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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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

Researching California’s extreme weather, storm-by-storm

Tashiana Osborne on the Scripps Pier. Photo by Jeff Dillon.

Tashiana Osborne is a PhD student with the Scripps Institution for Oceanography at UC San Diego where she works within the Center for Western Weather and Water Extremes on atmospheric river research.   

As a graduate student, you already have an incredible amount of experience, including working as a storm chaser and intern at NASA. Can you tell us a little more about your current research?  

I investigate extreme rain and snow events that affect the western U.S., where many extreme weather events are tied to atmospheric rivers. Atmospheric rivers are like rivers in the sky. They are long, narrow bands of enhanced water vapor traveling in the lower atmosphere.

When atmospheric rivers reach land, they can have widespread impacts. While the precipitation they produce provides water for residential and agricultural use, they can also lead to destructive flood or snow events. At the other end of the spectrum, a long absence of atmospheric rivers can lead to prolonged droughts. Overall, there are implications for public safety, water and food security, and the economy, including costly droughts, wildfires, snow events, floods, and mudslides.

Currently, I'm exploring using radar data to investigate the behavior of the atmospheric snow level, where falling snow melts to rain. Especially in higher-elevation regions like the Sierra Nevada, the snow level is key in determining whether a basin receives rain or snow, which then determines the impact of the event. For example, snow accumulates and contributes to water supply gradually, though heavy snow may lead to power outages, traffic delays, and even avalanches. Rain, on the other hand, flows into rivers and reservoirs more quickly, and can rapidly contribute to flooding events. It is crucial, therefore, that we understand how the snow level fluctuates to prepare for impacts of precipitation events.

Launching weather balloons surrounding atmospheric river periods in Ukiah, CA. Photo by Maryam Asgari-Lamjiri.

You've said that it's important to you to work to empower younger students, and share the possibilities of STEM with disadvantaged and marginalized communities. How are you working on these issues?

Although we faced struggles at times, my brother and I were fortunate to be exposed to nature thanks to some of our quirky, nature-loving family members. Yes, nature is chaotic, but it can also provide an escape; a way to connect with something bigger than myself through some of life's most challenging times. I want others to have access to these bigger experiences too.

As a Voices for Science Advocate through the American Geophysical Union, I've committed to activate in science outreach, communication, and policy. As Advocates, we unofficially call ourselves the Science Avengers, taking action to empower others to “show their cape”!

It's also important to acknowledge that higher education programs, especially in STEM, can present additional challenges for students from underrepresented groups. We've seen that diverse perspectives contribute to better science, and that diversity initiatives without inclusion are not enough. In my eyes, investing in youth and amplifying community voices often left out of political conversations can directly help strengthen the nation and world.

For the past four years, I've served as a science mentor for the Preuss School's Girls in STEAM (Science, Technology, Engineering, Arts, and Mathematics) Conference, encouraging girls who strive to become the first in their families to graduate from college. For the past two years, I've volunteered during the Garibaldi Bowl, an ocean sciences competition for San Diego high school students. I've also been fortunate to interact with students by sharing my experiences during panels and visiting classrooms.

Exploring Rocky Mountain National Park as a Rocky Mountain Science and Sustainability Network Summer Academy alumna. Photo by Miguel Trejo Rangel.

I recently returned to Colorado as a Rocky Mountain Science and Sustainability Network Summer Academy alumna. The Academy aims to develop a diverse population of undergraduate students ready to collaborate on issues relating to sustainability and community engagement in the protection of natural resources. For some students, visiting a U.S. national park as part of the program was a first.  

Finally, I strive to reach politically-minded groups through science policy efforts and training. For example, I've had the honor of serving as a Scripps delegate for United Nations Climate Change Conferences. At the conferences, I share with and learn from a global crowd comprised of government representatives, journalists, and others. I've learned that research has the power to inform effective and responsible policy decisions to help us become better protected and prepared in our changing climate, which affects us right here in California.

Teaming up with fellow Scripps students Meredith Fish and Kara Voss to present on atmospheric rivers for a press conference during the 24th Conference of the Parties to the United Nations Framework Convention on Climate Change. Photo by Brittany Hook.

What do you find most exciting or challenging about your research?

There are many things that add excitement! Not to mention many others that create challenges from which to grow. As one example, from December through March, I sometimes do field work in northern California. I sign up for a couple weeks where I'm essentially “on-call.” This means, if forecasts suggest there will be an atmospheric river, I might suddenly be contacted to pack up and book a flight.

During field work, we work together to launch weather balloons every three hours to measure atmospheric variables at different altitudes in the atmosphere – yes, even overnight and in rain and wind! Field experiences like this, and other interactions and collaborations with fellow scientists from various backgrounds, rev-up my excitement for science, and make me feel part of a mission.

In science, one of the big challenges is constructing and investigating questions that have complex, unexplored answers. We push limits and learn new skills while applying what we've stored in our knowledge toolbox. We also find ways to creatively represent and communicate results. In doing so, we may realize our efforts make up just one piece of the larger puzzle. This can be disconcerting, but also motivating because we care a lot about the world around us.

My long-term goal is to explore questions that directly address problems society faces, and share findings in ways that help contribute to solutions. That way, there's a chance those individual puzzle pieces can fit into broader efforts focused on protecting people and ecosystems and, optimistically, improving the world we live in.

You can find Tashiana on Twitter @TashianaOsborne and the Center for Western Weather and Water Extremes @CW3E_Scripps.

Posted on Monday, July 15, 2019 at 5:16 PM

What does the future hold for irrigation management?

Isaya Kisekka explains to students how the small footprint cosmic ray measures soil water over a range of scales at the UC Davis research farm.

Climate variability, competition for water from other users including urban and environmental, and groundwater depletion threaten the sustainability of irrigated agriculture. To face these challenges, the irrigation industry must develop and adopt innovative technologies and management practices that optimize economic outcomes, while also minimizing environmental impact.

Lately, there is no shortage of irrigation technologies hitting the market. To get a glimpse of what is out there, I recommend visiting the annual Irrigation Show held each December, as well as other annual farm shows such as the World Ag Expo.

Changes since the 80s

Since the late 1980s, there has been high adoption of irrigation application technologies, specifically a shift from flood irrigation to pressurized systems. Two examples are the use of microirrigation in California and center pivot irrigation systems in the Ogallala Aquifer region of the U.S. High Plains. The high adoption of these irrigation systems can be attributed to government incentives but, more importantly, to their proven ability to enhance production or ease management. We are seeing increasing interest in mechanized sprinkler irrigation systems for some crops in California due to their proven ability to improve management. For example, growers can automatically control several center pivots using mobile apps or control drip irrigation blocks using web apps.

However, when it comes to irrigation scheduling, the story is very different. According to data from the U.S. Department of Agriculture Irrigation and Water Management Survey, the adoption rates of advanced irrigation scheduling technologies are less than 21 percent. I use the term “advanced irrigation scheduling” to refer to irrigation scheduling based on soil moisture sensors, evapotranspiration programs, plant-based sensors, and crop simulation models. Over 70 percent still use traditional methods of irrigation scheduling such as observing crop conditions, soil feel, water delivery schedule, or watching neighbors. The next survey will be released late this year or early 2020, and it will be interesting to see what has changed as more technologies get developed or refined.

Convincing growers

I recently attended the California Irrigation Institute conference, and one of the presenters who is also an irrigation dealer shared his experiences on why growers continue to use historical methods to schedule irrigation. He said that growers will not widely adopt the latest irrigation scheduling technologies unless they are mandated to do so through regulation or convinced that the technology will improve profitability.

I will focus on the latter reason noted for lack of adoption. A golden opportunity exists for an irrigation scheduling technology that is simple, integrates easily with existing systems on the farm, and can demonstrate return on investment. There also needs to be a shift in the business model from that which focuses on selling hardware or equipment to one focused on selling solutions that address clearly identified needs. There are many existing technologies with a lot of potential, and many land-grant universities have also developed irrigation schedulers that are free and robust (e.g., CropManage, KanSched, Wise, iCrop, and more).

Isaya Kisekka inspects a small footprint cosmic ray neutron probe soil moisture system that can also measure soil water over the entire tomato field at the UC Davis research farm.

The latest innovations in artificial intelligence and cloud computing combined with the ability to collect large volumes of data from low-cost soil water sensors, plant water status sensors, drones, airplanes, and satellites present opportunities for optimized irrigation water management on an individual farm-by-farm basis.

Precision irrigation is a very interesting concept that, if implemented properly, could transform irrigation management and improve economic and environmental outcomes. You can think of precision irrigation as a systems approach to irrigation management in which the irrigation system knows what to do, knows how to do it, knows what it has done and how it effects the overall production goals, and then learns from what it has done before performing the next irrigation. You can imagine such a system as having a brain and capable of not just automatic but autonomous operation of the entire irrigation system similar to a self-driving car.

While I confess that this is more of a vision for the future, we need a disruptive irrigation management technology that will meet growers' various goals, including production, regulatory compliance, labor shortages, water and energy use efficiency, greenhouse gas reduction, etc. In the same way that we all have smartphones because they have proven to be very useful gadgets for doing more than making calls, I envision precision irrigation technology being widely adopted because it meets a grower's real-world needs.

Isaya Kisekka, PhD, is an assistant professor of agricultural water management and irrigation engineering in the departments of land, air, and water resources and biological and agricultural engineering at UC Davis. This article was republished with permission from Irrigation Today (2019), Vol. 3, Issue 4, p. 28-29.

Posted on Monday, June 10, 2019 at 3:27 PM
  • Author: Isaya Kisseka, PhD

Irrigation specialist receives new investigator award to help farmers better apply water

Amir Haghverdi, an assistant cooperative extension specialist of irrigation and water management in the environmental sciences department at UC Riverside and California Institute for Water Resources affiliate, has been awarded a nearly $500,000 Food and Agricultural Science Enhancement New Investigator grant by the National Institute of Food and Agriculture of the U.S. Department of Agriculture.

These grants are highly competitive funds awarded to researchers at the beginning their career, with less than five years postgraduate career-track experience.

Haghverdi's research focuses on developing and disseminating scientific knowledge, practical recommendations, and tools for sustainable urban and agricultural water resources management. His approaches include field research trials, laboratory analyses, and computer modeling, with a goal of identifying opportunities for synergy between research and extension activities. 

The award will support a project to enhance irrigation management in Southern California desert agriculture.

“Long-term agricultural sustainability depends on the simultaneous optimization of farm productivity and enhancement of environmental stewardship on every farm, in every field,” said Haghverdi. “This project will develop tools to help farmers who currently use uniformly applied irrigation decide when and how to adopt newer irrigation technologies that apply water precisely and variably.”

The project will use field trials, training for growers, and the latest computer modeling techniques to improve agricultural water management in southern California deserts.

You can follow Haghverdi on Twitter: @UCRWater.

Posted on Monday, June 3, 2019 at 2:31 PM
  • Author: Holly Ober

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