Wyoming’s 10 year cloud-seeding experiment scrutinized

April 6, 2015
Cloud-seeding graphic via Science Matters

Cloud-seeding graphic via Science Matters

From the East Oregonian (Allen Best):

Wyoming just spent $14 million and the better part of 10 years on a rigorous scientific experiment to evaluate whether it’s possible to get extra snow from winter storm clouds through cloud seeding. The conclusion? The final results were thin: There was a 3 percent increase in precipitation, but a 28 percent probability that the cloud seeding had nothing to do with it.

Given the results of this and other winter weather-modification studies, the Bureau of Reclamation remains unimpressed. “As such,” said the agency in a draft analysis released in February, “the ‘proof’ the scientific community has been seeking for many decades is still not in hand.”

Proof in science requires a 95 percent probability of causality. But this standard is extremely difficult to achieve in complex atmospheric processes. Climate scientists, for example, mostly resort to asterisk-laden words such as “likely” to indicate lower levels of probability…

From the start, Wyoming’s cloud-seeding experiment was designed to ensure scientific rigor. Parallel mountain ranges southwest of Laramie, just north of the Colorado border, constituted the Wyoming laboratory. Propane was burned to loft silver iodide from ground-based generators into the clouds passing over the Sierra Nevada and Medicine Bow ranges. In the experiment, 154 storms during six winters had the temperatures needed for effective seeding, but only 118 developed adequate moisture content. And of those, 18 were tossed out because of contamination problems.

Dan Breed, project scientist with the National Center for Atmospheric Research, which designed and oversaw the Wyoming experiment, said that failing to achieve a 95 percent confidence level in results is not unusual in cloud seeding studies. The fundamental problem, he says, involves the difficulty of measuring atmospheric processes.

The challenge inherent in the complexity of the data has prevented most climate scientists from directly linking specific weather events, such as the September 2013 floods in Colorado, to rising global temperatures, or even to the 3 to 5 percent observed moisture in the global atmosphere.

“When it comes to the atmosphere, there are just too many variables, and that variability just keeps rearing its ugly head when it comes to cloud seeding,” says Breed. “Even in this case, where we tried to make things as homogeneous as possible to reduce that variability, variability still kind of hurt us.”

Breed thinks research might better be invested in understanding the interaction in the atmosphere of wind, temperature and precipitation. For example, how likely is it that silver iodide or other seeding agents released from the ground will get into the clouds? True understanding of atmospheric processes, says Breed, has mostly come from observations instead of experiments — because of that same variability.

This lack of certainty does not necessarily kill the prospects of cloud seeding, as is demonstrated by the continued interest of Wyoming legislators in funding projects. In the Colorado River Basin, cities and water districts seized upon the modeled projections of 5 to 15 percent snowpack augmentation as justification for continued or even expanded operations. Already, metropolitan Los Angeles, the Central Arizona Project and the Southern Nevada Water Authority, among others, pay for seeding clouds in Colorado, the source of half the water in the Colorado River, and last year they also paid to seed clouds in Wyoming, in the Green River drainage.

More cloud seeding coverage here.


Wyoming reconsiders cloud seeding and potential benefits for ag

February 17, 2015

More cloud seeding coverage here.


Cloud seeding study boosts hopes in parched West — WyoFile

December 30, 2014
Cloud-seeding graphic via Science Matters

Cloud-seeding graphic via Science Matters

From Environment & Energy Daily (Annie Snider) via WyoFile:

As a painful reckoning sets in throughout the West, where the Colorado River Basin is in its 15th straight year of drought, desperate water managers are welcoming a new cloud-seeding study as rare good news.

The concept of cloud seeding — using aircraft or ground-based generators to inject microscopic particles of silver iodide into clouds around which ice crystals can form and fall as snow — dates back to the 1940s.

Today, ski resorts, water districts and farmers across the West swear by the practice to produce both snow and water, spending millions of dollars a year on machines and flights.

But proving that money is well-spent has been tricky. Because, while it might snow or rain after a cloud’s been seeded, it’s hard to know whether the seeding actually caused the precipitation…

Wyoming’s Legislature took the challenge and, buoyed by coffers filled from oil and gas severance taxes, poured $14 million into a major study over the past 10 years that employs the latest scientific techniques recommended by the NRC panel, as well as an independent evaluation team.

The topline findings, recently unveiled to the Legislature: Seeding the right storms the right way can produce 5 to 15 percent more precipitation. That could increase streamflows by as much as 3.7 percent, the researchers’ initial findings indicate.

The study also found seeding to have next to no downwind impact, suggesting seeding storms to get precipitation in one place is not decreasing precipitation elsewhere.

“We know that silver iodide produces ice crystals, so really it ends up being an engineering problem: Can the ice crystals get into the right cloud at the right place and can we do all this?” said Roy Rasmussen, a senior scientist with the National Center for Atmospheric Research who led the study’s outside evaluation team.

“That’s what the Wyoming program demonstrated: That, yes, they can do it,” he said. “With modern technologies — through satellite-controlled silver iodide generators, and with good forecasting, with good real-time modeling — we can figure out when the storms are right for seeding and apply the seeding, and there is a measurable effect.”

More cloud seeding coverage here.


Water Lines: Cloud seeding can work, but it won’t fill Lake Powell — Grand Junction Free Press

December 22, 2014
Cloud-seeding graphic via Science Matters

Cloud-seeding graphic via Science Matters

From the Grand Junction Free Press (Hannah Holm):

In the arid West, the perpetual search for new water supplies, like the mythical search for the Holy Grail, has given rise to numerous fantastical adventures and grand schemes. Some of these have resulted in the impressive feats of engineering that have re-plumbed much of the Colorado River Basin, and some have remained fantasies, like towing ice bergs from the Arctic and building pipelines from the Great Lakes.

“Cloud seeding” to wring more moisture from the sky has long been hard to classify in those terms. Water agencies and ski resorts have been doing it for decades, mostly by sending plumes of silver iodide from ground-based burners into likely-looking clouds. Cloud seeding has been done in Colorado since the 1950s and ramped up significantly after the 2002 drought. Still, until recently, no one could say with any certainty if cloud seeding really worked, or if so how well.

Draft conclusions from a much-anticipated, very rigorous nine-year study conducted in Wyoming indicate that cloud seeding can, in fact, increase the water yield from some storms, but the ultimate effect on the water supply is quite modest. The draft executive summary of the Wyoming Weather Modification Pilot Program study, conducted by numerous collaborators, was presented to the Wyoming Water Development Commission on Dec. 10; it is due to be finalized in March of 2015.

The study combined physical, modeling and statistical studies of the effects of cloud seeding in Wyoming’s Medicine Bow, Sierra Madre and Wind River Ranges and concluded that seeding could increase snow accumulations from some storms by 5-15 percent. This does not, however, translate to a 5-15 percent increase in the seasonal snowpack because not all storms are “seedable,” and those that are cover only a limited area.

In order for the inserted silver iodide to stimulate significant additional snowfall, atmospheric temperatures must be below 17 degrees Fahrenheit, with sufficient moisture in the air and favorable winds. These conditions were met less than one-third of the time during the winter in the study area. Using modeling, the study concluded that increased precipitation from seeded storms of 5-15 percent affecting 30-80 percent of the cloud-seeding impact area could increase streamflow in Wyoming’s portion of the North Platte River Basin between 0.4 to 3.7 percent.

Depending on numerous factors related to the operations of the cloud seeding program, the cost-per-acre-foot of water produced through cloud seeding ranges from $27-$427 per acre-foot. This compares favorably with other options for producing “new water.” In a 2013 article in the Mountain Town News, Allen Best reports that the Bureau of Reclamation has estimated that desalting brackish groundwater in Arizona would cost $650 per acre-foot, and desalting ocean water near Los Angeles would cost $2,100 per acre-foot. Cost estimates for building new storage reservoirs run from a few hundred dollars per acre-foot to over $1,000 per acre-foot.

In addition to assessing the potential impact of cloud seeding as a feasible strategy for impacting Wyoming water supplies, the study also assessed the environmental impacts of seeding and impacts on precipitation outside the seeded area (i.e. does it steal water from downwinders?).

The environmental analysis found that concentrations of silver iodide in the affected snowpack was in the parts per trillion range, while concentrations already in the soil were much higher, in the parts per billion range, indicating a very minimal impact from cloud seeding. Modeling of impacts on precipitation outside the seeded area indicated effects of less than 0.5 percent, which is consistent with previous studies and undermines claims that cloud seeding injures those downwind of seeded areas.

This study indicates that cloud seeding likely deserves its relatively newfound respectability as a water supply strategy, but also that its impacts are far too small for it to be a panacea for the West’s water woes.

To read the draft executive summary for yourself, go to the Wyoming Water Development Commission’s website at http://wwdc.state.wy.us.

More cloud seeding coverage here.


Report: Wyoming cloud seeding program said to increase snowpack

December 13, 2014

wyomingweathermodificationpilotprogramexecsummaryfinaldraft12102014

Click here to read the draft executive summary. Here’s an excerpt:

The Wyoming Weather Modification Pilot Program (WWMPP) was conducted to assess the feasibility of increasing Wyoming water supplies through winter orographic cloud seeding. Following a Level II feasibility study that found considerable potential for cloud seeding in the state (WMI 2005), the Wyoming Water Development Commission (WWDC) funded the WWMPP (2005-2014) as a research project to determine whether seeding in Wyoming is a viable technology to augment existing water supplies, and if so, by how much, and at what cost. The WWMPP then established orographic cloud- seeding research programs in three Wyoming mountain ranges considered to have significant potential: the Medicine Bow, Sierra Madre, and Wind River Ranges…

Orographic cloud seeding is a technology designed to enhance precipitation in winter storms with an inefficient precipitation process due to a lack of natural ice nuclei. This inefficiency allows supercooled water to persist for long periods instead of being depleted by ice crystals, which grow and fall as snow. This fact is well documented by the measurement of sustained supercooled liquid water in orographic clouds taken by aircraft and ground-based instruments, such as radiometers. In contrast to natural ice nuclei, artificial ice nuclei, such as silver iodide, will nucleate substantial numbers of ice crystals at subfreezing temperatures of −8 °C (+17 °F) and cooler, creating ice crystals in clouds that are typically too warm for natural ice formation. In the presence of supercooled water droplets, these ice crystals rapidly grow into larger particles that fall to the ground as snow. The technology of orographic cloud seeding uses ground-based generators to produce a silver iodide plume, which is then transported by the ambient wind into orographic clouds to increase precipitation. This process of seeding clouds to create additional snow is complex and to date has not been scientifically verified in well-designed statistical tests.

More cloud seeding coverage here.


Results from Wyoming’s cloud-seeding efforts expected next month #ColoradoRiver

November 12, 2014
Cloud-seeding graphic via Science Matters

Cloud-seeding graphic via Science Matters

From the Casper Journal (Greg Fladager):

Wyoming’s $13 million cloud seeding experiment may be about to pay off, or at least further knowledge in the science of rainmaking.

In a talk to the Wyoming Water Association last month, Wyoming Water Development Commission Director Harry LaBonde, Jr., said the results of over eight years of study would finally be released this December.

“All I will tell you about the results is that it appears that it is positive,” LaBonde told the group in Casper. “Of course what we want to know is, what can you anticipate with winter orographic seeding? Is that a 2 percent increase in precipitation? Is that a 10 percent increase in precipitation, or what can you expect?”

Broad interest

LaBonde said Wyoming’s experiment has drawn regional as well as international attention.

“Everybody wants an answer to the question that we have been asking, and so you are going to see a lot of interest. It will then hopefully be considered and utilized in other states across the West, as well as other operations across the world,” LaBonde said.

The cloud seeding program was conducted in the Medicine Bow/Sierra Madre Mountain Range in southern Wyoming. The study was based on eight snow generators placed in two closely related areas, and in double blind experiments data gatherers were not told which valley had been seeded for a given seeding event.

“The last data collection was last spring. It ended in April, representing about eight years of data collection,” LaBonde said. “We went through some drought years which limited seed-able events. But last year was a very good year. We had about 30 seeding events last year. We ended up with a total of about 160 events over the period of time. That was determined to be a suitable amount of events that … we can make a good scientific conclusion of does weather modification work? Is there an increase in precipitation when you are seeding these mountains with silver iodide, which is the product that we have been using.”

“So, with that data complete, the scientists have been poring over that — we certainly have issues with data quality and some of that, they’ve been looking at all of those issues — but what we hope to have, and what is on the schedule now, is their final report by December of this year,” LaBonde added. “It is our hope that in fact that schedule will be kept, and that document will become public information.”

Wyoming Range and Wind River seeding projects

In the meantime, Wyoming has two other cloud seeding experiments and operations.

“Another weather mod item in Wyoming is that we funded, last year, a Level II weather modification study in the Wyoming Range,” LaBonde said. “I think a lot of you know that Idaho Power runs a very active weather modification (program) out of the Star Valley, and some (of those) seeding effects do roll over into the Wyoming Range. But we wanted to take a more thorough look at what we might be able to do if we are going to set up an operational program in the Wyoming Range. Where might you site those generators? What kind of benefits would accrue to the Colorado River drainage on the East slope of those mountains, as well as the Snake River on the backside (and) the West side of those mountain ranges? So that study is underway. We expect to have the results of that next summer. That was the continuation of what was in essence a Level I study that was started in 2008, completed and then put on the shelf pending the outcome of our scientific programs.”

Moving from study to operations

LaBonde also announced that the WWDC was successful in its effort to get funding to continue cloud seeding in the Wind River Range, and changing (operations) from a scientific study to an operational program.

“The proposal that Water Development put forth to the legislature last year was that we wanted to keep those 10 generators in operation. We wanted to shift from scientific to an operational mode,” LaBonde explained. “However, we did not feel that all of the costs should be borne by the state of Wyoming. The Green River has not appropriated water. Those waters flow out-of-state, and ultimately benefit the lower basin states. So the proposal that was put forth is that Wyoming would pay for 25 percent of the cost of the operation of those generators, but we were required to go forward and seek funding partners from other states to pay for 75 percent of the program.”

Funding buckets

“I’m happy to report today that, in fact, we have achieved the outside funding sources that were required as part of that bill, as a result we will have an operational seeding program run in the Wind Rivers this year,” LaBonde said.

“The funding partners that we’ve put together are: the Arizona Department of Water Resources; Central Arizona Water Conservation District: the Six Agency Committee, which is a group of agencies in California; Southern Nevada Water Authority; Utah Division of Water Resources — of course the Green River flows into Utah, and I think that was a little bit of a surprise that they came forward and wanted to help with the funding; the Bureau of Reclamation has stepped up and it is funding, in essence, the forecasting part of our programs. They’ve got a direct contract with NCAR (National Center for Atmospheric Research), and that outside funding source is $684,000. The respective Wyoming share is $28,000. There will be seeding in the Wind Rivers again, subject to appropriate storms coming across. We’ll start in November, and run into the April season, LaBonde said.”

Augmenting water

LaBonde further noted that he viewed the Wind River Range project as a first step in ‘water augmentation’ in the Colorado River Basin.

“With the ongoing drought in the Colorado River Basin — we have dropping lake levels in Powell and Mead — we thought that maybe, even though we did not have the results of the scientific study, it was appropriate to look at continuing those generators, but moving from a scientific to an operational program.”

“Colorado has a weather modification program. So does Utah. But how do we bring the lower basin states into that program?” LaBonde continued. “I know there are some committees that have been formed, they are talking about that. But with 10 generators in place last year, it was too good an opportunity to go forward — at least for a one-year program — and we, again my hope is, it is going to morph into a more basin wide program.”

LaBonde concluded he was optimistic about cloud seeding expanding to other mountain ranges in the state.

“All in all, I think it’s good news,” LaBonde said. “Finally, there’s some pieces that are going to fall into place with our scientific study coming out. Then hopefully we will see some more operational programs going forward in the future.”

More cloud-seeding coverage here and here.


Radiometer near Mancos used to forecast cloud-seeding potential

April 5, 2014
Calibrating the radiometer via The Durango Herald

Calibrating the radiometer via The Durango Herald

From The Durango Herald (Mary Shinn):

On Monday meteorologist, Marta Nelson, installed a temporary radiometer at Jackson Lake near the Mancos Water Conservancy District. The instrument is able to determine the best combination of water content in clouds and temperature to use a cloud-seeding generator.

Cloud-seeding generators throw up silver iodide into the atmosphere to harvest the extra water because snow will form around it.

“We can see relative humidity and vapor and the potential for a cloud to form. We can also see inside a cloud that’s already formed, so if we’re looking for liquid water versus ice that is frozen in the cloud the radiometer can tell the difference and help tell the cloud-seeding people when to run the generators or when it’s not going to do any good,” she said. Nelson works for Radiometrics Corp., based in Boulder, which installs similar machines all over the world.

The new data also will help scientists decide if the local cloud-seeding generator at Spring Creek should be run later into the winter season, said Jeff Tilley, director of weather modification at the Desert Research Institute in Reno. The institute operates the local cloud-seeding generator remotely. The data collected over the next month will be applied to operations next winter because the Spring Creek generator is almost out of cloud-seeding solution, he said.

The institute is collaborating with the Colorado Water Conservation Board on the project, and the board is paying the $8,500 to lease the radiometer for a month.

Across the state, about $1 million is spent on cloud seeding, and about 65 percent of the funds are provided by local entities such as ski areas, water districts and towns. The other 35 percent of the funds are provided by state and other funding.

The generator near Mancos has been in place for about five years, and in that time, there has been some benefit in the area, Tilley said.

“The impression we have is that we have seen some difference,” he said.

Cloud seeding is safe because silver iodide won’t break down in any way that’s harmful, Nelson said.

More cloud-seeding coverage here. More San Juan River Basin coverage here.


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