Twentyone Mile Dam near Montello , Nevada broke in February 2017 and caused flooding to the Union Pacific Railroad line near Lucin, Nevada and flooded the town of Montello. Photo credit Deseret News.
FromThe New York Times (Troy Griggs, Gregor Aisch and Sarah Almukhtar):
Nearly 2,000 state-regulated high-hazard dams in the United States were listed as being in need of repair in 2015, according to the Association of State Dam Safety Officials. A dam is considered “high hazard” based on the potential for the loss of life as a result of failure.
By 2020, 70 percent of the dams in the United States will be more than 50 years old, according to the American Society of Civil Engineers.
“It’s not like an expiration date for your milk, but the components that make up that dam do have a lifespan.” said Mark Ogden, a project manager with the Association of State Dam Safety Officials…
The earthen dam, built in the early 1900s and less than 50 feet tall, is one of more than 60,000 “low hazard” dams, according to the Army Corps of Engineers. Typically, failure of a low hazard dam would cause property damage, but it would most likely not kill anyone.
In 2016, the Association of State Dam Safety Officials estimated that it would cost $60 billion to rehabilitate all the dams that needed to be brought up to safe condition, with nearly $20 billion of that sum going toward repair of dams with a high potential for hazard.
In 2015, Representative Sean Patrick Maloney, Democrat of New York, introduced the Dam Rehabilitation and Repair Act, an amendment to the National Dam Safety Program Act, to provide grant assistance to rehabilitate publicly owned dams that fail to meet minimum safety standards.
The bill is still pending, but it would not apply to a majority of the dams in the United States because more than half of them are privately owned. Oroville Dam is owned by the State of California, but the Twentyone Mile Dam is owned by Winecup Gamble Ranch, a cattle operation in northeastern Nevada.
While most legislation involves inspection and rehabilitation, hazardous dams that have outlived their usefulness can also be removed.
Here’s the release from Colorado State University (Jim Beers):
The Colorado River in Cataract Canyon, just above Lake Powell, where water officials are keeping a close eye on water levels. Photo: Brent Gardner-Smith/Aspen Journalism
Story by Mari N. Jensen at the University of Arizona
Warming in the 21st century reduced Colorado River flows by at least 0.5 million acre-feet — about the amount of water used by 2 million people in one year — according to new research from Colorado State University and the University of Arizona.
The research is the first to quantify the different effects of temperature and precipitation on recent Colorado River flow, said authors Bradley Udall of CSU and Jonathan Overpeck of UA.
“The future of the Colorado River is far less rosy than other recent assessments have portrayed,” said Udall, a senior water and climate scientist/scholar at the Colorado Water Institute, a unit within CSU’s Office of Engagement. “Our findings provide a sobering look at future Colorado River flows, and send a clear message to water managers that they need to plan for significantly lower river flows.”
The paper by Udall and Overpeck, “The 21st Century Colorado River Hot Drought and Implications for the Future,” went online Feb. 17 in the American Geophysical Union journal Water Resources Research. The Colorado Water Institute, National Science Foundation, the National Oceanic and Atmospheric Administration and the U.S. Geological Survey funded the research.
Significant water reduction
From 2000 to 2014, the river’s flows declined to 81 percent of the 20th-century average, a total reduction of about 2.9 million acre-feet of water per year, with a warmer climate accounting for 0.5 million acre-feet per year and a reduction in precipitation levels making up the remainder. One acre-foot of water will serve a family of four for one year, according to the U.S. Bureau of Reclamation. Forty million people in seven U.S. Western states, plus the Mexican states of Sonora and Baja California, rely on the Colorado River for water.
From one-sixth to one-half of the 21st-century reduction in flow can be attributed to higher atmospheric temperatures since 2000, according to the researchers. Their analysis shows as temperatures continue to increase, Colorado River flows will continue to decline.
Current climate change models indicate temperatures will increase as long as humans continue to emit greenhouse gases into the atmosphere, but the projections of future precipitation are far less certain.
“This paper is the first to show the large role that warming temperatures are playing in reducing the flows of the Colorado River,” said Overpeck, Regents’ Professor of Geosciences and of Hydrology and Atmospheric Sciences at the University of Arizona and director of the UA Institute of the Environment.
Glen Canyon Dam June 2013 — Photo / Brad Udall
The Colorado River Basin has been in a drought since 2000. Previous research has shown the region’s risk of a mega-drought – one lasting more than 20 years – rises as temperatures increase.
“We’re the first to make the case that warming alone could cause Colorado River flow declines of 30 percent by mid-century and over 50 percent by the end of the century if greenhouse gas emissions continue unabated,” Overpeck said.
The team began its investigation because Udall learned that recent Colorado flows were lower than managers expected given the amount of precipitation. The two researchers wanted to provide water managers with insight into how future projections of temperature and precipitation for the Colorado River Basin would affect the river’s flows.
Udall and Overpeck began by looking at the drought years of 2000-2014. About 85 percent of the river’s flow originates as precipitation in the Upper Basin – the part of the river that drains portions of Wyoming, Utah, Colorado and New Mexico. The team found during that time, temperatures in the river’s Upper Basin were 1.6 degrees F (0.9 C) higher than the average for the previous 105 years.
25 years of data
To see how increased temperatures might contribute to the reductions in the river’s flow that have been observed since 2000, Udall and Overpeck reviewed and synthesized 25 years of research about how temperature and precipitation affect the river’s flows. Water loss increases as temperatures rise because plants use more water, and higher temperatures increase evaporative loss from the soil and from the water surface and lengthen the growing season.
In previous research, Overpeck and other colleagues showed current climate models simulated 20th-century conditions well, but the models cannot simulate the 20- to 60-year mega-droughts known to have occurred in the past. Moreover, many of those models did not reproduce the current drought.
Those researchers and others suggest the risk of a multi-decadal drought in the Southwest in the 21st century is much higher than climate models indicate, and that as temperatures increase, the risk of such a drought increases.
“A mega-drought in this century will throw all our operating rules out the window,” Udall said.
Udall and Overpeck found all current climate models agree that temperatures in the Colorado River Basin will continue rising if the emission of greenhouse gases is not curbed. However, the models’ predictions of future precipitation in the Basin have much more uncertainty.
“Even if the precipitation does increase, our work indicates that there are likely to be drought periods as long as several decades when precipitation falls below normal,” Overpeck said.
The new study suggests Colorado River flows will continue to decline.
“I was surprised at the extent to which the uncertain precipitation aspects of the current projections hid the temperature-induced flow declines,” said Udall.
The U.S. Bureau of Reclamation lumps temperature and precipitation together in its projections of Colorado River flow, he said.
“Current planning understates the challenge that climate change poses to the water supplies in the American Southwest,” Udall said. “My goal is to help water managers incorporate this information into their long-term planning efforts.”
Rivers of meltwater and a mantle of soot, dust, and microbes darken the surface and speed melting. Surface melting has now surpassed the discharge of icebergs into the ocean as a major cause of ice loss. Photo credit Marco Tedesco/Lamont-Doherty Earth Observatory.
The scientists flying over the world’s largest thawing chunk of ice have selected a particularly auspicious summer to be studying the melt. The edges of Greenland’s 1.7-million-km2 ice sheet regularly melt in summer, even in years when the ice sheet as a whole grows because of snowfall in its higher, colder center. But in 2016, the melting started early and spread inland fast. By April, 12% of the ice sheet’s surface was melting; in an average year the melt doesn’t reach 10% until June. And just before the scientists’ journey, a violent river of meltwater, one of hundreds coursing out from the ice sheet, swept away a sensor, bolted to a bridge to measure the water’s turbidity. It was the second time in 4 years such a device had fallen victim to the liquid fury of the glaciers. “I’ve been doing these trips for years, but I’ve never seen so much water,” the helicopter pilot told the researchers.
In Greenland, the great melt is on. The decline of Greenland’s ice sheet is a familiar story, but until recently, massive calving glaciers that carry ice from the interior and crumble into the sea got most of the attention. Between 2000 and 2008, such “dynamic” changes accounted for about as much mass loss as surface melting and shifts in snowfall. But the balance tipped dramatically between 2011 and 2014, when satellite data and modeling suggested that 70% of the annual 269 billion tons of snow and ice shed by Greenland was lost through surface melt, not calving. The accelerating surface melt has doubled Greenland’s contribution to global sea level rise since 1992–2011, to 0.74 mm per year. “Nobody expected the ice sheet to lose so much mass so quickly,” says geophysicist Isabella Velicogna of the University of California, Irvine. “Things are happening a lot faster than we expected.”
It’s urgent to figure out why, and how the melting might evolve in the future, because Greenland holds the equivalent of more than 7 m of sea level rise in its thick mantle of ice. Glaciologists were already fully occupied trying to track and forecast the surge in glacial calving. Now, they are striving to understand the complex feedbacks that are speeding up surface melting.
Although the Arctic is warming twice as fast as the rest of the world, high temperatures alone can’t explain the precipitous erosion of Greenland’s ice. Unseasonably warm summers appear to be abetted by microbes and algae that grow on the increasingly wet surface of the ice sheet, producing pigments that boost the ice’s absorption of solar energy. Soot and dust that blow from lower latitudes and darken the ice also appear to be playing a role, as are changes in weather patterns that increasingly steer warm, moist air over the vulnerable ice.
To track this complex set of factors, scientists have enlisted satellite instruments: imagers to monitor the color and reflectivity, or albedo, of the ice and altimeters to measure its erosion millimeter by millimeter. They are also organizing expeditions like this one, called Black and Bloom, which has enlisted experts in algae (the Bloom) and soot (the Black), some of whom have never before worked in the Arctic. By inspecting the changing ice sheet close up, they hope to understand how biological and physical processes are conspiring to destroy it. As team leader Martyn Tranter, a biogeochemist at the University of Bristol in the United Kingdom, explains, “We’re driven by curiosity, but also the fear that all this new biology may accelerate global sea level rise.”
An hour after taking off from an airstrip about 90 km from the western edge of the ice sheet, the helicopter lands on flat, dry, crunchy snow. The brightness is dazzling, making sunglasses a necessity. But when Joe Cook of the University of Sheffield in the United Kingdom takes light readings with a sensor connected to a mini-laptop, they show the snow isn’t quite as white as it looks. It is absorbing a bit of the visible light it would otherwise reflect, and the absorption is greater in invisible infrared wavelengths. Cook explains that the darkening is the result of a melt-induced feedback that polar scientists have long documented: Upon melting and refreezing, ice crystals lose their spiky shape and grow larger and rounder, which can reduce the reflectivity of the snow by as much as 10%. As absorption rises, so does temperature, accelerating the melt.
Their measurements complete, the team packs into the helicopter and flies west, back toward the ice’s edge. At the second stop the winter snow is gone, and the exposed ice is bumpier and wetter than at the first stop. It is also increasingly dirty and dark. Satellite data show that the margins of the ice sheet have darkened by as much as 5% per decade since 2001. That’s why we’ve come to this place, which some have dubbed a “dark ice” zone. Earlier sampling revealed several culprits. Dust trapped over the centuries has become concentrated at the melting edge of the ice sheet. Soot from European factories and Canadian wildfires, along with increasingly prevalent patches of bare ice, contribute as well.
Researchers have yet to quantify the relative contribution of each darkener, but a third player could be the biggest driver: a bloom of algae and bacteria. The surface of the ice here is pocked with holes just wide enough for a researcher’s finger. Each is filled with crystal-clear meltwater, but a dollop of black sludge darkens the bottom. Much of the sludge—known as cryoconite—is living bacteria, as the Finnish-Swedish explorer Nils A. E. Nordenskiöld suggested nearly 150 years ago. It thrives thanks to another feedback effect: Solar energy captured by the dark cryoconite helps keeps the water from freezing and deepens the cone. It also creates a favorable environment for more bacteria to grow, fueling continued melt.
In 2010, microbiologist Marian Yallop of Bristol found more life on the ice margins: a thriving community of algae that extends beyond the cones. “To the amazement of everybody, we found this algae growing in this extreme cold, under high ultraviolet light conditions, tolerating regular freezethaw cycles,” says Yallop, who is taking part in this year’s expedition. The brown pigments that protect the plants from the sun stain and darken massive swaths of ice…
At the third sampling stop, 80 km west of the first, the algae’s power to melt ice is devastatingly evident. Not only has winter snow long vanished, but so have several meters of the underlying ice. What’s left is a far cry from the Greenland that most people picture. “People think of the Greenland Ice Sheet as pretty pristine,” says atmospheric scientist Jim McQuaid of the University of Leeds in the United Kingdom. But this scene is a mess: Cryoconite cones have coalesced into cruddy puddles and basins, while a robust river, a few meters across, gushes across the dirty icescape. The researchers eagerly scrape brownish snow into plastic bags. Later they’ll analyze the samples for DNA and other markers to identify algae species as well as inorganic contaminants.
About 20 km from the final sampling station is an experimental plot that Black and Bloom researchers monitored for 5 weeks last summer. Their goal was to ground truth satellite measurements of the darkening, quantifying each of the darkening factors and their effects on melting. They called their study plot the “pixel” because, at 500 m across, it corresponded to the maximum resolution of a NASA satellite sensor that maps Greenland’s color each day. The team used drone flights, regular sampling, and a series of reference poles to track how seven different microhabitats—among them streams, bare ice, and slush—were evolving in terms of albedo, cryoconite formation, and biological activity. Members of the team hope the results will eventually make it possible to use satellite data to infer local melting conditions across the entire ice sheet…
Albedo isn’t everything. 2012 was a whopper summer for melting on Greenland; by 12 July of that year, fully 98% of the ice sheet was covered in liquid water, according to satellite data. At one weather station, a layer of ice as much as a meter thick melted in 4 days. That brief episode and a subsequent 2-day melt contributed to 14% of the season’s ice loss.
But a recently published modeling study of the 2012 melting showed it wasn’t sun falling on darkened snow that drove the melt—in fact, the skies were pretty cloudy over much of the island during the two melting events. Instead, it was warm temperatures and rainfall, provided by big “blocking” high-pressure systems that kept the mild weather in place. As the Arctic warms, such melt episodes are likely to “occur much more frequently in the future,” says Dirk van As of the Geological Survey of Denmark and Greenland in Copenhagen. Earlier this year, climate scientist Marco Tedesco of Columbia University published data supporting an earlier proposal that the retreat of Arctic sea ice has disrupted the polar jet stream, causing weather systems to meander more slowly from west to east.
The topography of the ice sheet also plays a role in the accelerating melt. Each increase in temperature drives the upper edge of the melt zone farther inland and higher up the ice sheet. But because the ice sheet is steep at its edges but flatter toward the middle, each successive degree of warming exposes a larger area of ice to melting than the last. This nonlinear response to warming means that about 60% more meltwater was released from the ice sheet over the past decade than would have been the case if the ice slope were uniform, scientists estimated in a recent paper.
Researchers hope to incorporate all of these factors into computer models of ice sheets, which still struggle to mimic how real ice sheets respond to climate change. In a recent comparison of four ice models, for example, the amount of meltwater they produced under current conditions varied by more than 40%. Forecasts of future ice sheet behavior appear even more uncertain: Under the same high–global warming scenario, eight ice sheet models predicted anywhere between 0 and 27 cm of sea level rise in 2100 from Greenland melt.
Better melt models would improve forecasts not only for Greenland, but also for the Antarctic Ice Sheet. It holds 10 times more water than Greenland, and for now is losing nearly all of its ice through glacier calving, not surface melting. But sooner or later the thaw will reach the bottom of the world.
In the meantime, the modelers working back in their cozy offices want to know more about the feedbacks driving Greenland’s decline. One key question is how meltwater that drains to the base of the ice sheet affects the glaciers’ march to the ocean, and the rate at which they shed icebergs. Researchers also wonder how meltwater flows unleashed in the spring affect summer runoff. Scientists have recently discovered that, during spring melt-and-freeze cycles, massive “ice lenses,” as thick as 6 m, form just below the snow surface. Data from sensors in the snow suggest that the lenses block summer meltwater from percolating into deeper, older snow, known as firn. Instead, the meltwater is apparently getting trapped near the surface, amplifying summer flows. Next spring Tedesco will participate in a 150-km trek by snowmobile across southeast Greenland, in –30°C temperatures, to see how widespread the phenomenon is. “It’s going to be pretty brutal, but there’s no other way to get the data,” he says.
Melting brings other challenges for field research, as Black and Bloom researchers discovered last year when they tracked their “pixel” of eroding ice. The researchers faced endless slush and puddles, and a weekly chore of moving their working and sleeping quarters as the ice disappeared around them, leaving the tents stranded on bizarre pedestals half a meter high. But they also felt a sense of wonder at the transformation of the icescape, McQuaid says. “Each evening we marveled as the sun went low, enjoying the fact that we were somewhere no one else had been, and would never be again, because of the melt.”
John Shomaker, TVAA Hydrologist, will discuss the hydrology of the Rio Lucero Storage Project and the Mitigation Wells. Rebecca Dempsey will also be in attendance to answer any legal questions on the Storage Project or Mitigation Wells.
The Rio Lucero Storage project will be discussed at 11:00 a.m.
The Mitigation Wells will be discussed at 2:00 p.m.
It is very important commissioners attend and invite your parciantes to attend this special meeting to pass along correct information on the Storage Project and Mitigation Wells.
As of Feb. 21, Colorado’s snowpack was sitting at 140 percent of what is considered normal, according to the U.S. Department of Agriculture’s Natural Resources Conservation Service.
That amount has dropped some, though, as only a week earlier, the statewide snowpack was at 147 percent of normal.
Still, this bodes well for Fort Morgan in terms of having plenty of water this summer and fall. It also looks good for Northern Water, which provides that water to the city through the Colorado-Big Thompson pipeline.
“Late spring and early summer snowmelt and runoff from the Rocky Mountains provides most of Colorado’s water supply,” Northern Water’s website explains. “Greater snowpack means favorable water supplies; lower amounts can signal an impending drought.”
The two major river basins that play roles in the water supply for the C-BT pipeline are the Upper Colorado and South Platte, and they had snowpacks of 147 and 142 percent, respectively, in mid-February. Those percentage fell to 140 and 132 as of Feb. 21…
Further, the C-BT pipeline’s water storage level was “above average” at the start of February, tracking at 121 percent of normal as of Feb. 1.
The High Plains Aquifer provides 30 percent of the water used in the nation’s irrigated agriculture. The aquifer runs under South Dakota, Wyoming, Nebraska, Colorado, Kansas, Oklahoma, New Mexico and Texas.
FromThe La Junta Tribune-Democrat (Bette McFarren):
On Tuesday, farmers and ranchers from all over the area attended the Water Quality Workshop at Otero Junior College: Impacting Your Farm’s Bottom Line. They were informed by a series of three panels of speakers, plus introductory remarks by John Stulp, Director for the Interbasin Compact Committee and Water Adviser to Governor Hickenlooper.
Stulp was happy to see organizations and communities working together to solve our common problems. “Water quality is everyone’s issue,” said Stulp. He is also pleased with technological advances in agriculture. “The center pivot sprinklers are a great invention, also the low pressure nozzles operated by computers that water according to humidity.” The new equipment enables the farmer to reduce the amount of fertilizer by 50 percent and get the same yield, contributing to better water quality. “Conferences like these bring out practical ideas,” said Stulp, a farmer and rancher from Prowers County who served as Colorado Commissioner of Agriculture from 2007 to 2011 and Prowers County Commissioner for 13 years.
Moderator Carol Ekarius, CEO of Coalitions & Collaboratives Inc., a nonprofit dedicated to fostering on-the-ground efforts to address environmental challenges, introduced the first panel, “Lessons from the Field.” The presenters were Phillip H. Chavez, managing partner for Diamond ‘A’ Farms in Rocky Ford; Ryan Hemphill, progressive family farmer from near Hasty; Jerry Allen, Irrigation Water Management Specialist for Shavano Conservation District on the western slope; Joel Moffett, Resource Conservationist, Ecological Division Colorado National Resource Conservation Service…
Hemphill manages the family farm. His main concern is the bottom line, and he has found good conservation practices not only save his back but produce a good return on investment. The family started improvements back in the seventies with concrete ditches, and their latest innovation is central pivot sprinklers operated by electrical motors. These sprinklers also have nozzles which descend to just above plant level and deliver water in a fine spray.
Former ag teacher Jerry Allen, originally from Cheraw, described all the good things ground cover planted after the harvest of the main crop or concurrently with it can do: increase organic matter in the soil, increase plant diversity, provide winter food for livestock, keep the soil cool and workable, to name just a few. Planting turnips and radishes along with or after other crops has multiple benefits. These root vegetables bring protein up through the soil again, besides providing great fodder for cattle in the winter. Cattle love the leaves and leave the roots in the ground to do the rest of their job.
NRCS’s Joel Moffett couldn’t agree with him more. “We’ve been farming the same way for 5,000 years, and all we’ve improved is our tools,” said Moffett. He thinks it’s high time we quit plowing up the fields, keep them as undisturbed as possible and planted with various types of plants, improving biodiversity and discouraging plant diseases and insect infestations, making fewer chemicals necessary in the production of food. Thereby we not only improve the soil but also the quality of the water percolating through it.
A beach along the Colorado River, not far below the confluence with the Green River. Photo credit Brent Gardner-Smith @AspenJournalism
FromAspen Journalism (Allen Best) via The Aspen Daily News:
It’s detective time on the Colorado River. There’s been a massive thievery. Who or what has purloined the agua?
Precipitation in the seven-state Colorado River Basin during 2000-2014 averaged 6.1 percent less than in the 20th century, but flows declined 19.3 percent. In other words, despite a few sour winters of marginal snow, most notably 2002 and 2012, it’s mostly been business as usual at elevations of 9,000 to 11,000 feet.
That elevation band, the money belt for Colorado’s ski industry, provides 85 percent of the river’s water when it reaches Lee’s Ferry at the entrance to the Grand Canyon. Colorado alone is responsible for 70 percent of the river’s flows.
Where did this water go? Rising temperatures, say researchers Brad Udall and Jonathan Overpeck in a new study, explain roughly a third of reduced flows.
Drought alone has been the conventional explanation for reduced flows in the river. The poster for the drought has been the ever-more bleached rocks of the rivers’ two giant reservoirs, Powell and Mead, looking like a swimsuit tugged indecently below the tan line.
But precipitation has declined relatively little in the 21st century. However, temperatures in this century have increased 1.6 degrees Fahrenheit as compared with the 20th-century record. Therein lies the major difference, according to Udall and Overpeck.
They believe that flows will almost certainly decline further, by 35 percent or more during this century, as temperatures inexorably rise due to increasing heat-trapping greenhouse gases in the atmosphere.
“Our work demonstrates that flows are unlikely to return to the 20th century averages if we only wait,” they write in a study being published in a journal called Water Resources Research.
Things could really turn strange if rising temperatures pile on top of natural droughts that last several decades. Tree rings document several such multi-decadal droughts between 900 A.D. and 1400 A.D. in the Southwest.
Might heat-induced drought coupled with natural drought also result in empty reservoirs such as, say, Ruedi Reservoir above Basalt on the Fryingpan River?
An empty Ruedi is far out on the limb of hypotheticals, but it’s among the possibilities that water managers should contemplate as they examine an ever-changing human-driven climate, said Udall, who is affiliated with the Colorado Water Institute at Colorado State University. Overpeck is with the University of Arizona.
Udall said the major contribution of this new study is that it examines temperature as driving changes in how much water flows in Colorado River tributaries, including the Roaring Fork River, apart from precipitation changes.
Previous studies have stepped up to the same conclusion but then walked away. Instead, they amalgamated temperature with precipitation in an effort to project how accumulating greenhouse gases will change the climate in the American Southwest. Amalgamation, said Udall, hides the true risk, because uncertain increases in precipitation shown in some climate models obscure the known and dramatic temperature-induced declines from all models.
“Combining the two effects is not the right way to look at risk,” Udall said. “Future temperatures are known, but precipitation is not. We have to prepare for this downside risk and not pretend that it doesn’t exist.”
Eric Kuhn, the general manager for the Glenwood Springs-based Colorado River Water Conservation District, said he started wondering in 2010 whether rising temperatures were at least partly responsible for the reduced flows being observed. If the Udall and Overpeck conclusions don’t surprise him, he finds them “troubling.”
“The No. 1 thing is there is no return to normal,” he said. “Everything is going to be different in the future.”
A dam and reservoir on he headwaters of the Yampa River, a tributary of the Green and Colorado rivers. Photo credit @AspenJournalism.
Is storage the answer?
The study says nothing about new water storage projects. And when asked what the study says about the conditional water rights held by the city of Aspen for potential reservoirs on Castle and Maroon creeks, or about storage in other mountain towns, Udall declined to talk about new dams in general.
Kuhn said he sees the need for additional storage “but it will be specific to the location. The need for storage for lower-elevation demands will be greater than the higher-elevation demands.”
At the other end of the Colorado River, in places like Arizona’s Yuma Valley, growing seasons — and water demand — are expected to expand. The region produces 80 to 90 percent of the lettuce, broccoli and other produce found in grocery stores in the United States during the winter. But any additional reservoirs will also be vulnerable to increased evaporation due to rising temperatures.
A wall bleached, and stained, in Lake Powell. Photo credit Brent Gardner-Smith @AspenJournalism.
Not like the past
During the 20th century, water managers and virtually everybody else presumed that past was prelude to the future. Droughts occurred, yes, and sometimes lasted for years, as occurred in the 1930s and then, more deeply yet in Western Colorado, during the 1950s. Again in 1976-77 and 1980-81, winters were time for rock skis.
Then things would get back to normal. But climate scientists point to a constant shift in temperatures and perhaps in precipitation as accumulated greenhouse gases drive changes that overlay natural variability.
“We’re going to be reacting to unforeseen (or unpredictable) conditions, not just more severe droughts,” says Kuhn. “It might be something like California is experiencing this year. As temperatures increase, the atmosphere carries more moisture and storms can be much more intense. It will be different.”
Some water agencies, including Denver Water, are trying to plot their futures, given the large uncertainties that remain, using a process called scenario planning. Scenario planning contemplates a wide array of futures, but also a great many options.
Assumptions of climate stability led to massive investments in water plumbing in the 20th century. These include Ruedi Reservoir, built to benefit the Western Slope for the federally financed Fryingpan-Arkansas Project’s diversions to farms along the Arkansas River. To the north, Green Mountain Reservoir was similarly built to benefit the Western Slope as part of the federally financed Colorado-Big Thompson Project.
Between are the tunnels, both at Winter Park and from Summit County, used by Denver Water to draw the water for use by residents of that city and many of its suburbs under the Continental Divide. Other cities, including Aurora and Colorado Springs, have other diversions—including Homestake Reservoir and Tunnel, located partially in the northeast corner of Pitkin County.
All these dams, reservoirs and water tunnels have one thing in common: They were constructed after 1922. That’s the year that the seven basin states struck an agreement about how to apportion what was then presumed to be 16.5 million acre-feet of average flows on the Colorado River. In fact, the river has mostly fallen short.
But with the projections by Udall and Overpeck of at least 20 percent declines in Colorado River flows by mid-century, all that infrastructure could be the equivalent of a dry dock. That’s true especially if deep, lingering drought overlays the new temperature-induced drought.
“It could mean a lot of dried up stuff,” says Udall, ticking off Ruedi, Green Mountain, Dillon, and other dams built in the 1930s and since to create reservoirs.
Silt walls in upper Lake Powell. Photo credit Brent Gardner-Smith @Aspen Journalism.
Change the Compact?
Those with pre-1922 compact water rights are more secure. Palisade peaches and Olathe corn look safer, and also a lot of hay pastures. Irrigators tend to have older, more senior rights. For that matter, Aspen has mostly very senior rights, too.
Here’s Udall’s thinking: The 1922 compact has somewhat vague language about the entitlements of water by Arizona, California, and Nevada to water from Colorado and other headwater states. Does that mean that, in the event of extended drought, that those with post-1922 water rights in Colorado must allow water to flow downstream to the deserts? This scenario is called a compact curtailment.
By one debatable interpretation of the Colorado River compact, Colorado and other upper-basin states would have half as much water as California, Arizona, and Nevada.
“That puts us into a gray area where we have no historical precedent for sharing a shortage with the lower basin,” says Udall. “There’s nothing in the compact that addresses that. We have no roadmap for how to do it.”
A rethinking of the Colorado River Compact and other agreements is needed, says Udall. Water management laws, agreements, and policies adopted over the last 100 years never expressly included risk management for climate change nor contained provisions for how to handle the relentless flow reductions that he and Overpeck foresee.
Editor’s note: Aspen Journalism and the Aspen Daily News are collaborating on the coverage of rivers and water. More at http://www.aspenjournalism.org.
The once-mighty Colorado River, which has regularly failed to reach the ocean since the 1960s, is already in the grip of the worst 15-year drought on record with the flow of water in the 21st century nearly a fifth lower than the 20th century average, a new study found.
And the scientists warned the river could be reduced by anything from 35 to 55 per cent by the end of this century if nothing was done to reduce greenhouse gas emissions.
Rising temperatures cause increased evaporation from the river, but also prompt plants to use more water.
A paper about the study in the journal Water Resources Research said: “With continued anthropogenic [human-caused] warming, the risk of multi-decadal megadrought in the Southwest increases to over 90 per cent over this century if there is no increase in mean precipitation.
“Even if modest precipitation increases do occur, the risk will still exceed 70 per cent.”
In the event of “huge and unlikely” increases in rainfall, there would still be a megadrought risk of just under 50 per cent…
But the researchers found that the river’s flow between 2000 and 2014 was 19 per cent lower than the average from 1906 to 1999 – equivalent to the amount of water used by two million people over a year.
One of the paper’s lead authors, Bradley Udall, of Colorado State University, said: “The future of Colorado River is far less rosy than other recent assessments have portrayed.
“Current planning understates the challenge that climate change poses to the water supplies in the American Southwest.
“A clear message to water managers is that they need to plan for significantly lower river flows.”
However he added that a prolonged drought – such as has occurred in the past – could make things substantially worse.
“A megadrought in this century will throw all our operating rules out the window,” Mr Udall said.
