Sustainable Groundwater Management Act) ranges from $42 to $96 million for this part of the San Joaquin Valley, depending on well retirement age – information known only approximately (Figure 2). If groundwater levels decline further during drought to defined limits below the management targets (Minimum Thresholds defined in SGMA plans) allowed during periods of shortage, costs increase to $120 to $249 million. Costs for groundwater levels declining to the Measurable Objectives are comparable to those that would occur from a repeat of the 2012 to 2016 drought. Costs for declines to the Minimum Thresholds are somewhat more than those estimated for twice the groundwater level decline of the 2012 to 2016 drought. The highest costs are in the northern and central study area where well densities are greatest (Figure 3). The deeper Minimum Threshold groundwater levels increase the area and depth of mitigation needs. Including older wells significantly increases costs. 

Map

Description automatically generated
Figure 3. Geographic distribution of mitigation cost for groundwater management limit (Minimum Threshold) with no retirement age. Costs are presented for each section of the US Public Land Survey System within the study area.

Although these costs are large for domestic well owners and users, they are quite small compared to the economic benefits to agriculture from additional pumping during droughts.  This remains true, even considering that the additional water pumped must be replenished after the drought, because the Sustainable Groundwater Management Act prohibits long-term groundwater overdraft.

Prices for agricultural water in this region during non-drought and drought periods are approximately $250 and at least $1,000 per acre-foot, respectively.  Because additional groundwater extraction during drought must be replaced after the drought (from additional water purchases and recharge or future reductions in non-drought pumping), the value of agricultural pumping during drought may be estimated as the avoided cost of purchasing water during drought (the difference between drought and non-drought prices conservatively estimated at $750 per acre-foot). For this cost savings and considering the estimated change in storage from the Measurable Objectives to the Minimum Thresholds, the value of drought pumping for agriculture in the study area is estimated at $9 to $27 billion, or approximately $2 to $5 billion per year over a five-year drought. This compares to $34 billion in agricultural revenue during 2019 for the eight counties in the San Joaquin Valley. Domestic well costs are less than two percent of the value to agriculture from managing to the Minimum Thresholds during droughts.

Despite uncertainty in estimating specific impacts (due to incomplete records on well construction, well retirement and groundwater hydrology), it seems clear that domestic well mitigation needs and costs from agricultural pumping are likely to be large. These include thousands of pumps being lowered in wells and hundreds of kilometers drilled for well replacement. The scope of mitigation may be still greater since 1) the study area includes only 59 percent of domestic well construction records for critically-overdrafted groundwater subbasins in the San Joaquin Valley and 2) additional mitigation work would be needed for shallow agricultural wells. Although other mitigation actions, such as expanding and consolidating centralized community water systems, would often be best, maintaining well supplies is often the best or only near-term option.

The estimated labor for the largest cost (well replacement) indicates the level of effort required to mitigate domestic well impacts. For the Measurable Objective, approximately 50 to 132 km of drilling would be required depending on assumed retirement age. The requirements increase to 148 to 347 km for drawdowns to Minimum Thresholds. The unknown future timing and magnitude of droughts, and therefore potential departures from Measurable Objectives to the Minimum Thresholds, creates uncertainty in the timing and intensity of needed mitigation. Given the substantial effort and scarce skilled labor to accomplish mitigation actions for domestic wells, there may be insufficient capacity (funds and skilled labor) to complete this work as impacts occur, so pre-mitigation for the most vulnerable areas should be addressed preventatively before impacts occur. 

Given the high costs to agriculture of making groundwater management plans more stringent, preventative mitigation should be undertaken for vulnerable, high-impact areas. Such measures could greatly reduce drought damages and interruptions for domestic well supplies, and reduce the cost and response time of mitigation. Assuming that mitigation measures do not create additional water quality problems, the cost of such mitigation is much less than the benefit to local agriculture from pumping additional groundwater during a multi-year drought.  Domestic well mitigation in advance of droughts is a cheap way to build drought storage for agricultural water supply.

Rob Gailey 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 Co-Director for its Center for Watershed Sciences.

Further Readings

California Department of Food and Agriculture (2020) California agricultural statistics review 2019-2020

Gailey, R.M. and Lund, J.R., Managing Domestic Well Impacts from Overdraft and Balancing Stakeholder Interests,” CaliforniaWaterBlog.com, May 20, 2018.

Gailey RM (2020), California supply well impact analysis for drinking water vulnerability webtool, Community Water Center, January 2020.

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.

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

State of California (2021), Household water supply shortage reporting system.

Stone K and Gailey R (2019), “Economic Tradeoffs in Groundwater Management During Drought,” CaliforniaWaterBlog.com, June 10, 2019.

Posted in Uncategorized | 2 Comments

Ecosystem Restoration and Water Management

– Curated by Jennifer Cribbs (jecribbs@ucdavis.edu)

Note from the Curator:

Restoration implies returning to a prior state. A broken cup carefully glued, might appear nearly as whole as the original, but will always differ from the original. 

Ecosystem restoration attempts to return an evolving web of interconnected species and physical processes to a prior state. This endeavor raises complex questions: what prior state should be the restoration target? How do ecosystem needs and human values interact in determining the restoration goal? Is it most important to restore physical processes (process-based restoration) or populations of critical species (species-based restoration)? The following collection of art explores these questions and the connections between restoration and water management. 

The Voyage of Life (Thomas Cole 1842) source This quadriptych illustrates the stages of human life from childhood to youth to adulthood, and finally old age. The river symbolizes the passage of time and the uniqueness of every moment. As with human lives, it is impossible to restore a river to a previous point in time. However, process based restoration, as described by Wohl et al. (2015), focuses on restoring essential functions of the river rather than restoring to conditions at a previous point in time.  –Angelica Ortiz 

The Oxbow (Thomas Cole 1836)source Thomas Cole’s paintings epitomize the romanticism of the Hudson River School which reflects the desire to restore a different relationship between nature and society. Similarly, river restoration raises questions about what the relationship between nature and society should be. In The Oxbow, the landscape predominantly shows signs of humans extracting resources from nature. Whether that is the right relationship between nature and society remains an open question.    –Abbey Hill

Kintsugi tea bowl (17th Century Japan, Edo period, currently at Smithsonian’s Freer Gallery of Art) – source Kintsugi, meaning “golden joinery,” is a Japanese method of repairing broken ceramics. The technique uses lacquer and powdered gold or silver to emphasize, rather than hide, the cracks. Kintsugi shows that the object may never be wholly restored, but it can be beautiful and useful. Similarly, process-based restoration projects intend to restore the form and function of a river rather than return the system to an unimpacted or past state (Wohl et al., 2015). Rivers that are “broken” (i.e., impaired water quality, biodiversity loss) will not be made whole by restoration projects, but they will gain new form, function, and value for people and the environment.  –Eleanor Fadely

Glen Canyon Dam (Normal Rockwell 1969) – source The Navajo family in the foreground emphasizes the costs of Glen Canyon Dam–the people displaced, the ecosystems drowned, the river’s natural path arrested.  The dam dramatically influences flow regimes in the Grand Canyon, transforming the Colorado River below the dam from high sediment, high flood water, with variable temperatures to much lower sediment, smaller managed floods, and consistent cooler temperatures (Schmidt et al., 1998).  Options for managing the river range from traditional management (business as usual) to full scale restoration (removal of all dams) as well as options in between.  Schmidt et al. (1998) explores the benefits and drawbacks of these options, recognizing that it is impossible to turn back the clock in any ecosystem. –Jenny Cribbs

Tanner Springs Park, Portland Oregon by Atelier Dreiseitl & Green Works (2005) source  Can decentralized water treatment and reuse systems integrate into communities in an invisible or even beautiful way? Tanner Springs Park combines landscape architecture and water treatment. This formerly culverted creek collects runoff from the surrounding city in its bioswale, filtering contaminants and slowing water flow. Tanner Springs Park exemplifies how decentralized treatment and reuse systems can work in tandem with centralized water systems, combining economical sanitation with functional beauty.  –Eleanor Fadely

Jenny Cribbs is a masters student in Environmental Policy and Management and an incoming PhD student in Ecology at the University of California at Davis. This post is a product of a pandemic, remote, discussion-based class on Art and Water Management in Winter, 2021. Contributing authors Eleanor Fadely, Abbey Hill, and Angelica Ortiz all participated in this class; Jay Lund served as faculty facilitator.

Further Readings

Schmidt, J., Webb, R., Valdez, R., Marzolf, G., & Stevens, L. (1998). Science and Values in River Restoration in the Grand Canyon. BioScience, 48(9), 735-747. doi:10.2307/1313336

Wohl, E., Lane, S. N., & Wilcox, A. C. (2015), The science and practice of river restoration, Water Resources, 51, 5974–5997. doi:10.1002/2014WR016874.

Posted in Uncategorized | 1 Comment

Jobs and Irrigation during Drought in California

Jobs and Irrigation during Drought in California

Farmworkers harvesting cauliflower in Monterey County. Photo by John Chacon/California Department of Water Resources

by Josué Medellín-Azuara and Jay Lund

During droughts organizations and stakeholders look for ways of getting the most from every water drop. This is not an exception in California where roughly 40 percent of all water use (on average) is agricultural, 10 percent to cities and the rest is uncaptured or environmental uses (mostly on the North Coast). Cities particularly in southern California have adhered to aggressive water conservation measures, and economically worthwhile irrigation efficiency improvements have already been adopted by thriving agriculture in the state. Yet the notion that applied water in agriculture is often wasteful is common in media drought coverage.

As it turns out, farmers strategically apply water to maintain higher net economic returns.  Farmers irrigate to supply crop evapotranspiration needs, plus a bit more to ensure each plant across a field is well watered and reduce management costs.  In some areas, salts need to be flushed from soils to avoid crop yield losses.  In most areas, most of the additional irrigation beyond immediate crop needs becomes groundwater recharge, which helps prepare for future droughts. Drier soils and higher temperatures during droughts may also demand higher applied water to compensate for additional temperature losses. 

With all these nuances in California agricultural water use, the regional economic benefits of growing crops are sometimes neglected. In California’s San Joaquin Valley, agricultural crop production and processing are nearly a fourth of gross revenues and a sixth of the region’s employment. Rural areas across the state depend disproportionately on irrigated agriculture.

The table below presents estimated irrigated crop area by major crop group, applied water and employment (Medellin-Azuara et al. 2015). While data in the table merits an update (keep posted for a follow-up blog), the story remains unchanged. Fruits, nuts and vegetables support most agricultural gross revenues, employment and income in California’s agriculture when combining hired and contract labor.

Figure 1 puts the story into perspective, if major crop categories are arranged in acreage from the highest value the lowest gross value and employment (from Table 1), nearly 85 percent of all employment and revenues are from growing fruits, nuts and vegetables, which are about half of California’s irrigated acreage.

Figure 1. Cumulative value and employment in California’s major crop groups (Lund et al. 2018). Prepared by Josue Medellin-Azuara with the assistance of Nadya Alexander, UC Davis Center for Watershed Sciences. Contact: jmedellin@ucmerced.edu

Droughts bring new challenges for supplying water even to highly profitable crops, including permanent crops. Adaptation and profits usually point towards reducing irrigation of field, grain and other less profitable agricultural commodities. One limiting factor is the feed crop needs of California’s highly ranked dairy’s sector. Silage corn is the preferred wet roughage for dairies to support high milk yield.

Some old and new insights are worthwhile mentioning:

  • The top 5 crop groups in revenue per unit of water use are grown on about 25 percent of California’s irrigated cropland and account for 16.4 percent of all the net water use. Those crops are responsible for two-thirds of all crop-related employment.
  • Grains, livestock forage and other field crops rank lower in revenue and jobs per drop because their farming is highly mechanized, requiring much less labor. These crop groups nonetheless are critical to the livestock industry. California’s dairy production is the largest in the country.
  • Vegetables, horticulture, fruits and nuts account for more than 90 percent of employment directly related to crop production.
  • Farm contractors, who provide bulk labor for growers, supply about half the labor force for most crop groups.
  • California agriculture accounts for more than 400,000 full-time jobs (or their equivalent, with nearly 200,000 in crop and animal production, another 200,000 in agricultural support services (contract labor).

California’s dynamic and highly adaptive agricultural sector is likely to continue increasing value and employment per unit of water use. Over the past 30 years there has been an intensification in value that retains commodities with the highest gross value and employment. Such value intensification along with a globalized economy prevent catastrophic economic (including employment) losses from drought in agriculture to occur, particularly when groundwater is available to maintain permanent crops.

Despite this robustness of agriculture overall, some hurdles merit additional planning and forethought. First, additional reductions in applied water might sound attractive, but should be put in the context of the farm (or basin) water balance and the need to recharge groundwater for droughts.  Second, within the first few years of implementing the Sustainable Groundwater Management Act, adhering to drought year provisions on water use and pumping will be a challenge, and some irrigated area reductions might occur.

Increased water pumping during drought will likely dampen higher overall agricultural economic losses once again.  Yet even if pumping adheres to drought year provisions in the groundwater sustainability plans, the effects on rural community wells from increased agricultural pumping nearby is a concern.

Growing water scarcity for agriculture is probably best managed using water markets and pricing so the industry and the state can make the most of limited supplies. Efforts to impose detailed arbitrary limits on crops and regions are unlikely to serve the economic and environmental interests of California, but rather further impoverish rural areas and distract from discussions needed for long-term progress.

Josué Medellín-Azuara, Jay Lund are respectively associate director and co-director at the UC Davis Center for Watershed Sciences. Medellín-Azuara is an associate professor at the Department of Civil and Environmental Engineering at UC Merced. Lund is a professor of Civil and Environmental Engineering at UC Davis.

Further reading

California Department of Water Resources. 2015. “Irrigated crop acres and water use.” Last visited April 24, 2015

Martin P. and Taylor E. 2013. “Ripe with Change: Evolving Farm Labor Markets int he United States, Mexico and Central America.” Migration Policy Institute, Washington, D.C. Last visited April 24, 2015

Medellin-Azuara J. and Lund J.R. 2015. “Dollars and drops per California crop.” California WaterBlog. April, 14, 2015

Sumner D. 2015. “Food prices and the California drought.” California WaterBlog. April 22, 2015

Lund, J., Medellin-Azuara, J., Durand, J., & Stone, K. (2018). Lessons from California’s 2012–2016 drought. Journal of Water Resources Planning and Management, 144(10), 4018067.

Medellin-Azura, J. Lund, J.R. and Howitt, R.E. Jobs per drop in the California Crops. California Water Blog, April 28, 2015.

Posted in Uncategorized | 7 Comments

Assessing portfolios of actions for winter-run salmon in the Sacramento Valley

by Francisco Bellido Leiva, Robert Lusardi and Jay Lund 

We may be entering a time when more mechanistic understanding can be used to estimate effects of habitats and flows on fish populations and health, and help design ecosystem restoration efforts.

An integrated portfolio approach to protecting and restoring winter-run salmon would begin with a model estimating the effectiveness of a set of restoration actions on juvenile salmon out-migrating populations. The recently-published Winter-Run Habitat-based Population model (WRHAP) does just this. 

A summary of this model is presented in this blog and the accompanying video. This work was   motivated by the absence or misrepresentation of important juvenile rearing habitats (Phillis et al. 2018) in existing modeling efforts.

Video summary of paper on modeling winter-run salmon life-cycle in the Sacramento Valley (9 minutes)

WRHAP’s conceptual structure allows analysis of the effects of rearing history and alternative habitat and flow availability on juvenile growth and out-migration success. Table 1 and Figure 1 illustrate outputs from this analysis, which identified intermittent off-channel and floodplain habitats as those providing enhanced rearing conditions, following reported parameter values (Sommer et al. 2001; Limm and Marchetti 2009). The model suggests that these off-mainstem habitats contributed substantially to total out-migration biomass (Figure 1), despite their limited spatiotemporal availability throughout the Central Valley (Table 1). Larger, healthier juveniles are also thought to improve initial ocean survival (Woodson et al. 2013).  This suggests off-channel habitats may also enhance early marine-stage survival of winter-run Chinook.

The model found that the greatest fry-to-smolt mortalities occurred during brood years with low flow conditions and sparse alternative habitats (e.g., brood years 2001, 2006 and 2014), suggesting that off-mainstem habitats are crucial to out-migration success. Actively managing such habitats during a drought or low flow periods may be critical to the long-term recovery efforts for winter-run Chinook salmon populations.

 TotalMainstemTributariesOff-ChannelFloodplain
Out-migrants1,132,364100% (21.9%)45.1%33.9%17.5%
Biomass [kg]19,30341.3%19.9%9.9%28.9%
Avg. Rearing Time [days]16778.1%11.2%3.3%7.4%
Table 1: Proportion of simulated juveniles that used each available rearing habitat at any life stage and proportion of the total biomass generated within them. Parenthetic value is percentage of simulated juveniles rearing only in the mainstem (from Bellido-Leiva et al 2021).
Figure 1: Model-estimated out-migrating biomass and fraction of growth for each available rearing habitat. Note large and varying fractions from off-mainstem habitats, especially in successful years (from Bellido-Leiva et al 2021).

The WHRAP habitat-flow-population model is an initial step to understanding the relative value of managing new and existing habitats to sustain winter-run Chinook salmon. Information from analysis of model outputs illustrates the model’s potential to assist in decision-making for this endemic and federally endangered fish.

For water resource management, links between water operations and Sacramento Valley environmental conditions (i.e., flow and temperature regimes that define habitat availability and quality) can help define environmental flows that support specific salmonid life stages and estimate the effectiveness of proposed combinations of restoration policies or alternatives on federally listed populations.

The next focus of this work is to employ this population model to explore optimized portfolios of habitat restoration actions and their relative effects on winter-run Chinook (Figure 2). As such, additional modules are being developed to better simulate expected changes in winter-run abundance over several generations for each proposed restoration action and the combined effect of multiple restoration alternatives (denoted as WRHAP-Sea).  

Figure 2: Conceptual framework embedding WRHAP into an optimization algorithm to define optimized portfolios of habitat/water management actions to recover the winter-run Chinook salmon ESU.

The paper upon which this blog is based also is available as a 9-minute video at: https://www.youtube.com/embed/Ztx658oNCgg

Francisco Bellido Leiva is a PhD Candidate in Environmental Engineering at the University of California – Davis.  Robert Lusardi is an Adjunct Assistant Professor in the Wildlife, Fish, and Conservation Biology at the University of California – Davis.  Jay Lund is a Professor of Civil and Environmental Engineering at the University of California – Davis. The authors thank CalTrout, especially Jacob Katz and Jacob Montgomery, for providing valuable input during model development and sharing helpful datasets.

Further reading

Bellido-Leiva, F., Lusardi, R.A., and Lund, J.R. (2021), “Modeling the effect of habitat availability and quality on endangered winter-run Chinook salmon (Oncorhynchus tshawystscha) production in the Sacramento Valley,” Ecological Modelling, Vol. 447, May 2021.  9-minute video version: https://www.youtube.com/embed/Ztx658oNCgg

Limm, M. P. and Marchetti, M. P. (2009), ‘Juvenile Chinook salmon (Oncorhynchus tshawytscha) growth in off-channel and main-channel habitats on the Sacramento River, CA using otolith increment widths’, Environmental Biology of Fishes 85(2), 141–151.

Phillis, C. C., Sturrock, A. M., Johnson, R. C. and Weber, P. K. (2018), ‘Endangered winter-run Chinook salmon rely on diverse rearing habitats in a highly altered landscape’, Biological Conservation 217, 358–362.

Sommer, T. R., Nobriga, M. L., Harrell, W. C., Batham, W. and Kimmerer, W. J. (2001), ‘Floodplain rearing of juvenile Chinook salmon: Evidence of enhanced growth and survival’, Canadian Journal of Fisheries and Aquatic Sciences 58(2), 325–333.

Woodson, L. E., Wells, B. K., Weber, P. K., MacFarlane, R. B., Whitman, G. E., and Johnson, R. C. (2013), ‘Size, growth, and origin-dependent mortality of juvenile Chinook salmon Oncorhynchus tshawytscha during early ocean residence’, Marine Ecology Progress Series, 487, 163-175. https://www.int-res.com/abstracts/meps/v487/p163-175/

Posted in Uncategorized | Leave a comment

Dollars and Drought – Windfalls for innovation or entrenchment?

by Jay Lund

California’s Governor Newsom recently declared a drought emergency throughout much of California and announced over $5 billion in new water program investments.  These twin emergency and funding announcements are a classic “bad-news creates good news story” (and potentially vice versa) for California’s water problems. They are opportunities for innovation and making long-term improvements for California’s water problems.  They also can reward and entrench less effective programs and approaches.

Problems and opportunities

“Money is like muck, not good except it be spread.” – Sir Francis Bacon (1625)

As a diverse dynamic state in a semi-arid region, California will always have water problems.  Compared to other regions with Mediterranean climates, California has done relatively well with water and environmental problems.  But in absolute terms, we need to do much better for some problems, especially with climate change.  The Governor’s proposed infusion of funds can help.  Here are several areas most needing improvement from additional attention (drought) and investment (budget surplus).

  • Ecosystem management is California’s greatest and least effectively organized water challenge.  California’s diverse native ecosystems are mostly declining from human development and climate change.  So far, agencies and expenditures have only slowed declines, but been unable to systematically stop or reverse these declines.  Research and small field successes point to some promising directions.  More money will help, but more fundamental changes in approach, organization, and sustained resources are needed to save and support what can be saved of what remains.
  • Groundwater overdraft and quality is a major challenge that is becoming much better organized since passage of the Sustainable Groundwater Management Act (SGMA) during the previous drought.  Deeper technical and policy coordination between California’s Department of Water Resources and Water Resources Control Board is needed to help local efforts address state objectives, particularly for drought management, and achieve the painful pumping reductions often needed for groundwater sustainability. (The state’s Flood-MAR efforts are useful, but excessive and distract from deeper needs to reduce pumping in the most overdrafted areas.)
  • The Sacramento-San Joaquin Delta is at the hub of California’s major water and environmental systems, and so is inherently controversial.  Its problems are also dynamic and face growing challenges from sea level rise and higher temperatures with climate change.  The State has recognized these challenges, but has yet to build broadly effective multi-agency science and policy programs to explore long-term solutions for these evolving challenges.  Particularly with climate change, broader and more comprehensive solutions seem needed.
  • Rural water systems always face problems of few resources, small size, and diverse supply and safety vulnerabilities.  These problems manifest as unreliable well supplies during drought, nitrate and other drinking water safety problems, and unaffordable costs for service.  These water problems parallel other health, safety, welfare, education, and environmental problems for rural households and communities.  Ideally, state funds can be integrated with other resources and changes to help counties improve capabilities to support rural communities.
  • Floods are the other water extreme which will increase with climate change.  It seems odd to invest in flood protection during a drought, but, like drought, the best way to reduce flood damages and loss of life is from preparation before the flood.
  • Water accounting is fundamental to all water management.  A common inter-agency water accounting system is needed to civilize and improve water management, including implementation of SGMA, water rights administration, and support environmental flows, water markets, and negotiated agreements of all sorts.  Developing a common state water accounting system will be difficult, but is a neglected foundation for good management. 
  • A common scientific and technical program is needed across state agencies for many water problems.  Scientific and technical work on water is currently fragmented across state agencies with insufficient connective tissue across agency and intra-agency silos.  This has expensively hindered the development and use of solid information for informing agencies and stakeholders in operations, planning, and policy problem and solution discussions.

The Governor’s proposed funding support responds, sometimes specifically, to many of these problems.

More than money is needed. 

Sending money to these problems will always be appreciated, but will not always be proportionately helpful.  The state should take complementary actions to make the best use of these additional funds, and not cultivate additional long-term dependence on state general revenue and bond funding.  These include:

  • Changes in government procedures.  State agencies have excellent, dedicated, and creative people, as well as highly risk-averse staff who hinder state and agency missions by excessive dedication to process.  Government timeliness, budget accounting, personnel, and accountability are plagued and often break down from internal frictions.  Such frictions are inevitable and have some useful purposes, but must be managed to keep any bureaucracy effective.
  • Long-term spending, long-term performance, and accountability.  Each agency receiving additional funds should detail plans for this spending, how long-term performance will be maintained when these funds are exhausted, and how the agency will be accountable for this performance from expenditures.  Then keep score.
  • Internal and external inspections and reviews of program effectiveness, as discussed below. 
  • Embrace interagency science.  Many state water challenges fall increasingly across agency boundaries, especially with climate change.  The state needs stronger and more explicitly organized scientific efforts to help lead us into the future.
  • Sustained dedicated funding is needed for under-resourced areas, such as ecosystems and safe drinking water for poor communities.  Special water or other taxes or fees should provide some of this funding, perhaps matched with general revenue funds.

Today’s combination of drought and financial windfall provide a unique opportunity to implement more fundamental and long-lasting reforms.  California has both carrots and sticks, simultaneously, to make changes needed for the future.

Reforming underperforming state assets

“Happy families are all alike; every unhappy family is unhappy in its own way.” – Leo Tolstoy (1877)

State agencies are the Governor and legislature’s main means to address difficult challenges.  Given the hard important problems typically delegated to government agencies, these assets often under-perform relative to hopes and expectations.

Governance is hard, and better policies generally come from consulting broadly.  However, many state agencies and programs prolong policy discussions into “dynamic inaction”, a safe form of perpetual inclusion, satisfying interests who enjoying the status quo, and avoiding controversies from substantive action.  Dynamic inaction diminishes government’s reputation.  Some agency programs might become more effective with sunset deadlines or effectiveness assessments.

  • Sunset deadlines might be as simple as a deadline for a final report with conclusions and actions, or be further motivated, in this case, by a sunset on the program or availability of funds if specified objectives are not achieved.
  • Internal agency assessments of agency program effectiveness.  Such assessments are common in private industry, academia, and for major military and federal government programs.  These might occur bi-annually for major agency programs, and provide opportunities for agency leadership to reform (and occasionally cull) less effective programs, and identify and reward better middle managers, as well as an opportunity to identify larger agency problems of coordination, personnel development, budgeting, and administration.  (Developing effective mission-focused middle managers is a major gap in state government.)
  • External assessments of program effectiveness are vital, as shown by the 2018 external assessments of DWR and SWP dam safety inspections from Oroville spillway’s failure in 2017.  External assessments of major programs should occur regularly, before catastrophic failures.  Major problems, such as SGMA implementation, would benefit from honest external assessment and recommendations.  California’s Delta Independent Science Board (DISB) is an attempt to provide some periodic external assessments of scientific programs supporting adaptive management of the Delta, across all agencies.  Its recent disruption and effective defunding by the Delta Stewardship Council shows how bureaucratically difficult and important external reviews are for the effectiveness of government programs.

If you want to make any program fail, give it too much money relative to its leadership and management capabilities.  Rarely does a weak program become strong by only adding money – strong leadership, management support, and accountability also are needed.  These last three resources often are scarcer than money.

The drought and state budget windfall provide opportunities to reduce California’s water problems, but also can distract from longer-term solutions. 

Long-term success will rely on how effectively the money is spent, as much as how much is spent. 

Further reading

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

Pinter, N., J. Lund, and P. Moyle. “The California Water Model: Resilience through Failure,” Hydrological Processes, Vol. 22, Iss. 12, pp. 1775-1779, 2019.

Oroville spillway forensic investigation and presentations:

Video #1 COGGE: Oroville Dam Webinar Series – March, 5, 2018 on physical failure mechanism (58 min): https://www.youtube.com/watch?v=3JygTm8iiWQ

Video #2 COGGE: Oroville Dam Webinar Series – March 14, 2018 on overall failure mechanism and lessons (59 min): https://www.youtube.com/watch?v=YjgugkIfwWQ

February 2018 forensics report: https://damsafety.org/sites/default/files/files/Independent%20Forensic%20Team%20Report%20Final%2001-05-18.pdf

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

Posted in Uncategorized | 2 Comments

A few Lessons for California’s New Drought

We asked some colleagues for lessons that might be useful in managing the California’s new drought. Here is a first sampling of thoughts.

1: Market-based approaches to water management will lessen the costs of drought. Katrina Jessoe. Agricultural and Resource Economics, UC Davis

Climate models indicate that California’s droughts will become more frequent and severe. Warming temperatures will further reduce surface water availability, by increasing evaporation from soil, reservoirs, and irrigated land. While reductions in surface water supplies will be costly to agriculture, residential users and the environment, these costs could be substantially reduced through the reallocation of scarce supplies. Supplying water to those who value it most will not eliminate the costs of drought, but will make them less painful. 

Policymakers and utilities have three pragmatic economic instruments to mitigate the cost of this drought. First, establishing well-defined rights for groundwater and surface water would reduce groundwater extraction, and foster water transfers among and across user groups. Second, water transfers among agricultural, urban and environmental users or between these groups would move water from lower value to higher value uses. While transfers have occurred since the 1976-77 drought, high transaction costs deter wider scale deployment. The state could help broker transactions and reduce the red tape involved with them. Third, water should be priced to reflect the cost of supplying and/or extracting it. This is particularly relevant for groundwater, since agricultural groundwater is rarely priced. Prices would reflect the cost of extraction on other agricultural pumping costs, groundwater quality, and the availability of future groundwater supplies. Revenues could fund alternative water supplies, such as recycled water deliveries and artificial groundwater replenishment. This would improve the long-run availability of groundwater resources, and their ability to act as a critical buffer to surface water reductions during droughts. 

Further reading –

Bruno, E. M., & Jessoe, K. (2021). “Missing markets: Evidence on agricultural groundwater demand from volumetric pricing.” Journal of Public Economics, 196, 104374.

Bruno, E. M., & Jessoe, K. (forthcoming). “Using Price Elasticities of Water Demand to Inform Policy.” Annual Review of Resource Economics.

Leonard, B., Costello, C., & Libecap, G. D. (2019). “Expanding water markets in the western United States: barriers and lessons from other natural resource markets.” Review of Environmental Economics and Policy, 13(1), 43-61.

2: Central Valley agriculture is the most vulnerable economic sector to drought, and has long relied on a large chronic overdraft of groundwater. Josue Medellin-Azuara, Civil and Environmental Engineering, UC Merced

Shortly after the 2012-2016 drought, followed by the bonanza of several unusually wet or not too dry years, groundwater sustainability plans (GSPs) from the recently established groundwater sustainability agencies were submitted as the locally-driven pledge to attain balance in recharge and extraction by 2040. This drought will become the acid test for the effectiveness and resilience of agriculture in adhering to such plans in the early stages of Sustainable Groundwater Management Act (SGMA) implementation. Unlike historical droughts, agriculture is now required to adhere to the GSP guidelines for pumping in dry years. As the drought progresses, other systemwide vulnerabilities lingering from the recent droughts in the Valley such as small rural water systems on shallow wells, groundwater dependent ecosystems and infrastructure damage will likely resurge in some new forms. This gives the state and stakeholders opportunities to revisit GSPs water portfolios and procedure effectiveness  in order to address this multi-objective problem. The current drought also will unveil or affirm areas in which the state is making some slow progress such as developing and organizing open access data and modeling platforms to inform management decisions, a wide adoption of low environmental impact water exchanges, managed recharge, and more participative management of small water systems and communities. 

Further reading –

Cantor, A., Owen, D., Harter, T., Green Nylen, N., & Kiparsky, M. (2018). Navigating Groundwater-Surface Water Interactions under the Sustainable Groundwater Management Act. UC Berkeley: Berkeley Law. Retrieved from https://escholarship.org/uc/item/720033b2 

Hanak, E., Escriva-Bou, A., Gray, B., Green, S., Harter, T., Jezdimirovic, J., Lund, J., Medellín-Azuara, J., Moyle, P., & Seavy, N. (2019). Water and the future of the San Joaquin Valley. Public Policy Institute of California: San Francisco, CA, USA.

Jasechko, S., & Perrone, D. (2020). California’s Central Valley Groundwater Wells Run Dry During Recent Drought. Earth’s Future, 8(4), e2019EF001339. https://doi.org/https://doi.org/10.1029/2019EF001339

Lund, J., Medellin-Azuara, J., Durand, J., & Stone, K. (2018). Lessons from California’s 2012–2016 drought. Journal of Water Resources Planning and Management, 144(10), 4018067. https://doi.org/10.1061/(ASCE)WR.1943-5452.0000984 

3:  Native fishes like Chinook salmon, splittail, and Delta smelt are adapted to persist and even thrive  through severe droughts, but  they are not well adapted to persist through modern droughts.  Peter Moyle, Wildlife, Fish, and Conservation Biology, UC Davis 

The well-honed drought survival strategies of California’s native fishes  don’t work very well in contemporary California, as seen by their  rapid decline through recent droughts. Dams block access to most cold water spawning and rearing areas once used by salmon and steelhead.  Dams also fragment native fish populations so re-colonization of once-dry streams is not possible. Reservoirs cover the deep pool refuges present in the rivers and support mostly non-native fishes which exclude native fishes, especially through predation. Flow below dams can create good conditions for native fishes during drought, but can be abruptly shut off, becoming ecological traps rather than refuges. Low or no inflow to estuaries can make them too salty or warm, even for tolerant natives.  

In general, drought in California reduces native fish populations and, where there is water, favors non-native fishes more tolerant of changed habitat and flow conditions. 

So how do we save our fishes from the effects of extended drought?  The answer lies in a combination of creative thinking and assured water supplies for fish refuges.  Basically, extended drought creates a need for more frequent, rapid, and flexible actions to save fish.  Better monitoring of all native fishes is needed to start. This monitoring should include an evaluation of every species status at least once every five years, including identification of drought refuges.  During droughts, fishes with small and/or fragmented populations should be evaluated annually and action taken to prevent loss of isolated populations, such as moving fish to more secure habitats or moving water to the refuges. Some especially vulnerable fishes include Red Hills roach, Northern roach, Long Valley speckled dace, McCloud River redband trout, and Klamath River summer steelhead.  Without an active program of evaluation and intervention, these native fishes will decline to extinction, drought by drought. 

Further reading – 

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

Lennox R.J., D.A. Crook, P. B.  Moyle, D. P. Struthers, and S. J. Cooke 2019. Toward a better understanding of freshwater fish responses to an increasingly drought-stricken world. Reviews in Fish Biology and Fisheries 29:71-92  https://doi.org/10.1007/s11160-018-09545-9.  Open Access.

Howard, J.K, K. A. Fesenmyer, T. E. Grantham, J. H. Viers, P. R. Ode, P. B. Moyle, S. J. Kupferburg, J. L. Furnish, A. Rehn, J. Slusark, R. D. Mazor, N. R. Santos, R. A. Peek, and A. N. Wright. 2018. A freshwater conservation blueprint for California: prioritizing watersheds for freshwater biodiversity.  Freshwater Science 37(2):417-431. https://doi.org/10.1086/697996

Moyle, P.B., J. D. Kiernan, P. K. Crain, and R. M. Quiñones. 2013. Climate change vulnerability of native and alien freshwater fishes of California: a systematic assessment approach. PLoS One. http://dx.plos.org/10.1371/journal.pone.0063883

4: Environmental flows and temperature mitigation are critical to ecosystems during droughts, and difficult to achieve. John Durand, Center for Watershed Sciences, UC Davis

The recent 2012-16 drought seriously degraded environmental conditions in the Sacramento River and Delta. At that time, a coordinated approach by the Real-Time Drought Operations Team, with representatives from water, fish and wildlife management agencies, was extremely helpful in managing some of the worst effects of the drought.  

Current reservoir levels show we are back where we were in 2014 and 2015. Having little stored water then had implications for water supply and quality, as well as environmental conditions. Decreased flows increased salinity in the Delta, which jeopardized local agriculture and urban water supplies, as well as contaminating water exports from the south Delta. To minimize these risks, a temporary salinity barrier was installed at False River, near Franks Tract in 2015, which proved effective. The rapid deployment of such a barrier might provide some  control in the current situation, and help to maintain fresh water for agricultural and urban use, with less disruption to the Delta ecosystem.The barrier also helped to preserve water storage north of the Delta, in case it would be needed in future years for environmental or human uses.

Preserving stored water also is important for stream temperature management. The last drought was  extremely hot. Both winter and summer temperatures were high for extended periods of time. This jeopardized the cold water pool in Shasta Reservoir, which is needed to maintain the last spawning grounds of winter-run Chinook salmon (their original cold-water spawning grounds, high in the Cascades, are now blocked by Shasta dam). Nearly two-thirds of the entire wild population was lost when temperatures rose uncontrollably in 2014 and 2015, leading to nearly complete recruitment failures in both years. This situation is likely to recur without a serious effort by the US Bureau of Reclamation to reserve sufficient water in the reservoir to last through a hot summer season. Hatchery support will be needed if we face catastrophically high temperatures again–but once a species goes into hatchery support, it becomes harder to restore to the wild ever again.  

This is also true of Delta Smelt, which mostly disappeared in the last drought. Efforts are being made to support the population using hatchery stock, but Delta conditions are likely to continue to degrade in ways that frustrate this effort, especially during a drought. The combination of low, slow flows, increased water clarity,  and warmer temperatures stress native fish populations and encourage the growth of invasive aquatic weeds. During the last drought, aquatic vegetation transformed parts of the north Delta to resemble the south Delta: warm, slow-moving water clogged with weeds. The weeds themselves exacerbate these conditions, leading to self-sustaining feedbacks that preclude conditions that support Delta Smelt and other native fishes: too-warm water, degraded spawning habitat, and limited pelagic food. 

Actions to support native fishes and habitats are best implemented during non-drought conditions, which allows restoration, planning, and stock enhancement to occur. At this point in the ongoing drought, we can invoke emergency mitigation measures to try to counter the worst effects of low flows and high temperatures. But this drought is coming hard on the heels of the last drought. From the perspective of history, it may well be an extension of the last, or a harbinger of conditions that will become chronic, as predicted by most climate change models. 

Further reading:  John R. Durand, Fabian Bombardelli, William E. Fleenor, Yumiko Henneberry, Jon Herman, Carson Jeffres, Michelle Leinfelder–Miles, Jay R. Lund, Robert Lusardi, Amber D. Manfree, Josué Medellín–Azuara, Brett Milligan, Peter B. Moyle. Drought and the Sacramento–San Joaquin Delta, 2012–2016: Environmental Review and Lessons. San Francisco Estuary and Watershed Science, 18(2). 

5: Successful cold-water management requires major changes to dam regulation. Ann Willis, Center for Watershed Sciences, UC Davis

Streams and lakes with cold-water thermal regimes support native ecosystems throughout California. Given our extensive investment in cold-water management through dam regulation, California appears well-positioned to sustain cold-water habitat. But when we look at differences between regulated and unregulated stream temperature patterns, managed streams are a lukewarm substitute. Historical headwater habitats show distinctive thermal regimes compared to currently accessible, dam-regulated reaches. Although dam regulation has done a reasonably good job at mimicking desirable summer temperatures, the predominant focus on managing summer stream temperatures has overlooked the problem of increasing winter stream temperatures. California’s dams generally appear incapable of replicating stable cold-water regimes, with the possible exception of Shasta Dam, which will be severely tested this year. But when only one of scores of dams throughout the state shows promising results for environmental stream temperature management, we must question whether this approach is truly viable. 

Maintaining stream temperatures for cold-water ecosystems prompts great concern. Every drought renews temptation to feed our addiction to infrastructure. Stream temperature research shows that we cannot build our way to a sustainable future through regulation. California has to confront the incompatibility of near-ubiquitous dam regulation of its streams and the desire to restore and sustain cold-water ecosystems. Difficult decisions about dam removal versus species extinction and the collapse of cold-water ecosystems lay ahead.

Further reading – Willis, Ann. 2020. Keeping it Cool: Sustainable Stream Conservation Using Process-Based Thermal Regime Management. Doctoral dissertation. 

Posted in Uncategorized | 3 Comments