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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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


Ghost pines, live oaks, black oaks, and madrones, among other trees, make their stand interspersed with annual and perennial grasses at the headwaters of a California watershed. Photo by David Lewis.

I am standing where stream flow begins, in a nameless tributary of the Russian River to the east of Hopland, California. This particular spot and location has been a grazing livestock ranch, primarily sheep, going back more than 100 years. This is one of thousands of spots in the watershed where water comes to the surface, joins in a channel, and starts its path downstream.

Many of us have stood at a confluence of two rivers or an estuary where a watershed's outfall meets an ocean. These locations are the stream's or river's end, their terminus. Where I am standing now is instead the headwaters of the stream system, where water is initially released and visible as a thin, shallow, bouncing band.

Watersheds collect, store, and transport water. The transport function is performed by streams and rivers. These are dynamic, pervious channel networks, each with a beginning and an end. At any part of the network, the channel is that lowest point in the landscape, stretching from one stream bank to the other, and generally widening in the downstream direction, until the stream mouth empties into another water body.

At the other end of a network is the channel head, where the channel begins. This is where I am standing. Channel heads are found in small intimate folds in the landscape. These depressions are referred to by many names—draws, bowls, hollows—the place in hills where the slopes become shallow and coalesce.

Like an amphitheater, the surrounding hillslopes rise around me. Reaching out at shoulder height, I can almost touch these slopes. The mixed oak woodland and interspersed grasslands are in attendance across these slopes. Ghost pines, live oaks, black oaks, and madrones, among other trees, make their stand interspersed with annual and perennial grasses blanketing the ground.

This mosaic of vegetation is hosted and sustained by the complex mix of marine sediments that have been pushed up, forming these hills, and erosion carving the stream channel. Below the surface are soils one to the three feet deep that have developed from the underlying geology.  

It's March 3, 2019 and on the cusp of spring. Between the light breezes, the stream water sings its way downstream. I think back to the intense storms that moved across this part of California the week before and the resulting floods in the lower portion of the Russian River. Those and earlier winter storms soaked into the soil until the soil reached its capacity to hold water.

Once the soils were primed, water was released to the channel network. That water is still being released now, days later, and will be for several more months into May or even June. Rainfall for this area and most of California has been substantial, matching amounts not seen since 1983, and definitively ending the nearly 5-year drought. This contrast in extremes is the norm for California, meaning the next drought or next flood is only a year away.

Downstream, the Russian is perennial, flowing year-round. But here at the channel head, flow is intermittent on an annual cycle. Rains begin in the fall, with headwater surface flows starting in late fall or early winter, once soils are saturated. This wetting up process reverses in the spring, until the channel head is dry.

At some point this year, flow in the headwaters will stop. Saturated soils releasing water laterally below the ground surface will gradually release less and less water to the channel. Trees and grasses will demand more and more water as they leaf out and grow. As soils pores empty of free water, the remaining moisture is held more tightly to soil particles and plant root surfaces through a physical tension. Eventually the channel head will run dry.

While you may not have the opportunity to visit a channel head and experience the place where stream flow starts and stops each year, you are often closer to one than you think. Driving a rural road or hiking in a favorite park or open space will invariably find you crossing one of these unnamed headwater streams. As you do, give a look upstream, from where the water going past you has come. Up the channel into the bowl is one of the channel heads and headwaters for the watershed you are in.

I don't know when I will get to this channel head again. However, this place where surface flow is initiated will be close in my mind, particularly, as I visit the confluences and estuary of the Russian River, during the wet and dry periods and high and low rainfall years to come.


I have the privilege of engaging California's communities with the aspiration of safeguarding the sustenance and well-being that its oak-woodland watersheds and the people that are a part of them provide. This millennia long integrated relationship of humans and land has parallel histories in other Mediterranean parts of the world.

This is the first of occasional installments about working Mediterranean landscapes in California and around the globe. Combined they will explore the concepts of watershed functions, working landscapes, and Mediterranean climate, vegetation, and management. Join me in experiencing these settings, growing our appreciation for the integrated nature of these landscapes and people, and gaining understanding and tools for our tenure as stewards.

To learn more about these specific watersheds and research conducted in them this article is suggested. If interested in learning how stream flow is generated in California oak woodland watersheds you may want to read this article.

Posted on Monday, April 15, 2019 at 1:24 PM

Improving water governance through informed decision-making

Nell Green Nylen (right) and her colleagues stop for a view of San Francisco Bay on a hike in the East Bay Hills above the UC Berkeley campus. Photo by Lidia Cano Pecharromán.

Nell Green Nylen is a Senior Research Fellow with the Wheeler Water Institute in the Center for Law, Energy & the Environment (CLEE) at Berkeley Law. Her research engages law, science, and policy to tackle critical California water issues. Nell earned a J.D. from Berkeley Law and a Ph.D. in Geological and Environmental Sciences from Stanford.

You have done an incredible amount of research and policy work on some of California's thorniest water issues. Can you tell us a little more about your efforts?

Sure! During my time at CLEE, I've worked on everything from innovative stormwater management and the impacts of citizen enforcement under the Clean Water Act to sustainable groundwater management, water data, drinking water access and affordability, and state drought response. Although my work ranges widely, it all shares a common goal: informing decision making to improve water governance.

As an example, I led a report outlining considerations for evaluating whether, and under what conditions, a local groundwater market might be a viable tool for sustainably managing a groundwater basin. Because groundwater trading changes where, when, and how groundwater is pumped and used, it alters the social and environmental impacts of groundwater use. Our research suggests that while markets can contribute to sustainable management in some basins, success isn't assured. Careful market design and implementation are vital, including unambiguous trading rules developed with robust stakeholder engagement and effective oversight and enforcement.  

Another area I've worked on is water system consolidation—essentially, merging aspects of two or more drinking water systems, or extending water service to those not connected to a public water system. Consolidations can create economies of scale that help address persistent water quality and reliability problems in small and disadvantaged communities, but the costs and benefits of different options have not been well documented. So, we held a workshop with stakeholders, decision makers, and outside experts to learn from past and ongoing consolidation efforts in California. Our workshop synthesis takes stock of these efforts, identifying both barriers to effective consolidations and potential solutions.

Sandhill Cranes fly over flooded fields in the Sacramento San Joaquin Delta, a major hub of state water supply. Photo by David Zinniker.

I'm also doing work to improve water rights administration and oversight during droughts. Droughts are likely to become more frequent and intense in the future, posing increasing challenges for water managers and raising the stakes for effective response. In a pair of reports, my colleagues and I examine how the State Water Resources Control Board (Board) carried out its water rights responsibilities during past droughts and offer recommendations for improvements. We focus on the Board because its actions—or inaction—during droughts can have significant repercussions for nearly every person, entity, and ecosystem around the state.

Our analysis suggests the Board often needed to improvise response strategies in the midst of drought crises. Taking proactive steps, like developing a contingency-based framework to support drought decision making, will enable more timely and effective future drought response. I've recently been working on a blog series about this where people can learn more about the problem and our recommendations for addressing it.

Given your work on such a wide variety of water issues, what do you see as some of the most important issues on the horizon?

What comes to mind are issues I feel need more attention and concerted effort from researchers and policymakers. These include better aligning water law and policy with scientific understanding, and developing better guidance for climate change adaptation.

For example, California water law maintains artificial distinctions between groundwater and surface water, creating challenges for holistically managing these interconnected resources. The Sustainable Groundwater Management Act (SGMA) takes small steps towards closing the gap by requiring groundwater managers to avoid causing “significant and unreasonable” impacts to beneficial uses of surface water—we have an in-press journal article about this—but there is much left to do. Additional legislative changes may help, but a lot of progress can be made by doing the difficult work of reconciling existing requirements and responsibilities under state and federal law.

Snowy mountains surrounding Mono Lake. In 1941, the City of Los Angeles (350 miles away) began diverting water from four creeks that feed into the lake, creating challenges for local ecosystems and residents. Photo by David Zinniker.

There is also a need for more guidance to support what I'll call “managed adaptation.” Climate change will increasingly force decisions about whether to maintain certain land uses. These decisions involve important value judgments and are best made proactively and deliberately, based on considered analysis of the values stakeholders associate with the land use—such as its economic, cultural, and aesthetic values or its role in maintaining public health—and its resilience to potential threats.

The concept of “managed retreat” has, to date, largely focused on coastal adaptation to sea-level rise. However, many land managers will be facing other challenges in coming years, such as limited water supplies, inland flooding, wildfire, deferred maintenance, and dependency on carbon-based fuels. For example, the impacts of climate change on water resources will force decisions about how much—and which—land to remove from agricultural production over time. People are already thinking about this—for example, PPIC has written a recent report—but more guidance is needed to help decision makers and stakeholders think through their options and choose paths forward with foresight and intention. Otherwise, we might be looking at a future in which many decisions that affect lives and livelihoods are made passively, or put off until no good options remain.

You and your research group have been really successful at doing research that is relevant to decision-makers. Do you have tips for other researchers about how to do “useful” research? 

There are many ways to do useful research, but I think two keys are targeting an area of need and creating research products that support complex decision making.

First, we always try to target our research to address important unmet needs. One context in which there are often opportunities to make useful contributions is in the aftermath of new legislation. Figuring out how to translate new laws into action can be challenging. Researchers can help those tasked with implementing a new law understand what their responsibilities are, the tools at their disposal, and the potential consequences of different implementation pathways. Those who are affected by new laws need access to similar information to help them participate in the decision making process.

Second—and I already previewed this—we generally steer clear of telling decision makers what specific choices to make. Instead, we try to identify considerations that should inform their thinking, and then present those considerations in an organized and useful way. This is especially important when the goal is to provide statewide guidance for a decision context in which local conditions, values, and needs may strongly influence potential outcomes, so there's no viable one-size-fits-all approach.

Our work related to SGMA is a good example. SGMA calls for the creation of local groundwater sustainability agencies in priority basins, tasks them with developing and implementing plans to achieve basin sustainability, and offers a broad palette of potential management tools. Right now, two state agencies and hundreds of local agencies are trying to figure out how to carry out their duties under the law. To help them, we developed guidance on local groundwater governance options, using local groundwater markets as a management tool, navigating groundwater-surface water interactions, the concept of recharge net metering, and understanding when groundwater recharge will be considered a “beneficial use.”

What do you find most interesting or challenging about working on California water issues?

Since California water issues are limitlessly interesting—and challenging—this is a tough one. I find the complex spatial and temporal linkages in California water management really fascinating. These connections mean that water management decisions made in one place or for one set of hydrologic conditions can have far-reaching consequences for people and ecosystems in other places and under other hydrologic conditions. This is why I recently wrote about how important it is to prepare for drought during wet years, like this one, at Legal Planet. As I say there: in the midst of the wet winter storms bringing rain and snow to California this year, you might not expect drought preparations to be among the state's current priorities, but they need to be.

Posted on Monday, March 25, 2019 at 3:17 PM

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