by Trish Zornio, Colorado Newsline
August 4, 2021

Without a doubt, one of the largest threats to American infrastructure is climate change.

This was illustrated yet again as upwards of 10 landslides ravaged sections of Colorado’s Interstate 70 corridor, closing the Glenwood Canyon portion of the highway indefinitely. This came after weeks of intermittent slides that have exhausted personnel and had a chilling effect on local economies.

Yet despite the impacts, few have sought to elaborate on the relationship between extreme debris flows and the burning of fossil fuels.

This is a grave oversight.

Dismissing the role of climate change in infrastructure resiliency fails to appreciate the inherent relationship between infrastructure and environment. As global temperatures rise, so, too, will the number of extreme events. This places existing structures and byways in new dangers, ranging from some damage to full destruction.

In the case of mudslides, as wildfires burn bigger and hotter due to rising temperatures and severe drought, ground vegetation of the forest floor is burned off at alarming rates. This creates a layer of dusty ash over bare, scorched soil, resulting in a decreased ability of the soil to absorb water.

While healthy forest floors can hold several inches of water per hour, high or moderately burned areas might only hold one-third of an inch. This results in top layers that can be easily washed away, at least until enough ground vegetation is reestablished — roughly the first year or two post-burn. Meanwhile, even small amounts of rainfall can result in dangerous runoffs, posing great risks to structures and byways located in slide paths. Combined with more intense rainfall — also due to climate change — landslides may occur more frequently and over larger areas with greater force and debris.

This dynamic is consistent with recent events on I-70. Based on post-fire assessments conducted by the Burned Area Emergency Response team, the Grizzly Creek Fire — which was fueled by especially hot and dry conditions last year — burned areas surrounding the canyon. Soil testing revealed that 55% of this area had incurred moderate to high soil burns, leaving the region with unusually high risks of extreme runoffs. Only 12% of the 32,370 acres were estimated to be unburned.

Certainly, mudslides are possible in any canyon so steep — and it’s happened before. However, the size and severity of this particular burn created enhanced risks for severe infrastructure damage. Accordingly, at the recommendation of BAER, mitigation efforts were made.

Shortly after the fire, one large, natural berm was created to protect the most critical infrastructure in the canyon — a mostly hidden command center in the heart of Glenwood Canyon that serves to monitor the interstate. As predicted, less than a year later, some 100,000 cubic yards of debris was diverted with that very berm. John Lorme, the Colorado Department of Transportation director of maintenance and operations, hailed the effort as saving the state millions of dollars and extensive closed highway time — a testament to the role of climate research in protecting infrastructure.

There are, however, limits to our current preventative measures — as evidenced by the current debris damage. During a 47-minute press conference with CDOT, Region 3 director Mike Goolsby acknowledged the lack of radar technology and understanding in predicting slides with enough time to close or protect the highway.

According to the U.S. Geological Survey — the only science agency to exist within the U.S. Department of Interior — much additional research funding and efforts regarding landslides are needed as climate change intensifies. Especially relevant are the needs to better understand debris flow mechanisms, forecasting and mitigation strategies, all efforts that would help safeguard core infrastructure.

One Colorado-based hydrologic engineer, Kelsey McDonough, agrees, adding that some in the private sector may also have access to better, more localized technology. “This could be really useful in a state like Colorado where local knowledge can be utilized to build better regional monitoring and modeling systems than are currently available at the national scale,” she says.

Certainly, Colorado has a number of cutting-edge national laboratories and private companies that may be inclined to help find solutions with the right incentives. Securing these funds is just one of many roles local representatives can play in helping the state navigate the new challenges.

Still, perhaps the most important thing we must do is disentangle the notion that discussions of human-driven climate change during extreme events are signals of political interference. They are not. Climate change is well established in scientific literature, as is its impact to structural integrity. Addressing the role of reducing fossil fuels in related press conferences and articles is therefore necessary to serve the long-term goal of infrastructure stability.

Colorado Newsline is part of States Newsroom, a network of news bureaus supported by grants and a coalition of donors as a 501c(3) public charity. Colorado Newsline maintains editorial independence. Contact Editor Quentin Young for questions: info@coloradonewsline.com. Follow Colorado Newsline on Facebook and Twitter.

Here’s a short video (~4 minutes) from CDOT to give you an overview of the slide area.

From The Fort Collins Coloradoan (Miles Blumhardt):

For the past month, Coloradans have been inundated with flash flood watches and warnings and a weather event — called a monsoon…

Neither flash floods nor the annual monsoon season have grabbed Colorado headlines the past several years because neither had much impact on the state.

That changed this year.

“This year is more normal of what we would expect from monsoon season compared to the past couple of years,” said Jennifer Stark, a meteorologist who manages the National Weather Service office in Boulder. “We are seeing bigger impacts, and people are really beginning to take notice because it is impacting their ability to recreate and move across the state and affecting homes.”

A series of events that has led to devastation started last year when the state experienced its worst wildfire season in its recorded 145-year history…

This summer, those burn scars, largely left denuded, have been continually saturated with abundant monsoonal moisture, resulting in large debris slides.

Those slides have continually closed Interstate 70 in Glenwood Canyon, which remains closed Monday due to what the Colorado Department of Transportation has called “extreme damage” to the major transportation corridor. It also resulted in the deaths of three people with a fourth still missing and six residences destroyed in the Poudre Canyon…

The Colorado Climate Center said the monsoon pattern is created by abundant moisture that builds in the atmosphere from the Gulf of Mexico and Pacific Ocean.

A shift in wind pattern results from a high pressure system with clockwise flow over the Rocky Mountains and low pressure near the Gulf of Mexico with a counterclockwise flow that settles over the region and squeezes moisture northward into the atmosphere.

In Colorado, the moisture is more prevalent on the Western Slope but can spill over the Continental Divide, which is happening this year.

This creates persistent afternoon thunderstorms that park over areas that can produce large amounts of rain, sometimes in a short period of time…

When that happens on burn scars, soil that repels water is washed down canyons, gullies and ravines that act as funnels of accumulating water. As it gains momentum, the slide brings with it large boulders and burned trees.

Stark said many of the state’s most devastating floods have taken place during the monsoon season, including the 1976 Big Thompson flood and 1997 Spring Creek flood in Fort Collins, both of which occurred in late July.

Susan J. Prichard, University of Washington; Keala Hagmann, University of Washington, and Paul Hessburg, United States Forest Service

After so many smoke-filled summers and record-setting burns, residents of Western North America are no strangers to wildfires. Still, many questions are circulating about why forest fires are becoming larger and more severe – and what can be done about it.

Is climate change fueling these fires? Does the long history of fighting every fire play a role? Should we leave more fires to burn? What can be done about Western forests’ vulnerability to wildfires and climate change?

We invited 40 fire and forest ecologists living across the Western U.S. and Canada to examine the latest research and answer these questions in a set of studies published Aug. 2, 2021. Collectively, we are deeply concerned about the future of Western forests and communities under climate change.

So, why are wildfires getting worse?

Climate change is a big part of it. Summer wildfire seasons are already 40 to 80 days longer on average than they were 30 years ago. Annual droughts are more pronounced, making it easier for fuels to dry out and fires to ignite and spread. Extreme weather events, marked by dry fuels, lightning storms and strong winds, are also increasingly common and provide essential ingredients for rapid fire growth, as witnessed by the Bootleg Fire burning in Oregon and record-setting fires in California and Colorado in 2020.

Ironically, a chronic lack of fire in Western landscapes also contributes to increased fire severity and vulnerability to wildfires. It allows dry brush and live and dead trees to build up, and with more people living in wildland areas to spark blazes, pressure to fight every forest fire has increased the risk of extreme fire.

The problem with fighting every wildfire

Historically, fire was a regular visitor to most Western forests, except moist locations like those along the Pacific Northwest coast and in British Columbia. Frequent or periodic fires from Indigenous burning and lightning strikes created patchworks of grasslands, shrublands and regenerating forests of all ages.

Past fires influence the way subsequent fires burn and what they leave behind. For example, Indigenous burning practices not only enhance cultural resources and wildlife habitat but also reduce the amount and connectedness of fuels that drive large, severe wildfires. Similarly, patchy burns from lightning ignitions create forest landscapes that are less likely to burn all at once.

The U.S. and Canada effectively suppress all but 2%-3% of wildfire starts. However, this small percentage of fires burn at the height of each fire season, when dry conditions and extreme fire weather thwart even the most aggressive attempts to suppress them.

Unintentionally, by focusing on short-term risks of wildfires, the U.S. is predisposing forests to burn under the very worst conditions. Active fire suppression contributes to what is often referred to as the wildland fire paradox – the more we prevent fires in the short term, the worse wildfires become when they return.

In one of the new studies, Paul Hessburg and co-authors explain how fire managers can mitigate the severity of future fires by managing fire-excluded forests to foster resilience to wildfires and drought. Management approaches include thinning dense forests, reducing fuels through prescribed burning and managing wildfires to restore more typical patterns of forests, meadows, shrublands and woodlands.

In a second paper, Keala Hagmann and her co-authors describe how more than a century of fire exclusion and past forest management practices have jeopardized forest biodiversity and social and ecological values, including culturally important resources, the quantity and quality of water, stability of carbon stores, recreation and air quality.

For example, fire exclusion has compromised aspen stands – biodiversity hot spots for everything from bears to butterflies. Increased forest cover diverts water from downslope meadows, allowing conifer forests to further encroach on aspen habitat.

A path forward

Amid the daunting reality of climate change and severe wildfires, there is a path forward for Western forests.

In a third article, Susan Prichard and her co-authors examine which adaptive forest management approaches have worked to increase resilience to wildfires and climate change. There is strong scientific evidence that fuel reduction treatments – including forest thinning, prescribed burning, Indigenous cultural burning and managed wildfires – are effective approaches for mitigating future fire impacts to Western forests. However, land managers can’t expect these treatments to work if they are applied to only a small fraction of Western forest landscapes.

When combined, forest thinning and prescribed burning in dry ponderosa pine and in dry and moist mixed-conifer forests have been shown to be highly effective at reducing the fire damage to forests. However, this type of treatment is not appropriate for all forest types. Fire managers in some wilderness areas and national parks have allowed fires started by lightning to burn in some wind and weather conditions. Over the past 40-plus years, these wildfires have been allowed to burn and reburn landscapes, generally limiting the size and severity of subsequent wildfires.

Given the immense diversity of Western forests, there is no one-size-fits-all solution. However, in forests that historically supported more frequent fire, revitalizing and continuing cultural burning practices, prescribed burning, and forest thinning combined with prescribed burning can reduce overcrowding and the potential for severe fires. Thinning and prescribed burning aren’t appropriate or feasible everywhere. In reality, only a portion of landscapes can be treated this way. Allowing wildfires to burn in more areas under moderate weather conditions is also part of the solution.

Promoting resilient Western forests will require that our society builds a new relationship with fire by creating fire-adapted communities and looking for opportunities to restore fire to Western forest landscapes.

In this era of warmer, drier summers and longer fire seasons, there are no fire- or smoke-free solutions. The current approach to fire management poses unnecessarily high stakes for Western forests. There is no doubt that the future of Western forests is a fiery one. How we choose to live with fire is still up to us.

[Over 100,000 readers rely on The Conversation’s newsletter to understand the world. Sign up today.]

Susan J. Prichard, Research Scientist of Forest Ecology, University of Washington; Keala Hagmann, Affiliate Assistant Professor, University of Washington, and Paul Hessburg, Research Ecologist, United States Forest Service

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The situation in the Northwest across to the Northern Plains is frankly, bleak. 100% in WA, 98% in MT, 91% in ND, 90% in OR. The surrounding states aren’t much better.

From The Summit Daily (Taylor Sienkiewicz):

Drought conditions improve across the state but not erased west of the Continental Divide

Summit County is experiencing both a monsoon and a lingering drought.

How does that work? To put it simply, a drought takes a long time to release its grip. Whether the downpours will lift the area out of drought conditions or not, the precipitation is welcome relief, according to National Weather Service meteorologist Greg Hanson.

“We are in a monsoon pattern right now, and so that means we’re getting … a plume of moisture that comes up from the tropics, from the Gulf of Mexico and the Gulf of California,” Hanson said. “It’s not the individual storms; it’s the weather pattern that brings the storms to the area.”

The Dillon weather station recorded 3.76 inches of rain in July, which is more than double the month’s 1.87-inch average. On Saturday morning, July 31, the weather station recorded 1.13 inches of rain for the previous 24 hours, which is the most in a single 24-hour period so far this summer. According to National Weather Service records, it has been the rainiest July since 2011.

While an extra inch or two might not sound like much, Hanson said it makes a difference in the High Country…

Hanson said there have been some drought improvements in western Colorado, and areas east of the Continental Divide are in “great shape.” He said the wet spring and snowy March erased the drought in the east. In western Colorado, where conditions have been more severe, the precipitation has helped but has not gotten rid of the drought.

Summit County’s drought conditions have not changed since the beginning of June, according to weekly updates from the U.S. Drought Monitor. The county currently ranges from no drought in the east to severe-to-extreme drought in the northwest.

From The Pueblo Chieftain (Heather Willard):

Pueblo has received enough rain since January that records will still show Pueblo as receiving above-average rainfall for the year — even if not another drop of rain falls until December…

According to the National Weather Service’s data, Pueblo has received 12.91 inches of rain since Jan. 2021, which is 0.89 inches more than the annual average. This is a marked difference from 2020, when the area only received 5.33 inches during the whole year.

From The Guardian (Chris McGreal):

Gold Hill has received a state grant to thin out the forest around the town in the hope of slowing if not stopping future fires. But that is a fraction of the cost that the surrounding county says it will take to deal with the impact of global heating.

Boulder county estimates it will cost taxpayers $100m over the next three decades just to adapt transport and drainage systems to the climate crisis, and reduce the risk from wildfires.

The county government says the bill should be paid by those who drove the crisis – the oil companies that spent decades covering up and misrepresenting the warnings from climate scientists. It is suing the US’s largest oil firm, ExxonMobil, and Suncor, a Canadian company with its US headquarters in Colorado, to require that they “use their vast profits to pay their fair share of what it will cost a community to deal with the problem the companies created”.

Boulder county, alongside similar lawsuits by the city of Boulder and San Miguel county in the south-west of the state, accuse the companies of deceptive trade practices and consumer fraud because their own scientists warned them of the dangers of burning of fossil fuels but the firms suppressed evidence of a growing climate crisis. The lawsuits also claim that as the climate emergency escalated, companies funded front groups to question the science in order to keep selling oil.

“It is far more difficult to change it now than it would have been if the companies had been honest about what they knew 30 or 50 years ago,” said Marco Simons, general counsel for Earth Rights International, which is handling the lawsuit for the county. “That is probably the biggest tragedy here. Communities in this country and around the world were essentially robbed of their options.”

Boulder county’s lawsuit contends that annual temperatures in Colorado will rise between 3.5F and 6.5F by 2050 and imperil the state’s economy, including farming and the ski industry.

Extremes of weather are already melting the mountain snowpack, causing increased evaporation and a shortfall in the amount of water flowing down the region’s most important river, the Colorado, which supplies drinking water to the state’s largest cities and irrigation all the way to California and Arizona…

Exxon and Suncor are alarmed at the prospect of the cases being heard by local jurors with first-hand experience of the impact of global heating in Boulder. The companies are pressing to move the trials out of state courts and into a federal system where laws on deceptive marketing and consumer fraud do not apply.

“Their strategy is to say that these cases need to be in federal court because federal jurisdiction applies. Then they will turn around and argue that federal law provides no remedy,” said Simons. “It is all about a route to dismissing these cases.”

The outlines of the oil industry’s defence have emerged in newspaper columns pushing back against any parallels with big tobacco and claiming it is the end user, ordinary Americans, that causes pollution…

Max Boykoff, a professor in the environmental studies department at the University of Colorado Boulder, acknowledged the problem, alongside the popularity of high fuel consumption vehicles. But he said that should not be used by the oil companies to absolve themselves of responsibility for a crisis they have played a leading part in creating.

“These lawsuits are one of the tools to hold both these companies accountable,” he said.

Here’s the release from the Colorado Department of Natural Resources (Chris Arend):

The Colorado Department of Natural Resources is seeking applicants to serve on the Colorado Forest Health Council (Council), a volunteer stakeholder body whose role is to provide a collaborative forum to advise the Governor, through the Executive Director of the Department of Natural Resources, and the Colorado General Assembly, on issues, opportunities, and threats to Colorado’s forests.

“Colorado’s forests face unique challenges including climate change, year-round wildfire risk, and population growth. The reconstituted Council, now at the Department of Natural Resources and with increased diverse membership, will have the opportunity to help shape our State’s forest management and wildfire risk management policies and priorities for the future. I encourage interested Coloradans to apply,” said Dan Gibbs, Executive Director, Colorado Department of Natural Resources.

The Council was reconstituted during the Colorado 2021 Legislative Session through SB21-237, and will consist of 26 members, including two state legislators, 18 seats from all corners of Colorado appointed by Governor Polis, along with other agency representatives.

Applications are due August 16, with the Governor’s seat selections due September 2. The Council will meet multiple times per year for half- or full-day meetings with virtual attendance options, with meeting frequency and schedule confirmed by the new council. Applicants should anticipate at least 5 hours of Council-related business per month.

Please note that the council may still be listed under its old name, the “Forest Health Advisory Council,” but will be updated shortly to its new name, the “Colorado Forest Health Council”. Applications submitted under the council’s old name will still be fully considered.

From Colorado Public Radio (Michael Elizabeth Sakas):

The North American monsoon has returned to Colorado, and the rain has brought some much-needed relief to some of the driest parts of the state — after multiple back-to-back years of almost no summer rain…

The seasonal moisture from the tropics creates afternoon cloud cover that protects his drought-stricken creeks from baking in the sun. The rain helps lower the risk for wildfires.

The timing of the monsoon is vital to Colorado’s ecosystem, which evolved on its schedule. Science suggests that climate change is making these rains less helpful.

Colorado’s Western Slope has been labeled a climate hot spot, where average temperatures are increasing faster than the global average. A climate change-fueled megadrought has plagued the state and parts of the West for 20 years…

[Bill] Trampe said hotter days and four years of almost no monsoon rain turned into “horribly dry” conditions during the summer of 2020. Many ranchers in Gunnison couldn’t grow enough hay to feed their cattle, which meant they had to buy it — a pricey added expense, he said.

Trampe was worried the land was too dry to feed the number of cattle in his herd, so he was forced to slaughter more animals in the fall than he planned. He also sold cattle over the winter, something he doesn’t usually do. Trampe said he was fearful 2021 would be another dry year…

While Trampe can grow hay on his private land using irrigated water from the Gunnison River, his cattle graze on federal land. Trampe said the federal rangeland is running out of water. “These rains are super important,” he said.

Monsoon rains are getting less reliable and less effective. Recent research from the Desert Research Institute in Nevada has found that less rain is making it into rivers as the climate warms.

This deficiency starts with snowpack, which collects in the mountains during the winter, said Rosemary Carroll, an associate professor of hydrology and the lead author of the study. If a big snowpack lasts into the summer, the soil can stay moist if temperatures are cooler.

Those conditions would mean rainfall would more likely reach a stream. If the snowpack is low, temperatures are higher and the soil is dry, less monsoon rain makes it into the stream, Carroll said. With climate change, an average water year can look more like a moderate drought.

Carroll stood on the edge of a high dirt road in Gothic, Colo., overlooking a winding tributary that eventually feeds water to the Colorado River, which supplies 40 million people in the Southwest. The nation’s two largest reservoirs are on this river — Powell and Mead. Those levels are dwindling to record lows, and climate change means less water is making it into the system.

Carroll is worried about where things are headed.

“It would be hard not to be,” she said. “With decreasing snowpack, warmer temperatures and now the volatility of the monsoon itself, this is just not great news for everybody.”

Next, the team explored the ability of these summer rains to produce streamflow during cool years with high snow accumulation, and during warm years with less snow accumulation. During cool years with more snow, soil moisture levels were higher going into summer, and greater streamflow was generated by the monsoon rains. During warmer years with low snowpack, dry soils absorbed much of the monsoonal rains, and less runoff made it to the streams.

“You can think of the soil zone as a sponge that needs to fill up before it can allow water to move through it,” Carroll said. “So, if it’s already depleted because you had low snowpack, the monsoon then has to fill it back up, and that decreases the amount of water you actually get in the river.”

As the climate warms, snowpack in the Rocky Mountains and other mountain systems is expected to decline, leading to reduced streamflow. Rising temperatures also lead to increased soil evaporation and increased water use by plants. According to the results of Carroll’s study, these changes will reduce the ability of water from the monsoon to make it to the river as streamflow.

“Our results indicate that as we move toward a climate that is warmer and our snowpack decreases, the ability of monsoon rain to buffer these losses in streamflow is also going to go down,” Carroll said. “So, the monsoon is not some silver bullet that is going to help mitigate those changes.”

Research from the University of Arizona finds dry periods are lasting longer across the West as the climate changes. When rain does fall, it often comes in fewer and larger storms, which hurts grasses with shallow roots that need a steady supply of moisture.

Even if the total amount of rainfall is the same during a growing season, it’s not as helpful if it comes in the form of occasional large rainstorms, said Joel Biederman, a research hydrologist with the U.S. Department of Agriculture who co-authored the paper.

Without consistent rain, dry plants become fuel for wildfires.

Separate research from the University of Arizona suggests that wildfires are harder to rein in without monsoon rains, which effectively end the fire season after July. Tree ring studies in neighboring states like Arizona and New Mexico link years that have weak monsoons to widespread fires in mountainous areas.

Cumululative time spent in severe #drought conditions in US. ⁦Data via The National Drought Mitigation Center at the University of Nebraska-Lincoln.

Click on a thumbnail graphic to view a gallery of drought data from the US Drought Monitor.

US Drought Monitor map July 27, 2021.

High Plains Drought Monitor map July 27, 2021.

West Drought Monitor map July 27, 2021.

Colorado Drought Monitor map July 27, 2021.

Click here to go to the US Drought Monitor website. Here’s an excerpt:

This Week’s Drought Summary

A robust Southwestern monsoon circulation delivered drought-easing rainfall but sparked localized flash flooding across large sections of the Four Corners States, as well as the southern Great Basin, but critically dry conditions persisted across northern California and the Northwest. In the driest areas, wildfires—some sparked by lightning—dotted the landscape, with containment of some blazes hampered by high temperatures, low humidity levels, erratic winds, and abundant fuels. Farther east, another round of blistering heat across the northern Plains further stressed rangeland, pastures, and a variety of summer crops. The central and southern Plains also experienced some hot weather, although agricultural impacts were tempered by mostly adequate soil moisture reserves. Meanwhile, mostly dry weather covered the Midwest, continuing a trend that had developed in mid-July. Short-term dryness was not yet a concern in the previously well-watered lower Midwest. However, reproductive corn and soybeans in drier areas of the upper Midwest were subjected to increasing levels of stress, especially as temperatures began to rise. Elsewhere, Southeastern rain—which maintained abundant moisture reserves for pastures and summer crops—primarily fell from the Mississippi Delta to the southern Atlantic Coast…

High Plains

Drought’s footprint remained rather limited across Kansas, eastern Colorado, and southern Nebraska. Farther north and west, however, worsening drought impacts were observed across much of Wyoming and the Dakotas. According to the U.S. Department of Agriculture, topsoil moisture on July 25 was rated 87% very short to short in North Dakota, along with 82% in South Dakota and 79% in Wyoming. Rangeland and pastures were rated at least 60% very poor to poor in Wyoming and the Dakotas, led by North Dakota at 85%. On July 25, North Dakota was the national leader in oats rated very poor to poor (56%), along with soybeans (41%) and corn (39%). South Dakota led the nation, among major production states, in sorghum rated very poor to poor (31%). Nationally, the U.S. spring wheat crop was rated just 9% good to excellent and 66% very poor to poor on July 25, the lowest overall condition at this time of year since July 25, 1988, when the crop was categorized as 4% good to excellent and 72% very poor to poor. Harvest was underway for drought-ravaged crops on the High Plains; 3% of the spring wheat had been cut by July 25. Periodic extreme heat on the northern Plains has greatly aggravated drought impacts. During the most recent heat wave, high temperatures in South Dakota on July 27 soared to 108°F in Pierre and 107°F in Rapid City. In the latter location, that represented the highest temperature since August 29, 2012…

West

Further expansion of moderate to exceptional drought (D1 to D4) was introduced in parts of California and the Northwest, as agricultural, wildfire, and water-supply impacts continued to mount. Oregon’s third-largest wildfire in modern history, the Bootleg Fire, has burned more than 410,000 acres of timber and brush, but was more than 50% contained. California’s largest active blaze, the Dixie Fire, has scorched nearly 220,000 acres only about 15 miles northeast of the town of Paradise, which was devastated by the Camp Fire in 2018. Washington continued to lead the country in several drought-related agricultural categories, according to the U.S. Department of Agriculture, including topsoil moisture rated very short to short (99% on July 25), as well as very poor to poor ratings for rangeland and pastures (97%) and spring wheat (88%). In addition to Washington, at least two-thirds of the rangeland and pastures were rated very poor to poor on July 25 in Montana (91%), Arizona (82%), Oregon (80%), and Utah (69%). Montana rivaled Washington for agricultural drought severity, with topsoil moisture rated 97% very short to short and a nation-leading 70% of its barley rated very poor to poor. Farther south, however, an active monsoon circulation delivered drought relief in the form of diurnal showers and thunderstorms, some heavy. Up to one category of improvement was introduced in parts of Arizona, New Mexico, southwestern Colorado, and southern sections of Utah and Nevada. In Arizona, Tucson received more rain in 6 days (4.20 inches fell from July 20-25) than during all of 2020, when annual precipitation of 4.17 inches was the lowest on record. Despite the positive effect of monsoonal showers on surface conditions (e.g. improved vegetation health, topsoil moisture, and streamflow), serious long-term, underlying drought persisted, with obvious impacts on groundwater and reservoirs. The surface elevation of Lake Mead, on the Colorado River behind Hoover Dam, fell to a new record low—1,067.59 feet above sea level—on July 23. In Utah, the surface elevation of the Great Salt Lake fell below 4,191.4 feet in late July, breaking the previous record low set in 1963…

South

Arkansas, Louisiana, and Mississippi remained free of dryness and drought, while only small patches of abnormal dryness (D0) and moderate drought (D1) were noted in Oklahoma, Texas, and Tennessee. Most Southern crops continued to fare well amid plentiful rainfall and relatively mild temperatures. On July 25, three-quarters (75%) of the nation’s peanuts were rated in good to excellent condition, according to the U.S. Department of Agriculture, along with 73% of the rice and 61% of the cotton…

Looking Ahead

Cooler air will overspread the northern Plains and upper Midwest, though many drought-affected areas will remain in need of moisture. Large sections of the central and southern Plains will also remain mostly dry, accompanied by some of the hottest weather of the summer. Farther east, periodic showers and thunderstorms will affect the Great Lakes and Northeastern States. Meanwhile, hot, humid weather will linger into the weekend across the South, where an approaching cold front will generate showers and thunderstorms. Elsewhere, the Southwestern monsoon circulation will remain active, with beneficial showers dampening interior sections of the western United States as far north as Wyoming and southern Idaho.

The NWS 6- to 10-day outlook for August 3 – 7 calls for the likelihood of above-normal temperatures in Alaska, southern Florida and from the Pacific Coast to the northern Plains and upper Midwest, while cooler-than-normal conditions will cover much of the southeastern half of the country. Meanwhile, near- or below-normal rainfall across most of the United States should contrast with wetter-than-normal weather in a few areas, including western Alaska, the southern Atlantic region, the southern Plains, and the Northwest.

Steven R. Fassnacht, Colorado State University

Creeks, rivers and lakes that are fed by melting snow across the U.S. West are already running low as of mid-July 2021, much to the worry of farmers, biologists and snow hydrologists like me. This is not surprising in California, where snow levels over the previous winter were well below normal. But it is also true across Colorado and the Rocky Mountains, which in general received a normal amount of snow. You’d think if there was normal amount of snow you’d have plenty of water downstream, right?

Over a century ago, snow scientist James Church at the University of Nevada, Reno, began examining how the amount of snow on mountains related to the amount of water in rivers fed by the melting snow. But as hydrologists have learned over the many decades since, the correlations between snows and river flows are not perfect. Surprisingly, there is a lot researchers don’t know about how the snowpack is connected to rivers.

Of course, a dry winter will result in meager flows in spring and summer. But there are other reasons snow from the mountains won’t reach a river below. One growing area of research is exploring how droughts can lead to chronically dry soil that sucks up more water than normal. This water also refills the groundwater below.

But another less studied way moisture can be lost is by evaporating straight into the atmosphere. Just as the amount of snow varies each year, so too does the loss of water to the air. Under the right conditions, more snow can disappear into the air than melts into rivers. But how snowfall and loss of moisture into the air itself relate to water levels in rivers and lakes is an important and not well understood part of the water cycle, particularly in drought years.

Losing moisture to the air

There are two ways moisture can be lost to the atmosphere before it reaches a creek or river.

The first is through evaporation. When water absorbs enough energy from the Sun, the water molecules will change into a gas called water vapor. This floating water vapor is then stored in the air. Most of this evaporation happens from the surface of lakes, from water in the soil or as snow melts and the water flows over rocks or other surfaces.

Another way moisture can be lost to the atmosphere is one you might be less familiar with: sublimation. Sublimation is when a solid turns directly into a gas – think of dry ice. The same can happen to water when snow or ice turns directly into water vapor. When the air is colder than freezing, sublimation happens when molecules of ice and snow absorb so much energy that they skip the liquid form and jump straight to a gas.

A number of atmospheric conditions can lead to increased evaporation and sublimation and eventually, less water making it to creeks and streams. Dry air can absorb more moisture than moist air and pull more moisture from the ground into the atmosphere. High winds can also blow moisture into the air and away from the area where it initially fell. And finally, the warmer air is and more Sun that shines, the more energy is available for snow or water to change to vapor. When you get combinations of these factors – like warm, dry winds in the Rockies called Chinook winds – evaporation and sublimation can happen quite fast. On a dry, windy day, up to around two inches of snow can sublimate into the atmosphere. That translates to about one swimming pool of water for each football field-sized area of snow.

Sublimation is mysterious

It is relatively easy to measure how much water is flowing through a river or in a lake. And using satellites and snow surveys, hydrologists can get decent estimates of how much snow is on a mountain range. Measuring evaporation, and especially sublimation, is much harder to do.

Today researchers usually estimate sublimation indirectly using physics equations and wind and weather models. But there are lots of uncertainties and unknowns in these calculations. Additionally, researchers know that the most moisture loss from sublimation occurs in alpine terrain above the treeline – but snow scientists rarely measure snow depths there. This further adds to the uncertainty around sublimation because if you don’t know how much moisture a system started out with, it is hard to know how much was lost.

Finally, weather and snowpack depths vary a lot from year to year. All of this makes measuring the amount of snow that falls and then is lost to the atmosphere incredibly difficult.

When scientists have been able to measure and estimate sublimation, they have measured moisture losses that range from a few percent to more than half of the total snowfall, depending on the climate and where you are. And even in one spot, sublimation can vary a lot year to year depending on snow and weather.

When moisture is lost into the atmosphere, it will fall to the surface as rain or snow eventually. But that could be on the other side of the Earth and is not helpful to drought-stricken areas.

Important knowledge

It is hard to say how important loss of moisture to the atmosphere is to the total water cycle in any given mountain range. Automated snow monitoring systems – especially at high elevations above the treeline – can help researchers better understand what is happening to the snow and the conditions that cause losses to the atmosphere.

The amount of water in rivers – and when that water appears – influences agriculture, ecosystems and how people live. When there is a water shortage, problems occur. With climate change leading to more droughts and variable weather, filling a knowledge gap of the water cycle like the one around sublimation is important.

Steven R. Fassnacht, Professor of Snow Hydrology, Colorado State University

This article is republished from The Conversation under a Creative Commons license. Read the original article.