Climate change is shrinking the West’s water supply

Three new studies show dry times ahead.

 

Picture a snowflake drifting down from a frigid February sky in western Colorado and settling high in the Rocky Mountains. By mid-April, the alpine snowpack is likely at its peak. Warming temperatures in May or June will then melt the snow, sending droplets rushing down a mountain stream or seeping into the soil to replenish an aquifer.

The West’s water supply depends on each of these interconnected sources: the frozen reservoir of snow atop mountain peaks, mighty rivers like the Colorado and groundwater reserves deep below the earth’s surface. But the snowpack is becoming less reliable, one of the region’s most important rivers is diminishing and in many places the groundwater level has dropped. Three recent studies illuminate the magnitude of these declines, the role climate change has played and the outlook for the future.

All three studies point to the influence of a warming climate. “Climate change is real, it’s here now, it’s serious and it’s impacting our water supplies in a way that will affect all of us,” says Bradley Udall, a water and climate researcher at Colorado State University. The situation is dire, he says, but reining in greenhouse gas emissions now could help keep the mountains covered with snow and the rivers and aquifers wet.

Courtesy EcoFlight

The study: “The twenty-first century Colorado River hot drought and implications for the future,” Water Resources Research, February/March 2017.

The takeaway: On average, Colorado River flows were nearly 20 percent lower between 2000 and 2014 compared to the historical norm. Warm weather caused by climate change — not just a lack of precipitation — was the culprit. As the mercury continues to climb, the Colorado could drop by more than half by century’s end.

What it means: The Colorado River basin has been in a drought since 2000. Warmer-than-normal temperatures were responsible for about a third of the flow declines. The upper basin is 1.6 degrees Fahrenheit warmer now than during the 1900s, meaning more water is lost to the atmosphere through evaporation from soil, streams and other water bodies. Plants also use more water when it’s hot, partly because the growing season is longer.

Declining flows will further stress the already over-allocated river, which supplies nearly 40 million people in two countries. The authors note that the basin would need a precipitation spike of 4 to 20 percent to counterbalance the flow-reducing effect of future warmer temperatures — “a major and unprecedented change” compared to the past.

Arizona, California and Nevada have been negotiating to reduce their demands on the Colorado, but haven’t agreed on a final plan to address future shortages. “Frankly, that drought contingency plan needs to be put in place just to deal with the river as it is today,” Udall, a study co-author, told the Washington Post. And while the plan will help get the lower basin into balance, it may not be enough to deal with future declines big enough to impact the entire basin, which also includes parts of Colorado, New Mexico, Utah and Wyoming.


Courtesy EcoFlight

The study: “Large near-term projected snowpack loss over the western United States,” Nature Communications, April 2017.

The takeaway: The West’s mountain snowpack supplies about two-thirds of the region’s water. But it dropped by 10 to 20 percent between the 1980s and 2000s. Within the next three decades, the snowpack could further shrink, by as much as 60 percent.

What it means: Measurements of the amount of water held within snow from hundreds of stations from Washington to New Mexico revealed the extent of the decline in recent decades. Simulations showed that natural elements alone, like volcanic and solar activity, were not enough to account for the dip. Including factors influenced by humans — like changes in greenhouse gas concentrations — produced models that matched historical reality, implicating climate change as the cause of the snowpack loss.

The study’s predictions for the future range from a drastic drop in snowpack to even a slight gain by 2040. Climate change alone will likely cause a further decrease of about 30 percent, says study co-author John Fyfe, a researcher at Environment and Climate Change Canada. But natural variations in atmospheric conditions above the Pacific could temporarily make the decline worse — or nix it, depending on how they fluctuate. So water managers need to be prepared for both extremes. “It’s a cyclic phenomenon,” Fyfe says. “It’s eventually going to come around and bite you.”


J. Carl Ganter/Circle of Blue

The study: “Depletion and response of deep groundwater to climate-induced pumping variability,” Nature Geoscience, January 2017.

The takeaway: Aquifers have been drawn down in several areas across the country. In parts of California and Nevada, however, groundwater levels have actually risen, perhaps reflecting the success of regulations and recharge projects.

What it means: Aquifer levels declined in about half of the deep groundwater wells monitored nationwide between 1940 and 2015. The lower Mississippi basin, the High Plains over the Ogallala Aquifer, and California’s Central Valley overall have experienced some of the nation’s highest rates of groundwater depletion in recent years. The study found that during dry periods, water users pump more even as natural recharge diminishes, leading to rapid drawdowns in aquifers. Regional studies in Idaho and California reveal a similar pattern of overdraft, particularly during droughts. That can lead to dry wells, land subsidence, ecological damage and other problems.

Sometimes, however, those trends can be reversed. Researchers also found that groundwater levels rose in about 20 percent of the wells, including around Las Vegas and in limited sections of the Central Valley, while the remainder of the wells showed no change. Tess Russo, a hydrologist at Pennsylvania State University and study co-author, cautions that the groundwater level increases could be misleading in places — some wells were monitored for as little as ten years, and if that period happened to be particularly rainy, measurements may not represent an area’s long-term history.

But wet periods and groundwater recharge projects have helped replenish some aquifers. “In many cases, we have plenty of water,” Russo says. Alleviating water stress may be a matter of changing policies and management, including how and where specific crops are grown.

Emily Benson is an editorial intern at High Country News.

High Country News Classifieds
  • WATERSHED RESTORATION DIRECTOR
    $58k-$70k + benefits to oversee watershed restoration projects that fulfill our strategic goals across urban and rural areas within the bi-national Santa Cruz and San...
  • CUSTOMER SERVICE ASSISTANT - (PART-TIME)
    High Country News, an award-winning media organization covering the communities and environment of the Western United States, seeks a part-time Customer Service Assistant, based at...
  • OPERATIONS DIRECTOR
    We are a Santa Fe-based nonprofit that builds resilience on arid working lands. We foster ecological, economic, and social health through education, innovation, and collaboration....
  • COMMUNITY ORGANIZER
    Come work alongside everyday Montanans to project our clean air, water, and build thriving communities! Competitive salary, health insurance, pension, generous vacation time and sabbatical....
  • CAMPAIGN MANAGER
    Oregon Natural Desert Association (ONDA), a nonprofit conservation organization dedicated to protecting, defending and restoring Oregon's high desert, seeks a Campaign Manager to works as...
  • HECHO DEPUTY DIRECTOR
    Hispanics Enjoying Camping, Hunting, and the Outdoors (HECHO) was created in 2013 to help fulfill our duty to conserve and protect our public lands for...
  • REGIONAL REPRESENTATIVE, COLUMBIA CASCADES
    The Regional Representative serves as PCTA's primary staff on the ground along the trail working closely with staff, volunteers, and nonprofit and agency partners. This...
  • FINANCE AND OPERATIONS DIRECTOR
    The Montana Land Reliance (MLR) seeks a full-time Finance and Operations Director to manage the internal functions of MLR and its nonprofit affiliates. Key areas...
  • DIRECTOR OF CONSERVATION
    The Nature Conservancy is recruiting for a Director of Conservation. Provides strategic leadership and support for all of the Conservancy's conservation work in Arizona. The...
  • EXECUTIVE DIRECTOR
    The Amargosa Conservancy (AC), a conservation nonprofit dedicated to standing up for water and biodiversity in the Death Valley region, seeks an executive director to...
  • BIG BASIN SENIOR PROJECT PLANNER - CLIMATE ADAPTATION & RESILIENCE
    Parks California Big Basin Senior Project Planner - Climate Adaptation & Resilience ORGANIZATION BACKGROUND Parks California is a new organization working to ensure that our...
  • SCIENCE PROJECT MANAGER
    About Long Live the Kings (LLTK) Our mission is to restore wild salmon and steelhead and support sustainable fishing in the Pacific Northwest. Since 1986,...
  • HUMAN RESOURCES GENERALIST
    Honor the Earth is an affirmative action/equal opportunity employer and does not discriminate based on identity. Indigenous people, people of color, Two-Spirit or LGBTQA+ people,...
  • NEW BOOK BY AWARD-WINNING WILDLIFE BIOLOGIST, BRUCE SMITH
    In a perilous place at the roof of the world, an orphaned mountain goat is rescued from certain death by a mysterious raven.This middle-grade novel,...
  • MOUNTAIN LOTS FOR SALE
    Multiple lots in gated community only 5 miles from Great Sand Dunes National Park. Seasonal flowing streams. Year round road maintenance.
  • RURAL ACREAGE OUTSIDE SILVER CITY, NM
    Country living just minutes from town! 20 acres with great views makes a perfect spot for your custom home. Nice oaks and juniper. Cassie Carver,...
  • A FIVE STAR FOREST SETTING WITH SECLUSION AND SEPARATENESS
    This home is for a discerning buyer in search of a forest setting of premier seclusion & separateness. Surrounded on all sides by USFS land...
  • CARPENTER WANTED
    CARPENTER WANTED. Come to Ketchikan and check out the Rainforest on the coast, HIke the shorelines, hug the big trees, watch deer in the muskeg...
  • CAUCASIAN OVCHARKA PUPPIES
    Strong loyal companions. Ready to protect your family and property. Proven against wolves and grizzlies. Imported bloodlines. Well socialized.
  • ENVIRONMENTAL GEOPHYSICS
    "More Data, Less Digging" Find groundwater and reduce excavation costs!