Groundwater Nitrate Sources and Contamination in the Central Valley

by Katherine Ransom and Thomas Harter

In California’s Central Valley, many communities depend significantly or entirely on groundwater as their drinking water supply. Studies estimate the number of private wells in the Central Valley to be on the order of 100,000 to 150,000 (Viers et al., 2012; Johnson and Belitz, 2015).

Elevated nitrate concentrations in groundwater can be a problem for private well owners, community service districts, and municipalities who rely on groundwater wells. Drinking water with a nitrate concentration greater than 10 mg/L NO3-N (the drinking water standard known as the maximum contaminant level, or MCL) has been linked to health effects such as low infant blood oxygen levels, miscarriage, and certain cancers.

We recently completed several studies that show the extent of nitrate contamination in shallow groundwater and the likely sources of the contamination in the Central Valley. The results show that, at the private well depth, a relatively small area is predicted to exceed the MCL, but a large portion of the valley is predicted to have elevated nitrate (at the 5 mg/L rate, a concentration considered to indicate elevated nitrate levels from human impacts). The public well depth is overall less at risk, but still has a decent amount of area predicted to exceed 5 mg/L.

The Central Valley is a highly productive agricultural region with approximately 7 million of California’s nearly 9 million acres of irrigated farmland (California Department of Water Resources, Agricultural Land and Water Use Estimates, 2010). In addition, over 80% of California’s 1.8 million adult cows live on dairies in the Central Valley.

Nitrate is a naturally occurring form of nitrogen, but is also created in areas with excess fertilizer, manure, urban and food processing waste effluent applications, or septic leach fields spaced at high density.  Much of the excess nitrogen (N) is converted to nitrate, which eventually makes its way into groundwater where it can persist for decades or even centuries – a process known as nitrogen leaching.

We estimate that 550 thousand tons of N fertilizer, 240 thousand tons of manure N, and 4 thousand tons of urban and food processing waste effluent N are annually applied to or recycled in Central Valley agricultural lands for food production. About 130 thousand tons of N are fixed from atmospheric nitrogen directly by leguminous crops (mostly alfalfa). While harvest removes about half of the nearly one million tons of N input to cropland,  and some nitrogen is lost to the atmosphere, about 360 thousand tons N per year is potentially leaching to groundwater from agricultural lands.

Other sources in the Central Valley are estimated to leach 20-25 thousand tons N to groundwater (urban areas: 10, municipal wastewater and food processing percolation basins: 4, dairy lagoons and animal holding areas: 6, and septic leach fields: 3). Manure production has increased exponentially since the middle of the 20th century through the mid-2000s, when dairy cow numbers levelled off. In contrast, fertilizer use increased predominantly in the decades after World War II and has largely levelled off since the late 1980s. Crop production has continued to increase steadily over the past 70 years (Harter et al., 2012; Tomich et al., 2016; Harter et al., 2017).

Estimated potential groundwater nitrate-nitrogen loading from cropland (not including alfalfa, left); and from alfalfa, urban areas, golf courses, dairy corrals, and wastewater/manure lagoons (right) in the Central Valley in the mid-2000s. Cropland leaching was estimated using a mass balance approach. Other leaching was based on reported nitrogen fluxes, measured leaching rates, or estimated from surveys. 1 kg N/ha/year = 0.9 lb N/acre/year (Harter et al., 2017).

Land use, nitrate leaching, and domestic groundwater

The amount of nitrate that leaches to groundwater (nitrogen loading rate) can be highly variable between different crop or land use types and among an individual crop or land use. This is due to differences in crop nutrient demands, soil and climate properties, and farm management techniques. Most measurements of nitrogen loading from crops are based on a few field studies performed over 30 years ago. The above estimates of potential nitrogen loading to groundwater are based on reports of N applications and N removal to harvest for nearly 60 different crops and on research about atmospheric N losses and other nitrogen pathways. But independent confirmation of estimates that are based on actually measured groundwater nitrate data has been lacking.

We performed a Central Valley analysis of domestic well nitrate data to relate groundwater nitrate to surrounding land uses and to estimate the amount of nitrogen loading from 15 crop and land use groups. This study focused exclusively on data from private domestic wells since they are typically more shallow and more likely to show impacts from more recent (5-30 years ago) surface activities on water quality. A database of recent nitrate measurements (past 15 years) from 2,149 private wells was assembled and the land use surrounding each well was determined (Ransom et al., 2017a). Using these data, we estimated a range of likely loading rates for each crop or land use type.

Results of the study indicate confined animal feeding operations (dairies), citrus & subtropical crops, and vegetable & berry crops to have the highest estimated nitrogen loading rates, while rice, water & natural land use, and alfalfa & pasture crops have the lowest. Many crop and land use groups have overlapping estimated ranges.

The groundwater nitrate-based estimates and the average potential leaching rates obtained from mass balance analysis are fairly consistent for Citrus & Subtropical, Vegetables & Berries, Field crops, Grapes, and the Water & Natural group. However, mass balance-based estimates are greater for Manured Forage crops, Nuts, Cotton, Tree Fruit, and Rice. Groundwater-nitrate-based estimates for urban areas and CAFOs appear largely consistent with reported data.  Lower estimates of nitrate leaching, when compared to estimates of nitrogen loading, are partially due to the (multi-)decadal travel time between the source of nitrogen leaching and the location of domestic  or other production wells where nitrate was sampled. But possibly also due to some natural attenuation of nitrate in groundwater (denitrification).

Land use from the CAML data set for the 15 crop and land use groups used in the study and the same crop and land use groups keyed to the median estimated nitrogen loading rate in kg N ha-1 yr-1 for the corresponding group (right side).

Identifying nitrate sources

Other sources besides manure and fertilizer may also contribute to groundwater nitrate concentration, including septic waste and natural sources (though natural sources typically contribute very minimal amounts.) Also, the amount of nitrate in an individual well is often the result of several nitrate sources. We quantified the amount of nitrate from each of four sources (manure, fertilizer, septic, and natural) in 56 private wells in the San Joaquin Valley (Ransom et al., 2016). Results of this “fingerprinting” study indicate that multiple nearby sources have likely contributed to an individual well’s nitrate concentration; it also shows some regional patterns in groundwater nitrate sources: manure sources are often more dominant in private wells located in dairy regions such as Hilmar, while fertilizer sources are more dominant in the citrus crop regions of Orosi and Woodlake. Septic system sources were shown to be a dominant source in some wells on the outskirts of urban centers where septic system density is high. The study also demonstrates that – without detailed site-specific investigations – significant uncertainty exists about a specific nitrate source’s contribution to the nitrate measured in a particular drinking water well.

Estimated amount of nitrate from each of the four sources, as percent of total, for each study well. Wells with overlapping pie charts were offset to prevent overlap.

Concentration of contamination

Finally, a joint effort between UC Davis and the USGS resulted in a high resolution estimation of nitrate concentrations across the Central Valley, at the average depth of a private domestic well and, separately, for the average depth of public supply wells (Ransom, et al. 2017b). These maps were developed by considering 146 mapped variables that potentially relate to the risk for groundwater nitrate contamination. These included soil and climatic variables, and recent estimates of groundwater age, nitrogen accounting, and groundwater chemistry.

The 146 maps were compared to nitrate measurements from over 5,000 private and public wells, taken during the past 15 years. Using a machine-learning algorithm to find patterns in the data, we created a ranking of which variables were the most likely to affect groundwater nitrate concentrations at the two depths. Among the 146 mapped variables, groundwater chemistry related to denitrification, historical nitrogen application amounts in agriculture, groundwater age, well distance to rivers, and amount of natural land use surrounding wells (among others) were rated as the most important to determine a location’s nitrate concentration.


Well locations of wells used in Ransom et al. (2017b) color coded by well nitrate concentration (3508 wells total) for shallow (1400 wells, mostly private) and deep (2108 wells, mostly public supply) zones.

Prediction of groundwater nitrate at median depths of private and public supply wells (54.86 m and 121.92 m, respectively). Unmapped (white) area within the Central Valley boundary was due to missing data.

Efforts are ongoing by agriculture and State of California agencies to better control sources of nitrate contamination through improved crop nitrogen management, while also developing programs to support affected communities with drinking water treatment and alternative supplies. These programs recognize that nonpoint source pollutants require an approach that is different from traditional groundwater pollution programs given the large number and broad distribution of nitrate sources, and the resulting wide-spread groundwater nitrate pollution. Our work supports the strategy taken by these efforts, which focus on regional source control and more support for drinking water treatment and alternative supplies. With this research, we hope to highlight areas where nitrate contamination is most likely to be elevated, provide further evidence for the regional scale contribution from various nitrate sources, and help focus nutrient management and educational efforts.

Katherine Ransom graduated in June 2017 with a PhD from the University of California Davis, Hydrologic Sciences Graduate Group. Her work has focused on statistical models of groundwater contamination. She is currently working as a postdoctoral researcher with the United States Geological Survey through UC Davis on predicting and mapping groundwater parameters in the Great Lakes region. Thomas Harter is a groundwater expert at the University of California, Davis.

Further Reading

Harter, T., K. Dzurella, G. Kourakos, A. Hollander, A. Bell, N. Santos, Q. Hart, A.King, J. Quinn, G. Lampinen, D. Liptzin, T. Rosenstock, M. Zhang, G.S. Pettygrove, and T. Tomich, 2017. Nitrogen Fertilizer Loading to Groundwater in the Central Valley. Final Report to the Fertilizer Research Education Program, Projects 11‐0301 and 15‐0454, California Department of Food and Agriculture and University of California Davis, 325p.,  and

Harter, T., J. R. Lund, J. Darby, G. E. Fogg, R. Howitt, K. K. Jessoe, G. S. Pettygrove, J. F. Quinn, J. H. Viers, D. B. Boyle, H. E. Canada, N. DeLaMora, K. N. Dzurella, A. Fryjoff-Hung, A. D. Hollander, K. L. Honeycutt, M. W. Jenkins, V. B. Jensen, A. M. King, G. Kourakos, D. Liptzin, E. M. Lopez, M. M. Mayzelle, A. McNally, J. Medellin-Azuara, and T. S. Rosenstock, 2012. Addressing Nitrate in California’s Drinking Water with a Focus on Tulare Lake Basin and Salinas Valley Groundwater. Report for the State Water Resources Control Board Report to the Legislature. Center for Watershed Sciences, University of California, Davis. 78 p.

Johnson, T. D., and K. Belitz, 2015. Identifying the location and population served by domestic wells in California, Journal of Hydrology: Regional Studies, 3, 31–86. Available at

Ransom, K. M., A. M. Bell, Q. E. Barber, G. Kourakos, and T. Harter, 2017a. A Bayesian approach to infer nitrogen loading rates from crop and landuse types surrounding private wells in the Central Valley, California, Hydrology and Earth System Sciences Discussions, 2017, 1–27. Available at

Ransom, K.M., B.T. Nolan, J. Traum, C.C. Faunt, A.M. Bell, J.M. Gronberg, D.C. Wheeler, C. Rosecrans, B. Jurgens, K. Belitz, S. Eberts, G. Kourakos, and T. Harter, 2017b. A hybrid machine learning model to predict and visualize nitrate concentration throughout the Central Valley aquifer, California, USA. Science of the Total Environment, 601-602: 1160-1172. Available at

Ransom, K. M., M. N. Grote, A. Deinhart, G. Eppich, C. Kendall, M. E. Sanborn, A. K. Souders, Wimpenny, Q.-z. Yin, M. Young, and T. Harter, 2016. Bayesian nitrate source apportionment to individual groundwater wells in the Central Valley by use of elemental and isotopic tracers, Water Resources Research, 52(7), 5577–5597. Available at .

Tomich, T., S.B. Brodt., R.A. Dahlgren, and K.M. Scow (eds)., 2016. California Nitrogen Assessment.

Viers, J., D. Liptzin, T. Rosenstock, V. Jensen, A. Hollander, A. McNally, A. King, G. Kourakos, Lopez, N. D. L. Mora, A. Fryjoff-Hung, K. Dzurella, H. Canada, S. Laybourne, C. McKenney, Darby, J. Quinn, and T. Harter, 2012. Nitrogen sources and loading to groundwater, Addressing Nitrate in California’s Drinking Water with a Focus on Tulare Lake Basin and Salinas Valley Groundwater. Report for the State Water Resources Control Board Report to the Legislature. Technical Report 2, Center for Watershed Sciences, University of California, Davis. Available at

Posted in Agriculture, California Water, Groundwater, Nitrate, Water Supply and Wastewater | Tagged , | 3 Comments

Floodplains in California’s Future

by Peter Moyle, Jeff Opperman, Amber Manfree, Eric Larson, and Joan Florshiem

Sacramento River meander migration, from 1904 to the present. Image credit: Amber Manfree

The flooding in Houston is a reminder of the great damages that floods can cause when the defenses of an urban area are overwhelmed.  It is hard to imagine a flood system that could have effectively contained the historic amount of rain that fell on the region—several feet in just a few days.  However, these floods are a stark reminder of the increasing vulnerability of urban areas across the world and the need for comprehensive strategies to reduce risk.  The evidence is clear that green infrastructure, as defined below, can increase the resiliency of flood management systems and, when managed for multiple services, can reduce flood risk for many people while also promoting a range of other benefits.

Floodplains provides an overview of floodplains and their management in temperate regions.

California has a history of large floods, some almost as dramatic as those that have devastated Houston. They occur just infrequently enough that many forget they can be a problem and then complain about cost of flood insurance.  During this past winter of record precipitation, California did a remarkable job of containing and diverting the water. Damaging floods were not an issue.  Of course, the 200,000 citizens of Oroville who had to be evacuated because of the threat of flooding from a broken dam spillway may feel differently.

Unfortunately, climate change models tell us that big floods in California may become bigger and more frequent in the future because there will be more rain and less snow as the result of warmer air temperatures.  Fortunately, in Central California, part of the solution for dealing with big floods already exists: the Yolo and Sutter Bypasses.  These huge floodplains fill with flood waters from the Sacramento River and its tributaries that cannot be contained by dams.  The floodwater is passed rapidly to the Delta and San Francisco Estuary, and then out under the Golden Gate over weeks and months.

Illustrated river-ecosystem concepts from Floodplains. Image credit: Amber Manfree

While flooded, the bypasses provide productive habitat for fish and waterbirds.  When not flooded, they are farmed or managed as wildlife areas. They are examples of “green infrastructure,” soft, flexible flood protection that also benefits the environment.  There are other examples from all over the world, although hard infrastructurelike walls, levees and dams is much more common.  In California, the new Central Valley Flood Protection Plan 2017 Update emphasizes investment in green infrastructure (although it is not called that in the plan) as a long-term approach to flood management.

We think the world needs a lot more such green infrastructure to meet the forecasted challenges and to support floodplain ecosystems that can also function for farming and recreation. Engineered floodplains are a prime opportunity for multi-benefit outcomes. We have documented this trend, and reasons why green infrastructure works so well, in a new book: “Floodplains: Processes and Management for Ecosystem Services”, published by University of California Press.

Our focus is reconciliation ecology, the science of integrating habitat for wild plants and animals into landscapes dominated by people. The book is based on our many years of studying floodplains in California, which is a leader in using floodplains for flood management.  But we also venture to other regions, especially Europe, Australia, and Asia, for new insights.   Towards the end, we provide 15 maxims to guide flood management such as “A bigger flood is always possible than the biggest experienced so far.”

“Our time spent on rivers and floodplains has certainly shown us that much has changed and been lost over time. But we have seen more than just glimmers of hope in reconciled floodplains that are diverse and productive. We take heart from the huge flocks of migratory white geese and black ibis that congregate annually on California floodplains and from knowing that, beneath the floodwaters, juvenile salmon are swimming, feeding, and growing among cottonwoods and rice stalks, before heading out to sea. We can envision greatly expanded floodplains that are centerpieces of many regions, protecting people but also featuring wildlands, wildlife, and floodplain-friendly agriculture. Connectivity among floodplains, people and wild creatures is within reach, as is a future in which people work with natural processes rather than continually fighting them.” (p. 218).

Peter B. Moyle is a UC Davis Professor Emeritus of fish biology and an associate director of the Center for Watershed Sciences. Jeffrey J. Opperman is a research associate at the Center for Watershed Sciences at the University of California, Davis and is the Global Freshwater Lead Scientist for World Wildlife Fund, working with teams across the world to develop and implement strategies to protect and restore rivers and floodplains. Amber Manfree is a postdoctoral researcher in Geography with the UC Davis Center for Watershed Sciences. Eric W. Larsen is a research scientist and fluvial geomorphologist in the Department of Human Ecology at the University of California, Davis. Joan L. Florsheim is a Researcher in fluvial geomorphology, hydrology, and earth surface processes at the Earth Research Institute, University of California, Santa Barbara.

Further reading

Opperman, J.J., et al. 2017. Floodplains: Processes and Management for Ecosystem Services.

Posted in Around the World, Climate Change, flood, Floodplains, reconciliation | Tagged , | 3 Comments

The Little Shasta River: A model for sustaining our national heritage

by Ann Willis, Rob Lusardi, Alex Hart, Susan Hart, Blair Hart, Andrew Braugh, Amy Campbell, Ada Fowler

Ranchers coexist with salmon streams in the Shasta Valley. Photo credit: Carson Jeffres.

Rancher: farms. Conservationist: fish. Researcher: science.

Too often, identity is used to divide us. Stereotypes are used to stake out conflicting positions. It’s a zero-sum approach that ignores the commonality of our natural – and national – heritage.

Most Californians – indeed, most of the country – have no idea who or where we are. Tucked up in the State of Jefferson, the Little Shasta Valley is a picturesque landscape not commonly associated with California: rolling hills and arid, wide rangeland, bounded by mountain ranges.

But within this landscape, we’re building a community of collaboration that reflects our values as landowners, conservationists, and scientists and stands as an example of what is possible when we put aside our preconceptions: a sustainable future for us all.

As landowners, stewardship is not just second nature, but a core value that ensures our livelihood, honors our heritage, and provides opportunity for future generations. Our family, the Harts, has ranched in the Little Shasta since 1852; the land is part of our legacy. We see our place as part of the ecosystem, not in spite of it. We know that when ecosystems falter, so has our stewardship. But we also know that working with partners who know as much about fish as we know about cattle, there’s a groundbreaking opportunity for wildlife and agriculture alike.

As conservationists, we see how people are integral in preserving our natural heritage. Worldwide, 80 percent of the places where animals live are under a high level of threat because of human presence. The new environmentalism recognizes that we’re not just visiting nature – we’re part of it. To be sure, there are places that require preservation. But as we look at the interconnected scale of our environmental challenges, we know that our conservation strategies must move beyond postage-stamp preserves and embrace the entire landscape, including people and their livelihoods.

As scientists, our mission goes beyond discovery to inspiration. Rather than simply gathering data to inform, we must listen to the vision stewards are trying to achieve and use science to understand whether and how it’s possible – or whether that vision may need to change. When landowners volunteer to keep water in a stream, it’s our duty to use science to know when, where, and how much of that water will do the most good. With science, we put people back into the landscape in a way that’s connected, not contrary, to the way the land works.

Just like an ecosystem includes many species that are vital to its success, we recognize that our community will only succeed when we work together.

That’s why our groups recognized the tremendous opportunity presented four years ago, when The Nature Conservancy and California Trout approached the Harts to talk about coho salmon. TNC and CalTrout had already developed strong conservation programs in the Shasta River watershed. With the help of the UC Davis Center for Watershed Sciences and other partners, conservation projects in the upper watershed like Big Springs Creek had already shifted the direction of coho salmon from degradation towards recovery. Those projects gave the Center an opportunity to develop a scientific approach to conservation that would sustain conditions for cold water species on a working ranch – an approach that could be used on working landscapes throughout the West.

Those projects also gave landowners in the valley an opportunity to see how our groups worked and what we produced, both in terms of guidance and results. So when we were approached, we knew we were talking with partners who used good science to find workable solutions.

Good stewardship preserved stream habitat for fish in the middle of a commercial-scale, working cattle ranch that’s been in production since 1852. Photo credit: Ann Willis.

The Harts’ stewardship had preserved an oasis of salmon habitat and a working ranch for the past 150 years. Trees provided stability to stream banks and shelter to aquatic life;  while also diverted, water flowed through the stream, keeping gravels clean and pools connected. The problem was too little water when young coho would migrate from their freshwater nurseries to the ocean.

Such problems seem obvious. But as we’ve found over a decade of collaboration, science helps us dismiss issues that at first glance might seem like “obvious” problems, but in fact are not. By doing so, we can direct our resources to places where they’ll have the biggest benefit, and avoid investing in projects that might look good, but produce little. And, our work provides a strong foundation from which we could show others in our community why were some actions were taken, but not others, and how those actions allowed both the rangeland and fish to endure.

This kind of community-driven, science-based conservation is critical, not just in the Little Shasta Valley, but across the American West. Rangelands, forests, and farms all overlap some of the most diverse ecosystems in the United States – landscapes we need to support generations of people, flora, and fauna to come.

Ann Willis is a research engineer who focuses on water management for working land conservation at the Center for Watershed Sciences. Robert Lusardi is the California Trout/UC Davis Wild and Coldwater Fish Lead Researcher. Susan, Blair, and Alexandra Hart are fifth and sixth generation ranchers in the Little Shasta Valley. Andrew Braugh is the Mt. Shasta/Klamath Regional Director for California Trout. Amy Campbell is the Mt. Shasta/Klamath Project Director for the Nature Conservancy. Ada Fowler is a Project Scientist with the Nature Conservancy.

Further reading

How Protecting Water Helps Industry and Nature. New York Times T Brand Studio.

Willis et al. 2013. Water resources management planning: conceptual framework and case study of the Shasta Basin.

Nichols et al. 2016. Little Shasta River Preliminary Assessment.

Nichols et al. 2017. Little Shasta River Aquatic Habitat Assessment 2016.

Posted in Agriculture, Conservation, Fish, reconciliation, Restoration, Sustainability | Tagged , , | 3 Comments

Preliminary Analysis of Hurricane Harvey Flooding in Harris County, Texas

by Nicholas Pinter, Nicholas Santos, and Rui Hui

Located in Harris County, Texas, Houston is the 4th most populous city in the US.  The flooding now unfolding in the Houston area is a human and economic disaster likely to rank with Hurricanes Katrina and Sandy among the worst in US history.  At the present moment, little quantitative information is available about the extent of flooding or economic damages.  The inundation is so widespread that detailed assessment has not yet been possible.  Even measurement of the flooding by visible-light based satellite has been impossible because the remnants of Hurricane Harvey have stalled over the Gulf Coast for the past week, dumping record precipitation and obscuring the skies from satellite view.

Our team in the Natural Hazards Research and Mitigation Group at the University of California, Davis conducted two sets of analyses to provide preliminary information on the pattern of flooding and to provide some context on historical flood damages in the Houston area.  Specifically, we:

(1) Processed radar data from the Sentinel-1A satellite from Aug. 29, at the peak of flooding in many areas.

(2) Analyzed data from the US National Flood Insurance Program (NFIP) to look at the nature and pattern of flood exposure in Harris County, including Houston.

Satellite Analysis

The Sentinel-1 system, which consists of two satellites, was launched by the European Space Agency.  The Sentinel-1 satellites carry radar sensors, which can scan the surface at night and through cloud cover.  In addition, this radar imagery is sensitive to standing water, making it an ideal tool for mapping the extent (but not depth) of flood water covering an area.

A Sentinel-1 satellite passed over Houston on August 29, which we used to create a map that highlights water and flood inundation on the surface.  We overlaid the resulting map on flood-zone boundaries from FEMA’s National Flood Hazard Layer and on other geographical data. Finally, we further compared the surface water extent with known pre-storm extents by flood-zone in order to determine flooding extent in each area in the portion of the county we assessed.

The resulting inundation map shows the striking extent of flooding in Houston and provides context for the on-the-ground photos coming out of the area.  Reservoirs are overflowing, streams and rivers surging high over the surrounding floodplains, and highways and roads are now themselves rivers.


An image of the flood inundation map in Harris County, Texas, showing the flooding extent of Hurricane Harvey. Click to open and explore.

Table 1 shows the extent of flooding mapped by flood zones, as defined by FEMA.  The flooded area in square miles is not an accurate measure of total area underwater because image pixels with vegetation or buildings will not be classified as standing water.   For example, designated floodways (river channels, mostly) were certainly 100% full of water throughout the study area on 8/29, but the radar signal categorized only 30% of those pixels as water.  However, the distribution of water-designated pixels correctly illustrates the pattern of flood inundation.  In the future, we plan to create a raster map that shows the boundary between flooded and not-flooded land in Harris County, from which accurate total inundation areas can be calculated.


Table 1. Distribution of flood inundation in Harris County, Texas in different mapped flood zones.

In Table 1, the percentages of total flooded area illustrate the great intensity of flooding resulting from Harvey.  About two-thirds of the inundation is outside of FEMA’s Special Flood Hazard Area, which is the so-called “100-year” floodplain, or area with a 1% or greater chance of flooding in any given year.  The 13.44% of inundation in the 500-year floodplain is very similar to the total portion of the study area in the mapped 500-year zone, suggesting that on average, flooding on Aug. 29 completely filled Harris County’s 500-year floodplain.  More than that; over 50% of estimated inundation occurred outside of any mapped flood zone.

History of Flood Damage and Exposure in Harris County

Texas has a long history of damaging flooding, and Houston has seen some of the worst of it, well before Harvey.  Since 1964, Harris County has had 27 federally declared disasters related to flooding and/or coastal storms.  We obtained databases of NFIP policies nationwide back to 1994 and insurance claims back to 1972.  For the analysis here, we identified current policies and past claims in the City of Houston, Harris County, and Texas as a whole.  We also examined repetitive flood losses.

As of June 30, 2017, Harris County policyholders held 249,212 NFIP flood insurance policies, covering $70.34 billion of assets, and generating $138.4 million in annual premiums. Over 40% of Texas NFIP policies are from Harris County.  Texas-wide, there are 593,115 policies in force, covering $161.2 billion, with $ 364.0 million in premiums.  Texas represents about 12% of NFIP policies nationwide and about 10% of annual premiums to NFIP.  Notably, and in contrast to the trend nationwide, the number of NFIP policies both in Harris County and in Texas has declined during the past several years (Figure 2).  Numbers of policies peaked in 2008 and have declined every year since that time.  This decline occurred despite several large floods in Texas during that time, which tend to sharply increase flood-insurance penetration in other areas of the country.  In addition, policy totals in Texas began declining well before Biggert-Waters 2012, federal legislation that raised NFIP premiums for some policyholders.

NFIP policies in force, by year, in Texas and in Harris County.

From 1975 to early 2015 (span of our NFIP claims data), NFIP policyholders in Texas experienced 194,029 paid flood losses, totaling over $9.2 billion (2015 dollars) in claims. The largest number of losses and NFIP claims occurred in 1979, 2001, and 2008 (Figure 3).  From 1975 to early 2015, Harris County had 77,697 paid flood losses, totaling about $3.6 billion (2015 dollars).

NFIP flood losses, by year, in Texas and in Harris County (in 2015 dollars).

Repetitive Flood Losses in Harris County

In 1998, the National Wildlife Federation report, Higher Ground, identified a major challenge to the NFIP – policyholder who made flood claims again and again, with some of them receiving cumulative payments many times the structure’s value.  In 1998, the worst case was one home that was flooded 16 times.  Today, the largest number of claims on a single structure has risen to 40.  And Texas has a disproportionately large share of repetitive loss structures and losses.

FEMA maintains a list of properties flagged as Severe Repetitive Loss Properties (SRLPs); defined as those that have had at least four claims (each ≥$5000) or total claims exceeding the value of the structure.  Of about 30,000 designated SRLP properties across the US, 4889 are in Texas, the second highest of any state (after Louisiana).  SRL properties in Texas have received $962 million in NFIP payments, the 2nd highest of any state (after Louisiana).  It seems likely that Harvey will push Texas to #1.

A total of 2794 of Texas’s SRL properties are located in Harris County, where 1925 of those are in the City of Houston. This number, summed together, is more SRLPs than any in other jurisdiction in the US. The total number of NFIP paid losses for SRL properties in Harris County is 15,685 (10,321 in Houston), the largest of any area in the US. The total of NFIP payments for SRL properties in Harris County is $596,025,224 ($195,971,067 in Houston), also the largest total of any area in the US.

We have also examined individual SRL properties, tabulating the worst of these in a variety of ways.  By counting the maximum number of paid claims, one property in Houston has been rebuilt at taxpayer expense 29 times.  We have also calculated total claims per property as a multiple of that structure’s value.  We tabulated the 30 largest of these ratios for single-family residential structures nationwide (structures valued <$10,000 excluded).  Harris County and Houston have 9 of these 30.  For example, one Houston-area home, valued at $116,335, has received NFIP payments totaling $1,848,916, or 15.9 times the structure’s value.  Other properties show even larger ratios.

There is room for some optimism in Texas.  FEMA provides funding to reduce long-term flood losses by mitigating individual properties, including acquiring and demolishing the most flood-prone structures.  In Harris County since 2000, 996 such properties have been acquired, at a cost of $63.5 million.  This optimism must be tempered, however, by the vastly greater pace of new construction in the Houston region.

The catastrophic flooding in the wake of Hurricane Harvey will certainly generate extensive discussion.  By some calculations, the current flooding represents the third “500-year” flood in the Houston area in the past three years.  Harris County flood managers have suggested that these extreme events represent rare, but plausible expressions of natural and stationary hydrology.  In contrast, credible counterarguments focus on climate-change tipping points as well as the rapid and extensive suburban development.  The catastrophic extent of current flooding in Texas points not only to a truly extreme event this year, but to a pervasive pattern of repetitive flooding. This pattern, in Texas and the Houston area in particular, points almost inescapably to local factors such as runaway development and lack of balanced hydrologic planning.  Recognition of these root causes is a vital first step in reshaping policies and guiding recovery in the wake of Harvey.

Nicholas Pinter is the Roy Shlemon Professor of Applied Geosciences in the Department of Earth and Planetary Sciences and an associate director of the UC Davis Center for Watershed Sciences. Nick Santos is a GIS developer and researcher at the Center for Watershed Sciences. Rui Hui is a postdoctoral researcher with the Center for Watershed Sciences.

Posted in Around the World, flood, Floodplains, Planning and Management, Tools | Tagged , , | 31 Comments

Trump Killed Obama’s Flood Protection Rule Two Weeks Ago

by Nicholas Pinter

This post was originally published as an op-ed in Fortune.

Jesus Rodriguez rescuing Gloria Garcia after rain from Hurricane Harvey flooded Pearland, in the outskirts of Houston, on Sunday. Image source: REUTERS/Adrees Latif via Business Insider

Whether or not you like President Donald Trump, the current administration has not been gifted with great timing. Just 10 days before Hurricane Harvey made landfall, the White House rescinded one of the most progressive flood-risk management tools on the books, an Obama-era executive order that added caution when building structures in flood-prone areas.

Obama’s order improved flood safety standards of the U.S. National Flood Insurance Program (NFIP). The NFIP was established in 1968 to provide federally underwritten flood insurance to residents of states and communities that agree to control development in land the government deems prone to flooding. The NFIP and its flood maps are imperfect, but they beat the pre-1968 alternative, which was basically uncontrolled development on U.S. floodplains. How much worse would things be without the NFIP? Much of U.S. floodplain land might look like Houston does today, and Houston’s floodplains would be even worse.

The biggest problem with flood maps in the U.S. is that they are drawn as “lines in the sand”—implying that there is a flood risk on one side and none on the other. That is a false and dangerous message. The best way to approach a line on a flood map is like seeing a poisonous snake: Don’t panic, but stay well clear.

This issue was handled deftly by the Obama administration. In January 2015, Obama issued Executive Order 13690, which established the new Federal Flood Risk Management Standard (FFRMS). In brief, this standard called for a more cautious approach to construction at the boundaries of flood hazard zones. The approach was flexible and didn’t even require an admission of climate change as being the cause—just more caution.

Within days, eight Republican senators sent a letter opposing the new standard as an impediment to land development and economic growth. Among the signatories was John Cornyn of Texas. Within three months of sending that letter, large areas of Cornyn’s district were underwater, including damage to new buildings that may not have been there had the FFRMS been in place earlier. Then severe flooding happened again in 2016 on the Brazos River. And now Harvey is wreaking havoc.

The new FFRMS would have limited the construction of new structures in Houston in the path of floods like the ones we’re seeing from Harvey, and the standard was an important step toward greater flood resiliency nationwide.

The senators who signed the letter opposing Obama’s Executive Order 13690 were from Texas, Louisiana, Mississippi, Arkansas, Georgia, and Missouri. These states include some of the largest net recipients of NFIP funds. From 1994–2014, Mississippi received $5.60 in NFIP disaster payouts for every dollar in premiums its residents paid, compared to three cents for Wyoming and four cents for Utah, for example.

Why such imbalances? Bad luck, in part—Louisiana’s $3.82 is sharply reduced if you subtract Katrina. But climate change seems to be ticking up the magnitude and frequency of storms, and uncontrolled development without a doubt puts more and more infrastructure at risk. Three 500-year floods in Houston in the past three years, as some suggest, is beyond random bad luck.

Federal flood insurance payouts and other disaster relief are not just another form of political pork sent home, like highway dollars fixing potholes. Every dollar is a tiny compensation for the misery endured by flood victims. The White House’s rationale for killing Executive Order 13690 was to establish “discipline and accountability in the environmental review and permitting process for infrastructure projects.” Score one point for partisan dogma.

Instead, our shared goal should be to find prudent measures to wind down flood losses, not convulsively labeling any limitation on developing flood-prone land as a “job killer.” The Federal Flood Risk Management Standard was just such a prudent measure, a reasonable precaution to limit damages from future Harveys.

Nicholas Pinter is the Shlemon professor of applied geosciences and associate director of the Center for Watershed Sciences at University of California, Davis.

Posted in Around the World, Climate Change, flood, Floodplains, Planning and Management | Tagged , , , | 9 Comments

We hold our convenient truths to be self-evident – Dangerous ideas in California water

by Jay Lund

View of strawberry fields, Elkhorn Sough Reserve, power plant, and the Monterey Bay.

Success in water management requires broad agreement and coalitions.  But people often seem to group themselves into communities of interests and ideology, which see complex water problems differently.  Each group tends to hold different truths to be self-evident, as outlined below.

These beliefs, when firmly held, do not stand up to scientific scrutiny, appear to other groups as self-serving nonsense, and hinder cooperative discussions on better solutions.  The counter-productive aspects of these ideas make them dangerous to policy discussions.  Since accomplishment in water policy requires a pretty broad consensus, these ideas ultimately become dangerous even to their advocates:

  1. There is a silver bullet solution. If only California [desalinated seawater, built more storage, used less water, recycled wastewater, imported water from Canada, captured more stormwater, …, invested in my project], its water problems would be solved.  The most effective water systems in California, such as those that were most successful during the drought, adopt a portfolio approach, with a variety of thoughtfully integrated water supply and demand reduction activities.  Strategic water management is more like good diversified financial investing, rather than betting on a winning horse.
  1. I win if you lose. It is often hard to know if you are winning in California’s water conflicts.  How much better off will the environment or farming be with more water?  Some, rather than answering this complicated question, find it easier to measure success by the amount of water denied to a competing interest.  Identifying villains is often convenient for politics and fund-raising, even as it distorts issues and solutions, and makes cooperation almost impossible.  The stereotypical Westlands vs. delta smelt conflict is an example where each “side” views their success in terms of how much water it prevented the other from receiving.  The strategy of opposing success by others only makes effective solutions more difficult to discuss and achieve.
  1. We can “solve” or “fix” water problems. Some problems can be solved permanently.  But California is a dry state with a huge, dynamic economy, massive irrigated agriculture, and a diversity of native ecosystems; it will never completely solve its water problems.  California will always have water problems and conflicts, which will change with time – as they always have.  Yet, California has managed to have tremendous economic prosperity and agricultural productivity while remaining a relatively good place for people to live despite its dry Mediterranean climate.   Even with water problems, we largely succeed anyway. But we can do better, especially in protecting our native ecosystems.  Discussions of solutions should be realistic about not solving all problems for all time.
  1. Someone else should pay. Finance is always easier if someone else pays.  We all want federal or state funds.  Water bonds pass costs on to the not-yet-voting future.  Alas, the water sector is one of the wealthiest parts of government.  State, federal, and bond funds are supported by general taxes or reductions in programs that serve poorer-than-average folks.  Reliance on state, federal, and bond funds often adds costs and skews programs away from being effective.  Getting money from others becomes a substitute for effective water management.   Water development in California should be set up more on a ‘pay as you go’ basis, with more stable funding for public and environmental purposes.
  1. Regulation will protect the environment. Regulations are good for preventing bad things, and environmental regulations have stopped many environmentally bad things since the 1970s.  But regulations alone have been ineffective at rebuilding the environment and protecting it in the face of many poorly anticipated changes – such as invasive species, non-point pollution, climate change, and population growth.  If we want good things to happen environmentally, we need to organize and fund ourselves so that good things happen.  Historically, we largely overcame massive public health problems only when we organized local, state, and federal agencies to solve these problems broadly and inspect and work with each other, with steady and substantial local and state funding.
  1. We were promised. Over the last 150 years, almost every water interest has been promised their ideal water delivery by some politician or law.  At some time, we (or our revered predecessors) accepted the promise in lieu of a less convenient but more realistic statement of what could be done. We all know that such promises can rarely be met.  This applies to water contractors, water right-holders, environmentalists, floodplain residents, and water users alike.  We all have unrequited aspirations.  Dwelling on these disappointments disrupts discussions and work towards better solutions.
  1. We need trust. No group can manage California’s water problems alone.  Trust makes working with others much easier.  But there is often little trust.  We all buy cars and houses from people we do not trust and vote for politicians that we should not trust.  If trust were a pre-requisite for business dealings, we would all be growing our own food, living in tents, and mostly dying young.  “Lack of trust” as a reason not to talk or advance is self-fulfilling and ultimately self-defeating – unless you are enamored with the status quo.  Earning each other’s trust is good, but finding ways to work together anyway is needed, in all walks of life.
  1. It will work as planned. California is a complex system that is always changing and has many uncertainties.  Planning is essential, but the idea that everything will go as planned is absurd.  Still, it is often politically convenient to represent plans as perfect.  We need to prepare plans and resources so that they can accommodate imperfections.  This is sometimes called adaptive management.

These dangerous ideas often have short-term benefits to particular groups – bringing public attention, raising money, establishing a firm negotiating position, and garnering and promoting internal cohesion within a community of interest.  But sticking to such ideas is ultimately self-defeating, impedes actual advancement for all interests, and demonstrates a lack of long-term seriousness of purpose and thought.

Success in water management in California will never be absolute, but we can do better if we avoid cynicism and work out how to more effectively discuss and better cooperate.  Doing so will require effort, creativity, trade-offs, working across diverse agencies and groups, and dispensing with some convenient but dangerous ideas that get in our way.

My own ideological affiliation?  “More research is needed.”  My ideological heresy? We don’t need all that much money for research if we work and communicate earnestly, and often collectively, to make research relevant and useful.

Further reading

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

Hanak, E., J. Lund, A. Dinar, B. Gray, R. Howitt, J. Mount, P. Moyle, and B. Thompson. 2010. “Myths of California water: implications and reality.” West-Northwest 16(1): 3-73

Lund, J. (2017), Reflections on Cadillac Desert, J. Lund, July 9,

Lund, J. (2016) How bad is water management in California?, June 26,

Sabatier, P.A. and H.C. Jenkins-Smith (1993), Policy Change And Learning: An Advocacy Coalition Approach, Westview Press.

Wiens, J. , J. Zedler, V. Resh, T. Collier, S. Brandt, R. Norgaard, J. Lund, B. Atwater, E. Canuel, and H.J. Fernando (2017), “Facilitating Adaptive Management in the Sacramento-San Joaquin Delta,” San Francisco Estuary and Watershed Science, Vol. 15, No. 2, July.

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, Planning and Management | Tagged | 8 Comments

Habitat Preferences of various Delta species

Cartoon reprinted reprinted with permission from the Sacramento Bee. Originally published June 28, 2017.

Like fish, the different human professions involved in the Delta have different habitat preferences:

Lawyers: high turbidity and fear, complex egosystems, either high and cynical levels of expectation, abundant funds

Engineers: high clarity, data-rich nutrient sources, high expectation concentrations, abundant funds

Biologists: thrives on uncertainty and inconclusiveness, extreme biodiversity, highly dynamic ecosystems with complex structure, abundant funds

Spin-specialists: high turbidity, abundance of predators, corrosive water quality, data-free environment, abundant funds

Agency managers: seeks abundant refuge structure, low expectation concentrations, abundant funds

Academics: anywhere where more research is needed (everywhere with any funds).

None of these species is endangered.  They all thrive in the Delta, and seem to grow in population with declines in fish populations and Delta flows.

Posted in Wild and Wacky | 3 Comments

California WaterFix and Delta Smelt

by Peter Moyle and James Hobbs

Frank’s Tract, May 22, 2009. Large expanses of open water are likely to increase in the Delta, providing a justification for WaterFix. Photo by Peter Moyle

The delta smelt is on a trajectory towards extinction in the wild.  Heading into 2017, the spawning adult population was at an all-time low although this past wet winter has apparently seen a small resurgence.  However, increasingly warm summer temperatures in the Delta may dampen any upswing.  Given the long-term trajectory of the population and climate predictions for California, maintaining Delta smelt in the Delta for the next 20-30 years is not likely to happen without significant improvements to the habitat.

So, what happens to the remaining smelt when they encounter California WaterFix? This is the proposal centered around building two tunnels under the Delta to move Sacramento River water directly to the export pumps in the South Delta, benefiting Bay Area and southern California cities and southern Central Valley farms, as well as reducing the problem with reverse flows across the Delta.

In Hobbs et al. (2017) we gave cautious support to WaterFix. In this blog we discuss our reasoning for qualified support for such a controversial large-scale infrastructure project that will affect Delta fish and fisheries.  Our motivation comes from two facts:

(1) The status quo is not sustainable; managing the Delta to optimize freshwater exports for agricultural and urban use while minimizing entrainment of delta smelt in diversions has not been an effective policy for either water users or fish.

(2) Delta infrastructure (mostly levees) is old and increasingly vulnerable to catastrophic failure. Large-scale collapse of Delta levees will likely result in massive intrusion of salt water into Delta, shutting down water exports from the South Delta. Flushing this salty water will require large amounts of fresh water, further stressing water supplies.   The most likely fix will be construction of an emergency freshwater transfer system, which may actually make conditions worse than the status quo, from an ecosystem perspective.

So where do we see reasons to be optimistic about WaterFix from a fish perspective?

  • Entrainment of smelt into the export pumps in the south Delta should be reduced because intakes for the tunnels would be upstream current habitat for delta smelt and would be screened if smelt should occur there.
  • Flows should be managed to reduce the North-South cross-Delta movement of water to create a more East-West estuarine-like gradient of habitat, especially in the north Delta.
  • Large investments should be made in habitat restoration projects (EcoRestore) to benefit native fishes, including delta smelt.


There are huge uncertainties associated with WaterFix and EcoRestore, especially in terms of their effects on fishes.  Together, they are a giant experiment that may or may not work as promised, no matter what the models and experts say.  The giant fish screens for WaterFix, for example, will be pushing screening technology to the limit, having to protect weak swimmers like smelt and small sturgeon, as well as juvenile salmon.

WaterFix is supposed to operate using an adaptive management framework, to deal with uncertainty.  This means management activities can change as construction and operations proceed, as conditions change, and as new information becomes available. The framework for adaptive management is just being established by the Delta Stewardship Council for EcoRestore; it appears to involve many diverse agencies and it isn’t clear how consensus decisions will be achieved.  ‘True’ adaptive management treats each management action as an experiment with testable hypotheses and continuous monitoring that allows success or failure to be determined.  Large-scale experimentation with projects of this magnitude is difficult, even with adequate monitoring.  In short, adaptive management is a good idea but making it work at this scale would be unprecedented.

EcoRestore has many uncertainties as well.  Although restoration of tidal marshes should benefit salmon, water birds, and many other species, the potential for restored tidal wetlands to support delta smelt and other pelagic fishes is at best weakly supported with current scientific data.  Large-scale experimentation with EcoRestore projects will be challenging and will likely require 20+ years of data to make reasonable assessments

There are also trust issues with WaterFix. For it to work as promised, we have to accept that

  • Water will continue to be exported at roughly the same rates as it has been, with no increase in exports, but no decrease as well.
  • It will be operated without significant increases in water being diverted upstream of the Delta.
  • Full implementation of EcoRestore will occur and alleviate many of the endangered species issues.
  • Water for the environment will not be sacrificed every time there is a water emergency (the co-equal goals promise).

Trusting the operation of the project is a problem because under emergency conditions, such as another severe drought, environmental water could be re-allocated for other uses (e.g., through Temporary Urgency Change Petitions to the State Water Resources Control Board).  An additional worry is the current administration in Washington DC, which shows little concern for environmental issues and endangered species, could apply additional pressure or new regulations to change the water allocation system.

If you don’t trust that WaterFix will be operated as promised, what alternatives do you have? Here some general alternatives:

1. Status quo. This means continuing to rely on ad hoc responses to droughts and floods as well as delaying large-scale infrastructure improvements necessary to accommodate sea level rise, big storm surges, extended drought, and earthquakes. Under this scenario, invasive species will become even more dominant and native species, like smelt, will disappear.  There is room here, of course, for innovative programs that reverse island subsidence, control invasive species, and reverse declining trends in native fishes through large-scale habitat restoration and pulse flow releases from dams.  This will take a visionary effort, led by the Delta Stewardship Council, coordinating the actions of many agencies, a difficult task (See Lund and Moyle 2013 for suggestions on how to do this).

2. Build one tunnel, not two. The idea is to build a single tunnel that has just enough capacity to supply urban water needs or function as an emergency conveyance system when large levee failures or severe drought draws seawater into the Delta.  This could protect California’s urban water supply from catastrophic failure, but from a smelt’s perspective, this is just a step above the status quo, because ultimately the pumps in the South Delta will continue to be relied upon for most water exports (the dual conveyance solution). Cross-Delta movement of water will continue, if somewhat reduced, as will entrainment mortality of native fishes. Presumably, EcoRestore would be at least partially implemented, providing some relief for native fishes.

3. Roll back water delivery volumes to pre-1980 levels. The goal would be increased flows down the Sacramento and San Joaquin Rivers through the Delta and estuary. This would have many positive effects (Cloern et al. 2017) and would be especially beneficial to native fishes, like delta smelt, that require estuarine gradients of temperature, salinity, and water clarity. It would also allow for pulse flows to carry juvenile salmon out to sea and to flood parts of the Yolo Bypass for fish rearing on an annual basis.  Higher flows would also enhance the benefits of restoration projects under EcoRestore.  Unfortunately, given the politics and value of water in California, this option is very unlikely to happen, unless the environment is assigned an inviolable water right to make it truly ‘coequal’ with other water users.

4. Construct a North-South cross-Delta channel with reinforced levees, tidal gates, weirs, and barriers that would deliver Sacramento River water to the South Delta under most situations (see Lund et al. 2010). This version of dual conveyance would anticipate the need for emergency construction of such a facility should levees fail as the result of sea level rise, flooding, land subsidence, and earthquakes, or all four. However, this option would ignore most estuarine ecosystem needs of the Delta, especially if it was operated with little consideration for environmental water during drought conditions.  It could be partially mitigated through EcoRestore, provided the restoration efforts were tied to guaranteed flows down the Sacramento River and through the Delta, at key times.

Each of these four options face common challenges: they have to deal with major changes to the Delta wrought by sea level rise, subsidence of farmed islands in the south and central Delta, increased frequency of large storms/floods, and earthquakes.  While these projections, most featuring levee collapse, may seem alarmist, scientific studies predict large-scale change is going to happen; it’s merely a question of when. Thus, at some point, the south and central Delta will contain large expanses of salty water with reduced tidal influence, ending farming in this region. This new Delta will be a much more difficult place in which to move fresh water to the south Delta pumping plants.  Fish and invertebrates will continue to be abundant but the assemblages are likely to be made up of salt-tolerant forms, such as yellowfin goby, Mississippi silverside, starry flounder, striped bass, northern anchovy, Black Sea jellyfish, and overbite clam.  Lake-like regions might even be seasonally used by Delta smelt, although they will be too warm in summer. Fighting this magnitude of change to keep the status quo will require large investment in levees and barriers, as well as in EcoRestore, making the Delta even more artificial and highly managed than it is today.

So what happens to Delta smelt under these options?  Assuming partial recovery in response to the wet winter of 2016-17, assuming successful supplementation from a smelt conservation hatchery, and assuming EcoRestore and additional measures improve smelt habitat, guided by present Biological Opinions, the extinction of Delta smelt may be prevented.  If the tunnels survive lawsuits and political opposition, their operation is at least 10-20 years in the future. Thus, smelt recovery will have to be well on its way for the tunnels to have a detectable effect.  Meanwhile, the longer we delay, the more likely drastic large-scale emergency measures will be put in place, with little consideration for environmental or recreational needs.

So, the best option for smelt, and other native fishes, especially salmon, is #3, because it should result in a large increase in freshwater flows through smelt habitat (Moyle et al. 2012).  This conclusion is essentially the same as that of the much-ignored Recovery Plan for the Sacramento/San Joaquin Delta Native Fishes (USFWS 1996).  The realities of California water politics, however, dictate that one of the other three options is much more likely to happen. Of these options, the WaterFix + EcoRestore option deals best with future changes to the Delta and seems most likely to keep delta smelt, salmon, and other desirable fishes as part of the Delta ecosystem.  We are past the point where passive management and ad hoc responses to emergencies will keep delta smelt and most other native fishes as participants in the Delta’s ecosystem. Large scale changes require large scale, active management solutions, like WaterFix+EcoRestore.

Peter B. Moyle is a UC Davis Professor Emeritus of fish biology and an associate director of the Center for Watershed Sciences. James Hobbs is a research scientist with the UC Davis Department of Wildlife, Fish and Conservation Biology.

 Further reading

Cloern, J. E., J. Kay, W. Kimmerer, J. Mount, P. B. Moyle, and A. Mueller-Solger. 2017. Water wasted to the sea? San Francisco Estuary and Watershed Science 15(2). jmie_sfews_35738. Retrieved from:

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.  PPIC, San Francisco. 482 pp.

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

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

Lund, J., E. Hanak, W. Fleenor, W., R. Howitt, J. Mount, and P. Moyle. 2007. Envisioning Futures for the Sacramento-San Joaquin Delta. San Francisco: Public Policy Institute of California. 284 pp

Lund, J. R. and P.B. Moyle. 2013. Adaptive management and science for the Delta ecosystem. San Francisco Estuary and Watershed Science 11(3).

Moyle, P.B. 2008. The future of fish in response to large-scale change in the San Francisco Estuary, California. Pages 357-374 In K.D. McLaughlin, editor.  Mitigating Impacts of Natural Hazards on Fishery Ecosystems.  American Fisheries Society, Symposium 64, Bethesda, Maryland.

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

Moyle, P. B., L. R. Brown, J.R. Durand, and J.A. Hobbs. 2016. Delta Smelt: life history and decline of a once-abundant species in the San Francisco Estuary. San Francisco Estuary and Watershed Science 14(2)

US Fish and Wildlife Service. 1996.  Recovery Plan for the Sacramento-San Joaquin Delta Native Fishes. US Fish and Wildlife Service, Portland, Oregon.  193 pp

Posted in California Water, Conservation, Delta, Fish, Planning and Management, Restoration, Sacramento-San Joaquin Delta, Sustainability | Tagged , | 16 Comments

Small, self-sufficient water systems continue to battle a hidden drought

by Amanda Fencl and Meghan Klasic

Workshop participants in Salinas in July 2017 discuss ways to build local and regional drought resilience. Photo by A. Fencl

California’s drought appears over, at least above ground. As of April 2017, reservoirs were around 2 million acre feet above normal with record breaking snowpack . This is great news for the 75% of Californians that get their drinking water from large, urban surface water suppliers. Groundwater, however, takes longer to recharge and replenish. What does this mean for the more than 2,000 small community water systems and hundreds of thousands of private well-reliant households that rely on groundwater?

Of the ~25% of Californians not served by large, surface water suppliers, this pie chart shows the breakdown of populations served by system size and water source.

Small water systems are defined in our study as those have fewer than 3,000 connections, i.e. those that are not required to file an Urban Water Management Plan (UWMP). A large proportion of small systems serve low-income communities in rural areas. These communities are burdened with high unemployment, crime, and pollution, and their water systems typically have lower technical, managerial, and financial capacity for operations. Of the approximately 13 million people living within disadvantaged communities (DAC), nearly 2 million get their drinking water from a small system. These low income communities are disproportionately exposed to contaminated drinking water, usually from small systems that struggle to comply with regulations.

These same small systems were hit hard by the drought, and in many cases are the least prepared. The state knew this headed into the drought: “California also has small, rural water companies or districts with virtually no capacity to respond to drought or other emergency [… a portion of the small systems]  in the state face running dry in the second or third year of a drought (p.56, emphasis added). In contrast, urban drinking water suppliers (larger systems) are required to have a water shortage contingency plans (Shortage Plan) since the passage of the Urban Water Management Act in 1983. Aside from lower reservoir levels and toxic algal blooms, the majority of large surface water suppliers weathered the recent drought (2012-2016) without supply disruptions or other negative impacts to their customers. A 2015 survey distributed by the UC Davis Policy Institute shows that more large systems (89%) have written drought contingency plans (Plan) than small systems (63%) (manuscript in prep). When asked whether their Plan was sufficient to mitigate the drought’s impacts on water supply, 22% of large and 28% of small system respondents said it was not sufficient or only somewhat sufficient, which begs the question of how can these be improved before the next drought?

A private, domestic well on rural property outside of Visalia in Tulare County where one of the authors lived during fieldwork. Photo by A. Fencl

Small, rural water systems and their frequently disadvantaged residents remain vulnerable to quality and supply concerns (see Water Deeply’s Toxic Taps series for a look at these concerns in the Central Valley). They usually only have one or two different water sources and have few permanent or emergency interties with neighboring systems; this limits their supply flexibility, which is critical during multiple dry years. Small systems account for 71% of systems that faced drought-related supply or quality emergencies and sought financial assistance from the State Water Resources Control Board (Water Board).

Furthermore, 2800+ households on private, domestic wells reported problems due to the drought. The severity of private well failures prompted the Water Board to create a one-time funding program to assist households and local/state small systems (those under 15 service connections): $5 million was available as low-interest loans or grants.

Recognizing the extra burden of small systems, the 2016 Executive Order Making Conservation a Way of Life directed DWR to “work with counties to facilitate improved drought planning for small suppliers and rural communities”. The explicit focus on these systems and communities highlights the state’s acknowledgement that, “The ongoing drought has brought attention to the reality that many small water suppliers and rural communities are struggling to meet demands with significantly reduced water supplies – or even running out of water altogether” (p.3-17, emphasis added).

DWR’s Draft Executive Order Framework gives counties two years to figure out how to ensure drought resilience for households and areas under their jurisdiction that are otherwise not covered by an existing drought contingency plan. Hopefully, this will ensure that during the next severe drought, we won’t see 2800+ households running out of water; they will have long-term solutions in place. The East Porterville project underway in Tulare County shows what’s possible when state financing and local political will align.

A meeting of community members in East Porterville. DWR explains its plan for connecting ~1000 households on private wells, without running water, to the nearby City of Porterville. June 2016. Photo by A. Fencl

A team of UC Davis researchers interviewed a subset of California’s small “self sufficient” water system operators, managers, and board members during Summer 2016 about drought impacts, responses, and barriers to and options for adaptation. Self-sufficient systems do not purchase or import water from the Central Valley Project nor the State Water Project. In Summer 2017, the team organized three regional drought resilience workshops to complement the interview-based findings: Clear Lake, Modesto and Salinas. These workshops served to underscore the ongoing challenges facing smaller systems, the added water supply and quality pressures during extreme dry years and multi-year droughts, and the important role of the state in supporting local drought resilience.

The final phase of the research project will be day-long Forum on Drought Resilience for Small Systems in Sacramento next month. The forum is jointly hosted by the UC Davis Policy Institute and the Environmental Justice Coalition for Water. It will provide a venue for small system managers, state agency staff, technical assistance providers, and other interested stakeholders to discuss how best to overcome barriers to drought resilience for small systems. For more information on the Drought Forum, contact Meghan Klasic (

Amanda Fencl is a PhD Candidate in Geography at UC Davis.  Her dissertation is on California’s complex drinking water system and its adaptation to drought and climate change.  Meghan Klasic is a 3rd year PhD student in the UC Davis Geography Graduate Group studying transboundary water quality management and climate change adaptation. Many thanks to Dr. Julia Ekstrom and Dr. Mark Lubell for their review and edits. This research was made possible by funding from an NSF Graduate Research Fellowship, California’s 4th Climate Impact Assessment, and EPA STAR.

Further reading

Arnold, Brad, Alvar Escriva-Bou, Jay Lund (2017) San Joaquin Valley Water Supplies – Unavoidable Variability and Uncertainty. California WaterBlog.

Balazs, Carolina and Isha Ray (2014) The Drinking Water Disparities Framework: On the Origins and Persistence of Inequities in Exposure. Am J Public Health. 104(4): 603–611.

DWR (2017) Making Water Conservation a California Way of Life: Implementing Executive Order B-37-16.

Ekstrom, Julia, Louise Bedsworth, Amanda Fencl (2017). Gauging climate preparedness to inform adaptation needs: local level adaptation in drinking water quality in CA, USA. Climatic Change.  February, Vol. 140, Issue 3–4, pp 467–481.

Feinstein, Laura et al. (2017). Drought and Equity in California. Pacific Institute.

Harter, Thomas (2017). Post-drought groundwater in California: Like the economy after a deep “recession,” recovery will be slow. California WaterBlog.

Lohan, Tara (2017). Toxic Taps. Water Deeply.

Posted in California Water, Drought, Stressors, Sustainability, Water Supply and Wastewater | Tagged | 7 Comments

Fish, flows, and 5937 – legal challenges on the Santa Maria River

by Karrigan Bork, JD, PhD

Santa Maria River as seen from a bike trail on the Santa Barbara County side, with the 101 Freeway bridge visible. Image source: Wikipedia

Driving down the 101, you cross a half-mile long bridge over the Santa Maria River into the city of Santa Maria, California. It’s a large bridge, with big levees to constrain the river on either end. But the Santa Maria River, like many southern California rivers, is dry throughout much of the year and has been for at least of part of every year on record. On average, the wide, sandy channel is dry over 90% of the time. Some dry periods stretch up to three years.

So why the big bridge?

The Santa Maria River watershed supports one of four key populations of federally endangered southern California steelhead that, according to the National Marine Fisheries Service, is essential for their recovery. Although these fish often go unnoticed, they are at the center of a pending lawsuit that focuses on ensuring dam operations comply with California Fish and Game Code Section 5937, which requires dam operators to keep fish downstream of a dam in good condition. If the lawsuit succeeds, minor changes in dam operation may produce significant improvements in wild steelhead populations.

The Santa Maria River watershed. Image source: USGS

The Santa Maria watershed covers 1,880 square miles (1.2 million acres), making it one of the largest coastal watersheds in the state. The Santa Maria forms at the junction of two rivers, the Cuyama and the Sisquoc. The Twitchell Dam blocks the Cuyama River just a few miles upstream from the junction, while the Sisquoc River flows unimpeded from its headwaters in the Los Padres National Forest. The national forest dominates the watershed, and most of the mountainous higher reaches of the watershed do little to slow runoff during rare rain events.

Although the watershed averages only 15 inches of rain per year, when rain does fall, much of the rain reaches the Santa Maria River quickly, transforming the dry riverbed to a raging mix of muddy water. Prior to construction of the large levee system, these floodwaters regularly inundated the city of Santa Maria, transforming the city streets into the canals of Venice.

Flooding during a 1913 storm in the City of Santa Maria. Santa Maria flooded on a regular basis before the levee system was built. Image source: Santa Maria Historical Museum

This is an incredible river system: from year to year, it ranges from desert to flood, with little in between. Nevertheless, its groundwater supplies water to the city of Santa Maria and helps support annual agricultural production in Santa Barbara County of roughly $1.4 Billion. Incredibly, it also supports a vital population of the federally endangered southern California steelhead.

How do steelhead, which by definition require outmigration to the ocean followed by eventual return migration to their birth stream to spawn, survive in a river system that almost never flows to the ocean? Both the adult steelhead migration and the smolt outmigration depend on precise flow conditions, and these conditions are rarely met. Historically, 80% of monitored years failed to provide opportunities for adult steelhead to migrate upstream, and 75% of monitored years failed to provide opportunities for smolt outmigration. Still, in spite of these historical impediments to passage, the steelhead were once one of the most common fish in the Santa Maria system, and the Santa Maria run was the second largest in Southern California.

Southern California steelhead. Image source: Aquarium of the Pacific

The southern California steelhead exhibit several life history adaptions to the Santa Maria River’s extreme environment. First, the steelhead population spends as little time as possible in the Santa Maria River itself. The population spawns far upstream in the perennial headwaters of the Sisquoc River, where their offspring grow and wait for good conditions for outmigration. The adults and smolts move quickly through the Santa Maria as flood waters recede at the end of periodic high flow events. In the winter, adult steelhead in the ocean wait near the Santa Maria River lagoon, anticipating these high flow events, and adults may spend several years waiting for a single flow event that will allow them to migrate upstream.

Second, the steelhead population is intimately linked with the resident rainbow trout population in the Sisquoc River headwaters. The resident rainbow trout interbreed freely with the steelhead, and 14-42% of the resident fish possess genes associated with anadromy. When the steelhead population is unable to migrate for a prolonged period of time, the resident population sustains them, and when poor conditions wipe out part of the resident population, the returning steelhead repopulate the stream. These populations protect each other, and long-term stability of either population requires the other.

These adaptations, coupled with additional adaptations to higher temperatures and other local conditions, have enabled the historic persistence of this steelhead population. But the establishment of the Twitchell Dam on the Cuyama River in 1958 started the steelhead on a long decline, and now they hang on by a thread. The dam stores as much of the winter and spring flow of the Cuyama River as possible, then slowly releases the water during the summer months in an effort to ensure that all of the water from the Cuyama goes into groundwater and never makes it to the sea. Although the steelhead never made much use of the Cuyama River itself, the flow changes have altered the flow regime on the Santa Maria in several important ways, most notably by reducing the total number of up- or downstream migration opportunities and by increasing “false positives,” flows in the Sisquoc that induce migration without any chance of letting fish make it through the Santa Maria River alive. These changes have decimated the steelhead population.

Twitchell Dam on the Cuyama River, a tributary of the Santa Maria River. Image source: USBR

California law prohibits operation of a dam in this way. California Fish and Game Code Section 5937 requires “ The owner of any dam shall . . .  allow sufficient water to pass over, around or through the dam, to keep in good condition any fish that may be planted or exist below the dam.” Under California Fish and Game Code Section 5900, the term “Owner” includes the United States . . . , the State, a person, political subdivision, or district (other than a fish and game district) owning, controlling or operating a dam or pipe. The state of California has generally failed to enforce 5937, leaving enforcement to private nongovernmental organizations like California Trout or the Natural Resources Defense Council. In the most recent 5937 lawsuit, the Environmental Defense Center, representing Los Padres Forest Watch, and Lawyers for Clean Water, Inc., representing San Luis Obispo Coastkeeper, filed suit against the Santa Maria Valley Water Conservation District, which operates Twitchell Dam. The lawsuit seeks a court order requiring the water district to comply with Section 5937 by releasing water to support additional steelhead migration.

As in many water disputes, the issue is less the total amount of water and more the timing of releases. Both an independent report and the experts supporting Los Padres Forest Watch and San Luis Obispo Coastkeeper estimate that the steelhead need only 2-4% of the water stored annually by Twitchell Dam released strategically during flow events that would otherwise almost, but not quite, support steelhead runs. As required by 5937, smarter water management can save these steelhead. At this point, whether that happens is up to the Water District and the Court.

Karrigan Bork is a Visiting Assistant Professor with a joint appointment at the McGeorge School of Law and the Dept. of Geological & Environmental Sciences, both part of the University of the Pacific. His research interests include environmental law, natural resources law, international law, and administrative law, focusing on the interplay of science and law. He is currently serving as a consultant to Lawyers for Clean Water, Inc., in the lawsuit discussed here.

Further reading

Stillwater Sciences and Kear Groundwater. 2012. Santa Maria River Instream Flow Study: flow recommendations for steelhead passage. Prepared by Stillwater Sciences and Kear Groundwater, Santa Barbara, California for California Ocean Protection Council, Oakland, California and California Department of Fish and Game, Sacramento, California.

Karrigan Börk, Joe Krovoza, Jacob Katz & Peter Moyle. 2012. The Rebirth of Cal. Fish & Game Code 5937: Water for Fish, 45 U.C. Davis L. Rev. 809

Peter Moyle and Brian Gray. 2011. Dammed Fish? Call 5937.


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