ENSO-neutral conditions continue and are expected to remain through the fall. Let’s hit the road (virtually) and take a trip around El Niño/Southern Oscillation land! Who needs Carhenge when you have the Walker circulation?
Buckle your seatbelts
Perhaps you recently looked at the table of historical ENSO episodes, where the Oceanic Niño Index is recorded. This index, the three-month-average sea surface temperature anomaly in the Niño3.4 region (anomaly = departure from long-term average), is our primary metric for ENSO. (In climate prediction, we refer to any three-month-average period, e.g. February–April, as a season, so I’ll use that going forward here.)
Perhaps you looked at the table, and perhaps you noticed that the last five seasons, starting with October–December 2019 and going through February–April 2020, are all at or (very slightly) above 0.5°C, and colored red in the table. What’s that about? Was El Niño going on all winter and we were asleep at the wheel? Not so fast.
There are a few things going on here. First, as we are always talking about here on the Blog, ENSO is a coupled system, involving both the tropical Pacific Ocean and the atmosphere. In the case of El Niño, warmer-than-average ocean surfaces in the central and eastern equatorial Pacific lead to more rising air, clouds, and rain, changing the Walker circulation. The atmosphere in turn affects the ocean through changes in the near-surface winds. When the surface temperature anomaly is expected to persist, and the ocean and the atmosphere are both showing characteristic changes, we call this El Niño conditions—and coupled conditions did not persist this past winter.
There’s no clear threshold where ocean-atmosphere coupling switches on. We have examples in recent years (2014-15 and 2018–19) where the ocean surface warmed up and it took a few months for an atmospheric response to kick in. (Check out Nat’s post and paper investigating the delay.) Those years, the ocean surface was predicted to continue warming, and El Niño was expected. This time around, the Niño3.4 surface temperature anomaly was predicted to hover right around 0.5°C for a few months, but forecasters did not expect the surface to continue warming, nor for the atmosphere to exhibit the characteristic El Niño response.
Stakeholders request a simple, official metric for ENSO and the 0.5°C anomaly in the Niño3.4 region was chosen because it is most representative of ENSO. (Tony covers the history of this choice here.) Usually, the atmosphere responds to a consistent anomaly of 0.5°C or more, but not always. So, occasionally we’ll end up with red on the ENSO table—meaning ocean criteria were met—without evidence of a full-blown El Niño. Such is the agony of borderline conditions!
The world’s tallest haystack
Finally, there’s another issue that is likely coming into play here. The tropical Pacific is experiencing climate change along with the rest of the world, and it’s affecting the “average.” What counts as “average” is getting warmer over time. NOAA uses a 30-year period to define average, and right now that is 1986–2015 for the Oceanic Niño Index. In January of 2021, we’ll update the average period to 1991–2020.
This update will result in changes to the ONI values dating back to 2006. Some seasons that were warm enough to qualify as El Niño when compared to the older (cooler) average won’t be when compared to the more recent (warmer) average. Since winter 2019–2020 was right on the edge, it’s likely that at least one season will drop to 0.4°C, and we’ll no longer have five consecutive seasons at or above the El Niño threshold.
The short version of all of the above is “no, El Niño was not present this past winter.” It’s like meeting the age requirement to get a driver’s license, but not passing the written test.
On the road again
Where are we headed next? There’s a 65% chance that ENSO-neutral conditions will last through the summer. As predicted, ocean surface temperature anomalies decreased through April and into May. Winds over the surface of the tropical Pacific, the trade winds, have been stronger over the past few weeks, helping to cool the surface. Also, an area of cooler water beneath the surface has expanded over the past weeks.
Some of the computer models are hinting at increasing chances for La Niña next winter, although there is a wide range of potential outcomes. Forecasters estimate the odds of La Niña developing in early winter are about equal to the odds that neutral will continue, with lower chances for El Niño.
June will find us emerging from the spring predictability barrier, a time where it’s more difficult to accurately predict ENSO development. Nature’s in the driver’s seat, so it’s guaranteed to be an interesting trip.
The Northern Water Board of Directors allocated 15,000 acre-feet of Regional Pool Program (RPP) water during its May 14, 2020, Board meeting. RPP water is available for lease by eligible Northern Colorado water users, with sealed bids due May 28, 2020. Bid prices per-acre-foot must be greater than or equal to $27.40, a floor price the Board selected based on the 2020 agricultural assessment rate.
Due to the COVID-19 pandemic, interim procedures have been instituted for the May 2020 RPP allocation. The interim procedure and additional Regional Pool information are available at http://northernwater.org/regionalpool.
The following forms are required to submit a bid:
Pre-Approval Form – To confirm eligibility, interested bidders must email or mail the Pre-Approval Form to Northern Water. In person delivery will not be accepted in 2020. A new Pre-Approval Form is required each year.
Carrier Consent Form – If the RPP water will be delivered by a carrier, such as a ditch or reservoir company, bidders and their carriers must complete the Carrier Consent Form or provide a signed agreement stating that the carrier will deliver the RPP water to the bidder. This form must also be emailed or mailed to Northern Water; in person delivery will not be accepted.
Bid Form – Sealed bids will be accepted at Northern Water’s headquarters through a “self-serve” process. Bidders will sign in at a kiosk in the lobby and print a bid label for their sealed bid envelope. The label will identify the bidder name, date and time stamp, and bid number. Secure the label to the bid envelope and place in the drop box. Sealed bids may also be mailed to Northern Water, but must be received before the deadline.
Sealed bids are due by 2 p.m. May 28 at Northern Water’s headquarters, 220 Water Ave., Berthoud, CO 80513. As described above, sealed bids can be mailed or hand delivered; email and fax bid forms will not be accepted. RPP leases will be awarded based on highest bids per acre-foot. Sealed bids will be opened during a 9 a.m., June 1 Zoom video conference. The link to the Zoom video conference will be available at http://northernwater.org/RegionalPool.
Many staff are working remotely due to the COVID-19 pandemic and are not available to answer questions in person. Questions regarding the Regional Pool Program and bid submittal can be emailed to firstname.lastname@example.org or by calling Sarah Smith at 970-622-2295 or Water Scheduling at 970-292-2500.
FromThe Washington Post (Brady Dennis and Juliet Eilperin):
The Environmental Protection Agency has decided not to limit perchlorate, a chemical that has long been detected in the drinking water of many Americans and linked to potential brain damage in fetuses and newborns and thyroid problems in adults, according to two agency officials briefed on the matter.
They spoke on the condition of anonymity because the decision hasn’t been announced.
The move, which comes despite the fact that the EPA faces a court order to establish a national standard for the chemical compound by the end of June, marks the latest shift in a long-running fight over whether to curb the chemical used in rocket fuel.
Under President Barack Obama, the EPA had announced in 2011 that it planned to set the first enforceable limits on perchlorate because of its potential health impacts. Both the Defense Department and military manufacturers have long resisted any restrictions on the chemical, which is also used in fireworks, munitions and other ignition devices. It naturally occurs in some areas, such as parts of the Southwest.
In an email Thursday, EPA spokeswoman Corry Schiermeyer said the agency “has not yet made a final decision” on whether to limit perchlorate in drinking water. “The next step in the process is to send the final action to the Office of Management and Budget for interagency review,” she said. “The agency expects to complete this step shortly.”
The EPA also issued a news release Thursday in which Administrator Andrew Wheeler hailed the fact that levels of perchlorate exposure have declined since 2011. Though no federal standards regulating perchlorate levels in drinking water exist, some states have already acted to reduce the amounts in their drinking water systems. California and Massachusetts, for example, have set limits for perchlorate at levels far lower than what the EPA had previously proposed.
Here’s the release from the University of California Riverside:
Grasslands across the globe, which support the majority of the world’s grazing animals, have been transitioning to shrublands in a process that scientists call “woody plant encroachment.”
Managed grazing of drylands is the most extensive form of land use on the planet, which has led to widespread efforts to reverse this trend and restore grass cover due to the belief that it results in less water entering streams and groundwater aquifers.
A new study led by Adam Schreiner-McGraw, a postdoctoral hydrology researcher at the University of California, Riverside, modeled shrub encroachment on a sloping landscape and reached a startling conclusion: Shrub encroachment on slopes can increase the amount of water that goes into groundwater storage. The effect of shrubs is so powerful that it even counterbalances the lower annual rainfall amounts expected during climate change.
Until now, researchers have thought that because woody plants like trees and shrubs have deeper roots than grass, woody plant encroachment resulted in less water entering streams and groundwater aquifers. This belief stemmed from scientists performing their related studies on flat ground.
“It is striking that ecosystem composition is what controls projected future changes to groundwater recharge,” Schreiner-McGraw said. “This does not mean that climate change is not important, but that vegetation change is potentially more important and something that scientists and land managers should focus more effort on understanding.”
Co-author Hoori Ajami, an assistant professor of groundwater hydrology at UC Riverside, said the paper looks at the combined effects of climate and vegetation change on groundwater-recharge processes in arid environments.
“Most studies to date have looked at these changes in isolation,” Ajami said. “Here we illustrate that the combined effects of vegetation change and climate change could be greater or less than the sum of its parts.”
The intrusion of shrubs into grasslands is often considered a problem because it reduces the amount of forage available for livestock grazing and can lead to more bare ground patches and subsequent increase in soil erosion. This process of creating more bare ground is called “xerification.” Climate change contributes to xerification, but fire suppression and overgrazing play the biggest roles.
It makes sense that shrubs, which have deep root systems along with thick stems and many leaves, capture more water than grass does as it percolates down through the soil, leaving less available water to replenish the underground aquifers. Research on “diffuse recharge,” the process by which water replenishes groundwater supplies over a large area, seems to bear this out for flat landscapes. Xerification of grasslands has thus been viewed as bad for both livestock and the water cycle.
“We approached this research with a simple premise that topography plays a role in redistributing available water, and this should affect the outcomes of xerification,” said co-author Enrique R. Vivoni, a professor at Arizona State University.
The group looked at focused recharge, which occurs when hillslopes funnel water into concentrated areas, such as streambeds. Streambeds often have sandy bottoms, which allow water to quickly infiltrate and prevent the deep-rooted shrubs from sucking it up.
Data from a highly monitored desert mountain slope in New Mexico was used to simulate the effects of woody plant encroachment and climate change on water resources. The team discovered that not only did the shrubs increase focused groundwater recharge, but that they did so even under conditions where climate change reduced the amount of rainfall.
They also modeled a more extensive form of shrub encroachment called thicketization, in which plants grow in dense stands with no bare patches, and found, as in prior flat landscape research, the shrubs reduced the amount of groundwater recharge on slopes as well.
On hillslopes, bare soil in between patches of shrubs is necessary to drive water into streambeds. Increased runoff increases focused groundwater recharge.
“We were surprised to find that a transition from grassland to shrubland can increase sustainability of groundwater aquifers,” said Schreiner-McGraw. “The best way to increase focused recharge in this system is to increase the amount of runoff from hillslopes that gets concentrated in the streambeds.”
Climate change will most likely increase groundwater recharge by making rainstorms larger, but less frequent. Larger storms increase the amount of runoff that reaches sandy-bottom channels and increases groundwater recharge. Findings from this study suggest vegetation will also play an important part in groundwater recharge in the future.
Though the study took place in New Mexico, Schreiner-McGraw said it applies to similar environments. Large parts of California are also desert savannahs. Southern California and the Central Valley have landforms similar to those found in the New Mexico study site. These areas could experience similar hydrological processes, though atmospheric rivers create storms very different from monsoon storms, so more research is required.
“The study highlights the role of long-term monitoring in understanding water balance dynamics of watersheds, and the role that process-based modeling plays in understanding system dynamics,” Ajami said.
Here’s the release from the Cary Institute of Ecosystem Studies:
In the Grand Canyon reach of the Colorado River, two species play an outsized role in the fate of mercury in the aquatic ecosystem, and their numbers are altered by flood events. So reports new research, published in Science Advances, that is among the first to meld ecotoxicology and ecosystem ecology to trace how mercury flows through aquatic food webs and then spreads to land.
Mercury is an environmental contaminant that occurs in ecosystems globally. In its organic form, it is a potent neurotoxin that can harm people and wildlife. Mercury accumulation in animals and how it magnifies along food chains is well studied. Less well understood are the pathways mercury takes through food webs to reach top predators, such as fish and birds, and how those pathways might change after large ecosystem disturbances, such as floods.
Emma Rosi is an aquatic ecologist at Cary Institute of Ecosystem Studies and co-lead author on the paper. She explains, “By combining data on mercury concentrations in aquatic life with well-studied food webs, we were able to reveal how mercury moves through an ecosystem. We found that flooding and an invasive species both influenced the flow of this contaminant of global concern.”
The traits of organisms living in an ecosystem – their physiology, what they eat, and what eats them – determine contaminant movement and exposure. These factors have rarely been included in models of contaminant flux and fate. “Pairing contaminant concentrations and highly detailed food webs has the potential to improve the management of contaminants in ecosystems,” Rosi notes.
To study these pathways, the research team developed mercury-based food webs for six sites spanning 225 miles of the Colorado River, extending downstream from the Glen Canyon Dam in Grand Canyon National Park. Food web sampling took place seasonally over two years. At each site, they measured algae, invertebrates, and fish to determine who was eating what – and what that meant for mercury exposure at each level of the food web.
Insects (blackflies and midges) and invasive New Zealand mudsnails were the dominant invertebrates in the river. These animals play a vital role in moving energy and contaminants from the bottom of the food web to fish predators at the top. Fish included native Bluehead Sucker, Flannelmouth Sucker, Speckled Dace, and Humpback Chub, as well as non-native species such as Common Carp, Fathead Minnow, and Rainbow Trout.
The stomach contents of invertebrates and fish were assessed to identify what they ate and in what amounts. Algae, detritus, and animals were analyzed for mercury concentrations and, combined with the diet data, the team estimated the amount of mercury that animals were consuming throughout the year.
Food web complexity varied across the study sites. Just below the Glen Canyon Dam, food webs were simple with few species and food web connections. Further downstream, food webs had higher species diversity and more connections. Across the study sites, regardless of food web complexity, relatively few species were key players in the movement of mercury.
Algae and tiny particles of detritus were the source of 80% of mercury flowing to invertebrates.
In sites closest to the dam, invasive mudsnails dominated the food webs. Trout were the only fish in this part of the river, and they are unable to digest mudsnails. Mercury accumulated by the snails did not move up the food chain. Because the snails are fully aquatic, mercury cycled back into the river’s detrital food web when they died.
Blackfly larvae were the source of 56-80% of the mercury flowing to fish. Blackflies are preferred prey for fish, such as Rainbow Trout, and blackflies had higher mercury contaminations compared to other invertebrates. Blackflies that escape predation and emerge from the river as flying adults move mercury from the river to land. This can expose terrestrial predators, such as birds and bats, to mercury that started out in the river.
The amount of mercury that blackflies moved to land was dependent on the number of hungry fish in any part of the river. At some sites, fish ate nearly 100% of the blackfly larvae, leaving few left to emerge. At other sites, there were a lot more blackflies than the fish could eat. When these blackflies emerged as adults, the mercury inside them hitched a ride to terrestrial food webs along the river.
One year into sampling, the study sites were flooded as part of a planned dam release. The team was able to explore the effects of the flood on mercury movement in the food webs. At sites near the dam, the flood washed away large numbers of New Zealand mudsnails and led to a boom in blackfly populations. With the rise in blackflies, more mercury flowed to trout. Because trout gobbled up nearly all the blackflies in their larval form, very little of the mercury accumulated in these abundant insects was transported to land by the flying adults.
Rosi explains, “Changes to the animal populations in an ecosystem will impact how mercury moves through a food web. This was especially apparent at sites where flooding changed the proportion of blackflies relative to fish. Flooding dramatically altered mercury pathways in the simple tailwater food web near the dam, but not in the more complex food webs downstream.”
“Invasive species and dams are common in rivers globally, and both factors were at play in the Grand Canyon reach of the Colorado River.” Rosi says. “We found that flooding changed the species present at our study sites, and mercury flow changed with those shifts.”
“Understanding the factors that control the movement of mercury through food webs can help resource managers protect ecosystems that are susceptible to mercury pollution,” says David Walters, USGS scientist and co-lead author of the study.
Rosi concludes, “This study is exciting because it sheds light on the depth of understanding we can achieve when we merge ecological and ecotoxicological thinking. Species traits, animal populations, predator-prey interactions, and disturbance can all influence the movement of contaminants in the environment. Understanding the complex interplay of these factors can improve risk management of animal exposures in the environment.”
From the Water Education Foundation (Gary Pitzer):
Western Water in-depth: A key reservoir for Colorado River storage program, Powell faces demands from stakeholders in upper and lower basins with different water needs as runoff is forecast to decline
Sprawled across a desert expanse along the Utah-Arizona border, Lake Powell’s nearly 100-foot high bathtub ring etched on its sandstone walls belie the challenges of a major Colorado River reservoir at less than half-full. How those challenges play out as demand grows for the river’s water amid a changing climate is fueling simmering questions about Powell’s future.
The reservoir, a central piece of the storage program for the Colorado River, provides water, hydropower and recreation to millions of people. It was designed to ensure that Wyoming, Colorado, Utah and New Mexico can meet their legal obligation to let enough water pass to Arizona, California and Nevada, as well as supplying water to Mexico.
But persistent drought in the Colorado River Basin over the last 20 years and the need to keep Lake Mead, Powell’s twin reservoir downstream, from reaching critically low levels have left Lake Powell consistently about half-full. Some environmental advocacy groups, aiming to restore Glen Canyon, have called for the dam’s decommissioning.
Water managers say that’s unlikely, given Lake Powell’s key role in meeting downstream obligations and the interest of some upstream who hope to tap its waters. Recent studies point to warmer and drier conditions ahead, with reduced runoff into the river. A rewrite of the river’s operating guidelines is on the horizon, and already there is talk about how those guidelines could affect Powell.
Lake Powell and Lake Mead currently adhere to an operations protocol that determines release volumes from Lake Powell to Lake Mead and how Lower Basin water users enjoy the benefits of surplus conditions or the shared sacrifice of delivery cuts during shortage. The rules for these scenarios are found in the 2007 Interim Guidelines, the 2019 Drought Contingency Plans and international agreements with Mexico.
Chief among the Guidelines’ provisions is better coordination of the operations of Lake Powell and Lake Mead each year.
As key stakeholders prepare to forge the next set of management guidelines that will update those from 2007, there may be a reassessment of Lake Powell’s operations so that it can take on the coming challenges.
“I think an honest and thorough look into the future of Lake Powell is absolutely warranted,” said Matt Rice, director of American Rivers Colorado Basin Program.
Rice, part of a February forum on the future of Lake Powell, said the crisis wrought by the coronavirus pandemic shows how rare “black swan” events can emerge and shatter existing management plans, such as those for watersheds.
The dry conditions have prompted Colorado River water agencies to undertake unprecedented, collaborative efforts to ensure water supplies are not disrupted. In Las Vegas, for instance, rebates to homeowners by the Southern Nevada Water Authority have converted 193 million square feet of thirsty grass lawns into water-efficient landscaping.
Staying ahead of future crises is critical, and officials are informally discussing the parameters of the next set of guidelines. How those talks affect future water levels at Lake Powell and Lake Mead will be significant.
A Reliable Lake Powell
Conditions on the river are never static. In some years, a large snowpack produces voluminous runoff, but the science is showing a pattern of decreased flow from tributaries into the mainstem Colorado River. Earlier this month, the National Oceanic and Atmospheric Administration’s Colorado Basin River Forecast Center projected inflow to Lake Powell from April to July would be 65 percent of average.
Upper Basin users, meanwhile, want to access their share of Colorado River water to meet growing demands. In Utah, a 140-mile pipeline proposal would divert as much as 86,000 acre-feet annually from Lake Powell to growing communities in the state’s southwest corner. Utah officials believe the $1 billion plan is necessary for places such as St. George that are bumping against their limits of water supply.
Furthermore, Utah officials say the state is well within its right to access water it has rights to.
“Utah’s right to develop water for the Lake Powell Pipeline is equal to, not inferior to, the rights of all the other 1922 [Colorado River] Compact signatory states,” Eric Millis, then-director of the Utah Division of Water Resources, said in a 2019 statement by the state’s Department of Natural Resources. The Colorado River Compact divided the Basin into an upper and lower half, with each having the right to develop and use 7.5 million acre-feet of river water annually.
Meanwhile, the Navajo Nation is also looking at tapping Lake Powell water via pipeline so it can supplement limited groundwater supplies.
“The continued existence of Glen Canyon Dam is imperative if the Navajo Nation is to obtain a reliable supply of water from the Colorado River,” said Stanley Pollack, an attorney for the tribe. “A water line only works if you have Lake Powell.”
In the Upper Basin, there is concern that Lake Powell has been increasingly called on to help Lake Mead, with not much to show for it.
“We are not improving the health of Lake Mead and … until and unless the Lower Basin addresses its overuse … Mead is not going to improve and it’s just going to bring the elevations of Powell down,” said Amy Haas, executive director of the Upper Colorado River Commission.
The storage/release paradigm between the two reservoirs has caused the most tension since adoption of the 2007 Interim Guidelines, said Colby Pellegrino, director of water resources for the Southern Nevada Water Authority.
The Upper Basin recognizes its obligation to let enough river flow pass to the Lower Basin, but occasional machinations with Lake Mead’s storage can be touchy. “Sometimes water is moved from Lake Mead downstream to other reservoirs or water users in a different pattern or timing, prompting concern from people in the Upper Basin that its neighbors seek to game the system,” she said.
The largest reservoir in the United States, Lake Mead receives the lion’s share of attention because of the efforts to keep it viable and supplying water to the many farms and urban areas – Las Vegas, Los Angeles and Phoenix, among them – south of Hoover Dam. In 2015, a third, deeper intake was completed at the lake to keep water flowing to Las Vegas’ 2 million residents and 40 million annual visitors. The lake supplies about 25 percent of the water needs of the Metropolitan Water District of Southern California – even more during drought.
Having a reliable Lake Powell to back up Lake Mead is crucial especially during a period of uncertainty, Lower Basin users say.
“As we get into flashier, more volatile hydrology cycles with climate change we can likely see the occasional huge storm years with less snow and more rain,” said Jeff Kightlinger, general manager of Metropolitan Water District, the largest supplier of treated water in the United States. “Having readily available storage capacity for the occasional mega year will be extremely valuable.”
‘The Most Wonderful Lake in the World’
Controversial from the start, Lake Powell remains polarizing to some degree. Former Bureau of Reclamation Commissioner Floyd Dominy, who spearheaded construction of Glen Canyon Dam that created Lake Powell in the early 1960s, said in a 2000 interview that Powell is “the most wonderful lake in the world [and] my crowning jewel.”
Former Reclamation Commissioner Dan Beard, who served in the 1990s during the Clinton administration, opposes the continued existence of Glen Canyon Dam. Because climate change and further reductions in runoff will cause Lake Powell to keep dropping, he said, stakeholders should focus their energy on saving Lake Mead.
“Lake Mead is the heartbeat of the Colorado River,” Beard said. “It is a vital and important part of the delivery system for water to the Lower Basin states and to Mexico. It is a critical facility and yet it continues to decline.”
Beard is a board member with the advocacy group Save the Colorado, which, along with the Center for Biological Diversity and Living Rivers last year sued the federal government to force examination of climate change science in the management of Glen Canyon Dam.
The litigants say Reclamation and the Department of the Interior should conduct a revised analysis and include a full range of alternatives based on predicted climate change-related impacts on the flow of water in the Colorado River.
“Such a full range must include an alternative that incorporates the decommissioning and removal of Glen Canyon Dam because the projections from the best available climate science indicate there likely will not be sufficient flow in the Colorado River to keep Lake Powell and Glen Canyon Dam operational,” a press release accompanying the lawsuit said.
At capacity, Lake Powell holds more than 26 million acre-feet of water that originates as snowpack from the Upper Basin states of Colorado, Utah, Wyoming and New Mexico. That water gets released to Lake Mead via the Grand Canyon and helps supply the Lower Basin — Arizona, Nevada, California – as well as Mexico.
However, since 2002 Lake Powell’s water elevation has rarely gone above its historical 50-year annual average of 3,639 feet above sea level, the point at which it contains about 15.8 million acre-feet of water. The operating system is flawed, some experts say.
Two years ago, the Colorado River Research Group, a highly respected group of Colorado River scholars including Colorado State University’s Brad Udall and University of Arizona’s Karl Flessa, produced a publication called It’s Hard to Fill a Bathtub When the Drain Is Wide Open: The Case of Lake Powell. In it, they noted that the system is stacked against Lake Powell in part because of an overallocated Colorado River system.
Lake Powell and Lake Mead operate under multiple laws and agreements that are collectively known as the Law of the River. Under the rules, Lake Powell is obligated to release a certain amount of water each year to Lake Mead for the Lower Basin states.
The Lower Basin states, however, collectively draw about 1.2 million acre-feet more water from Lake Mead than Lake Powell releases in a normal year. The result is a so-called “structural deficit.”
“The structural deficit is the true villain in this story, mixing with the operational rules to drain Lake Powell,” the Colorado River Research Group publication said. “If storage in Lake Powell cannot rebound in an era where the Upper Basin consumes less than two‐thirds of its legal apportionment, then the crisis is already real.”
Answers, the authors say, lie partly in the ability of Lake Powell storage to recover in wet years, reducing use in the Upper Basin and re-thinking exiting reservoir management. “Lakes Mead and Powell, after all, are essentially one giant reservoir and … thinking of these facilities as two distinct reservoirs, one for the benefit of the Upper Basin and one for the Lower, now seems outdated,” the publication said.
Haas, with the Upper Colorado River Commission, said the existing operating guidelines leave room for improvement. “I feel very strongly that as long as our reservoir operations are coordinated … the future of Lake Powell hinges on the future of Lake Mead,” she said. “We need to find a more equitable mechanism by which reservoir operations are coordinated.”
Marlon Duke, spokesman with the U.S. Bureau of Reclamation, the federal agency that manages the river, acknowledged that Lake Powell draws scrutiny.
“I often get asked, ‘What’s the deal with Lake Powell?’” he said. “Shouldn’t we just drain it or is it really doing what it is supposed to do?”
The answer, Duke said, means looking at the lake’s performance and how it has met expectations during difficult times. Powell was near capacity in 2000. Then a period of record-setting dryness set in. Through it all, enough water was released to meet the Upper Basin’s obligation to the Lower Basin.
People in the respective basins view Lake Powell and Lake Mead with a certain degree of ownership, and perspectives vary. Upper Basin interests generally want a more robust Lake Powell. South of the lake, the desire to tap into it further is not uncommon in the Lower Basin. The degree of change, ultimately, will likely fall between those sentiments.
All of that notwithstanding, it’s important to understand the two reservoirs are tightly woven, said Jack Schmidt, the Janet Quinney Lawson chair of Colorado River studies at Utah State University.
“It’s one big system and whether Powell [or Mead] goes up or down …those are intentional societal decisions of management that have little to do with climate change,” he said.
Schmidt in 2016 analyzed the concept of “Fill Mead First,” the idea of establishing Lake Mead as the primary water storage facility on the mainstem river and relegating Lake Powell to a secondary storage role when Mead is full. The savings in evaporation and seepage losses would be relatively small, Schmidt said, but the idea shouldn’t be completely discounted.
Fill Mead First “generates passions and emotions,” Schmidt said. It is embraced by some as a restorative opportunity for Glen Canyon. “Then there is the world of traditional water managers who say that’s a ludicrous idea and we don’t pay any attention.”
The disparate views “live in two worlds completely.”
But Kightlinger, with Metropolitan Water District, discounts the idea of draining Powell. “Politically, I don’t see any real support or push for a fill Mead first strategy,” he said. “Powell, even less full going forward, remains a valuable piece of very expensive infrastructure that will remain part of the Colorado River storage pool for decades to come.”
A Warmer and Drier Basin
A small army of water professionals and experts constantly analyze the Colorado River Basin, which supplies water to 40 million people and fuels a huge agricultural economy.
For years, scientists have looked at the drying conditions of the Colorado River Basin, employing techniques such as tree ring sampling. Analysis of that method has shown that the years 1905 to 1922 – just as the river’s waters were being allocated among the states — were exceptionally wet.
In 2012, Reclamation’s Colorado River Basin Water Supply and Demand Study confirmed there are likely to be significant shortfalls in coming decades between projected water supplies and demands in the Colorado River Basin. Since the study, a steady stream of research points to warmer and drier conditions.
In April, a study published in the journal Science said the current dry period in the Southwest is one for the record books, and that its “megadrought-like trajectory” is fueled by natural variability superimposed on human-caused warming. Also in April, experts with the Western Water Assessment, whose researchers work out of the University of Colorado, Boulder and several other institutions in the region, noted that the severity and length of drought conditions can be difficult to quantify.
“This is especially true for the Colorado River system, in which total consumptive use plus other depletions typically exceeds supply, such that under even average hydrologic conditions the levels of Lake Mead and Lake Powell will tend to decline,” according to Colorado River Basin Climate and Hydrology: State of the Science, the study conducted by the Western Water Assessment.
The continued variability justifies a robust Lake Powell, said Haas, with the Upper Colorado River Commission.
“We know that future flows are going to be more variable and almost clearly lower, but we also need to ensure that our non-depletion obligation is satisfied,” she said. “Powell is our repository for this water. Doing away with the reservoir, in light of our 1922 Compact obligation, is not realistic,” she said.
Furthermore, an improved, more accurate forecasting approach is needed ahead of the next set of operating criteria. “That’s especially true given the vicissitudes of hydrology and the impacts of climate change,” Haas said.
Increasing Lake Powell’s releases is potentially problematic because of the likelihood that predator fish from Lake Mead could make it upstream and devastate native fish in the Grand Canyon.
As it stands, Pearce Ferry Rapid, a rugged, impassable cataract located near the downstream end of the Grand Canyon, prevents predators such as catfish, bass and pike from getting upriver and destroying native fish. The rapid exists because Lake Mead, sitting at just 43 percent of capacity, is so low that the inflow to it from the river has carved a new entry where the river plunges over a bedrock ledge.
If Lake Mead ever began to fill again, it would inundate Pearce Ferry Rapid, allowing the non-native fish to migrate upstream and prey on native Colorado River fish. “They would just eat and eat,” said Rice, with American Rivers. “All the recovery of endangered fish could be for naught.”
Playing the Waiting Game
During a period of great uncertainty about what the next water year will bring, Colorado River water users will need to think creatively while using all their tools, including storage.
“Glen Canyon Dam exists because you need all that potential storage,” said Schmidt, with Utah State University. “In some freak years you are going to get really big runoff, and nobody wants to see that go through the system.”
Meanwhile, the lake’s future role in the Colorado River Basin is a key topic as Reclamation reviews the performance of the 2007 Guidelines, with results expected at the end of this year at the annual meeting of Colorado River water users.
Pellegrino with Southern Nevada Water Authority said it would be nice to get past the controversy about Lake Powell’s releases and instead find ways to store more water in it. “We have had a lot of consternation … more because of the balancing releases than the actual behavior of any water user or basin,” she said. “Going back to something that’s more constant or more fixed would remove an element of consternation between the Basins.”
What’s likely to happen is an approach that builds upon the years of collaboration and cooperation established between everyone working on Colorado River water management, said Tina Shields, water manager with the Imperial Irrigation District, the largest user of Colorado River water.
“We know how the river works – its incrementalism,” she said. “Nobody wants to make wholesale changes because it’s too big of a deal and what if it went south? We are not quick to change these relationships and negotiations. They took a lot of time.”
Chris Harris, executive director of the Colorado River Board of California, said Reclamation’s findings will be key in considering the continued conjunctive management of Lake Powell and Lake Mead.
“Certainly, the  Guidelines have shown that managing the reservoirs together has kept Lake Powell from crashing and has kept Lake Mead from a shortage condition,” he said. “I believe that there will be significant interest in evaluating opportunities, including with Mexico, for even more effective management of the reservoir system.”
That process will most likely look at different elevations and trigger points for excess releases from Lake Powell in a manner that’s acceptable to the Upper and Lower Basins.
“The question is, how do you get movement either way without someone saying, ‘That doesn’t work for me,’” Shields said. “Sometimes the status quo is easier to continue than the fear associated with changing those trigger points.”
As with virtually all Colorado River issues, the ramifications of actions can run far and wide. “This sounds like an esoteric argument about something hundreds of miles away, but the reality of it is what happens at Lake Powell affects the amount of water available to the Lower Basin states, Southern California and, indirectly, Northern California,” said Beard, the former Reclamation commissioner.
California’s extensive water plumbing network relies on a careful balance of imports to Southern California from Northern California and the Colorado River.
Even with Reclamation’s review of the guidelines expected to be issued at the end of the year, Schmidt with Utah State University said he believes stakeholders will let multiple years pass before committing to any radical operational changes.
“Every year that we wait buys a little more information about climate change and decreasing runoff and whether we go into a wet cycle,” he said. “There’s a lot of things that could happen and people will hope that nature provides a favorable condition so there can be a tiny bit more wiggle room and we don’t go into dire crisis.”
Haas echoed the comments of many stakeholders in noting that all options for Powell’s operation should be considered. “It’s not heretical to be thinking outside the norm on things,” she said. “It spurs a more robust discussion and we should not shy away from that.”
Reclamation’s Duke harkens back to Powell’s ability to consistently meet and sometimes exceed its release obligations during severe conditions.
“That is a testament to the people who came before and had to make those tough calls,” he said. “They built that reservoir and it’s done what we needed. Looking into the future, everything’s on the table, but we also need to remember there are 40 million people who rely on water from this river and over the last 20 years, we would not have been able to supply that water reliably without these storage reservoirs.”
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A fast-growing Douglas County city has filed a new claim for water on the South Platte River, a move that could allow it to boost its future water supplies by some 60 percent.
But the action could also undermine SPROWG, an innovative, collaborative effort by more than a dozen Front Range communities to capture and reuse water on the South Platte River near the Nebraska state line and return it to Eastern Plains farm communities, northern Front Range cities, and the metro area.
Parker’s legal move to claim water rights in the same region, in partnership with the Sterling-based Lower South Platte Water Conservancy District, is unfolding just as SPROWG completed a major feasibility study indicating its project could be built for roughly $3.2 billion to $4.2 billion.
Parker’s project, slated to be done in about 10 years, would add 20,000 acre-feet to the city’s current supply of 34,400 acre-feet…
Though SPROWG’s feasibility study has been completed, years of planning lie ahead before the cooperative effort is ready to deliver water, with a completion date yet to be set.
“We are light years ahead of them,” said Ron Redd, manager of the Parker Water and Sanitation District. “We’ve offered to partner on anything they want to do. I hope, especially when it comes to storage, they will want to partner. But we are just way ahead of them.”
The Berthoud-based Northern Colorado Water Conservancy District, whose boundary encompasses much of the northern Front Range and extends out to the Nebraska border, is alarmed by Parker’s $500 million proposal, saying it violates the spirit of collaborative water planning embodied in SPROWG and that it could dramatically shrink the amount of water available for others at the table.
“It’s disappointing to me,” said Brad Wind, general manager of Northern Water. “SPROWG was initiated as a community effort. We were going to share the good, the bad and the ugly. When one entity files, it’s a much different process to look at community involvement and decide how to share the yield.”
Parker and the Lower South Platte district plan to develop at least 20,000 acre-feet of water for urban use, a number that rises to 30,000 acre-feet when the agriculture component is added in, according to Joe Frank, manager of the Lower South Platte district.
Frank also said Parker’s project is important to northeastern Colorado because it won’t result in a permanent dry-up of farmland and will give farmers in his district a more reliable source of water, helping stabilize farm communities that are already struggling.
Parker’s Redd said he’s hopeful, given the similarities between the two proposals, that a partnership can be developed with the existing SPROWG collaboration.
“I like the idea of controlling our own destiny,” he said. “And right now we’re assuming we’re going it alone. But my hope is they will join us.”
Jerd Smith is editor of Fresh Water News. She can be reached at 720-398-6474, via email at firstname.lastname@example.org or @jerd_smith.