Drought-Stricken Colorado River Basin Could See Additional 20% Drop in Water Flow by 2050
By Jan Ellen Spiegel
Colorado is no stranger to drought. The current one is closing in on 20 years, and a rainy or snowy season here and there won't change the trajectory.
This is what climate change has brought.
"Aridification" is what Bradley Udall formally calls the situation in the western U.S. But perhaps more accurately, he calls it hot drought – heat-induced lack of water due to climate change. That was the core of research released in 2017 by Udall, a senior climate and water scientist at Colorado State University's Colorado Water Center, and Jonathan Overpeck at the University of Michigan.
Their revelation was that the heat from climate change was propelling drought. "Previous comparable droughts were caused by a lack of precipitation, not high temperatures," the study said. And all the factors at play were having compounding effects on each other that made the situation even worse. Those impacts were being felt most acutely on the biggest water system in the West – the Colorado River Basin.
Without a dramatic and fast reversal in greenhouse gas emissions to slow climate change, Udall and Overpeck said, the additional loss of flow in the basin could be more than 20% by mid-century and 35% at the century's end – worse than currently assumed.
"I always say climate change is water change," says Udall, whose father was Arizona congressman Morris (Mo) Udall, an iconic environmental activist. "It means too much water, not enough water, water at the wrong time. It means reduced water quality. You get all of these things together as the earth warms up."
In Colorado it's all pretty much coming true. The drought is the second worst 20-year period in the past 1,200 years, according to Udall. This summer/fall alone had some of the hottest spells on record and the worst wildfire season ever. On the other hand, 2013 brought catastrophic floods to the Front Range. "I got 17 inches of water in my house here in four days. It's all part of the same change," Udall says.
It's forced Colorado to start facing the reality that its perpetual struggle for water can no longer be written off as cyclical weather that will all balance-out over short periods of time. It's climate change at work, and it requires long-term planning and likely fundamental changes to the paradigm of how the state gets, uses, and preserves its water.
The state and individual municipalities are beginning to address their new reality with policies that range from the obvious – conservation, just using less water, to the more innovative – considering using beaver dams to restore mountain wetlands and generally remediating the landscape to better handle water.
But all those actions and more must face the political reality of the longstanding way water-sharing is handled in the basin. It pits state against state, rural against urban, agriculture against, well, everyone.
The Colorado River Compact
The Colorado River Basin provides water to a massive swath of the Rocky Mountain and western states. The Compact that rules it dates to 1922, with California, Nevada and Arizona – the lower basin states – essentially getting first dibs on water that flows from upper basin states – Colorado, Wyoming, New Mexico, and Utah – with secondary access to the water, so they generally absorb the brunt of water losses.
Colorado is a headwaters state – where the river flows down from the continental divide. It relies on whatever falls out of the sky: It does not have the luxury of access to whatever water may flow in farther downstream.
A process to re-evaluate aspects of the Compact is underway with a 2026 deadline. No one expects the basic structure to change, though other contingencies are likely to be layered on, as has happened a number of times in the intervening years.
River levels are off some 20% since the Compact was initiated, compounding the water crunch while the region's population has grown dramatically, especially in Colorado. That combination of factors have many water experts and administrators convinced any new strategy has to do more than divvy-up the water differently.
That's because it's climate change and not cyclical weather causing the problems, Udall says emphatically: "Yup. Yup. Yup." He notes that scientists already see impacts they hadn't expected to see until 2050.
"I think some of the predictions about reduced flows in the Colorado River based on global warming are so dire it's difficult to wrap your brain around them. We have no operating rules for that kind of reduction in supply," says Anne Castle, a senior fellow at the Getches-Wilkinson Center for Natural Resources at the University of Colorado. "Even with these discussions that will be taking place over the next five years for the Colorado River system, I'm not sure that they will be able to get to an agreement about what would happen if flow is reduced by 50%."
The critical climate change impacts seem to act in a loop: heat causes more evaporation of surface water. The resulting lower water level means water will warm more easily, and in turn evaporates more readily.
Global warming is also changing the dynamics of snowpacks. They melt faster and earlier and don't regularly continue to slowly dissipate, creating a gradual runoff that is more beneficial and sustaining to the water supply. Udall notes that on April 1, 2020, there was 100% of normal snowpack above Lake Powell, which with Lake Mead are the two enormous reservoirs in the system. In a normal year that would provide 90-110% of runoff. But it provided only 52% in 2020 as a result of dry warm weather through fall.
Sustainable water supplies are also threatened as weather events occur more often as extremes: major rains in a short period of time sandwiched by extended dry periods. Torrential rains that follow a long drought may help the soil, but runoff may never make it to the water supply.
Wildfires, in recent years larger and longer, complicate matters by dumping ash and crud into water bodies, which results in less water and contamination that can render unusable what water there is. And if difficult climate conditions keep trees from growing back after fires, the resulting ecosystem changes could further damage water supplies.
Big Ideas in Place
"This is not your average variability," says Andy Mueller, general manager of the Colorado River Water Conservation District, which covers most of the water used by the state. "Cooperative management of water resources can really help in these hot dry summers," he says.
Mueller says the district tried releasing additional water from a reservoir that also creates hydropower. The extra water helps cool the river it flows into – slowing evaporation and allowing fishing and other activities often stopped when the water gets too warm and low to resume. That same water was also used for other hydropower plants downstream. Some then continued to other river areas. And some was diverted for crop irrigation, important given that farming and ranching are the biggest consumers of water in the state.
Basic conservation – just using less water – is always the first step, but even Colorado Water Conservation Board senior climate specialist Megan Holcomb admits: "We're definitely beyond that conversation."
The Board is considering systems that employ the technique of demand management: finding ways to use minimal water to allow for storage for dry years. So far, the thinking involves a voluntary program.
Already in place is an online tool called the Future Avoided Cost Explorer or FACE: Hazards. It helps quantify impacts of drought and wildfires on sectors of the Colorado economy.
"We know these hazards are going to continue to impact our economy, but we have no numbers to even say how much we should invest now so that we don't have financial impacts in the future," Holcomb says.
Castle talks about ideas such as consideration of water footprints on new developments and re-developments; integrating land use planning with water planning including things such as landscaping codes; and use of technology at various levels of water monitoring.
In Search of More Equitable Sharing of Water
She notes also a drought contingency plan adopted in 2019 by the Compact states calling for reductions in deliveries to the lower basin. It's pointed in the right direction, she says. "At the same time pretty much everyone involved in those discussions and that agreement also agreed that it was not sufficient," Castle says.
Many experts have called for more equitable sharing of water reductions. But ideas on what is fair differ from state-to-state and also among different groups within a region where some interests are pitted against agriculture, which accounts for 80% of the water usage in the basin.
"I think people look at that huge volume of water being used in irrigated agriculture as a place where there's flexibility. And when you get to the politics of working through that in an equitable way, it gets really complicated," says Jennifer Pitt, Colorado River program director for the National Audubon Society.
The suggestions have included crop switching or alternative transfer mechanisms that call on farmers to periodically grow less water-intensive crops, or pay them not to grow, as a way to make water available for municipal use or storage.
"From a pure economic perspective, it may seem like you pay them and they're whole," Udall says. "There are actually a lot of things where they don't get whole. They potentially lose a market that they've established over years and a great relationship with a buyer. And if that goes away for a year, that buyer may not come back."
In the end, experts say people in the Southwest should definitely not count on more precipitation arriving to bail them out. "I would disabuse people of the idea that you're going to get more water," Udall says. "I think it's pretty clear you're going to have less water." So for folks who think building more reservoirs is a solution, Udall says: "It's not at all clear to me that that works."
But less conventional strategies just might.
Beaver Dams to the Rescue?
Beaver dams are a water management technique that has worked in nature for eons – at least for beavers. Sometimes for people? Not so much.
But the thinking is they could help slow water loss from high-elevation wetlands. That includes the real deals built by beavers or human-constructed beaver dam alternatives.
"We think there's a possible synergy there that helps to improve water supply for water users and helps to improve habitat conditions for species – birds in particular – that depend on that kind of wetlands being around," Pitt says.
The goal would be to protect remaining ones, help establish new ones, and do the same for high-elevation meadows.
A lot of research is still needed, Pitt says. "There's all kinds of instrumentation that has to go into place to understand the groundwater, the surface water, evaporation, the water balance, what it does to your river downstream," she says. There are water law considerations. And then the inevitable pilot projects.
Overall, she says, this type of holistic approach to water through natural ecosystem restoration could become a component of water-sharing agreements as have already been done with Mexico. In exchange for getting river areas restored to better flow, Mexico agreed to a sharing agreement it might not otherwise have.
More People, Less Water, and a Touch of Johnny Appleseed
More people and less water has forced Denver Water to work with uncertainties not previously considered. "Variability is the name of the game in Colorado," says lead climate scientist Laurna Kaatz. "And that variability's going to increase over time. That makes it incredibly challenging to continuously provide high-quality drinking water when you're not sure what's coming around the corner."
The situation calls for adaptive capacity, she says, to provide technical and legal flexibility to adjust for changing circumstances.
Kaatz pointed to the One Water project that pairs water with usage. For instance, treated wastewater could be used to water a golf course, saving the purest water for drinking.
Another project is called From Forests to Faucets, which works on watersheds as natural infrastructure to optimize water flow. It has already proved successful at keeping a wildfire in 2018 from encroaching on a reservoir. In April, Denver Water plans to expand its Airborne Snow Observatory, which uses technology developed by NASA to track snow availability, but now it can be deployed above an altitude of 8,000 feet.
Together the efforts seem to be working – since the 2002 drought, Denver Water has maintained a 22% per-person reduction in water usage from pre-drought levels.
Steamboat Springs is opting for tree-planting. The idea is that trees will help cool down the Yampa River, which is part of the Colorado River Basin. Hot, dry seasons had been pushing stream temperatures so high that part of the river wound up on EPA's impaired waterbody list.
"That was a call to action," says Kelly Romero-Heaney, Steamboat Springs' water resources manager.
The timing also dovetailed with the 2015 release of a Colorado Water Plan that included goals for stream management. Steamboat Springs did a streamflow management plan – released in 2018. In it was the idea of shading the Yampa.
"What we learned was that flow alone cannot overcome the thermal load for the solar radiation, as strength of that radiation increases over time," she says. "The more that we can prepare the river for that, the better it will buffer against the impacts of climate change."
They joined forces with the Yampa Valley Sustainability Council's ReTree program that began in 2010 as a reforestation effort to counteract trees killed by pine beetle infestations. It morphed into a three-year Yampa River restoration.
"That work also increases resilience to future changes," says Michelle Stewart, the council's executive director. "We're really learning the important role soil moisture plays in resilience."
ReTree planted 200 narrow leaf cottonwoods in 2019 and another 350 this past October. This coming October, its plans are for 450 cottonwoods and 150 mountain alders. All were raised at the Colorado State Forest Nursery from Yampa Valley clippings. "We're using local trees that are already kind of adapting to big swings in temperature and probably have a little bit more of that hardiness that we need and drought readiness," she says.
It's too early to know how the shading is working but there are plans for citizen help to monitor that and to implement a soil moisture monitoring network in the Yampa Basin.
"This is a Johnny Appleseed project," says Romero-Heaney. "We plant today and hopefully my children will get to enjoy it."
Reposted with permission from Yale Climate Connections.
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