Making it Snow: A Brief History and Review of the Science Behind Cloud-Seeding

Making it Snow: A Brief History and Review of the Science Behind Cloud-Seeding

Making it Snow: A Brief History and Review of the Science Behind Cloud-Seeding

March 15, 2023

By Elyse DeFranco

Cloud seeding
Atmospheric Research

Above: DRI researchers at cloud-seeding stations in the mountains. 

Credit: DRI

Clouds – those enigmatic formations of condensed water vapor which drift above our heads, forming rivers in the sky – can take many forms. They can be wispy and non-threatening, dark and menacing, towering or diaphanous. We tend to think of them as beyond human reach, as harbingers of forces outside of our control, but as scientists learn more about them, it’s increasingly clear that humanity isn’t merely subjected to whatever weather a cloud portends – we also create and influence it through our everyday actions. And scientists now regularly harness their moisture and pull it to Earth, bringing water to parched communities and landscapes around the world.  

This rain-inducing technique, called cloud-seeding, has been around for more than 60 years. The process involves “seeding” existing clouds with a harmless substance called silver-iodide to give water droplets a particle to converge around, allowing them to form an ice crystal. Every snowflake you’ve ever seen has initially formed this way – a small speck of dust or pollen floating around the atmosphere collects freezing drops of water, forming the intricate designs that we’re familiar with. The only difference between cloud-seeding and natural precipitation is that instead of dust or pollen, the nucleus of the ice crystal is a tiny particle of silver iodide that scientists released into the cloud. Although not a panacea for drought-stricken regions, cloud-seeding can increase seasonal precipitation by about 10%. In the Reno area alone, winter cloud-seeding efforts are estimated to add enough water to supply about 40,000 households for a year. 

Microscopic view of snowflakes

Microscopic view of snowflakes by Wilson Bentley. From the Annual Summary of the Monthly Weather Review for 1902. Bentley was a farmer whose hobby was photographing snowflakes. Source: NOAA Photo Library archives Weather Wonders collection,

Credit: NOAA

DRI researchers first joined pioneering efforts to draw more precipitation from otherwise reluctant clouds in the early 1960s, using it to increase the mountain snowpacks that supply much of the West’s water. Today, our scientists continue cloud-seeding efforts around Nevada, including in the Sierra Nevada mountains near Reno, the Spring Mountains near Las Vegas, and the Ruby Mountains near Elko. To bolster the snowpack feeding the Colorado River, DRI runs additional cloud-seeding efforts in Colorado.  

I feel really passionate that we can improve water resources across the Western U.S. with these cloud-seeding programs,” said Frank McDonough, DRI’s cloud-seeding program director. And we can run them relatively inexpensively. It’s really the only way to add precipitation to a watershed.” 

A map showing DRI's cloud-seeding sites in the Sierra Nevada range, the Spring Mountains near Las Vegas, the Ruby Mountains, and the Santa Rosa Mountains

Above: A map of DRI’s cloud-seeding locations around Nevada. DRI also has operations in Colorado. 

Cloud-seeding in a time of increasing drought 

Nevada is the driest state in the nation, with the statewide precipitation average a mere 10.3 inches — only about a third of the nationwide average of 30 inches. The rest of the Western U.S. isn’t faring much better, as the 21st century has been a time with the most severe drought in 1,200 years.  

Scientists examined tree rings to decipher the historical record for soil moisture across the region, finding that the years 2002 and 2021 were among the driest. Although historical records tell us the Western U.S. is prone to fluctuations in climate, the growing greenhouse effect of burning fossil fuels is exacerbating drying conditions. In 2022, DRI researchers published a study showing that as temperatures rise, the atmosphere pulls more moisture from streams, soils, and vegetation – what’s known as “atmospheric thirst.” Under these conditions, even consistent levels of precipitation will result in less available water for humans and ecosystems.  

We see the effects of this playing out before us as the country’s largest reservoirs, Lakes Mead and Powell, are at their lowest levels on record. As of February 2023, Lake Mead stood at about 70% empty, while Lake Powell was little more than 20% of capacity. Under these arid conditions, and with so much uncertainty surrounding water availability from season to season and year to year, cloud-seeding is one tool to help alleviate some of the human and ecological impacts of persistent drought.  

“Now, it’s not going to solve all our problems, because we need storms in the area to do cloud seeding,” McDonough says. “But I think that cloud seeding and making clouds more efficient at producing precipitation is a huge tool in water managers’ tool belt.” 

As the impacts of climate change reduce mountain snowpacks around the arid West and the world, the Intergovernmental Panel on Climate Change (IPCC) has recommended cloud-seeding as one way to help communities adapt to drier climates.  

A DRI researcher working on a cloud-seeding generator perched in the Sierra Nevada mountains

DRI researcher Patrick Melarkey performs maintenance on weather monitoring equipment in the Sierra Nevada Mountains above Lake Tahoe. 

Credit: DRI.

The complex science of cloud formation 

Cloud formation is a complicated field of research, and scientists are still learning about the way that water droplets and ice crystals interact with atmospheric particles to produce the many different types of clouds we observe. However, one thing is clear: without microscopic particles for water vapor to latch onto — like dust or salt from the sea — clouds cannot form.  

Small particles of water scatter in the air and require another speck of something microscopic in order to come together into larger, more visible water droplets. The effect is demonstrated well in a simple video taken in 2008 by scientists in the Arctic, who show that their breath fails to form visible water vapor due to the low atmospheric particle count (at sea, in areas with little to no wind, atmospheric aerosol levels are very low). They then proceed to steep a cup of tea, which also fails to form much of a visible cloud as the tea evaporates into the cold air. But when they spark a lighter over the top, small particles produced during fuel combustion grab onto the surrounding water vapor and a small cloud forms instantly.  

Due to this relationship between water vapor and atmospheric aerosols, human activities impact clouds in a number of ways. Atmospheric aerosols now include a wide range of pollutants produced by industrial emissions, tiny bits of plastics and rubber that wear from car tires and brakes, and vehicle tailpipe emissions.  

Not all atmospheric aerosols have the same impact on clouds. Research has shown that air pollution can prevent rainfall, because the water droplets in polluted clouds are too small – they float around in the atmosphere without merging to form large enough droplets to fall to the ground. A single drop of precipitation requires more than one million of these small droplets to converge. These pollutants can also prevent ice formation in subfreezing clouds. This means that our everyday activities in urban and industrial areas are already altering global rainfall patterns.  

“There’s increasing research showing that air pollution is actually having a negative impact on a cloud’s ability to produce precipitation,” McDonough says. “So, in some ways, we’re trying to restore the cloud’s ability to produce precipitation to what it would have been prior to all the air pollution coming in upstream.” 


An old C-45 plane in 1966 that DRI researchers used to seed clouds.

Above: An old Beechcraft C-45 plane that DRI researchers used to seed clouds in 1966. Credit: DRI

A snowstorm in a freezer inspired decades of research 

The history of cloud-seeding begins in the 1940’s with scientists who wanted to understand why ice sometimes accumulated on planes, creating dangerous flying conditions. Realizing they needed to know more about clouds that contain supercooled water (which is below freezing temperature but still in liquid form), researchers at General Electric simulated these conditions with a repurposed home freezer, as shown in this video. When they dropped dry ice into the freezer to mix with the water vapor from their own breath, millions of ice crystals formed, simulating a miniature snowstorm. In 1946, one of these scientists was the first to drop dry ice from a plane, watching as streams of snow fell from the cloud.  

Following these initial experiments, the research team (including Bernard Vonnegut, brother to famed author, Kurt Vonnegut) turned to silver iodide for its structural similarity to ice crystals. Silver iodide continues to be used today by DRI researchers, as a harmless substance that effectively creates a central point – or nucleus – for water droplets to converge around.  

Although many groups around the world continue to use airplanes for cloud-seeding, DRI scientists turned to a ground-based program after a fatal accident on March 2, 1980. The plane crash killed DRI researchers Peter Wagner, William Gaskell, John Latham, and Gordon Wicks. Following this tragic event, one of DRI’s pioneering experts on cloud-seeding, John Hallett, dedicated his expertise on ice formation in clouds to improving airplane safety.  

Hallett was recruited in 1966 to be one of the institute’s founding scientists: with his expertise in atmospheric physics, he helped establish DRI as a worldwide leader in the field. His focus on the behavior of ice in the atmosphere led to the discovery of a key mechanism for the transition of water molecules into ice, which is now known as the “Hallett-Mossop ice multiplication mechanism.” DRI continues to be a leader in cloud-seeding efforts and research around the Western U.S.  


A cloud-seeding generator perched on top of a mountain overlooking Lake Tahoe

Above: A DRI weather monitoring station perched on top of Slide Mountain overlooking Lake Tahoe. Credit: DRI

Measuring success in the chaos of a storm 

Taking cloud-seeding from a freezer to the skies meant finding evidence of the technique’s impact in the real world. Measuring the impact of cloud-seeding attempts isn’t simple, as it requires comparing precipitation from seeded and unseeded clouds under identical conditions – hardly an easy task due to the complex nature of the atmosphere and changing conditions over time. However, scientists have found several ways to assess their impact. By sampling levels of silver iodide in a mountain snowpack following cloud-seeding activities, researchers found it incorporated into ice crystals and deposited as snow – evidence that the compound works as an ice nucleating agent. A comprehensive review of available research published in 2019 concluded “clear physical evidence has been obtained that orographic clouds containing supercooled water, when seeded with silver iodide, produce plumes of ice particles that originate downwind of the seeding location and reach the ground through precipitation growth and fallout.”  

In 2020, a ground-breaking study known as the SNOWIE project used advanced radar and cloud-measuring technology to show that cloud-seeding coaxed moisture out of supercooled clouds, producing enough snow to fill 282 Olympic-sized swimming pools over approximately two hours. Studies like this allow scientists to build computer simulations that can facilitate more research, overcoming the difficulty of conducting field experiments under challenging conditions.  

Clouds with supercooled liquid water often form around mountain ranges as the air rising over them quickly cools with the elevation change. This is why DRI’s cloud-seeding efforts focus on mountain regions, including the Sierra Nevada and Spring Mountains. A small team of researchers, led by McDonough, plants generators in strategic locations for intercepting incoming storm clouds. These generators vaporize silver iodide particles with acetone, allowing them to rise into the air and enter supercooled clouds. The silver iodide causes the tiny drops of water in the cloud to freeze and go on to grow ice crystals large enough for gravity to pull them to the ground. Ground-based cloud-seeding allows the research team to safely and cost-effectively conduct their work, with each acre-foot of water produced only costing a few dollars.  

“There’s been a lot of good research done over the last decade or so that has really nailed down how well this works,” McDonough says. “We’re feeling more and more comfortable about our understanding of when cloud-seeding techniques work, and the scope of the impact.” 


A DRI cloud-seeding station and truck in a snowy, mountain-top setting.

Above: A DRI cloud-seeding generator and maintenance truck in a wintery, mountain-top setting. Credit: Jesse Juchtzer/DRI

Unfortunately, the internet contains many misleading ideas about cloud-seeding. Below is a series of misconceptions and questions about the common scientific practice.  


1. Is cloud-seeding producing so-called “chem-trails”? 

No. Those fluffy white lines zig-zagging across the sky are jet contrails, and they are the aviation equivalent of visible plumes of steamy breath on a cold morning. Warm water vapor produced during jet fuel combustion interacts with the cold atmospheric air to create strings of ice crystals that behave like high-altitude cirrus clouds. When a plane passes through an area of high pressure, which leads to low winds and clear skies, the trails will linger. Jet contrails have no connection with cloud-seeding activities.  

2. Is cloud-seeding “geoengineering”? 

Cloud-seeding is a well-researched and monitored form of small-scale weather modification. Other examples of ways that humans change the weather and the global climate include: driving a car, deforestation, and air pollution from industry.  

3. Who is funding cloud-seeding programs? 

Cloud-seeding programs occur worldwide. In the Western U.S., state and agency-supported efforts occur across California, Nevada, Colorado, New Mexico, Wyoming, Kansas, Oklahoma, Texas, North Dakota, Utah, and Idaho.  

4. Is silver iodide toxic? 

No. The silver used in cloud-seeding is silver iodide (AgI, or silver bonded to iodine), which can be confused with other molecular forms of silver. When silver is isolated as an ion (Ag+) it is biologically active, meaning it interacts with bacterial or fungal cell walls — which is why it’s often used for medicinal purposes and for sterilizing drinking water. Silver ion (Ag+) can be hazardous in aquatic environments because it can also interact with proteins and other parts of cell membranes, but silver iodide (AgI), not silver ion (Ag+), is used for seeding clouds. Silver iodide retains its form in water and does not break down into the potentially toxic silver ion. When the silver iodide particle falls to the ground with rain or snow, it separates from the water molecules that formed an ice crystal around it, essentially becoming a speck of dust no different from the silver naturally occurring in the soil.  

Although the chemistry can be a bit complicated, you can think of it as the difference between water (H2O) – the life-giving force that forms much of your own body – and hydrogen peroxide (H2O2), which is used as a sterilizer and bleaching agent and is hazardous at high concentrations .  

5. Is cloud-seeding used for military purposes? 

Following the (now declassified) use of cloud-seeding by the U.S. military during the Vietnam War, a 1977 international treaty banned the use of weather modification in warfare.  

6. Does DRI continue cloud-seeding during intense winters like the winter of 2022-2023?

DRI pauses all cloud-seeding activities when the snowpack reaches 150% of the historical average. In the Lake Tahoe region, this means that cloud-seeding activities halted in mid-December, 2022, due to the remarkable amount of natural snowfall occurring. 


More information:  

The Cloud Seeders
A short video about DRI’s cloud-seeding team

Where to find more water: eight unconventional resources to tap
The Conversation
By Manzoor Qadir and Vladimir Smakhtin, Deputy Director and Director of the United Nations Institute for Water, Environment, and Health 

Can cloud seeding help quench the thirst of the U.S. West?
Yale e360 

Wintertime Orographic Cloud Seeding—A Review 
Journal of Applied Meteorology and Climatology, Vol. 58, No. 10 (October 2019), pp. 2117-2140 

Quantifying snowfall from orographic cloud-seeding
PNAS, Vol. 117, No. 10 (February 2020), pp. 5190-5195 

Does cloud seeding really work? An experiment above Idaho suggests humans can turbocharge snowfall
Science Magazine 


More Information

To learn more about DRI’s cloud-seeding program, go to

Understanding Rain-on-Snow Events with Anne Heggli

Understanding Rain-on-Snow Events with Anne Heggli

Understanding Rain-on-Snow Events with Anne Heggli


March 6, 2023

By Elyse DeFranco

Anne Heggli
Rain on Snow
Extreme Weather


Above: Anne Heggli’s snowpits examining flooding beneath snowpacks in the Sierra Nevada mountains. 

Credit: Anne Heggli/DRI.

The Sierra Nevada Mountain range, as of March 2023, contains a snowpack with more than 200% of an average year’s snowfall. Water managers across California and Nevada, states that rely on the snowpack as the region’s largest supply of fresh water, are celebrating what this means for alleviating some of the worst impacts of a widespread and ongoing drought. But with snowfall occurring at low elevations in unusual places, the possibility for warm atmospheric rivers to cause flooding increases. These storms, called rain-on-snow events, are the focus of DRI’s Anne Heggli, who is studying ways to improve our ability to forecast and prepare for these potentially hazardous storms.

Under the guidance of DRI’s Ben Hatchett, Ph.D., Heggli is working with the Nevada Department of Transportation and the National Weather Service in Reno to build better forecasting tools for rain-on-snow events, which will improve safety alerts and storm preparation across the state. DRI sat down with Heggli to learn more about her work, when rain-on-snow events are the most problematic, and why snowpacks don’t simply absorb rainfall like a sponge.

Anne Heggli inside of a snowpit with only her head showing above the deep snow.

Above: Anne Heggli inside of a snowpit at the Central Sierra Snow Lab. 

Credit: Anne Heggli/DRI.

DRI: Your Ph.D. work focuses on rain-on-snow events, can you tell us more about that?

Heggli: My Ph.D. work is focused on leveraging existing monitoring networks to try to find ways that we can maximize the investment that we’ve already made to learn about patterns with our snowpack to further our understanding of rain-on-snow processes, and to help inform decision makers on what exactly is happening in the mountains, hour by hour as these rain-on-snow events take place.

I got started with this because a water manager for a hydropower company in California told me that ahead of these atmospheric rivers, she felt like they were flying blind. They had no idea how the snowpack was going to respond.


DRI: And how are you doing that?

Heggli: The western U.S. has this great snow telemetry monitoring network, called the SNOTEL network, that’s run by USDA Natural Resource Conservation Service. All the stations collect hourly data for air temperature, precipitation, snow depth, snow water equivalent, soil moisture and soil temperature.

We really use the daily data, but the hourly data has not been applied. And I felt like that was a great opportunity to analyze this data to shave away at some of the uncertainty and help inform the people who are managing our water in the Sierra Nevada.

This data is especially important for the warmer atmospheric rivers that move through and put rain up over the crest of the mountains. It’s a way for us to understand what’s really happening in the deeper snowpack and what percentage of the watershed is actually contributing to runoff. The benefit of the SNOTEL network is the soil moisture sensors. In the Sierra Nevada, those have been installed since 2006, so there’s quite a lengthy record of soil moisture data there. And when a rain-on-snow event occurs and the rainfall makes its way through the snowpack, there are these really prominent signals in the soil moisture data, so it’s a way to actually verify if the snowpack is releasing rainwater or snowmelt.

The soil moisture data is key for my research because I can identify when the snowpack is releasing water, and then look at the snow density, air temperature, and precipitation. That way I can identify the patterns that are present every time the soil moisture has these really dramatic responses to find the ingredients that produce more impactful runoff rain-on-snow events.


DRI: Is soil moisture a measure of melted snow, or is it rainfall that’s passing through the snowpack to the soil?

Heggli: That’s one of the things that is kind of unknown. There’s been an assumption that the snowpack is melting. But some of the research in my first paper shows that during these rain on snow events, snow melt is not the primary driver of runoff in deeper snowpacks. Shallow snow will be obliterated, but in the deep snowpack, sometimes that snow will actually absorb part of that rainfall. But essentially, except for very exceptional events — like the 1997 flood event and February 2017 in the Sierras — snow melt typically is not part of the runoff process in the deeper snowpacks. However, in the shallower snow at lower elevations, it can begin to melt and then that increases the amount of water available to runoff into the streams.

It’s really about trying to tease out whether the runoff during rain-on-snow events comes from melting snow, or is it just rainfall and increased runoff efficiency? What exactly is producing the runoff and why is it so hazardous? What are the ingredients of a perfect storm for those major rain-on-snow flood events?

tortoise detection dog sits for owner

Heggli’s snowpit at the Central Sierra Snow Lab during the December 2022 storm.

Credit: Anne Heggli/DRI

DRI: Why can rain-on-snow events be a problem?

Heggli: Well, it’s highly uncertain at times. There are times, like in 1997, where we knew that this very warm storm was coming in with a lot of moisture and precipitation and very high-elevation freezing levels. Sometimes when the atmospheric rivers make landfall, they’ll push against the Sierra Nevada and they’ll start to lift and at some elevation that rain is going to transition to snow. Understanding and forecasting the elevation that rain turns to snow is extremely difficult. And it can really change the amount of water that is being produced as runoff. In some storms, maybe 50% of the entire basin is contributing to runoff because of where the snow level is. But in other times, like in the 1997 event, you now have 100% of the basin actually contributing to runoff, and the more problematic floods have happened when we get a warmer atmospheric river just after a cold and low elevation snow event — just like something we just had — where there’s snow down to 2,000 or 3000 feet. When you take that shallow snow, and then you have rain come over it, it melts really quickly. Even if you only have three inches of snow at that lower elevation, the rain plus that three inches integrated over an entire area really increases the amount of runoff that’s available. My work is about trying to understand those vulnerabilities and when the situational awareness should be increased.

Another example was in 2017, when the Sierras had a rain-on-snow event in January that primed the snowpack and the soils, and then in February we had another atmospheric river rain-on-snow event, and that caused quite a bit of flooding. So, I’m trying to understand the evolution of how the first rain-on-snow event might impact the soils and the snowpack to kind of prime the system.

We can monitor these systems to understand if we have the capacity to take on some of that rain-on-snow, or if there are things like low elevation snow or prior rain-on-snow events that should really be alerting water managers. That way they can prepare by routing water to give it the most beneficial use up in the mountains or make sure they’re releasing some from reservoirs well ahead of the event so that there is the capacity to take on floods. In the worst-case scenarios, identifying the vulnerabilities early on can help inform emergency managers to decide if, or when, to start sending out sandbags and prepping for potentially failed levee systems well in advance of the impact.

Downtown Reno with severe flooding after a 1995 rain-on-snow event.

Flooding in downtown Reno after a 1997 rain-on-snow event. 


DRI: So, one thing that water managers can do, if they have enough warning that a rain-on-snow event might be imminent, is to release water from the reservoirs to make room for the flooding event?

Heggli: Yeah, a lot of that’s controlled by the Army Corps of Engineers, and there are strict rules for operating reservoir levels during flood season. But for hydropower companies that operate very complex networks up in the mountains, they can move water between their reservoirs. Depending on the capacity of one reservoir adjacent to another, they might be able to move water between them to keep it up in the mountains. That way, we have access to it in the summertime when it’s most needed. That’s why giving them information to prepare for storms can hopefully help us save water for the most beneficial use, so they don’t have to rely solely on releasing water downstream. Of course, that’s if there is the capacity in those reservoirs to actually take on a little bit more.


DRI: How common are rain-on-snow events in California and Nevada?

Heggli: They’re relatively common. One rain-on-snow event a year is pretty common, and we have years where we don’t get any. But we’ve also had years where we get as many as five rain-on-snow events. Everything in the West is highly variable but it’s definitely not uncommon and this is by no means something new – there are photos from 1955 of downtown Reno being flooded very similarly to 1997. So, it’s something that has always been a problem in this region.

What is new is that we are now confronting a changing climate where snow levels are rising, and it’s projected that more precipitation is going to be falling as rain than snow. This means we’re kind of approaching this period of peak rain-on-snow events while the atmosphere is warming, because more rain than snow is falling but we are still getting snow for the rain to fall on. So, it’s something that we very much need to be paying attention to and it’s going to continue to be — I don’t want to say a problem, it can cause problems — but it is definitely something that we need to make sure we’re adapting to and informing our emergency managers and water managers about so they can make the best decisions with our resources and infrastructure available.

woman and her dog
The Carson River flowing strongly after a storm in December, 2022.

Above: Two photos contrasting the Carson River’s flow before and after a December 2022 rain-on-snow event.

Credit: Anne Heggli/DRI.


DRI: There’s been some chatter amongst meteorologists right now about the possibility for rain-on-snow events later this week (around March 10, 2023). What are your thoughts about the likelihood of this event right now and where do you see it having an impact and at what scale?

Heggli: We have seen signals for a potential warm atmospheric river (AR) and over the last couple of days the models have been converging in agreement that a lower magnitude AR is approaching. The exact location of landfall and the freezing level in the atmosphere is still uncertain at this point. However, even a weak yet warm atmospheric river, combined with all the low elevation snow, could still be very impactful. The low elevation snow, high soil moisture content, and higher river levels, which we currently have, tick the ingredients boxes for increased potential impacts from a warmer atmospheric river. It’s something to keep an eye on, but the predictions don’t yet show something huge like 1997 — there is something coming but it’s still quite uncertain how it will evolve.


DRI: Is there anything else you think is important?

Heggli: I think it’s important to communicate that the snowpack isn’t a sponge — I think there’s a really common misconception that, “Oh, rainwater moves in this uniform wetting front and just slowly makes its way down.” That’s not at all what happens during rain-on-snow events, especially higher intensity ones. The rain will hit the surface and then it looks for the path of least resistance. It uses capillary attraction to find ways to work through the snowpack, and it’ll form what they call flow fingers, or preferential flow paths. It’s like the way that you see icicles line up, the water drips in specific places. It’s something similar to that where water will find the path of least resistance and warm the snow just enough there to make its way through, which makes it easier for all the other rainwater to follow. So, it doesn’t actually need to warm the snowpack evenly to be able to progress. It’ll find these little paths, and it just basically punches its way through the snowpack.

Part of the concern with rain-on-snow events is that we have higher runoff efficiencies because the rain can punch through the snowpack and make its way to the soil and then run off. And if there’s so much rain that’s coming through that the soils can’t take it on, then that rainwater actually starts to move through the base of the snowpack. I posted a photo from December 30 when I was up at the Central Sierra snow lab during the rain-on-snow event, digging a snow pit in the rain. When I got there, there was nine centimeters of standing water at the base of the snowpack. By the time I left there was 13 centimeters of standing water at the base. So, it just really shows that the water is not able to move through the soil anymore and enter the streams that way — it’s now making its way over the surface. And that is something that can really cause a lot of flooding, because it just moves so much quicker.

Unfortunately, a lot of the work on this seems to have been forgotten and isn’t well integrated into our forecasting models. A lot of the existing models cannot handle preferential flow paths or lateral flow through the snowpack. I think this is because people aren’t out in the field making observations as much anymore, they’re relying heavily on computer simulations. These are helpful, but they also tend to remove outlier events, and in the Sierra Nevada those outliers are the events that impact us the most. You know, none of the work that I do matters until it actually matters, and then it matters a lot. We can have years where what I do is of no use to anybody. But years like this is when we really need additional information because there’s nowhere else to get information — we can’t get satellite data because of cloud cover. So, all that we have to understand what’s going on in the mountains are observational networks. That’s part of the reason that I thought, “we’ve got to use this data.”

Instant coffee dripping through snow to demonstrate the way rainfall moves through snowpacks.

Heggli’s experiment using instant coffee to track the flow of water through the snowpack. 

Credit: Anne Heggli/DRI.

DRI: So, you’re going out in these rain-on-snow events and digging down to the bottom of the snowpack to see what’s happening?

Heggli: Yeah. You can see from the snow surface the development of the preferential flow paths. To try to better understand these flow paths, sometimes I take instant coffee and put it in a spray bottle and spray the snowpack, and then go and dig it out. I can do different quantities of spray and then let it sit overnight and see how far those preferential flow paths progress — that way I can see the contrast of the coffee against the snow. I do that to try to better understand and observe and document what is really happening with the rain-on-snow and hope that some of these visuals help get the idea across that snow isn’t a sponge, and this is why rain on snow events are so difficult, but also interesting.


For more information on Anne and her research, watch this video from her presentation at DRI’s public science seminar series, Science Distilled. 

Mary Cablk: Celebrating a Career in Canine Detection,  Biology, and Remote Sensing

Mary Cablk: Celebrating a Career in Canine Detection, Biology, and Remote Sensing

Mary Cablk: Celebrating a Career in Canine Detection, Biology, and Remote Sensing

February 15, 2023

By Elyse DeFranco

Mary Cablk
Remote Sensing
Canine Search and Rescue

Above: Dr. Mary Cablk standing on the side of a snowy mountain.

Credit: Mary Cablk/DRI.

Mary Cablk, Ph.D., recently retired from DRI after 23 years. Her journey into science began with remote sensing, and she later pioneered new fields of scientific research by integrating her experience as a canine search and rescue handler and trainer. In addition to her role as an Associate Research Professor in DEES, she served as Graduate and Adjunct Faculty at the University of Nevada, Reno, where she was instrumental to the creation of a Ph.D. program in forensic anthropology.

Among her many career accomplishments, she was the first to use detection dogs to track and locate threatened desert tortoises, as well as the first to establish that dogs can locate human teeth for recovery and identification purposes. She serves on the American Academy of Forensic Sciences Consensus Body and Standards Board, is a court recognized expert on the science of detection dogs, and is an auxiliary deputy with several County Sheriff’s offices in Nevada.

Cablk shared some of her career highlights, her plans for a busy retirement, and her perspective on how the scientific landscape has changed over the years.

Cablk takes a selfie on a snowy mountain

Cablk, who recently retired from DRI after 23 years.

Credit: Mary Cablk/DRI.

DRI: What first brought you to DRI?

Cablk: I met a now retired faculty member, Dr. David Moat, while doing my Ph.D. at Oregon State. He was on loan from DRI and was stationed at the EPA lab in Corvallis, Oregon, at the National Health and Environmental Effects Research Laboratory. He invited me to work on a D.O.D funded project in the California Mojave Desert, so I competed for, and was awarded, a National Research Council Postdoctoral Fellow position, two years in a row. When Moat returned to DRI in Reno during the project I followed to finish out that postdoc, and that’s how I ended up here.

DRI: How did your interest in scientific research begin?

Cablk: I was exposed to satellite imagery and image processing when I was in graduate school at Duke University. I took a course in remote sensing – this was back when times were very different than they are now. We didn’t have smartphones, and we certainly didn’t have imagery on anything handheld. I thought satellite imagery was beautiful.

Art is in my genes — my grandmother was a biological illustrator. If I didn’t go into science, I was going to go into art. I thought the imagery of earth was beautiful, and then it turned out to also be data, so I got sucked into it. Everything about it appealed to me – what you could see from afar – there’s a lot of art in science, if you know how to look for it.

DRI: How did you transition into doing a lot of work with dogs?

Cablk: That started early in my career, around 2001. Right around the time when I was finishing my postdoc here, and I was a new faculty member. A Government Accounting Office report came out examining how much money had been spent on desert tortoise research, which was a lot, and what they had received in return for all that money. It wasn’t much – we weren’t getting any closer to delisting the species or reversing the downward trend. 

At that time, I had started doing search and rescue myself with my own dog. I started to see what dogs could do searching for missing people, and I thought, “Wow, this is incredible. I wonder if dogs can find tortoises.” That was really the launchpad for what became a career studying canine detection. It didn’t come easy – I was told initially by a lot of people, “that’s the dumbest thing I’ve ever heard.” Now, of course, wildlife conservation detection is huge. But back then I was one of the first to pioneer interfacing dogs with actual animals, and not just scat. We had some success, and then things snowballed and progressed. Before I knew it, I was 10 years in and a few million dollars into the research. 

I would draw from the search and rescue community to hire dogs and handlers for my Desert Tortoise K9 program, because at that time there weren’t many professional handlers like there are now. Conservation canine work is commonplace now, but back then, we were pioneering everything. It was fun – a lot of time spent in the desert, and I spent months and months living outside of military installations. That was a big part of my career.

tortoise detection dog sits for owner

A tortoise detection dog-in-training performs his trained alert, the ‘sit,’ near a tortoise.

Credit: Photo from Cablk et al., 2008, “Olfaction-based Detection Distance: A Quantitative Analysis of How Far Away Dogs Recognize Tortoise Odor and Follow It to Source.”

DRI: I’d love to hear more about your search and rescue work and how you got started with that.

Cablk: I got into it very early on when I was a postdoc. I had someone close to me who needed rescue in Zion National Park, and search and rescue in Zion saved his life. There is some percentage of people who get into Search and Rescue because they have a first-hand experience, or someone close to them needs rescue or recovery. I’m one of them, and it just dovetailed with my wanting to work with dogs. I’d always had dogs, my degree was in biology, and I have a lot of background in animal behavior. I was never a laboratory person.

Search and rescue really opened my eyes to possibilities for research because back then this was all new. Nowadays, we’re in a super exciting time with research into canines, canine behavior and cognition. But back then, it was literally a desert of knowledge and science. So, I just integrated what I was learning from my research into how I was training dogs in search and rescue, and then taking things that we saw on deployments and in training, and turning that around and asking questions to see if we could address those scientifically. So, I’m a little bit unusual – maybe not unusual for DRI, but certainly for a lot of people’s careers – where there’s this integration between what I do professionally and what I do in my free time. It’s been a really fun way to have a career, looking back on it.

DRI: You’re very involved in the local search and rescue groups, right?

Cablk: Yes, very much. When you run dogs for search and rescue, you either do it for a little bit, and then you get out of it quickly, or you’re in it for life – I fall into the latter category.

I’m an auxiliary deputy with the sheriff’s office here in Washoe County, the Carson City Sheriff’s Office, Douglas County Sheriff’s Office, Lyon County Sheriff’s Office, and the Humboldt County Sheriff’s Office. Over in the state of California I’m integrated with their Office of Emergency Services with the Governor’s office there.

Search and Rescue requires a huge amount of time – very few people have the time and the means to be able to do it. I feel very fortunate that I had the wherewithal and the ability to land here at DRI where I could pursue whatever research interests I wanted as long as I could secure funding. We have complete flexibility to be able to integrate something like search and rescue with science. It’s really unique here.

Cablk with her dog, Dax, at a search and rescue training course

Cablk with her dog, Dax, at a search and rescue training course.

Credit: Mary Cablk/DRI.

DRI: Can you talk about some of your research projects?

Cablk: Well, after I learned about how difficult it was for forensic anthropologists to find teeth (which is important for body identification) I thought “You know, if dogs can find desert tortoises the size of a half dollar in hundreds of acres of desert, I bet they could find teeth.” And I saw a call for proposals that I think the Department of Justice had put out to develop more sophisticated methods to locate teeth. So, I called the program manager to get a little more information and said, “Hey, here’s my idea. I think we should look at running dogs to find teeth.” He said that was the most ridiculous idea he had ever heard. So, I hung up the phone and said to myself, “That’s fine. I’ll find another source of funding and publish the results anyway.” And that’s exactly what I did.

I published the study in the Journal of Forensic Sciences. And I was told that one year the findings were included in the American Academy of Forensic Sciences diplomate exam, which is a big deal. It was groundbreaking research at the time.

DRI: How have things changed since you first started your career?

Cablk: They have changed so much. Probably the biggest part is the development of technology. When I first started working with satellite imagery, we didn’t have the spatial resolution that we have now. I was computer line coding to do my analysis, and now people do analyses on their phones. Cellphone technology had just become smaller than a handheld brick when I finished my PhD in 1997. When we would go out in the field, we didn’t have communications with anybody. And you know, you just did what you had to do to get your research done. We were very creative. And it was fun – it was really fun.

I think for my generation of field scientists who would go out, we would dive in headfirst and get our hands dirty – that’s the fun part. Now, there’s a lot more oversight. And then of course, now we’re in constant communication.

But we also didn’t have the education-communication side of it, to tell the world about what we were doing. That wasn’t really a thing, for lack of a better term. We would communicate within our own discipline, peer to peer and colleague to colleague, but it was difficult to explain to the public what we were doing. I have a million stories about the personal interest side of science and fieldwork, but in my generation, we were never taught how to share those stories. It was not something that was appreciated. I’m proud of the work that I did, and I’d love to share the human side of it. Like the first time the dogs found tortoise hatchlings, which are the size of silver dollars. That ability wasn’t on our radar screen, and we just sat there and watched it happen. It was like watching Neil Armstrong step on the moon – we had no idea that what the dogs were doing was even possible. I wish that we’d had an opportunity and the means to communicate that pivotal finding. Now, I see that shift in DRI and in the scientific community as a whole, towards communicating our science to the public, but back then, it was a whole different environment.

DRI: How has working at DRI impacted your scientific research and network?

Cablk: Well, I think it’s the other way around. I mean, we’re the ones that are doing the research. And we can do it anywhere. I don’t see that DRI has necessarily impacted my work, but I think that DRI has created a tremendous opportunity, and the right framework to allow professional development and growth.

woman and her dog

Cablk with her dog, Dax.

Credit: Mary Cablk/DRI.

DRI: What advice do you have for young scientists?

Cablk: The world is so different now. Nowadays, we don’t have the hard lines between disciplines that we did before. I see the world now as an endless sea of opportunity. The one piece of advice that I’ve always given, is when you’re dealing with data analysis software, you need to learn the math behind it, and not just which buttons to push.

Go for it, have fun with it. Life at DRI is incredibly stressful. Now, on the other side looking back, I can’t imagine doing anything else. But it’s a double-edged sword. You have to have the stomach for it, especially as a woman. I do believe that challenges still exist for women, even though we’re in a different society than we were even a decade ago. I don’t know that there’s anything anybody can do externally to help women scientists find their voice and their confidence. I wish I could, because I wish I’d had a mentor like that when I was first starting out. When I showed up here, it was a sink or swim environment. But if you have the brains, and you have the passion, and the drive, and the dedication and motivation – young scientists can do anything nowadays. And they should.

DRI: What are your plans for retirement?

Cablk: Oh, I love retirement! I’m still working.  Every day is different and interesting. I am in a teaching role for the state of California Governor’s Office of Emergency Services. I teach search and rescue,  having almost 25 years of experience and training under my belt. We do week-long courses for what’s called “Winter Search Management.” We go down to Mammoth Lakes or Mount Shasta or Sequoia Kings Canyon, and teach law enforcement everything about winter searching: avalanche conditions, medical, equipment, you name it. We spend five days and at the end, they end up sleeping in a snow cave that they dug themselves.

I’m also working with Chico State forensic anthropologists and the state of California Office of Emergency Services to develop the canine portion of a new class called “search methods and identification in a burned environment.” So, when we have these massive, fatal fires that are tragic and have become an annual occurrence, we use the dogs to help locate missing people.

And of course, I’m still deploying dogs. I have the freedom and flexibility to deploy on searches and I’m still very active with the American Academy of Forensic Sciences. I still sit on their standards board and we’re working on developing national level standards. I am often invited to speak at professional conferences and meetings, for example I’ll be talking about water recovery canines with the International Water Rescue Professionals Association, MENSA, things like that. I’m still active and engaged with the canine community, and there’s certainly a scientific aspect to my involvement. Someday maybe I’ll end up on a beach, like some of my colleagues who are also retired, but I’m still pretty young and have more professional interests to pursue.

Cablk doing recovery work with her dog, Dax, at a burn site in California.

Cablk doing recovery work with her dog, Dax, at a burn site in California.

Credit: Mary Cablk/DRI.

DRI: Will you continue doing some work at DRI? 

Cablk: I’ll seek emeritus status, and then become an hourly to be able to take advantage of opportunities that might come through DRI. We have phenomenal scientists here. And I really loved working at DRI. I’m not saying it wasn’t stressful, and I’m not saying it wasn’t hard — but what a great career.

DRI interns join the search for elusive desert tortoises in Tule Springs Fossil Beds National Monument

DRI interns join the search for elusive desert tortoises in Tule Springs Fossil Beds National Monument

DRI Interns Join the Search for Elusive Desert Tortoises in Tule Springs Fossil Beds National Monument

Feb. 6, 2023

By Elyse DeFranco

Desert Tortoise
Occupancy Sampling
Tule Springs

Above: Tiffany Pereira, M.S. conducts field research at Tule Springs Fossil Beds National Monument outside of Las Vegas. 

Credit: Ali Swallow/DRI.

DRI’s Behind the Science Blog continues with the second installment of our fall 2022 Research Immersion Internship Series

This fall, DRI brought eleven students from Nevada’s community and state colleges to the Las Vegas and Reno campuses for a paid, immersive research experience. Over the course of the 16-week program, students worked under the mentorship of DRI faculty members to learn about the process of using scientific research to solve real-world problems.

Our Behind the Science Blog is highlighting each research team’s accomplishments over a series of five stories. Click here to read the first installment in our internship series.

In this story, we follow Tiffany Pereira’s student interns as they track elusive and threatened desert tortoises in the Las Vegas desert.

desert tortoise

A desert tortoise in Mojave National Preserve.

Credit: Photo courtesy of the U.S. National Park Service.

Student Researchers: Amelia Porter and Akosua Fosu

Faculty Mentor: Tiffany Pereira, M.S., Ecologist and Assistant Research Scientist

Despite their enormous size, desert tortoises are elusive desert dwellers, often spending most of their lives in underground burrows – giving them their scientific name, Gopherus agassizii.  They occur across the Mojave and Sonoran deserts of California, Nevada, Utah, and Arizona. Listed as threatened under the Federal Endangered Species Act since 1990, their numbers are declining due to a number of threats. Understanding the size and health of their populations is a priority for both government agencies and researchers. 

desert tortoise map

Desert tortoises occur across the Mojave and Sonoran deserts of California, Nevada, Utah, and Arizona.

Credit: Map courtesy of the U.S. National Park Service. 

“Desert tortoises face predation by ravens and other large birds, canids including coyotes and foxes, as well as insects such as fire ants,” said intern Amelia Porter. “They’re also victims of urbanization, military activity, mining, and alternative energy projects, which destroy their natural habitat as well as their food and water sources and deposit a multitude of pollutants.”

For their internship, Amelia Porter and Akosua Fosu worked with DRI ecologist Tiffany Pereira to survey parts of the Tule Springs Fossil Beds National Monument near Las Vegas for desert tortoises. Tule Springs was established in 2014 to protect the delicate desert habitat as well as rare, preserved fossils of Ice Age life – including mammoths, ground sloths, dire wolves, and American lions. The park borders northern Las Vegas and Highway 95.

“When it comes to urban-wildlife interface, Tule Springs acts as a barrier between active human development and pristine desert tortoise habitat,” said intern Akosua Fosu. “The thing is, Tule Springs National Monument is literally in people’s backyards, and it borders a major highway. The goal is to continue to use this park and enjoy all it has to offer, but to do so in a way that doesn’t disturb the desert tortoises within the monument.”

female scientists conducting surveys

Interns Akosua Fosu and Amelia Porter locate a desert tortoise while conducting surveys. 

Credit: DRI.

Searching the Desert Landscape for Clues 

To help Tule Springs resource managers better understand how many desert tortoises occur across the park, as well as how they use the landscape, the research team used a method called occupancy sampling. This method combines field surveys with computer modeling to help researchers determine the proportion of habitat within an area containing evidence of a targeted species. Occupancy sampling allows scientists to determine the abundance of a species that is otherwise elusive or difficult to track.

“One way to understand where tortoises are in the park is to walk transects across the entire monument – but that’s just not feasible,” said faculty mentor Tiffany Pereira. “So, we did a different type of population sampling that could provide information on where the tortoises are. Going to the site with the interns every week has been really fun.”

The research team conducted field surveys across 20 plots, each of which they visited four times. As they walked focused lines called transects, they recorded signs of tortoise occupancy including scat, tracks, and of course, observations of live tortoises.

akosua fosu

Intern Akosua Fosu surveys the desert landscape for signs of desert tortoise, including scat, tracks, and evidence of burrows.

Credit: DRI.

“Tortoise scat is cylindrical in shape and has lightened edges,” said Fosu. “It’s almost like a cigar – and when you break it apart, it contains plant material.”

When the researchers found a possible tortoise burrow, they looked for evidence of recent activity, like an “apron” in the dirt indicating digging, or visible tracks.

“A tortoise burrow is a half-circle shape with the top of it rounded and smooth, due to the shell eroding it over time,” Porter said. “They’re usually located in rocky areas or under vegetation.”

desert tortoise in burrow

Desert tortoises spend much of their lives in burrows that protect them from the harsh desert sun.

Credit: Tiffany Pereira/DRI.

The students recorded any sign of desert tortoises in a survey app, including the measurements and characteristics of burrows and the presence of live tortoises or carcasses. Using the survey data, the researchers marked each plot as active or inactive for desert tortoises using a binary system. The results are analyzed using the software program PRESENCE, which provides an estimated occupancy probability of desert tortoises within an area of interest.

“Tule Springs is a newer park,” said Porter, “so they will use the data that we’ve collected over the course of the season to help determine where to place signage, or hiking trails, without disturbing desert tortoise habitat.”

One of the most important findings from their study is that many tortoises are using parts of the park that are near human activity. “That’s a big deal for management of the park,” Pereira said. “In one case, we found a tortoise less than 200 meters from a paved road. When they think about their management plans, they need to account for that.”

joshua trees in tule springs

Joshua trees at Tule Springs Fossil Beds National Monument.

Credit: Matthew Dillon.

Embracing the Research Experience

For student interns Porter and Fosu, joining Pereira’s research team and spending time in the field was a truly immersive experience into the world of science.

“Being able to see some of our native flora and fauna up close was a highlight,” said Fosu. “There were days where we came across tortoises, snakes, and even jack rabbits. I also got to learn about some of our native plant species.”

Fosu, a student at Nevada State College studying biology and chemistry, entered the school year with plans to pursue a veterinary career. Her time working with Pereira reinforced her interest in working with animals, she says. “I may even consider conducting veterinary research in the future.”

akosua fosu and tortoise in desert

Student intern Akosua Fosu finds a desert tortoise while conducting surveys.  

Credit: DRI.

“Overall, I think this was a very eye-opening experience,” Fosu continued. “My goal was to gain some research experience before I graduate and I’m glad I was able to gain that through this internship. I would definitely recommend this to anyone considering a career in a STEM field.” 

amelia porter surveying in field

Intern Amelia Porter conducting a survey for desert tortoises in Tule Springs Fossil Beds National Monument.

Credit: DRI.

Porter, a student at the College of Southern Nevada studying environmental conservation biology, agreed that the DRI internship helped her feel more confident in her career choice. “It has not only confirmed my passion for a career in ecology and wildlife studies,” she said, “but sparked an interest in park service and in field surveying as well.”

The highlight of the semester, Porter said, was “feeling immersed in the methods of an established ecologist, and the opportunity to feel like I was a part of a project that benefitted the surrounding area.”

“I think the entire immersion program has been a fantastic opportunity,” she said, “and I hope that the program continues so it can be as inspiring to others as it has been to me.”

More Information

To learn more about the DRI Research Immersion Internship, go to

What can prehistoric ceramics of the California deserts tell us about the past?

What can prehistoric ceramics of the California deserts tell us about the past?

What can prehistoric ceramics of the California deserts tell us about the past?

Jan. 5, 2023

By Elyse DeFranco

Prehistoric Ceramics 
California Desert District

A Q&A With Archaeologist Greg Haynes

DRI archaeologist Greg Haynes, Ph.D., recently completed a synthetic report on the prehistoric ceramic artifacts of the Colorado and Mojave deserts for the Bureau of Land Management’s (BLM) California Desert District (CDD). The CDD manages the 11 million-acre California Desert Conservation Area, which holds cultural artifacts dating back thousands of years. Following a century of research on the prehistoric people and cultures of the Colorado and Mojave deserts of California, this is the first large-scale synthesis focused on ceramics and what they can tell us about the past.

Haynes’ report provides guidance for understanding prehistoric ceramics, identifies research questions for their study, and aids in the evaluation of ceramic-bearing resources for the National Register of Historic Places.

DRI sat down with Haynes to discuss this project, which he calls “one of the highlights of my career.”

DRI: Could you tell me a little bit about your background and how you came to DRI?

Haynes: I’ve been a professional archaeologist for about 35 years. I have a B.A., M.A. and Ph.D. in anthropology and my research focus is on the prehistoric archaeology of western North America. The hunter gatherer populations in the Great Basin, Mojave Desert, and the small-scale agricultural societies on the Colorado Plateau, namely the ancestral Pueblos or Anasazi. I was on staff at DRI as an Associate Research Scientist in archaeology between 1992 to 1998 and returned in 2019.

DRI: And how did you come to be involved with this particular report?

Haynes: The project is focused on creating a new synthetic context for prehistoric ceramics in the deserts of Southeastern California. I was awarded the project in large part because I have a professional background in the area, and I had a nationally recognized ceramic expert in the American Southwest on my team, Dr. Karen Harry, a Professor of Anthropology at UNLV.

map of mojave desert region

Left: Map of the Mojave Desert region. Right: Great Basin Brown Ware with incised decoration along rim, from the northeastern Mojave Desert.

Credit: Greg Haynes/DRI.

great basin brown ware decoration

DRI: Why is it important to catalog and identify ceramic artifacts?

Haynes: What the BLM wants to do, and what most archaeologists want to do with ceramic artifacts, is use them to identify cultural and temporal affiliations. Which groups made or used a particular site — that is, you find a pot sherd (piece of ceramic) and you want to infer what archaeological cultures made that ceramic and therefore used or made the archaeological site you’re looking at. They also want to know what time periods those ceramics date to. And many ceramics in the American Southwest are tied to a radiocarbon or tree-ring chronology, so they’re tightly constricted in time and space.

DRI: How are ceramics dated using radiocarbon dating methods or tree-ring chronology?

Haynes: In fact, they can’t be radiocarbon dated. They have to be in direct association with something that can either be radiocarbon dated or be dated through tree rings. For instance, if archaeologists find a pot in a house, and the house has a wooden roof beam over the top of it, the roof beam can be dated through a tree ring chronology (or dendrochronology). And by association, they therefore date the pot at that particular time period.

DRI: And radiocarbon dating only works for things that were previously living, right?

Haynes: Yes, that’s right. Now, there’s another type of dating nowadays called optically stimulated luminescence dating (OSL). And that you can use to actually date the ceramic itself, and as springboard projects develop from this particular one, I hope to learn more about OSL and perhaps use our own OSL lab here at DRI.

The important point though, is that the ceramics in the Colorado and Mojave deserts of Southeastern California, are primarily plain wares — they don’t have a lot of diagnostic features on them. And you need diagnostic features to be able to identify different types of pottery, and therefore the people who made them, as well as track them through time. Additionally, most of the pottery you find sits right on the ground surface. And if they are buried, there’s almost no association with organics that can be radiocarbon dated, tree rings, or stratification — that is, buried deposits that are layered so you can see how things change through time. So, they stump people. This inspired the BLM to seek a new synthetic context for these things, and new research directions about how we can use ceramics to tell us about precontact people and time.

DRI: When ceramics are found in the desert today, are they still collected and put into collections?

Haynes: In general, they’re not collected at all. And one reason is that there are hundreds of collections with tens of thousands of ceramic artifacts in repositories across the U.S. The BLM identified 16 repositories in the Western US that hold prehistoric ceramics from lands administered by the California Desert District. And while there is no absolute number of how many pieces of pottery are in those collections, it is tens of thousands — maybe even over 100,000.

example of a Tizon Brown Ware body sherd

An example of a Tizon Brown Ware body sherd from Arizona. The brown color is derived from residual mountain clays and the temper is visible on its surface.

Credit: Greg Haynes/DRI.

DRI: And how old are some of the artifacts that you documented in this report?

Haynes: They don’t date much before about A.D. 1000. Most of them date no earlier than A.D. 1100 or 1200.

DRI: Would ceramic artifacts last much longer than that?

Haynes: Ceramic artifacts certainly would — they’re fired stone, essentially. Clay molded into something and then fired until they’re essentially pieces of stone.

DRI: When you’re making these associations between the ceramics and the people, how does that work?

Haynes: Well, there are different attributes on the ceramics, like surface colors. For instance, a particular type of ceramic called Lower Colorado Buff ware was known to be made by ancestral Yuman-speaking populations and they have particular types of colors because of their clay sources (buff, orange, or red). And you can also do that with temper (small chunks of rock or other material mixed into the clay to give it some texture, so it doesn’t break apart when it’s being fired and used). The types of clay you might find in Lower Colorado Buff ware is different than the clay in other types of pottery like Tizon Brown ware, which is also found in the Mojave and parts of the Colorado deserts of California, and colored brown. And that’s because it’s made from residual, igneous clays formed in the mountains as opposed to alluvial clays formed on the valley floor near rivers.

example of Lower Colorado Buff painted ware

An example of Lower Colorado Buff painted ware from along the Colorado River. It is a red-on-orange bowl sherd with decorated elements on the interior of the vessel.

Credit: Greg Haynes/DRI.

DRI: And what can we learn from these artifacts?

Haynes: Well, what the BLM wanted to learn is, can these plain wares in the Mojave and Colorado deserts of southeastern California actually tell us who was at a site and at what time? That can be done to some extent, but it can’t be done with a lot of detail. So, if you find a site that has a whole bunch of Lower Colorado Buff Ware you can say, okay, the people who lived here were ancestral Yuman-speaking folk, but these same ceramic artifacts have not been tied to a very good chronology. You can’t tell when the site was occupied based on the ceramics, unfortunately. And people have tried to do that for years, but there simply has not been enough radiocarbon dating or stratified deposits associated with those ceramics to track them through time. OSL offers an opportunity to do that, but it has to be fairly widespread — it would take a lot of ceramic artifacts to develop a well-established chronology for plain ware artifacts.  

DRI: What do you mean by “wares”?

Haynes: A ware is a type of ceramic that is made by a particular prehistoric people.  If you were an archaeologist, however, we could debate what a ware is for quite a long time. I’ll just leave it at that simple, big idea.

DRI: I think you touched on this, but why are the ceramic resources in the Colorado and Mojave Deserts difficult to characterize and differentiate?

Haynes: It’s because they don’t have a lot of distinguishing attributes on them, like painted motifs. For instance, if you find a painted circle or a square on a piece of pottery that’s made in one location, but you don’t find it in the next region over, that may be related to cultural differences. For plain wares, there’s not a lot of decoration, they’re just plain wares, very utilitarian. So that’s what makes them difficult and the fact that they have not been tied to a well-established chronology. And we’re often working with just little fragments of ceramics, rather than large pieces or entire vessels.

Another important point about the ceramic context is that you will not be able to learn much about the ceramics in terms of culture and history unless you examine attributes that change through space and time – like one single attribute, how it changes or varies through time and where you find it. So, one thing you could look at are changes in rim morphology or shape over space and time. Or you could look at the distribution over space and time of stucco (something put around the base of a pot, presumably to strengthen it). Or you could source these ceramics using specialized techniques to identify their geochemical signature or fingerprint, and see how far and wide, through space and time, that geochemical signature or fingerprint can be found.

rim morphologies
example of a Lower Colorado Buff plain sherd

Top: Rim morphologies: a. straight walled; b. chimney neck; c. outward/gently recurved; d. outward flaring/exaggerated recurved wall; e. inward/gently recurved wall; f. inward flaring/exaggerated inverted wall.

Bottom: An example of a Lower Colorado Buff plain sherd from along the Colorado River. It has a thick stucco applied to its exterior.

Credit: Greg Haynes/DRI.

DRI: And by fingerprint, you mean a particular type of clay?

Haynes: That’s correct. You can do the same kind of analysis with what’s called burnishing, where the inside or the exterior of the pot is blackened, and then it’s polished. Where do you find burnishing, through space and through time?

DRI: Did you learn anything new or surprising while preparing this report?

Haynes: Part of the project was to go to a number of ceramic repositories and look at some of these collections. And I chose four museums to go to because they had by far the most ceramics. When you look at collections like that, you run across some incredibly interesting things that are just startling. For instance, I was at the Imperial Valley Desert Museum in El Centro. I was given this bag of prehistoric ceramics and they were Lower Colorado Buff ware, and I thought, “These are really weird — something’s wrong with them.” It was like the pottery itself had decorative waves in the clay, but they were clearly natural. So, I put the bag away because I was just confused by it. And I looked through other bags and looked at different pottery sherds. And the last day of the last hour, I came back to this bag because I’m just completely stymied by it. And I opened it up and looked at it and it dawned on me that this is an unfired pot. They had molded this either around the inside or the outside of a pot, but never fired it. And so, it was just natural clay shaped into a vessel that had somehow preserved on the surface.

LCBW vessels

Examples of LCBW vessels on display at the Imperial Valley Desert Museum (TOP: red-on-buff globular jar [olla] with chimney neck, medium to large; MIDDLE: flower pot recurved rim jar, medium to large, with stucco application; BOTTOM: globular [water] jar with chimney neck, medium to large).

Credit: Greg Haynes/DRI.

DRI: So, it just kind of baked in the sun naturally?

Haynes: Exactly. Another bag of pottery I was looking at was in the San Diego Museum of Us and it was from a collection obtained from the Cronese Basin, just west of Baker, California. I looked at these potsherds, and they were really grey and crumbly. And they were painted with black designs. I looked at them and thought “This is weird. I don’t know what this is.” So, I put it away. And I came back to it. And it dawned on me that whoever made this piece of pottery in the Cronese Basin was trying to mimic an Anasazi black-on-grey ware. They were trying to mimic a pottery vessel made perhaps hundreds of miles away. It was startling.

That was really one of the highlights of my career here at DRI.

DRI: And how will this report be used by the Bureau of Land Management?

Haynes: It’s been distributed to all the BLM field offices in the CDD and used as a synthetic overview. It also builds consistency for recording these artifacts in the field. When archaeologists go out and conduct inventory for regulatory compliance purposes under the National Historic Preservation Act, it aids them in recommending a ceramic-bearing site eligible or ineligible for the National Register of Historic Places. In addition, it can also be used by investigators to contextualize the ceramics in Southeastern California. And then offers a chapter on new research directions for their analysis.

DRI: Any final thoughts?

Haynes: Well, it was a tough project for two years. But it was incredibly fun to do — one of the highlights of my career.

We’re (the project principals) planning an invited symposium in 2024 in Riverside, California to discuss these plain wares with other archaeologists and other specialists, as well as Native American tribal members.

More Information

The technical report is the property of the BLM-CDD and will become available in the future on their website.

NSF-funded Study Finds Eolian Dust Systems Impact Cardio-Pulmonary Health

NSF-funded Study Finds Eolian Dust Systems Impact Cardio-Pulmonary Health

Baylor University paleoclimatologist analyzed gypsum- and quartz-dominated dune systems for possible fine, breathable dust fluxes detrimental to human health

Above: Mark Sweeney and Eric McDonald set up measurements of PI-SWERL at White Sands National Park. Credit: Baylor University. 

Reportsed from Baylor University:

WACO, Texas – A recent National Science Foundation funded study that included Baylor University paleoclimatologist Steven L. Forman, Ph.D., professor of geosciences, evaluates current and future dust sources in central North America with consideration for climate change. These fine dust fluxes are detrimental to asthmatic and general cardio-pulmonary health for populations downwind, particularly areas of west Texas and New Mexico that have large areas of significant dust sources with dry and drought conditions in the past decade.

The study, published in Geology, seeks to characterize dust emission potential from landforms in two end-member eolian systems, where wind is the primary source of sediment transport: the White Sands dune field in New Mexico and the Monahans dune field in west Texas. The study’s lead author is Mark Sweeney, Ph.D., University of South Dakota. Eric McDonald, Desert Research Institute, joined Sweeney and Forman on the research team.

The White Sands dune field is composed of gypsum and a hot spot for dust emissions because the dunes and adjacent playa yield high dust fluxes. However, the active Monahans dune field is composed of quartz and produce low dust fluxes. Adjacent to Monahans, stabilized sand sheets and dunes that contain silt and clay could produce high dust fluxes if reactivated by climate change or anthropogenic disturbance.

“We chose these sites because the gypsum dunes and playa lake environments should be hot spots for dust emission, and the Monahans composed of mostly pure quartz grains should be a low dust emission system. We were wrong about the Monahans,” Forman said.

Field- and model-based estimates of dust emissions from dune systems are difficult to characterize. By considering whole eolian systems — active and stabilized dunes, interdunes, sand sheets and playas — dust emissions can be more accurately estimated for estimating current and future atmospheric dust loading. Atmospheric dust has impacts on radiative forcing, biogeochemical cycles, extreme climate variability and human health.

The researchers utilized a Portable In Situ Wind Erosion Laboratory (PI-SWERL) to measure the dust emission potential in the field. The PI-SWERL, which was developed by a team from DRI, is a circular wind-erosion device, measures concentrations of inhalant particulate matter at different friction velocities from soil surfaces.

“The PI-SWERL is wind tunnel wrapped into a circle which makes this novel technology portable,” Forman said. “Thus, we can quantify the winds speeds and forces necessary to loft small, breathable particle sizes that at certain elevated concentrations induce an asthmatic response and heightened risk of pulmonary mortality and morbidity.”

The PI-SWERL measurements showed considerable differences in the dust emission potential across both systems. Active dunes, sand sheets and interdunes at White Sands generated similarly high dust fluxes. Comparatively, the playa had the widest range of fluxes with the lowest fluxes on moist or hard surfaces and the highest where loose sand and aggregates were at the surface.

In contrast, the Monahans active quartz dunes generated low dust fluxes. However, dry crusted interdunes with loose sand at the surface had much higher fluxes. Dust emissions increase exponentially with rising wind friction velocities for both systems, often associated with common winds 10 to 15 mph.

The results revealed intra- and extra-landform variability in dust fluxes from eolian systems, mostly due to the degree of surface crusting or soil moisture. More dust occurs on surfaces with loose sand or aggregates where saltation bombardment, when wind lifts particles and causes them to hit along the surface with increased velocity, could erode playas or interdunes and aggregates could break apart to create more dust.

Surprisingly, White Sands showed high magnitudes of dust emission from the abrasion of dune sand and erosion of playa sediments, indicating both landforms are particulate sources during dust storms. The Monahans system produced low dust emissions due to low rates of abrasion in active dunes and vegetative cover, which protects the surface from wind erosion. However, the most common landforms — sand sheets that surround the dune fields for miles — are rich sources for fine breathable particles, at the same magnitude as White Sands.

“The most surprising results was variability in dust emissivity for White Sands landforms and the very high dust flux from the flat sand sheet area that covers most surfaces in west Texas. There is a hidden dust source in these deposits and soils, which were unrecognized,” Forman said.

Dust emission assessments are important to current and future climate modeling. Wind-dominated and drought-sensitive systems could see stabilized dunes and sand sheets become reactivated, or adjacent playas may increase emissions. Potential atmospheric dust loading can occur from diverse landforms in active and presently stabilized eolian systems.

“Atmospheric dust concentrations are important for the global heat-balance and locally can lead to a thermal-blanking effect raising local temperatures. Recent studies associate ozone degradation with elevated dust concentrations high in the atmosphere,” Forman said. “As our planet warms from increasing greenhouse gases many deserts will expand, and grassland areas like on the Southern High Plains will diminish, revealing a limitless supply of dust that will worsen aridity and is detrimental to human health. Understanding the land surface response to climate warming is critical for future sustainability.”


About Baylor University

Baylor University is a private Christian University and a nationally ranked Research 1 institution. The University provides a vibrant campus community for more than 20,000 students by blending interdisciplinary research with an international reputation for educational excellence and a faculty commitment to teaching and scholarship. Chartered in 1845 by the Republic of Texas through the efforts of Baptist pioneers, Baylor is the oldest continually operating University in Texas. Located in Waco, Baylor welcomes students from all 50 states and more than 90 countries to study a broad range of degrees among its 12 nationally recognized academic divisions.

About DRI

The Desert Research Institute (DRI) is a recognized world leader in basic and applied environmental research. Committed to scientific excellence and integrity, DRI faculty, students who work alongside them, and staff have developed scientific knowledge and innovative technologies in research projects around the globe. Since 1959, DRI’s research has advanced scientific knowledge on topics ranging from humans’ impact on the environment to the environment’s impact on humans. DRI’s impactful science and inspiring solutions support Nevada’s diverse economy, provide science-based educational opportunities, and inform policymakers, business leaders, and community members. With campuses in Las Vegas and Reno, DRI serves as the non-profit research arm of the Nevada System of Higher Education. For more information, please visit

Seeking answers from the ashes

Seeking answers from the ashes

Seeking answers from the ashes

January 20, 2022

By Kelsey Fitzgerald

Above: A soil collection field site located within the perimeter of Dixie fire. November 18, 2021.

Credit: Vera Samburova.

DRI scientists study soil dynamics in the wake of Sierra Nevada wildfires

After a wildfire, soils in burned areas become temporarily water-repellent, resulting in increased risk of flooding and erosion in the months that follow. Scientists and land managers have never thoroughly understood why or how this happens – but when last summer’s Dixie, Tamarack, and Caldor fires burned through the Sierra Nevada in close proximity to DRI’s Reno campus, scientists Brad Sion, Ph.D., Vera Samburova, Ph.D., and Markus Berli, Ph.D., jumped into action. 

The team, led by Sion, obtained a Rapid Response Research grant from the National Science Foundation for a new project aimed at exploring the impacts of wildfires on physical and chemical properties of burned soils.

Brad Sion
vera samburova

Above, left: Brad Sion, Ph.D., Assistant Research Professor of Geomorphology, holds a frozen chunk of burned soil at a soil sample collection site  near Kirkwood in the wake of the Tamarack Fire.

Credit: Vera Samburova.

Above, right: Vera Samburova, Ph.D., inspects soils in a burned area near Frenchman Lake that was affected by the Beckwourth Complex Fire.

Credit: Brad Sion.

To collect soil samples before the burned areas were impacted by rain or snowfall, time was of the essence. In October, the team made several trips to nearby fire sites to collect soil samples and to conduct field measurements of soil water repellency.

Then, in late October, a major atmospheric river storm came through. The team’s next visit to the fire sites revealed a changed landscape – a real-world example of how wildfires and water repellent soils can impact ecosystems and infrastructure.

“When we first went out into the field, the sites were very dry and ash-covered,” said Samburova. “When we went back out after the atmospheric river storm, we saw lots of mudslides along the roads, and even dirt on top of the road in some places. The soil was very mushy at the surface, but bone dry within centimeters below. And a lot of water was staying on the surface. It was hard to walk on – very slippery.”

water droplet penetration test results
erosion and mudslides

Above, left: The results of a water droplet penetration test on burned soils at the Dixie fire show a high degree of soil water repellency.

Credit: Vera Samburova.

Above, right: After a late October atmospheric river storm passed through the region, researchers observed erosion and mudslides field sites at the Dixie fire. 

Credit: Vera Samburova.

An interdisciplinary approach

Although previous studies have examined impacts of fire on soils in a controlled laboratory setting, the new DRI study will be one of the first to investigate changes in soil properties and their interrelationships using samples collected directly from freshly burned forests. This work builds upon earlier research by co-investigators Samburova and Berli, which investigated the impacts of fire smoke on water repellency of sand samples.

The team, which includes experts from all three of DRI’s research divisions, is approaching their research questions from several angles. Sion is leading the effort to measure the hydraulic (water-related) and thermal (heat-related) properties of burned soils. Samburova is analyzing organic compounds found in the burned soil samples, and Berli is conducting tests to assess the degree of soil water repellency.

Together, their results will provide new insight into linkages between fire burn severity, changes in soil thermal and hydraulic properties, and more.

“Our goal is to understand from a basic science perspective, what the cause is for these various soil characteristics pre- and post- fire,” said Sion. “If we can look at different fire conditions and the soil conditions that result, then we can say something about how a soil may respond in the future, and eventually that information can be extrapolated to different landscape settings.”

At present, the researchers have completed sample collection and are analyzing samples in their respective laboratories in Reno and Las Vegas. They plan to return to their field sites next fall to see how the soil water repellency changes over time.

As climate warms and western wildfire activity increases, Sion and his colleagues believe that understanding how forest fires impact soil properties will continue to be a topic of growing importance.

“Climate change and wildfires are not problems that are unique to the Sierras,” Sion said. “Whether you’re in the Pacific Northwest, Canada, Alaska, or elsewhere, you’re seeing increases in fire activity. People are thinking about the landscape responses and what they mean.”

Diana Brown

Diana Brown, Staff Research Scientist of Geomorphology, analyzes samples in the Soil Characterization and Quaternary Pedology laboratory in Reno. The soil samples have been saturated with water and contain tensiometers and heat probes to analyze hydraulic and thermal properties of the soil.

Credit: DRI.

Funding for this study is provided by the National Science Foundation (award # 2154013). Additional DRI scientists participating in this project include Hans Moosmüller, Ph.D., Diana Brown, M.S., Chris Baish, M.S., Janelle Bustarde, Palina Bahdanovich, Shelby Inouye, Adam Hackbarth, Zimri Mena and Kendrick Seeber.


About DRI

The Desert Research Institute (DRI) is a recognized world leader in basic and applied environmental research. Committed to scientific excellence and integrity, DRI faculty, students who work alongside them, and staff have developed scientific knowledge and innovative technologies in research projects around the globe. Since 1959, DRI’s research has advanced scientific knowledge on topics ranging from humans’ impact on the environment to the environment’s impact on humans. DRI’s impactful science and inspiring solutions support Nevada’s diverse economy, provide science-based educational opportunities, and inform policymakers, business leaders, and community members. With campuses in Las Vegas and Reno, DRI serves as the non-profit research arm of the Nevada System of Higher Education. For more information, please visit