California Institute for Water Resources
California Institute for Water Resources
California Institute for Water Resources
University of California
California Institute for Water Resources

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Fire and water: Researching debris flows to mitigate post fire storm hazards

Graduate student Nathan Jumps revisiting Englewild Canyon to collect additional sediment samples. Photo by A. Gray.

Destructive debris flows, commonly known as mudslides, have affected many parts of California in the past few years. Debris flows can cause extensive damage to homes and infrastructure, and threaten human safety. A related issue that gets less attention is how debris flows affect water quality downstream following fires. A current study led by Andrew Gray of the University of California, Riverside, is therefore timely.

“Historically, we haven't known much about the quality and quantity of sediments exported from burned areas. Our approach to addressing this knowledge gap was to monitor debris flows and associated suspended sediment so we could get a better understanding of the changing conditions that might lead to a debris flow following a wildfire. We also wanted to characterize the effects of debris flows on water quality,” says Gray.

Debris flows are fast moving masses of rocks, soil, and water that occur when steep terrain cloaked in unstable sediments is exposed to high intensity rainfall. Urban populations and infrastructure adjacent to wildlands in Southern California have both grown in recent decades. Combined with increased risk of wildfire from a changing climate and a legacy of fire suppression, this means that residents are at a higher risk from dangerous debris flows.

For this study, Gray and his team, which included two other professors, three graduate students, and eight undergraduate students, selected research sites in the steep watersheds of Englewild and Las Lomas canyons above the Southern California cities of Glendora and Duarte, among others. At the time, these headwater catchments had recently burned during the Colby and Fish fires of 2014 and 2016, respectively. This context made the research especially timely and critical, as the fire activity rendered most of these areas, which are historically prone to damaging debris flows, particularly vulnerable. Collectively, the team has spent over 100 days in the field over four years taking samples, which has been no easy feat.

Graduate student James Guilinger taking measurements in the Box Springs burn area before the first rains hit in December 2017. Photo by A. Gray.

According to Gray, “working in steep hillslopes and channels destabilized by wildfire is extremely challenging.” Although Gray and his team took serious measures to protect themselves, there were always risks: “From the acute hazards posed by rock fall or falling ourselves, to the chronic presences of dust, ash, and poison oak, work with our group has become somewhat infamous. Even external participants with broad experience with steep, demanding field work have characterized our field sites as the worst!”

Rapidly deploying the research group to the various catchments after fire and storm events to take samples, combined with the time consuming and highly technical processing of the samples and data afterwards, also made this research challenging.

The researchers found that the more recently burned Englewild Canyon catchment had a lower threshold for debris flow than the Los Lomas Canyon catchment. These results indicate that as a burned system rebounds, vegetation comes back, soil health recovers, and there is less debris flow and sediment transport, as well as improved water quality downstream. In fact, Gray found it impressive how quickly these steep catchments re-stabilize following wildfire, even during drought periods.

Findings from the study will help scientists and the Los Angeles County Department of Public Works personnel working on debris flow management modify their approach to assessing debris flow risk after fires to help mitigate danger during post-fire storms.

The hard work and physically demanding field work seems to have paid off. Gray is excited that his group has been able to collect high quality data that reveal sediment transport processes at very fine scales. This will enable the researchers to gain a better understanding of how sediment sources and pathways change over time, and begin to explore what conditions cause changes in the composition of sediments on a hillside.

In addition, the data has brought up further questions for the group to explore. They plan to use the results of this study to modify how they characterize post-fire debris flow hazards in steep, mountainous regions. They also have plans to expand their research to larger spatial scales so they can examine how wildfire impacts sediment transfer and water quality through entire watersheds.

Gray says “given the increase in wildfires and urban growth into places where debris flows are likely, we are looking forward to helping managers reduce the risks from the most devastating events.”

Posted on Monday, October 28, 2019 at 3:34 PM

Bottled water sales track community response to water contamination

Plastic water bottles. Photo by ricardo /

Drinking water contamination is an ongoing issue across the United States. However, tracking water quality violations and notifying residents about them is challenging, and there is no systematic approach for prioritizing assistance once a violation is detected. Using a dataset intended to assess bottled water marketing trends, Maura Allaire, an assistant professor in Urban Planning and Public Policy at UC Irvine, and her collaborators are tackling these challenges and gaining a better understanding of how communities deal with contaminated water.

In a new paper published in the Proceedings of the National Academy of Sciences, the researchers explain how tracking bottled water sales might be help improve the process of identifying drinking water violations, notifying residents, and providing assistance. People reduce their exposure to contaminated water in many ways including boiling or filtering, but because bottled water sales can be traced, they may be a helpful new indicator of how communities react to water quality violations.

In the U.S., drinking water violations are split into two categories. The first are short-term, with acute effects that require immediate public notification. Allaire and colleagues found that for these kinds of violations, which are often due to pathogens like E. Coli, bottled water sales increased 14%. For the second type of violations, those related to long-term exposure risk and the category most violations fall into, bottled water sales increase on average 4.9%.

This means that, generally, bottled water sales are most responsive to violations that could cause acute health effects and require public notification within 24 hours. However, the actions that people take to deal with water contamination vary across communities. For example, low-income rural communities do not show a significant response to nitrate violations, which pose the highest health risks to infants under six months old.

“It was surprising for us to find that low-income rural communities did not respond to nitrate violations, since these populations are the ones facing the brunt of nitrate contamination. It is possible that these communities take other actions, such as installing nitrate filters, but we'd need to investigate further,” says Allaire.  

The researchers also expected to find that communities might make a more permanent switch to bottled water after experiencing a violation. However, Allaire says, “the effect we found was very small. After an acute violation occurred for the first time, bottled water sales are slightly higher at around 2%, but this declines as time goes on. For locations with many violations, sales of bottled water drop back to normal levels after violations end.”

Analyzing all those bottled water purchases was no small feat. “This was a two-year effort by a team of four researchers. At first, it was a challenge to work with such a large dataset of weekly bottled water sales. The raw data contained over 5,000 Universal Product Codes (UPCs) of bottled water purchased at over 25,400 stores. Sorting through terabytes of bottled water purchase data took quite a bit of time and processing before it could be used in the analysis. For some of the students, this was their first introduction to working with big data,” says Allaire.

There is yet more work to do. One outstanding challenge when it comes to drinking water violations is that regulations that guide public notification have not been updated in two decades. The guidelines recommend notifying people via radio, television, and notices posted in public places, and the researchers note that more modern forms of communication could improve public awareness and ability to respond.

In addition, tracking consumer purchases could detect emerging water quality concerns, especially for contaminants that are sampled infrequently and effect water taste or appearance. Additional monitoring could improve response of state and local agencies on issues that otherwise go undetected or unreported.

Allaire says that “it was exciting to use this extensive dataset to look at people's behavior. While this dataset was originally intended to assess marketing trends, it can shed light on how communities are affected by contaminated water, and help improve both notifications and assistance.” 

Posted on Tuesday, October 1, 2019 at 1:39 PM

Predicting food shortages: Scientists collaborate on Famine Early Warning Systems Network

Corn wilts on a farm in Mozambique. Photo by FEWS NET.

Tens of millions of people face malnutrition the world over. Fortunately, systems are in place to help anticipate famines and coordinate life-saving aid. Among them are the Famine Early Warning Systems Network, or FEWS NET, a cutting-edge drought early warning system, created some 30 years ago and run by scientists at UC Santa Barbara and several partner institutions.

FEWS NET identifies the location, severity, and causes of food insecurity and issues alerts to humanitarian NGOs and government agencies. It achieves this by taking advantage of satellite observations, in-situ measurements, Earth systems models, and field scientists' observations. FEWS NET covers Africa, central America, and parts of central Asia and the Caribbean.

Researchers at UC Santa Barbara and the FEWS NET team have published a paper detailing how the system works, how it has evolved, and the progress that's been made since, particularly since the tragic Somali famine in 2011.

The FEWS NET of today is a proactive system able to issue alerts based on predictions made months before any potential droughts strike. “Whereas I think decades earlier the reporting would have looked something like, ‘There are people starving here now. Send relief,' we can now provide advance warning of potential food crises months in advance,” said researcher Greg Husak, principal investigator of UC Santa Barbara's Climate Hazards Center and part of the FEWS NET team.

To illustrate this point, the group highlighted differences between the Somali famine and the East African drought just six years later. The 2011 drought over the eastern horn of Africa was one of the worst on record, the paper states, affecting over 12 million people. FEWS NET was able to issue an early warning, but conflict thwarted an effective response. The event claimed over 250,000 lives in Somalia alone.

In late 2016, FEWS NET forecasted another unprecedented drought. Predictions suggested it would span a larger area and affect more than twice the number of people as the 2011 drought. However, better data, new tools, and more effective communication enabled FEWS NET to mobilize governments and NGOs. Preemptive food aid arrived to the region early the following year, well before the spring rains failed. The juxtaposition between the two events provided an opportunity for the team to reflect on their progress and document their findings.

Advances in FEWS NET’s monitoring and communication contributed to a much better outcome when drought hit East Africa in 2016 and 2017 (b) compared to the 2011 Somali famine (a). Image from Funk et al.

The U.S. Agency for International Development established FEWS NET in 1987 in response to the devastation caused by the Ethiopian famine three years prior. Driven by limited data availability and infrastructure, the system's assessments were less timely in its early years, assessing conditions as they played out and making recommendations based on technical analyses.

Along with Husak, researcher Chris Funk joined the network in 1999, founding the university's Climate Hazards Group in 2003. “We're trying to make a scientific discipline out of something that has historically been more ad hoc,” said Funk, the center's research director. “This science involves combining and integrating multiple sources of information in ways that build on their relative strengths.”

To that end, several developments have enhanced FEWS NET's drought early warning capacities. There have been tremendous advances in data collection and modeling techniques, not to mention many new satellite monitoring systems that simply did not exist when the network was born. The team has also benefited from a better understanding of the climatic conditions that drive droughts, all courtesy of fundamental scientific research.

Authors from left to right: Shraddhanand Shukla, William Turner, Greg Husak, Pete Peterson, Chris Funk (above Pete), Frank Davenport, Sari Blakeley, Laura Harrison. Photo by Harrison Tasoff.

But the researchers also attribute much of the network's recent success to better communication. “Without that, then the rest doesn't really matter,” Funk said. Rather than one alert, the system now sends a series of alerts and recommendations leading up to a food shortage. “That stream of information is what allows the people who coordinate the humanitarian responses to do what they need to do,” Funk said. “In February of 2017, large-scale humanitarian assistance was already arriving in Somalia, so that when the rains failed in April it prevented a famine.”

FEWS NET's communication continues after an event as well. The team uses historical data to evaluate the fallout and response and compare it to past events. They also created public-facing, online databases that food security analysts can explore themselves.

FEWS NET is science at its most applied. If the team sends out an alert, it often triggers an immediate international response. However, the initiative's pragmatic nature has limited its exposure in the broader academic community. This new paper provides an opportunity to share the project's scientific developments and achievements more broadly. There's also still a lot to learn about how to effectively monitor and predict droughts. Given FEWS NET's success, the team sought to document their processes and improvements in the hope that it could help other organizations involved in similar efforts.

“Despite increasing wealth across the globe, there are still millions and millions of people who are facing extreme food insecurity,” said Funk. “But the latest satellite, weather, and hydrologic models can help us identify droughts that put these people at risk, and UC Santa Barbara is part of an international, multiagency team that is doing this in a systematic way.”

FEWS NET has indeed become a truly multiagency initiative, with members across the globe. UC Santa Barbara's Climate Hazards Center is one of several partners, which also include NASA, the National Oceanic and Atmospheric Administration, the U.S. Department of Agriculture, and the U.S. Geologic Survey, among others. The network also employs local field scientists who carry out monitoring and outreach within the affected areas.

The FEWS NET team has weekly teleconferences about current agricultural conditions and discusses the latest climate forecasts on a monthly basis, explained Laura Harrison, the center's operations analyst. This information supports the climate component of FEWS NET's Food Security Outlooks, which constructs hypothetical scenarios to anticipate where food insecurity is most likely to change in the upcoming eight-month period. Active monitoring of agro-climatic conditions is crucial for predicting drought in a timely manner. For its part, the Climate Hazards Center focuses on providing the best possible weather datasets to support its partner institutions and the network's field scientists.

FEWS NET also works with scientists, professionals, and agency leaders in these regions so that they can better understand the climate risks they face and counsel their government agencies, explained Associate Researcher Shraddhanand Shukla. Husak agreed. “We're giving them information and skills to help them better assess their countries' conditions,” he said.

The FEWS NET project funding was coordinated through the California Institute for Water Resources. Read more about the project on our website.

Posted on Tuesday, August 27, 2019 at 4:40 PM
  • Author: Harrison Tasoff, UC Santa Barbara

Improved oxidation is water wizardry against drought

Nothing beats summer heat better than diving into a pool or sipping a cold glass of lemonade. Luckily, like Hogwarts wizards, water engineers are working to ensure that water to beat the heat will be available, though the source might be unexpected. Increasingly, California's water will come from transforming the water we flush down our toilets, sinks, and washing machines into sparkling, pure water.

Indeed, potable water reuse seems like a no-brainer. So why don't we do it? In some places, we already do, and those places have lessons for the rest of the state and beyond.

Haizhou Liu, an associate professor of chemical and environmental engineering at UC Riverside has been collaborating with researchers at the Orange County Water District to find ways to seek and destroy more of the pesky pollutants that can squeak through even the most advanced purification systems, with support from the National Science Foundation.

The Orange County Water District operates the world's largest advanced water purification system for potable reuse. Highly cleaned wastewater that would ordinarily be pumped into the Pacific Ocean is instead put through a second purification process, after which it meets or exceeds state drinking water standards. In the 10 years since the reclamation facility has been in operation, more than 257 billion gallons of purified water has been produced to augment the region's local drinking water supply.

Instead of sending the purified water directly to customers' taps, a practice known as “direct” potable reuse, the recycled water is pumped to large ponds where it percolates through sand and gravel. It then rejoins groundwater, from which it will eventually again be drawn as drinking water, a process known as “indirect” potable reuse

To purify the water to drinking level standards, wastewater that has already had most of the organic contaminants removed passes through a microfiltration system to remove the finest particles. Next, the water squirts through a semipermeable membrane, a procedure known as reverse osmosis, which removes what mineral and organic compounds remain. But some tricky contaminants such as 1,4-dioxane, a potentially carcinogenic solvent used to make adhesives, dyes, textiles, and cosmetics, can occasionally squeeze through the membrane.

So in the final water purification step, the treated water is mixed with hydrogen peroxide and exposed to ultraviolet light, which liberates hydroxyl radicals to scrub the remaining pollutants. Researchers are working to improve this last step to make it more efficient and reduce the minute concentrations of contaminants—which are already below any level of health concern—even further.

In the ten years of operation of the Orange County Water District's advanced water purification facility, the concentration of 1,4-dioxane is routinely reduced to undetectable amounts after the ultraviolet and hydrogen peroxide advanced oxidation process. Because 1,4-dioxane is so stubborn, any above-ground engineered process that can remove it will also destroy almost anything else that survives the reclamation process. If 1,4-dioxane is removed, little else will also remain, making it a good proxy for measuring overall water purity.

This is where Liu comes in. Liu's lab is working with Dan Schlenk, professor of aquatic ecotoxicology, to examine unintended byproducts of oxidation and working with the Orange County Water District on ways to improve on the efficiency of 1,4-dioxane removal from the reverse osmosis permeate.

Like a tea strainer, the membrane used for reverse osmosis becomes clogged with the minerals, bacteria, viruses, and organic compounds it catches, so chloramines —chlorine substitutes derived from ammonia— are added by the water engineers as a disinfectant to keep it clean.

The added chloramines continue into the ultraviolet light treatment step, and Liu has found that under ultraviolet light the chloramines break down into chlorine radicals that act as oxidants to break down 1,4-dioxane. However, the chloramines can also consume some of the hydroxl radicals critical to the success of the ultraviolet treatment process, weakening its effectiveness.

When Liu's lab tested a different oxidant known as persulfate, it broke down into sulfate radicals that work synergistically with the chlorides to remove more 1,4-dioxane than hydrogen peroxide. Moreover, the sulfate radical is pickier about what it attacks. Because it doesn't waste energy destroying harmless compounds, it removes the bad chemicals more efficiently than the hydroxyl radical.

Unfortunately, the 1,4-dioxane does not just vanish or morph into something entirely benign. The researchers also discovered that oxidation by either hydrogen peroxide, persulfate, or chloramines changes changes 1,4-dioxane into glycolaldehyde and formaldehyde, both of which damage DNA and can lead to birth defects and cancer. To the researchers' relief, the oxidation reactions continue to degrade the aldehydes until they, too, disappear.

One could argue all of this is a moot point if people aren't willing to drink recycled water. A study led by UC Riverside psychology graduate student Daniel Harmon found disgust at the thought of drinking water that had once been in a sewer a powerful factor against direct potable water reuse, even when people could not taste the difference.

But water scarcity is a fact of life in California, as in many other parts of the world, and direct potable reuse will probably be coming soon to a faucet near you. “We are facing increasing water stress throughout the southwest U.S. and other parts of the world. Development of an efficient oxidation treatment for water reuse will be very important to sustain a reliable water supply for years to come,” Liu said.

Posted on Wednesday, August 21, 2019 at 8:37 AM
  • Author: Holly Ober, UC Riverside

A California-European Union workshop on sustainable groundwater management and conflict resolution

Jean Fried of UC Irvine presenting the rationale and the expected outcome of the workshop. Photo by Mimi Cruz.

A California-European Union workshop on sustainable groundwater management and conflict resolution was held June 24-25, 2019 at the University of California, Irvine. The workshop was hosted by Water UCI and sponsored by the Orange County Water District, Irvine Ranch Water District, Water Replenishment District of Southern California, State Water Resources Control Board, California Department of Water Resources, and USGS California Water Science Center.

Gathering California water policy and decision-makers along with groundwater stakeholders and users, the workshop gave participants the opportunity to meet European Union (EU) water specialists, exchange experiences and ideas, and compare California and EU issues and solutions.

The idea for a workshop bringing EU groundwater policy and decision-makers to California came from observing the similarities in management goals and overall regulatory pressures in both places. While groundwater management in California was non-regulatory and essentially voluntary until recently, the EU began legislating and managing groundwater in 1980, collecting more than 30 years of water and groundwater legislative experience, notwithstanding the specific legislation and regulations of each Member State.

However, the passage of the Sustainable Groundwater Management Act (SGMA) in 2014 set California on a fundamentally new course for how it manages groundwater. And, as already existing agencies, new Groundwater Sustainability Agencies, and regulators grapple with how to comply with SGMA, it proved beneficial for high-level EU water management specialists to meet with their California counterparts and various stakeholders. During the workshop, participants shared their experiences, discussed joint issues, and proposed solutions to shared challenges.

Lena Salamé leading a role-play exercise on conflict resolution. Photo by David Feldman.

These two days together enabled participants to discuss five general topics: governance and management; quantity and quality issues; water rights; conflicts and their nature; and techniques to manage and resolve conflicts. A role-play about conflict gave participants the opportunity to try negotiating in a practical exercise that simulated a real case.

In addition to the prepared contributions of the invited speakers, a summary of the rather dense discussions, based on the notes taken by two students, will be integrated into the proceedings and available on the Water UCI website in the coming months.

Erik Ekdahl of the State Water Resources Control Board presents the final conclusions. Photo by David Feldman.

From the discussions and exchanges, it appears the issues raised are critical, and that many more lessons can be learned. Therefore, the international dialogue and exchanges will continue in a series of annual workshops entitled “California Groundwater Policy, Governance, and Management: The Relevance of International Experience.” The next workshop will be held in June 2020, potentially focused on the economics of groundwater management.

Professor Jean Fried, PhD was the Chair of the Organizing Committee and is Project Scientist, Urban Planning and Public Policy and School of Social Ecology, University of California, Irvine.

Posted on Monday, July 22, 2019 at 4:14 PM
  • Author: Jean Fried, PhD

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