A simplified method to classify streams and improve California’s water management

by Belize Lane, Sam Sandoval, and Sarah Yarnell

Alterations to the natural flow regime for human water management activities have degraded river ecosystems worldwide. Such alterations are particularly destructive in regions with highly variable climates like California, where native riverine species are highly adapted to natural flooding and drought disturbances. In California, less than 2% of the total streamflow remains unaltered, while over 80% of the native fish species are now imperiled or extinct .

Determining the natural flow regime for altered stream reaches is difficult as unimpaired streamflow records are unavailable for many locations of interest. Where data is available, previous methods distinguished such specific stream types that their application was limited and unhelpful for regional management. To improve California’s water management, particularly around determining environmental flows for our diverse ecosystems, we needed a better method that addressed the diversity and scale of California’s streams.

Hydrologic Classification

Hydrologic classification is a strategy for distinguishing groups of stream reaches with similar streamflow characteristics for regional water management efforts. UC Davis researchers recently developed a hydrologic classification for California that is specific enough to make critical distinctions between natural streamflow patterns (also called natural flow regimes), but general enough to support the development of environmental flow targets in altered stream reaches across the state.

The California hydrologic classification is based on available hydrologic and geospatial data. First, key hydrologic metrics (e.g., measures of streamflow magnitude, duration, timing, frequency, and rate of change) pertinent to river ecosystems were calculated for all available reference streamflow gauge stations with long-term (>20 years) unimpaired or naturalized discharge data. These metrics were input to an initial streamflow gage classification model that distinguished statistically distinct natural stream classes; each reference streamflow gage was classified into a stream class based on its specific hydrologic metric values.

Then, a predictive linear regression model was developed based on relationships between the initial streamflow gauge classification and upstream catchment attributes (e.g., climate, topography, soils, and geology). The model was highly accurate at predicting the stream classes of reference gauges and performed well compared to regional hydrologic studies. This second model (Figure 1) was then used to predict the stream classes of all the reaches in California.

Predictive model of stream classes based on upstream catchment attributes, from Lane et al. (2017a).

The resulting hydrologic classification (Lane et al. 2017b) identified nine natural stream classes (Figure 2) with distinct streamflow patterns that are the result of several characteristics of rainfall-runoff response, including: dominant water source (snowmelt, rain, groundwater), hydrologic attributes (mean annual flow, extreme low flow duration and timing, etc), climate setting (mean annual precipitation, mean August and January precipitation, etc.) and topographic and geologic setting (slope, catchment area, dominant rock type, soils compositions, etc.).

Hydrologic classification of California, combing results of Lane et al. (2017a) and Pyne et al. (2017).

California’s Natural Stream Classes

Snowmelt (SM): SM streams exhibit highly seasonal flow regimes with spring snowmelt peak flows, predictable recession curves, very low summer flows, and minimal winter rain influence. These sites exist along the crest of the Sierra Nevada with most sites in the southern, higher elevation portion of the mountain range.

High elevation, Low Precipitation (HLP): HLP streams are distinguished from SM streams by their higher base flow (due to porous geology) and lower peak flows (due to less snow) but exhibit a similar seasonal signature and predictability.

High- and Low-volume Snowmelt and Rain (HSR and LSR): The transition from a SM to a LSR to a HSR regime closely tracks the elevation gradient from the peaks of the Sierra Nevada to the floor of the Central Valley. LSR and HSR streams exhibit similar bimodal snow-rain patterns but illustrate a transition toward earlier snowmelt peak and increasing winter rain contributions along the elevation gradient.

Rain and seasonal Groundwater (RGW): Generally at lower elevations, RGW streams exhibit higher minimum flows and earlier summer peak flows than LSR streams, as well as the distinctive influence of winter rain storms in high and unpredictable winter flows.

Winter Storms (WS): WS streams, driven by winter rain storms, exhibit distinct duration, timing and magnitude of high flows during the rainy season. They are characterized by high interannual flow variance, due to the variability of winter storm patterns, and very low base flows during summer. WS streams generally follow the spatial distribution of strong orographic precipitation in the north coast region.

Groundwater (GW): GW streams are distinguished by significantly higher and more stable flows year-round, mostly located along volcanic geologic settings.

Perennial Groundwater and Rain (PGR): PGR streams combine the stable, base flow-driven conditions of GW streams during summer with the high magnitude winter peak flows of WS streams in catchments with low annual streamflow.

Flashy Ephemeral Rain (FER): Prevalent in arid southeastern California, FER streams are characterized by the highest interannual flow variance, extended extreme low flows and large floods, and the lowest average daily flow of any class.

The following figure (Fig. 3) illustrates the extreme seasonal and interannual hydrologic variability between stream classes. For example, the SM flow regime exhibits a highly predictable spring snowmelt pattern with low interannual variability (<6) while the WS flow regime exhibits highly variable winter storm flows (<18) and very low summer flows.

Reference dimensionless hydrographs illustrate seasonal and interannual flow regime variability between natural stream classes for four of the nine classes (Lane et al. 2017b). Reference streamflow gauge time-series were aggregated for each stream class and daily streamflow was non-dimensionalized based on average annual streamflow to highlight pattern variability.

Environmental Water Management Implications

This hydrologic classification provides the fundamentals for understanding the diversity of natural streamflow patterns and their spatial arrangement across the state. It also supports the need for broad-scale environmental management of California’s many impaired rivers. The spatial extent and reach scale of the classification are expected to substantially improve the overlap of biological and hydrologic datasets statewide. The hydrologic classification provides a footprint of the locations of distinct natural stream classes which, combined with ecological and geomorphic information, can be used to design environmental flow targets. Future comparisons of ecological patterns between natural and hydrologically altered streams within each stream class are expected to yield flow-ecology relationships that can provide the basis for rapid statewide environmental flow standards.

Belize Lane recently received her PhD in Hydrologic Sciences from UC Davis and is now an Assistant Professor in Civil and Environmental Engineering at Utah State University. Samuel Sandoval is an Associate Professor in the Dept. of Land, Air and Water Resources and UC Agricultural and Natural Resources Cooperative Extension Specialist. Sarah Yarnell is a senior researcher at the Center for Watershed Sciences.

Further reading

Lane BA, Dahlke HE, Pasternack GB and Sandoval-Solis S (2017a). Revealing the Diversity of Natural Hydrologic Regimes in California with Relevance for Environmental Flows Applications.

Lane BA, Sandoval-Solis S, Yarnell SM, Stein ED (2017b) Characterizing diverse river landscapes using hydrologic classification and dimensionless hydrographs. In Preparation.

Magilligan FJ and Nislow KH (2005). Changes in hydrologic regime by dams. Geomorphology.

Pyne MI, Carlisle, DM, Konrad CP and Stein ED (2017). Classification of California streams using combined deductive and inductive approaches: Setting the foundation for analysis of hydrologic alteration.

Quiñones RM, Moyle PB (2015) California’s freshwater fishes: status and management. FISHMED

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

Reflections on Cadillac Desert

William Mulholland, pointing. (Image source: LA Times)

by Jay Lund

In 1986, when Mark Reisner published his book Cadillac Desert, I had just begun professing on water management. The book went “viral,” before the word viral had its present-day internet-intoxicated meaning.  The book offered a compelling revisionist history and understanding of water development in the American West, based on economic self-interest, ideology, and Floyd Dominy’s personal drives.  Since then, Cadillac Desert has been a “must read” book for Western water wonks.

Cadillac Desert, by Marc Reisner

Cadillac Desert fell in the tradition of Muddy Waters (1951), Dams and other Disasters (1971), Rivers of Empire (1985), and Water and Power (1983), all written by giants in the field critical of Western water development, but was much better written and marketed (though less scholarly) and the time was ripe for publication of such a thoughtful, popular work.  The era of large dam and water projects in the US had clearly ended, and needed a punctuation mark.  Mark Reisner provided an exclamation mark.

Main lessons at the time

The main lessons from the book (for me) were:

  • The 50-year era of building large regional and multi-state water projects was largely over (by 1987).
  • Why do we expect anything as important as water to not be political? The individuals, sociology, economics, and politics behind the era of large water infrastructure construction were fascinating and important. In fact, they proved to be more important than traditional engineering (my field) in shaping water management.  But contemporary and likely future politics and economics can no longer support continued traditional water project development.
  • The public institutions responsible for the successes and failures of the big infrastructure era were incapable of adapting to new conditions. The large federal and state agencies have largely lacked political and financial support needed to develop new talented and ambitious people to effectively lead these institutions in better adapted directions.
  • The West’s large water infrastructure systems have profoundly transformed and damaged the natural environment and pre-existing rural communities, particularly Native American communities.
  • In many ways, the water infrastructure of the Western US was over-developed, or at least mal-developed for contemporary society’s water management objectives.

Becoming conventional wisdom

Marc Reisner’s themes are now conventional wisdom.  Although these ideas were not new to well-read scholars, they were timely, well-written, and influential.  Almost all books and scholarship following Cadillac Desert have adopted or been underlain by these themes (such as The Great Thirst, 1992, The King of California, 2005, and Managing California’s Water, 2011).

But much has changed since Cadillac Desert was written (and revised in 1992).

Federal and State agencies no longer drive major water project construction.  The additional water deliveries from new major dam or canal projects are typically small and expensive.  The cheapest sites with the most capacity to deliver water already have water projects.  Remaining potential reservoir sites are usually much less cost-effective.

The economic and political drivers of Western water also have changed in fundamental ways.  The West is wealthier and much less agricultural.  Agriculture’s diminishing role in the West’s economy (now less than 5% of GDP and employment) and the steady urban water conservation efforts have made regional economic prosperity much less dependent on cheap and abundant water supplies.

Environmental laws and regulations now greatly hinder the development of new projects, and impinge on the operation of existing projects.  There is now great uncertainty and concern for the ability to preserve native aquatic species.

Federal and state budgets no longer have substantial funds available for large water infrastructure projects anyway.  There remains little political appetite to fund large federal and state water projects.

Floyd Dominy (Image source: LA Times)

Federal and State water agencies have become financially and intellectually impoverished and, tragically, have substantially lost most of their sense of mission.  Without a strong sense of mission, they often become mired in internal procedures and policies – and suffer greatly reduced effectiveness.  A Floyd Dominy would be completely hamstrung in today’s large agencies.

So where is Western Water going?  And where should we as professionals and interests work to make it go?  What should we teach students, the public, and policy-makers about Western water as it moves well beyond Cadillac Desert?

Emerging from the Desert

Cadillac Desert is now a bit dated in its lessons for the present and future water management and policy in the American West.  What should we be preparing for?

Water in the west will continue to be important and controversial.  But the structure of the West’s economy will continue to make it less dependent on abundant water supplies.  Modern urban economies need relatively little water to produce vast amounts of economic wealth.  Per capita urban water use continues to fall substantially, and can probably continue to do so for several decades.  Agricultural shifts to higher valued permanent crops, particularly vines and orchards, make farmers more interested in water reliability than total quantity.

Climate change will become more important, bringing more attention to variability and likely contraction of supplies and shifts in demands.  It will be hard to know how to change major water infrastructure for a warmer, more variable, and perhaps drier climate.  Larger reservoirs, while useful, might not be the most cost-effective solutions.

Local and regional water agencies have become increasingly important, and have been more successful at escaping the calcification of state and federal bureaucracies.  Cost-effective contemporary water innovations are largely in water conservation, water markets, conjunctive use of ground and surface waters, wastewater reuse, and other actions which are more appropriately and effectively led and financed at local levels.

Most modern water systems are built around carefully crafted portfolios of water supply and demand management activities involving local, regional, and larger actions, users, and management agencies.  State and federal agencies are most important in establishing legal and regulatory frameworks for local agencies and users to cooperate, as well as federal and state agencies continuing to run Dominy-era water supply projects.

Although individuals remain important, the success of adaptive water management portfolios over local, regional, statewide, and inter-state scales relies increasingly on networks of people.  It is hard and slow to organize a group of people distributed among many agencies and interests, but an effective convergence of ideas across such a network can be effective and powerful.  Water management has always relied substantially on the development of informal networks of experts across agencies, interests, and academia to lead progress and support the development of effective legal and institutional frameworks.

Implications for California and the West

Water problems and solutions for the American West continue to change.  The region is a dry place, with a highly variable (and probably increasingly variable) climate, that supports a growing population and economy.

Three more recent books give some options and optimism for improving water management in the West (Lund et al. 2010; Hanak et al. 2011; Fleck 2016; Mulroy 2017).  These all point to the importance of moving beyond the large projects of the Dominy era and the pessimism of Cadillac Desert.  They all point out that despite the inevitability of water problems in the dry Western US, substantial prosperity and relative ecological success can occur with thoughtful and cooperative management.  Excessive focus on conflict, and not the benefits of cooperation, is the surest recipe for failure.

Further reading

Arax, Mark and Rick Wartzman (2005), The King of California: J.G. Boswell and the Making of A Secret American Empire, PublicAffairs.

Fleck, John (2016), Water is for Fighting Over: and Other Myths about Water in the West, Island Press.

Hanak, E., J. Lund, A. Dinar, B. Gray, R. Howitt, J. Mount, P. Moyle, and B. Thompson (2011), Managing California’s Water:  From Conflict to Reconciliation, Public Policy Institute of California, San Francisco, CA, 500 pp.

Hundley, N. (1992), The Great Thirst: Californians and Water-A History, University of California Press, Berkeley, CA, revised 2001.

Kahn, Debra (2017), “Wry Jeremiah saw folly in dam construction’s ‘go-go years’,” E&E News, April 3, 2017

Kahrl, William (1983), Water and Power: The Conflict over Los Angeles Water Supply in the Owens Valley, University of California Press, Berkeley, CA.

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

Maass, A. (1951), Muddy waters; the Army Engineers and the Nation’s rivers, Harvard U. Press, Cambridge, MA.

Mulroy, Pat (ed) (2017), The Water Problem – Climate Change and Water Policy in the United States, Brookings Institution, Washington, DC., especially Chapter 4 on the Colorado River.

Morgan, Arthur E. (1971), Dams and Other Disasters: A Century of the Army Corps of Engineers in Civil Works, Porter Sargent Publisher.

Reisner, Marc (1986), Cadillac Desert: The American West and Its Disappearing Water, Revised in 1992, Penguin Books.

Worster, Donald (1985), Rivers of Empire: Water, Aridity, and the Growth of the American West, Pantheon Books.

Jay Lund is a Professor of Civil and Environmental Engineering at the University of California – Davis, where he is also Director of the UC Davis Center for Watershed Sciences.

Posted in California Water, Climate Change, education, Planning and Management, Stressors, Sustainability, Water Supply and Wastewater | 10 Comments

San Joaquin Valley Water Supplies – Unavoidable Variability and Uncertainty

Dry fields and bare trees at Panoche Road, looking west, on Wednesday February 5, 2014, near San Joaquin, CA. Photo by Gregory Urquiaga/UC Davis 2014

by Brad Arnold1, Alvar Escriva-Bou2, and Jay Lund1

1 UC Davis Center for Watershed Sciences

2 Public Policy Institute of California

Passage of the Sustainable Groundwater Management Act (SGMA) and the recent drought have brought attention to chronic shortages of water in the San Joaquin Valley. Although the portfolio of water flows available to the Valley is diverse, several major inflows – including groundwater use, Delta imports, and local streamflows – are unsustainable or threatened by climate change and environmental demands. Here we examine long-term balances for San Joaquin Valley’s water supplies and demands that we discussed in a prior blog post.

In addition to the San Joaquin Valley’s substantial long-term water imbalance, many of its individual water supplies are highly variable and involve substantial operational, regulatory, and planning uncertainties. Not only is there growing concern for water scarcity for the San Joaquin Valley, the character and causes of this scarcity are highly and unavoidably variable and uncertain. We look at how major flows into and from the Valley vary and the uncertainty in such water balance estimates, with some policy and management implications.  

Large Variations in Valley Water Supplies and Use

The San Joaquin Valley’s water supply portfolio varies each year. Precipitation and river runoff from the central and southern Sierra Nevada and Coastal Range all vary greatly each year. Changing water conditions, such as those in recent droughts and wet years, provide a stark reminder of their immense variability.

The San Joaquin Valley. Map prepared by USGS.

A typical year’s ‘natural availability’ of river inflows averages about 10.1 MAF/year, roughly 56% of all Valley inflows from 1986 to 2015. These total river flows vary substantially each year, from 3.0 MAF in a dry year (2015, minimum) to 21.9 MAF in a wet year (1998, maximum); typical variation of approximately 5.6 MAF from the average in any given year. Other Valley inflows also vary annually – specifically SWP and CVP Delta Imports – and this erraticism of inflows can cause major impacts to the water balance in any single year (especially affecting San Joaquin River flows and groundwater pumping).This variability brings planning and management challenges and uncertainties for the Valley’s water resources.

When surface water inflows, outflows, and uses are “out of balance,” the difference typically comes from drawdown or refill from groundwater or surface reservoirs. Reservoir storage generally follows a seasonal refill and draw-down pattern – with additional refilling in wetter years balancing drawdowns in drier years. Groundwater storage shows a seasonal drawdown-refill cycle, and much larger imbalanced drawdowns in drier years (averaging about 1.8 MAF/year of San Joaquin Valley overdraft). The plot below compares annual natural availability data to other annual outflow and inflow for the San Joaquin Valley.

Natural nvailability data plotted with outflows and uses for 30-year period.

From linear regression lines for these scatter plots, an average annual decrease of 500 thousand acre-feet in Valley-wide natural availability (decreased Sierra Nevada, Coastal Range, and precipitation flows) generally coincides with the changes presented here:

Approximate changes to San Joaquin Valley outflows and uses
resulting from changes in natural availability (for the period 1986-2015).

These statistical regression slopes – constrained so slopes close the water balance – illustrate the relative trends and magnitudes of water flows and management responses to wet and dry years in the San Joaquin Valley. In drier years the major response is much greater groundwater pumping, reduced San Joaquin River outflows, somewhat decreased agricultural and urban net water use, and more withdrawals from surface reservoirs. In wetter years, many of these responses reverse.

Balanced water management in California must prepare to operate across diverse wet and dry year conditions. Large outflow and water use changes, and long-term groundwater overdraft, are clearly seen, including recent droughts – where natural availability averaged 2.3 MAF/year less for 2007 to 2015 than its 30-year average. If natural availability becomes more variable, as predicted with climate change, the result will likely be larger fluctuations in the Valley’s water balance. Valley inflows, outflows, and uses vary greatly, and vary together.

Large Statistical Uncertainty in Major Inflows

Estimates of individual inflows or outflows are more straightforward, but always include some error from measurement inaccuracy, modeling uncertainty, and hydrologic variability. The “standard deviation of the average” is an index of uncertainty in average flows based on statistical chance the “actualaverage flow differs from the historical sample average. Long-term averages are statistically better-behaved than estimates for a single year. However, if climate and underlying hydrologic processes are changing, errors may become less well-behaved.

Average flow estimates, such as those for the San Joaquin Valley water balance, are the basis for many water policy, planning, management, and regulation decisions. Averages are central for implementing the water budgets required by SGMA, estimating impacts for an environmental flow policy, and decisions to invest in water infrastructure or to trade water. But such averages often mask great variability and uncertainty. Given the economic value of this water, and how economic valuations ($/acre-ft) change from dry to wet periods, errors and variability from averages are important.  

Here we look at uncertainty in annual inflows from the Central and Southern Sierra Nevada – the origins of most natural availability for the San Joaquin Valley. Confidence in these flows is important to analyzing water demands and uses (especially for calculating groundwater overdraft as a water balance “closure term”). Technical Appendix A of the recent PPIC report details the river/inflow selection process and data sources.

Uncertainty range of flows for major San Joaquin Valley surface inflows. Average plus and minus standard deviation of annual flows and (smaller) standard deviation of average annual flows.
Second columns do not include recent drought years 2007 to 2015 data.

These data show important results: total standard deviation in average central Sierra Nevada inflows is about 1.74 MAF/yr, and southern Sierra average inflows have a standard deviation of 600 TAF/yr. This means there is a 33% chance the ‘actual’ average flows may deviate more than these amounts from the historical averages, either more or less. Neglecting recent drought years from 2007 to 2015 doesn’t necessarily reduce this uncertainty. There is substantial uncertainty in published “Full Natural Flow” estimates, both in single year and long term average values. If climate model projections are correct, climate change could make this long-term uncertainty even greater than uncertainty estimates based only on historical statistics alone.

Regional water balances have large uncertainties and intricate internal variabilities. Planning around water balances often overlooks these uncertainties. Three important implications from these unavoidable uncertainties and variability are:

  1. Given California’s natural hydrologic variability, and the inherent uncertainty of our models, water and groundwater plans need to be prepared for simple long-term water balances to be substantially wrong. Plans must support adjustments and adaptations into the future. This is especially relevant for SGMA-required local Groundwater Sustainability Plans.
  2. Water plans and operations also need to prepare for substantial variability in sources of water available across years. Source and sustainability planning should also account for uncertainty estimates and try to reduce them over time to improve the accuracy of their water budgets estimations.
  3. To reduce and better understand water uncertainties and variability, and improve collaboration among local and state interests, more solid regional water accounting and measurement is needed.

Further Reading:

Arnold, Brad, Alvar Escriva-Bou, Jay Lund, and Ellen Hanak (2017). Accounting Water for the San Joaquin Valley. California WaterBlog.

Arnold, Brad, and Alvar Escriva-Bou (2017). Water Stress and a Changing San Joaquin Valley. Technical Appendix A: The San Joaquin Valley’s Water Balance. 13 pp. Public Policy Institute of California, San Francisco, CA.

Escriva-Bou, Alvar, Henry McCann, Ellen Hanak, Jay Lund, Brian Gray. 2016. Accounting for California’s Water. Public Policy Institute of California.

Hanak, Ellen, Jay Lund, Brad Arnold, Alvar Escriva-Bou, Brian Gray, Sarge Green, Thomas Harter, Richard Howitt, Duncan MacEwan, Josue Medellin-Azuara, Peter Moyle, and Nathaniel Seavy (2017). Water Stress and a Changing San Joaquin Valley. 48 pp. Public Policy Institute of California, San Francisco, CA.

Posted in California Water, Planning and Management, San Joaquin River, Water Supply and Wastewater, Water System Modeling | 5 Comments

Can Sacramento Valley reservoirs adapt to flooding with a warmer climate?

Englebright Spillway during the 1997 flood

Clementime Dam on the North Fork American River overtopping in 1997. Photo by Rand Schaal.

by Jay Lund and Ann Willis

Much has been written on potential effects and adaptations for California’s water supply from climate warming, particularly from changes in snowpack accumulation and melting, sea level rise, and possible overall drying or wetting trends.   But what about floods?

In a paper in the journal San Francisco Estuary and Watershed Science, we along with co-authors from the US Army Corps of Engineers review much of the literature to date and examine how Shasta, Oroville, and New Bullards Bar reservoirs might adapt to floods in a warmer climate, including a climate that is either wetter or drier.

Oroville Spillway during the 1997 flood

A torrent of water flowing from the Oroville Spillway during the 1997 flood

Since no one knows exactly what future floods will look like, the nine largest floods from the historical record were hydrologically modified to be warmer and either wetter or drier, using the National Weather Service hydrologic model used for flood forecasting.  These many modifications to past major floods were then run through a US Army Corps of Engineers’ model for flood operation of these reservoirs to evaluate what might happen, given the way we currently operate these reservoirs.  The results were both reassuring and disturbing.

1. Warming generally worsened flood inflows into reservoirs.  Even with less precipitation, warmer conditions often increased flood inflows to reservoirs.  When more precipitation fell as rain, rather than snow, and more existing snowpack melted, flood volumes increased.  This was particularly true for historical storms that were “cold”, where much of the precipitation was held as snowpack.  Warm storms, which historically produced less snow, were less affected by warming.

2. Reservoirs with flood operating rules that respond to the wetness of their watersheds seemed to adapt well to changes in climate, even fairly severe changes in temperature and precipitation.  This was true for Shasta and Oroville Reservoirs, whose existing flood operation rules vary with moisture conditions upstream.  This shows that existing reservoirs may have considerable ability to accommodate flooding effects of climate warming.

3. Reservoirs with flood operating rules that do not respond to upstream conditions may perform poorly with climate warming.  For example, New Bullards Bar’s flood rules do not change with upstream snowpack and wetness conditions.  For many plausible climate changes, modifications of past floods overtopped this dam, a potentially catastrophic flood risk for downstream residents.

Large uncertainties are common when dealing with both the future and the weather.  Nevertheless, some things can be known, or at least strongly suspected and supported, from reasoning that is organized, refined, and tested using computer modeling.

Accommodating changes in climate with changes in operating rules can often require changes in reservoir outlets (which can be costly) and changes in federal operating policies and authorizing legislation (which can be protracted and difficult).  Nevertheless, it is comforting to know that existing policies for some reservoirs seem to do well with changes in climate, and that making other reservoirs more reactive to upstream wetness conditions might make them more resilient to changes in climate, even before we know what the changes are.  Such changes in policies, while politically awkward and requiring some expense, appeared likely to be less expensive than major reservoir expansions or the costs of a major flood.

In terms of floods, climate warming need not mean that the sky is falling.  We are likely to have considerable ability to respond effectively, but in some cases, we will likely to need to make major changes.  Appropriate preparations will not be easy, but they should be possible with capable institutions at the federal (US Army Corps of Engineers), state (DWR, Central Valley Flood Protection Board), and local (counties, cities, and levee districts) levels.

Jay Lund is the director of the Center for Watershed Sciences. Ann Willis is a staff researcher at the Center for Watershed Sciences.

Further reading:

Willis, Ann D; Lund, Jay R.; Townsley, Edwin S.; Faber, Beth A (2011), “Climate Change and Flood Operations in the Sacramento Basin, California,” San Francisco Estuary and Watershed Science, July, Vol. 9, No. 2, 18 pages.

Posted in California Water, Climate Change, Floodplains | Tagged , , , , , , , | 2 Comments

Irrigation Management in the Western States, seen from overseas

by Fandi P. Nurzaman

The transformation of the western United States by irrigation offers hope for developing countries looking for models to improve their irrigation system for food security or agricultural prosperity.

The transformation of the American West from barren desert and low value grazing into one of the largest agriculture areas in the United States would be impossible without irrigation. Water supply infrastructure currently delivers waters for about 40 million acres of irrigated land (74% nationwide) across arid regions in the Western.

Replicating the same irrigation systems from the Western States would be impossible, but how irrigation institutions and financing mechanisms were developed to adapt some challenges in the past could still be useful practices.

Irrigation has been employed in the 17 western states for several centuries. At least since the 7th century, vast networks of canals were used by the Hohokam people in central Arizona for agricultural irrigation for the highest population density in the prehistoric of American Southwest. The Hohokam irrigation system was simple, but applied hydraulic engineering design features still used today and also became the precursor to modern-day Arizona’s major canal system.

During Spanish colonization in the American Southwest, irrigation was used to support agriculture and ensure political control in these areas by the Spanish Government. Settlers were granted access to irrigation water to secure and defend the colonized areas. The construction of complex and expansive irrigation systems, along with the introduction of water governance in those systems, became one of the most significant accomplishments of the Spanish Colonial period in the American Southwest.

Early in the 19th century, irrigation-based communities became more common and widespread in the western states as . The Mormons established the first irrigation-based economy and basic principles of water law. These principles became an important legal precedent for Western water law when they abandoned riparian water rights and adopted the doctrine of “prior appropriations for beneficial use.

After acquisition of the West by the United States, irrigation systems were rapidly developed to promote economic development and speed privatization of newly acquired arid and semiarid public land. Hundreds of irrigation projects and major dams were constructed as part of the Reclamation Projects, which currently irrigate about .

Expansion of irrigation in the western states also was supported by the transformation of institutions that deliver water and operate irrigation infrastructures. Neighbor-farmers created coownership in joint irrigation networks. These institutions ranged from unofficial organizations (unincorporated mutual systems) to legally constituted cooperative corporations under state law (incorporated mutual systems) or special local political subdivisions of state government (irrigation districts). Large irrigation projects with larger economies of scale and capital expenditures were not feasible by simple cost sharing among farmers. Institutional breakthroughs were developed to tackle financial barriers and to adapt regulatory challenges.

More recently, new problems pose challenges for water supply that developing countries should consider. As the population and concern for environment and sustainability grow, managing irrigation systems in the Western States becomes more challenging. Some water must be dedicated to ecological benefits, but environmental water uses were rarely counted as major water uses in the past. These , either for recreation or the environment, will increase competition for water and make irrigation water more vulnerable to water shortage, a perennial risk in the American West.

California’s recent Sustainable Groundwater Management Act (and similar regulations in other states) also will affect farmers and ranchers who use groundwater to supplement or replace shortages of surface water. These regulations will increasingly shape how groundwater is managed.

Western US farmers also have faced increasing discontinuance of irrigation due to inability to get irrigation water or economic driven factors such as rising costs for irrigation water. Decreasing irrigated acres in the long term could lead to economic losses for rural areas in the Western States. Farmers are likely to increase use of precision irrigation and to increase on-farm irrigation efficiencies. When severe drought happens again and water restrictions and curtailments occur, farmers might prefer to fallow some fields (to support other higher value crops) or sell their water during the drought. These irrigated areas significantly contribute to the United States’ economy and the Western States’ economies. Without irrigation, many agriculture products, especially wheat, vegetables, fruits, tree nuts, and berries, along with cattle farming and dairying products would be imported from other parts of the United States or other countries.

Irrigation has a foundational role in the development of the Western US. Developing countries could benefit by understanding the challenges encountered by the Western US and adjusting their irrigation system based on the Western US practices in order to address local issues they are facing.

Fandi P. Nurzaman is a graduate student at Department of Civil and Environmental Engineering, UC Davis and National Planner for Water Resources and Irrigation at the Indonesian Ministry of National Development Planning.

Further reading

Bretsen, S. N., Hill, P. J. (2007). “Irrigation Institution in American West.”  UCLA Journal of Environmental Law and Policy Vol. 25:283.

Howard, J. B. (1992). “Desert Canals: Hohokam Legacy.“ Pueblo Grande Museum Profiles No. 12. https://www.phoenix.gov/parkssite/Documents/d_048513.pdf.

Hutchins, W. A. (1931). “Summary of Irrigation-District Statutes.” United States Department of Agriculture, Miscellaneous Publication No. 103, January 1931.

Mays, W. M., (2016). “Irrigation Systems, Ancient.” Water Encyclopedia: Science and Issues. http://www.waterencyclopedia.com/Hy-La/Irrigation-Systems-Ancient.html. (November 29, 2016).

Nurzaman, F.P. (2017) Irrigation Management in the Western States, MS project Report, Department of Civil and Environmental Engineering, University of California – Davis.

Rivera, J. A., Glick, T. F. (2002). Iberian Origins of New Mexico’s Community Acequias.” The XIII Economic History Congress, Buenos Aires, Argentina, July 2002.

Zarr, G. (2016). “How the Middle Eastern Irrigation Ditch Called Acequia Changed the American Southwest.” AramcoWorld Vol. 67, No. 5, September/October, 2016.

Posted in Around the World, California Water, Planning and Management | 2 Comments

Summer Snowmelt Safety – Know the Flow Before You Go

Aerial image at sunset of the Sierra Nevada mountains covered in clouds and snow. Photo taken on June 9 by Megan Nguyen.

By Megan Nguyen

As recently as this weekend, winter storms have brought much snow to the Sierra Nevada after five years of drought. Warm temperatures have begun to melt the mountain snow that will flow down the valley through a network of rivers. The recreation opportunities seems endless: Mammoth Resort announced they plan to stay open until July 4th or even longer. Whitewater enthusiasts are enjoying flows not seen for a decade in rivers from the North Fork American to the Merced and beyond.

But though the rivers may be tempting this summer, the high flows and cold temperatures make rivers deceptively dangerous. Rivers with high flows and cold temperatures can claim the lives of even the most experienced and skilled swimmers. Three people on the Kern River have already died and 24 were rescued. And with the large snowpack, these fast-flowing, cold conditions are likely to continue long into the summer season.

Having been in drought for the last five years, we are not used to seeing these much colder and larger flows so late in the year. Water year 2017 (October 1, 2016-September 30, 2017) has surpassed the wettest year on record (1982-83) in the Sacramento and San Joaquin watersheds. According to NASA, this winter has brought more snow than the last four years combined.

Satellite imagery showing snowpack comparison between 2015 and 2017. Source: NASA

But these extremes aren’t unusual for California. California has a Mediterranean climate, where almost no rain falls during summer. During the cooler winter, there is large variability in yearly precipitation – the most extreme in the nation – resulting in a wide potential for flood or drought in any year.

Nevertheless, California species, both human and nonhuman, have adapted to these extremes. Snowmelt recession is an important environmental cue for species mating such as the foothill yellow legged frog in the Sierra Nevada. These frogs have adapted to California’s seasons and are genetically wired to lay eggs during the spring snowmelt when river flows recede and water temperatures increase.

A female foothill yellow-legged frog (Rana boylii) waiting to lay eggs (gravid). Source: Ryan Peek

Humans have also taken advantage of California’s wet winter patterns. Snowpack reserves are an essential and natural form of water storage. On average, the snowpack provides about 30 percent of California’s water supply as it melts in the spring and early summer.

In addition, the long snowmelt season provides surface water long into the dry season. The average snow water equivalent (SWE) measures the amount of water contained within the snowpack. It can be thought of as the depth of water that would theoretically result if the  entire snowpack melted instantaneously. The snowpack measured on April 1 is the standard that typically measures peak snowpack.

As of June 1, 2017 the Central Sierra snowpack was 72% of the April 1 average, which is a dramatic increase from the last five years (Table 1.) With a SWE of 20.9” on June 1, 2017, there is enough snowmelt to keep reservoirs and rivers swollen for months to come.

Snow Water Equivalents for the Central Sierra snowpack provided by the California Cooperative Snow Surveys. Source: CDEC

However, rising temperatures induced by climate change may result in drier summer conditions and more precipitation as rain than snow. Also, earlier snowmelt may threaten California’s water supply and species dependent on snowmelt cues. Throughout the American West, scientists have already seen snowmelt starting earlier compared to historic trends, as well as an overall decrease in the average amount of snow.

We are glad to see the mountains still capped with snow as they serve as an important water storage resource for California. Be prepared for snowmelt to stream down the mountains for many more months to come. Below you will find some useful resources to help you find information such as river stage height and temperature so you can be aware of river conditions and have fun this summer season.

  1. Daily Snowpack Readings
  2. Current River Conditions
  3. Daily Statewide Hydrologic Update

Megan Nguyen is a GIS researcher and Outreach Coordinator at the Center for Watershed Sciences. Her work and interests revolve around a variety of topics such as drought impacts, flood mitigation, environmental policy, and education outreach.

Further Reading

Snowpack Statewide Water Content is below Average.” 2017. Department of Water Resources.

Mote, P.W. et al. 2005. Declining mountain snowpack in Western North America.

Stewart, I.T., et al. 2004. Changes toward earlier streamflow timing across Western North America.

Peek, R., H. Dahlke, S. Yarnell. 2016. Linking water source signatures with native amphibian breeding timing in a Northern Sierra Nevada watershed. Hydroecology C10. Presentation for Annual Meeting at Society for Freshwater Science, Sacramento CA.

Posted in California Water, Climate Change, education | 1 Comment

Blacklock Marsh: Tidal Habitat No Panacea for Thoughtful Restoration

This view of a duck hunting club in Suisun Marsh shows both a highly modified environment and reflects its potential for being managed as a reconciled ecosystem. Photo by P Moyle.

by John Durand and Peter Moyle

Returning open tidal exchange to diked lands is a primary goal of Delta restoration, driven by the 2008 Biological Opinion from USFWS. This document requires 8000 acres of tidal and subtidal habitat to be created. California EcoRestore is coordinating with state and federal agencies to restore at least 30,000 acres, much of which will be tidal or subtidal.

Evidence from newly created tidal wetlands, however, does not support the basic concept behind these restoration actions: that dikes can be breached and then left alone, to create tidal habitat with high benefits to endangered fishes.  Our research shows that simply re-creating tidal flow alone will not provide habitat and food for delta smelt, juvenile salmon or other native fishes. An example of an early tidal wetland project in Suisun Marsh is the Blacklock Restoring Marsh, a former duck club located in Suisun Marsh, which was opened to full tidal exchange in 2006, when its dikes were breached.

We studied the water quality, food production and fish community at Blacklock from October 2013 to June 2015. During that period, Blacklock consistently underperformed adjacent tidal sloughs and managed wetlands. For example, its chlorophyll production, a measure of potential food web supply for native fishes, was generally low. In contrast, we found much higher high chlorophyll production in a nearby managed wetland (Luco Pond) and dead-end sloughs that were sampled concurrently.

Heat map showing the distribution of chlorophyll-a concentrations across the northwest region of Suisun Marsh during 2014 and 2015. A) Spring series of measurements, February-June; B) Fall series, October-November. Blacklock Marsh is shown in the box.

Likewise, zooplankton, the main food source for pelagic fishes like smelt, or larval fishes of all species, were in low abundance in Blacklock Marsh but high in our other sites, particularly Luco Pond.

Zooplankton densities, stacked by species, in three nearby habitats of the northwest Suisun Marsh. Note that the scale for Luco Pond is different, due to the high concentration of zooplankton found there.

Fish community composition and abundance was also poor for Blacklock when compared to adjacent sites. Catch in Blacklock was dominated by non-native fishes, including Mississippi Silversides, an invasive fish that feeds on eggs and larvae of native species. Adjacent sites had larger catches of native Sacramento Splittail (a species of special concern) and Tule Perch.

Data from trawl sampling of fish in Blacklock waterways. Blacklock was dominated by non-native fishes, including the invasive Mississippi Silversides, and had the lowest species diversity of any of the sites.

Why does a recommended restoration action not work on Blacklock Marsh? Likely, the biological opinion overstates the importance of tidal restoration to Delta Smelt. There remains no direct evidence that wetlands will directly benefit smelt. Although the San Francisco Estuary was dominated by tidal wetlands before the mid-1800s, today’s Bay-Delta is a very different place. Restoration based upon historical conditions will not provide the same benefits as they did over 100 years ago. For more insight as to why this might be the case, please refer to our earlier blog, Reconciling conservation and human use in the Delta.

In order to reap the benefits of tidal restoration, active management is required. Just as we actively manage the flow of water across the Delta for water supply, so we need to manage for desired ecosystem benefits. Managed wetlands, like Luco Pond, Wings Landing, and many others throughout Suisun Marsh, often provide important benefits to aquatic species, in addition to providing food and habitat for waterfowl.

In order to make Blacklock Restoring Marsh more beneficial for desirable aquatic organisms, it must be re-engineered. Currently a warm shallow pond sits in the middle of the site, providing silverside habitat. This should be removed by grading or aggrading, combined with emergent vegetation replanting. The two breaches that allow tidal exchange should be hydrodynamically separated by a levee, and the perimeter ditch should be made continuous to allow water circulation.

Blacklock Marsh, showing recommended modifications. Blue arrow indicates a directional tidal gate at the north breach; blue and white striped rectangle shows placement of a weir at the mouth of the south breach; dashed yellow line indicates placement of a berm to separate in- and out-flows at the breaches; green and white polygon shows placement of infill to eliminate shallow water tidal ponds. Blue lines indicate potential slough connections to upslope habitat.

Although this recommendation contradicts the USFWS biological opinion, our research supports gating at least one of the breaches (and preferably both) to control the flow of water across the site, allowing management of phytoplankton and zooplankton production rates, as well as access by invasive organisms. Such control would allow two additional benefits: 1) experimental manipulation to understand how the site responds to different flow strategies; and 2) the ability to drain the site if it becomes infested with undesirable organisms, an ongoing problem to restoration in the San Francisco Estuary.

Finally, connecting the perimeter ditch with slough channels to the southwest of Blacklock would increase the slough length relative to the tidal excursion ratio and would also allow upslope ephemeral creeks to periodically introduce sediment, nutrients and organic carbon, all of which promote native fish habitat and food production. The Department of Water Resources has already purchased the property; we look forward to working with them to integrate the landscape in a more integrated and functional way.

Breach-and-leave is no panacea for real, thoughtful restoration. While we do not fully understand the novel ecosystem that has been inadvertently created in the San Francisco Estuary over the last 150 years, we know enough to realize that a collection of small tidal marshes with breached levees, sprinkled across the landscape, will not create desirable outcomes. We should implement restoration in a careful way, using experimental practices that allow us to study, reverse, and redesign as needed to create the habitats that are demanded by various stakeholders, whether to benefit fish, water delivery, elevation reversal, water quality, or recreational opportunities.  In a complex estuary, one size does not fit all.

John Durand is a researcher specializing in estuarine ecology and restoration at the UC Davis Center for Watershed Sciences. He oversees projects in the north Delta Arc of habitat including the Cache Lindsey complex and Suisun Marsh.  Peter Moyle is a UC Davis Professor Emeritus of fish biology and an associate director of the Center for Watershed Sciences. 

Further reading

Hobbs RJ, Arico S, Aronson J, Baron JS, Bridgewater P, Cramer VA, Epstein PR, Ewel JJ, Klink CA, Lugo AE, et al. 2006. Novel ecosystems: theoretical and management aspects of the new ecological world order. Glob. Ecol. Biogeogr. 15:1–7.

Mount J, Bennett W, Durand J, Fleenor W, Hanak E, Lund J, Moyle P. 2012. Aquatic ecosystem stressors in the Sacramento–San Joaquin Delta. Public Policy Inst. Calif.

Moyle PB, Light T. 1996. Fish invasions in California: do abiotic factors determine success? Ecology 77:1666–16670.

Nichols FH, Cloern JE, Luoma SN, Peterson DH. 1986. The modification of an estuary. Science 231:567–567.

Rosenzweig ML. 2003. Reconciliation ecology and the future of species diversity. Oryx 37:194–205.

Whipple A, Grossinger RM, Rankin D, Stanford B, Askevold R. 2012. Sacramento-San Joaquin Delta historical ecology investigation: Exploring pattern and process. Richmond, CA: San Francisco Estuary Institute-Aquatic Science Center Historical Ecology Program Report No.: 672.

Posted in reconciliation, Restoration, Sacramento-San Joaquin Delta | Tagged , | 4 Comments

Better Information Can Help the Environment

by Henry McCann and Alvar Escriva-Bou

This blog was originally posted on the Public Policy Institute’s Viewpoints blog.

Salmon swimming near Lake Tahoe. Image courtesy of PPIC.

We know that California’s aquatic species are at risk from a host of stressors and that drought pushes them closer to the brink. Yet there are significant gaps in our understanding of key factors affecting ecosystem health that make it difficult to effectively manage water for the natural environment. Good practices from other dry places offer lessons for protecting our struggling species and improving conditions in troubled ecosystems.

Water accounting―tracking how much is there, who has claims to it, and what is actually being “spent”―can provide a clearer picture of how and when to allocate water for the environment. Other states have improved their water information systems and reduced environmental problems.

For example, the Colorado Water Conservation Board has a network of high-tech stream gages to monitor freshwater ecosystems. These gages send text or email alerts to state environmental water managers within minutes of approaching low-flow conditions. Staff can respond quickly by requesting an evaluation of priority water needs among local water users and, where possible, shifting water to meet environmental needs.

By comparison, California lacks stream gages on half of the rivers and streams that support critical habitats. This makes active management of environmental water during droughts very difficult, if not impossible, in many parts of the state.

Better accounting can also help us prepare for drought, rather than just respond to it. Making better use of water during average and wet years can stabilize or enhance at-risk ecosystems. This increases their resilience to drought.

For example, drought-prone Victoria, Australia, uses sophisticated water accounting tools to coordinate environmental flows for all types of water years. Victoria also collects and organizes information on a number of critical ecological indicators for thousands of miles of streams and wetlands. This inventory informs Victoria’s short- and long-term decision making about where and when water will be most beneficial to ecosystems and thus helps build drought resilience.

California has a significant body of research on freshwater ecological indicators, but the information isn’t organized in ways that make it readily useful to environmental water managers.

Managing water for the environment is more than a technical challenge. It’s a social process that relies on complex decisions made by water users, regulators, and other stakeholders. Examples from other arid regions suggest that this social process is improved by having access to accurate and timely information. Strengthening water accounting in California is key to improving our ability to manage water for the environment and building the social license necessary to act. Before the next drought pushes more freshwater species to the brink, we would be wise to follow the lead of other semi-arid regions and invest in accounting systems that improve our understanding and management of our rivers and streams.


Henry H. McCann is a research associate at the PPIC Water Policy Center, where he works on data collection, analysis, mapping, and legislative tracking. Alvar Escriva-Bou is a research fellow at the PPIC Water Policy Center.

Further reading

Read the report Accounting for California’s Water (July 2016)
Read “Three Lessons on Water Accounting for California” (PPIC Blog, August 8, 2016)

Posted in California Water, Conservation, Planning and Management, Sustainability | 5 Comments

The Future of California’s Unique Salmon and Trout: Good News, Bad News

Rainbow Trout. Photo taken by Mike Wier. Courtesy of CalTrout.

by Robert Lusardi, Peter Moyle, Patrick Samuel, and Jacob Katz

California is a hot spot for endemic species, those found nowhere else in the world.  Among these species are 20 kinds of salmon and trout. That is an astonishing number considering California is also literally a hot-spot in terms of summer temperatures and that these salmonids are cold-water adapted. These 20 endemic are joined by 12 other species with broader distributions, north along the Pacific Coast.  In California, native salmon and trout are at the southern end of the range.  They survive here because mountains intercept rain and snow in the cooler months of the year and the powerful California Current keeps the ocean and coast cool year-round.  The big question is: can California’s diverse salmon and trout continue to persist in the face of a warming climate and declining coldwater resources?

We think the answer to this question is yes. But first, the bad news.  A new report issued by the Center for Watershed Sciences and California Trout has found that nearly 75% of the state’s salmon and trout (salmonids) could be extinct within the next 100 years.  Nearly 45% could meet the same fate in just 50 years if present trends continue. The good news is that the report shows that most of these fishes can continue to persist if appropriate actions are taken.

Chinook Salmon jumping out of the water. Photo taken by Mike Wier. Courtesy of CalTrout.


The report, State of the Salmonids II: Fish in Hot Water, was officially released on May 16th.  Originally conceived as an update on a report published in 2008, this report contains new information on how to maintain resilient populations. The report explores three important questions: 1) what is the status of all California salmonids, both individually and collectively, 2) what are the major factors responsible for their present status, and 3) how can California’s salmonids be saved from extinction?  To answer these questions, we conducted a thorough literature review and interviewed more than 70 species experts from fishery management agencies over a 14-month period.  Based on this research and interviews, the authors generated a full scientific account for each species. Each account was then peer reviewed by at least one, and often two or more, species experts.

We evaluated the status and future of each species using a standard set of seven criteria: (a) area occupied, (b) estimated adult abundance, (c) degree of dependence on human intervention to keep the species going, (d) physiological tolerance to changing conditions, (e) genetic risks, (f) vulnerability to climate change, and (g) threats from other factors, such as dams and diversions (each factor was evaluated separately to produce a composite score).  Each of the seven criteria was scored on a scale of 1 to 5, with 1 indicating the most extreme threat.  The scores were then averaged to produce an overall score, rating the ‘level of concern’ for each species (Table 1).  The scoring indicated 14 species were of critical concern, with a high risk of extinction in the wild, nine were of high concern, seven of moderate concern, and one of low concern (Figure 1).  One species, bull trout, is already extinct in California.

Table 1. Status categories, score ranges, and definitions for California salmonids.

Figure 1. Respective listings by state and federal management agencies, status scores, and Levels of Concern for California’s native salmonids.

Looking at this another way, 71% of anadromous salmon and trout and 74% of inland trout in California scored as critical or high concern, indicating a high likelihood of extinction in the next 100 years.  Further, 25 taxa are worse off than they were in 2008.  Downward changes in status were attributed to a continued decline from multiple factors, an improved scoring system, and the recent historic drought.  Species most likely to disappear from California included coho salmon, chum salmon, pink salmon, Sacramento winter-run Chinook salmon, two distinct populations of spring-run Chinook salmon, two distinct populations of summer steelhead, steelhead of the south coast, California golden trout, Kern River rainbow trout, and McCloud River redband trout.

Chinook Salmon. Photo taken by Mike Wier. Courtesy of CalTrout.

The good news is that 31 of 32 salmonids are still present in California.  This speaks to their ability to persist during difficult periods.  In fact, salmonids have been able to persevere for more than 50 million years despite volcanic eruptions, earthquakes, mega-droughts, and other climatic extremes.  Their ability to make it through these events is a reflection of the evolutionary enriched behavioral and life history diversity among populations and species.  Behavioral and life history diversity contribute to population and species resiliency under changing conditions.  When times are challenging, some populations die off while others hang on, ensuring long-term species persistence.

Over the last century, however, the ability of most of these salmonids to adapt to changing conditions has been greatly reduced due to rapid and extreme habitat degradation and interactions of hatchery salmonids with wild salmonids.  As a result, salmonids are more vulnerable to changing conditions today than ever before. This is particularly alarming considering that our analysis found that climate change was a critical or high threat for 84% of all salmonids in California, making it the single largest threat.  Climate change is affecting streamflow and temperature, reducing habitat, shifting food webs, and changing interactions between native and nonnative fishes.

The State of the Salmonids II report makes it clear that many native salmonids in California are on a trajectory towards extinction, if present trends continue.  The report outlines a set of solutions, termed “return to resilience,” the central tenet of which is improving behavioral and life history diversity of salmonid species.  The general strategy can be broken into two sets of actions:  managing places and conceptual strategies.  Within “places,” we recommend focusing on protecting and/or restoring four important types of habitats throughout California.  These include the following, which are not mutually exclusive:

1) Stronghold Watersheds, or the remaining fully functioning aquatic ecosystems in California such as the Smith River, Blue Creek, and the Eel River, so that they may continue to protect and enhance salmonid diversity,

2) Source Waters such as mountain meadows, springs, and groundwater, which will be vitally important in buffering the effects of climate change and providing cold water during the late summer and drought, and

3) Productive and Diverse Habitats including floodplains, lagoons, coastal estuaries, and spring-fed rivers—these are some of the most productive aquatic systems in California which have been shown to increase salmonid growth rates, alter migration timing and life history diversity, and improve adult returns.

4) Endemic Trout Waters. These are the isolated waters scattered around the state that are important for species like Eagle Lake Trout, California golden trout, and McCloud River redband trout. If the waters are altered significantly, the factors that make the endemic species unique will be lost.  Good examples, in progress, include restoring streams that support Goose Lake redband trout, restoring Pine Creek (the principal spawning stream for Eagle Lake rainbow trout), or enhancing flows in streams that support southern steelhead.

The report also discusses three important, conceptually based strategies to enhance salmonid diversity and production.

The first strategy is to embrace reconciliation ecology as a management tool.  Most ecosystems in California are altered by human actions with people continuing to be a key part of the ecosystem.  If the mechanisms supporting enhanced salmon and steelhead growth and diversity can be replicated in working landscapes, then this concept should be embraced.  A good example of this is the Yolo Bypass in the Central Valley where rice fields are being used as surrogate floodplain habitat and have been shown to greatly enhance growth in juvenile salmonids.

Southern Steelhead. Photo taken by Mike Wier. Courtesy of CalTrout.

We also recommend improving habitat connectivity and passage to historical spawning and rearing habitat. In general, improving connectivity among habitats used by different life stages of salmon and trout is desirable, as is renewed connectivity to historical spawning and rearing habitats.  Restoring connectivity of main rivers to their floodplains is one example of this. This also includes providing volitional passage over dams or removing dams that are no longer economically viable.  Access to historical spawning and rearing habitat may enhance population diversity and resilience to change.

The final concept for managing coldwater fishes is genetic management. The genetic effects of hatchery salmonids on wild fish are numerous and well documented.  Broad changes in genetic management and a reduction in interactions between hatchery and wild fish is required and is of fundamental importance.  At a minimum, such changes include the need to reduce gene flow between hatchery and wild salmonids, minimize straying of hatchery fish into adjacent watersheds, and marking all hatchery fish so that they can be distinguished from wild fish.

These “return to resilience” strategies are not limited by geography or taxonomic boundaries.  Rather, the actions should to be applied broadly throughout California if we want to have these iconic fish around for future generations of Californians.  The challenges in improving salmonid behavioral and life history diversity are not easy and require collective will.  We are optimistic that positive change is imminent and that if the solutions are fully implemented, many of the species reviewed in the State of the Salmonids II report will thrive in the future.

Robert A. Lusardi is a researcher at the Center for Watershed Sciences and is the California Trout-UC Davis Coldwater Fish Scientist.  Peter Moyle is a UC Davis Professor Emeritus of fish biology and an associate director of the Center for Watershed Sciences.  Patrick Samuel is the Conservation Program Coordinator for California Trout. Jacob Katz is a Senior Scientist at California Trout.

Further reading

State of the Salmonids: Fish in Hot Water

Posted in Biology, California Water, Climate Change, Conservation, Fish, reconciliation, Salmon, Stressors, Uncategorized | Tagged , , , | 6 Comments

Facing Extinction II: Making hard decisions

Sacramento perch is an example of ‘gray’ extinction because it has been extirpated from its native habitats in the Central Valley. It exists only in a diminishing number of places where it has been transplanted. Photo is by Chris Miller of the Contra Costa Vector Control Agency and is from the CalFish website.

by Jason Baumsteiger and Peter Moyle

In part I of our blog, we projected a bleak future for many freshwater fishes, especially in California. Some difficult decisions will need to be made to prevent extinctions or to verify them.  However these decisions will rely on answers to one sweeping question: When is a species, in fact, extinct?

Some may argue this is a simple black/white or presence/absence question. But is it really? What if the species’ existence depends completely on humans? What if it no longer exists in its natural habitat or in the wild? What if it has been hybridized or genetically engineered? In such cases, is it fair to say this species is still the same as its wild predecessor?

In our recent paper, we attempted to tackle these questions and provide an honest, although imperfect, way to assess extinction. The first involves accepting that “grey extinction” exists. This is an area between formal threatened/endangered status and global extinction, where a species is in limbo – it is partially extinct. We know this sounds weird because under traditional usage extinction is an all or nothing proposition. However, there are in fact grey areas; they fall into five categories. Each represents ways a species may be partially extinct. These categories are by no means exhaustive, but do represent a reasonable framework where partial extinction can be examined closely. We look at these categories through the eyes of biologists trying to conserve species through either a single-species or a multi-species approach. We then weave these ideas into a decision tree to help managers recognize fishes (or any organism for that manner) which have reached “grey extinction” limbo.

Categorizing “grey extinction”

Mitigated extinction- This category represents the many ways that a species can become dependent on humans for its existence. The formal term is conservation-reliant but it just means that if we are not there to provide support, the species will quickly become globally extinct. Actions might include protection from predators, protection of habitat or even finding mating partners. Winter-run Chinook are a good example: they depend on humans for spawning habitat and early life-history protection (food, predator and disease avoidance). Without human intervention, winter-run Chinook (thanks to Shasta Dam) would quickly cease to exist.

Regional extinction – Here we are talking about what happens when a significant portion of a species’ range has been lost. Now you might say, isn’t that just extirpation? To which we would say, not necessarily. Regional extinction applies when a very distinct portion of that range is lost, such as a region occupied by a distinct population segment (DPS) or an evolutionarily significant unit (ESU). In California, a good example is the isolated population of bull trout that once existed in the McCloud River, which became extinct in the 1970s. The species is still widely distributed and a threatened species in much of its range, but it is now absent from California.

Native-range extinction – As the name implies, this is a species which no longer exists in its natural range but may exist elsewhere (say a reservoir somewhere). So while there are “wild” fish swimming about, they are not in the area in which they originally evolved. In California, Sacramento perch have disappeared from their native habitats in Central California. However, they were planted around the West as a gamefish that could live in alkaline waters, developing large populations in places such as Crowley Reservoir in the Owens Valley or Pyramid Lake in Nevada.

Fish were caught in Abbott’s Lagoon Pt Reyes. Photo by Peter Moyle.

Wild extinction – This category is one step further than native-range extinction. Now the species only exists as a captive population (think hatchery or zoo). Delta smelt are dangerously close to falling into this category.

Apparent extinction – This category is the final “holding pattern” category when we think the species is globally extinct because we cannot find it anywhere. However, we want to wait to be sure. We talked briefly about this in part I of the blog. Right now the International Union for Conservation of Nature (IUCN) tells us to wait 50 years before declaring extinction, but there is a big difference between species with 1 year vs. 25 year generation times. Therefore we propose a waiting period based on generation time: 1-5 years = 10 generations; 5+ years = 5 generations.

Single-species vs. Multi-species approaches

We have determined it is time to act. But how best to do so?  The current agency approach is based on single species (per the Endangered Species Act). As a species becomes endangered, we start doing everything we can to conserve that species, one species at a time. But as we mentioned, the endangered list is growing quickly.  These approaches will become cost-prohibitive as the list gets too big. And by law, work must continue until that species is “recovered”, which could essentially mean forever for many species. Instead we argue for taking a multi-species approach to conservation. Go in and restore the original habitat (or at least a reasonable portion of it). This saves both the species in peril AND all the species that naturally coexists with it. This might incur a huge cost initially, but if done right would be a one-time cost that returns native fishes to their native habitat in abundance. In other words, restore the system not just the numbers.

It is very important to note that we are NOT against human involvement in the saving of species. By no means! We are all for it. Some action is better than doing nothing. We simply want to stress the need to engage in conservation strategies that keep natural species in their natural habitats, where they can undergo natural selection for as long as possible. Administering artificial selection to save them, putting the species into “grey extinction,” should be a last resort. And we felt it is important to distinguish between those species which have been subject to such methods (artificial selection) from those which have not. The latter would seem to have a greater chance of survival in the wild. More information improves decision-making.

When we put these ideas together, we generated a decision tree to help navigate the many categories and approaches that one might take in assessing extinction (Fig. 1). This tree starts with the basic, but big, assumption that our society really wants to prevent more extinctions. Again our purpose is to show the pathways from traditional threatened/endangered listings to global extinction – or as the case may be, to  conservation successes. Our decision tree has checkpoints throughout which would be a great place for biologists and stakeholders to sit down and assess progress and future approaches. We recognize that this is not an all-inclusive look at all things extinction, but we do see it as a starting point to better management of species at every level.

Fig 1. Decision tree assessing extinction progression. Checkpoints are decision nodes and boxes are extinction categories. After checkpoint #2, two trajectories are indicated, one reflecting decreasing habitat availability (left) and the second reflecting increasing conservation-reliance and decreasing habitat availability (right). From Baumsteiger and Moyle (2017).

In an era where the integrity of science is being questioned, we can no longer afford to hide these facts and avoid these difficult questions. Transparency is paramount. People need to know how complex the issues are and what we are facing. Our paper is an attempt to meet this growing need, to lay our cards on the table to show what managers are up against when it comes to assessing extinction. Regardless of politics, we are all part of and depend on the same global ecosystem. How long should we allow species to drop out of that system before we become concerned? Extinction is very real, very permanent and the numbers in the gray area are increasing. The time is now to focus on these species before the slide accelerates. After all, decisions to save species from now on will only become increasingly harder.

Jason Baumsteiger is a Center for Watershed Sciences post-doctoral research fellow with Drs. Peter Moyle and Mike Miller. Peter Moyle is a UC Davis Professor Emeritus of fish biology and an associate director of the Center for Watershed Sciences. 

Further reading

Baumsteiger, J. and P.B. Moyle 2017. Assessing extinction. Bioscience 67: 357-366.

Posted in Biology, Conservation, Fish, Planning and Management | Tagged , | 3 Comments