Thursday, May 23, 2024

Rising temperatures will significantly reduce streamflow in the upper Colorado river basin as groundwater levels fall, new research shows

Climate change will dramatically impact streamflow and its contributions to the Colorado River by increasing forest water use and reducing groundwater levels, new study finds.

DESERT RESEARCH INSTITUTE

Fig2 — IMAGE:
*THE ILLUSTRATION ABOVE SHOWS HISTORICAL ATMOSPHERIC AND ENVIRONMENTAL WATER LOSS AND CONTRIBUTIONS. FROM FIGURE 2 OF CAROLL ET AL.*
view more
CREDIT: CAROLL ET AL

The Colorado River makes life possible in many Western cities and supports agriculture that sustains people throughout the country. Most of the river’s water begins as snowmelt from the mountainous watersheds of Colorado, Utah, and Wyoming, and a warming climate will drastically reduce these streamflows, new research finds.

Researchers from Desert Research Institute (DRI), USGS, and Lawrence Berkeley National Laboratory teamed up for the new study, published May 23 in Nature Water. By applying warming to historical conditions for the East River in Colorado and using computer simulations to observe the impact on streamflow and groundwater levels, the scientists found that groundwater storage would fall to the lowest known levels after the first extremely dry year and fail to recover even after multiple wet periods. When groundwater levels fall, streamflows are drawn into the water table instead of contributing to Colorado River flows.

“We found that groundwater matters a lot,” says Rosemary Carroll, Ph.D., DRI research professor of hydrology and lead author of the study. “Even with historically observed wet periods in the model, the groundwater can’t come back from a single dry water year under end-of-century warming.”

The Colorado River has been in a drought state for decades, creating tensions around water rights throughout the Southwest. Scientists have been perplexed by falling river levels even in relatively wet years – in 2021, the Upper Colorado River Basin reached 80% normal snowpack but delivered only 30% of average streamflow to the river. The study authors wanted to examine how warming in mountain basins may be contributing to this phenomenon. Increased temperatures alter the balance between snowfall and water availability in a number of ways, including more snow evaporation (known as sublimation), more precipitation falling as rain instead of snow, and more frequent melting throughout the winter.

Past research has largely overlooked the role of groundwater and how it may buffer, or intensify, streamflow loss from climate change.

“I’m very interested in the relationship of groundwater contributions to streamflow – that has been a running theme in my research for a long time,” Carroll says. “A lot of studies indicate that in the short term, groundwater release to streamflow will help buffer drought impacts, but before this study, we didn’t have any knowledge on what that would mean over the long haul.”

The study authors used the East River as the focus for the research because it is representative of the headwaters of the Colorado River, as well as the significant weather and water monitoring infrastructure available. Ground observations and airborne mapping measure snowpack depth and density, streamflow, plant cover, and groundwater levels, among many other measurements throughout the watershed.

Historical data from 1987 to 2022 was used to create the computer model. The research team then applied 4 degrees Celsius of warming to this time period in two ways: for one simulation, warming was applied constantly across time, while in subsequent simulations, warming was applied to each season independently. The approach allowed the scientists to examine the differing impacts of warming between seasons. Four degrees Celsius is representative of the projected climate at the end of the century based on observed warming of approximately 0.4 degrees Celsius per decade in the watershed. The simulation doesn’t account for likely changes in vegetation over the same timeframe.

The study showed that consistently warmer temperatures resulted in sharp declines in groundwater levels that were unable to recover to historical average levels during wet periods. Isolating the warming seasonally demonstrated the strong impact of warmer summers on water table declines, as the atmosphere increases evaporation rates, plants increase their water uptake, and soils dry out. The largest declines in water table elevations occur in the subalpine forests where conifer forests are most dense.

“As the groundwater level drops, you lose more streamflow to the water table,” Carroll says. “When precipitation is low, the East River stops flowing for a portion of the summer. Of course, this would have dramatic effects on ecological health and agricultural irrigation.”

By including declining water table levels in the analysis, the study found that streamflow reductions nearly double when compared to simulations that examined the impacts of climate change in the region without accounting for groundwater declines. This is because of the multiple impacts occurring simultaneously: less water flows to streams from the aquifers, while more stream water drains into the soil.

The research demonstrates the need to jointly manage forest and groundwater in the Upper Colorado River Basin, as well as account for the exchange of surface and groundwater in mountains basins, to minimize streamflow declines under climate change, Carroll says.

“I think of groundwater as your savings account,” she adds. “Snowpack is like your checking account; it changes from year to year. Groundwater is a longer-term investment -- it can smooth out the really wet and dry years. But if you start consistently reducing that groundwater year after year, then you can no longer modulate those extremes.”

Fig8 (IMAGE)

DESERT RESEARCH INSTITUTE

*The graphic above illustrates how declining water tables under climate change would decrease streamflows. By Jeremey Snyder, from Figure 8 of Carroll et al.*
CREDIT
Jeremey Snyder, from Figure 8 of Carroll et al.

More information: The full study, Declining Groundwater Storage Expected to Amplify Mountain Streamflow Reductions in a Warmer World, is available from Nature Water at (https://www.nature.com/articles/s44221-024-00239-0

Funding for the study came from the U.S. Department of Energy Office of Science and Office of Biological and Environmental Research.

Study authors include: Rosemary Carroll (DRI), Richard Niswonger (USGS), Craig Ulrich (Lawrence Berkeley National Laboratory), Charuleka Varadharajan (Lawrence Berkeley National Laboratory), Erica Siirila-Woodburn (Lawrence Berkeley National Laboratory), and Kenneth Williams (Rocky Mountain Biological Laboratory)

About DRI

We are Nevada’s non-profit research institute, founded in 1959 to empower experts to focus on science that matters. We work with communities across the state — and the world — to address their most pressing scientific questions. We’re proud that our scientists continuously produce solutions that better human and environmental health.

Scientists at DRI are encouraged to follow their research interests across the traditional boundaries of scientific fields, collaborating across DRI and with scientists worldwide. All faculty support their own research through grants, bringing in nearly $5 to the Nevada economy for every $1 of state funds received. With more than 600 scientists, engineers, students, and staff across our Reno and Las Vegas campuses, we conducted more than $47 million in sponsored research focused on improving peoples’ lives in 2023 alone.

At DRI, science isn’t merely academic — it’s the key to future-proofing our communities and building a better world. For more information, please visit www.dri.edu.

JOURNAL

Nature Water

ARTICLE TITLE

Declining Groundwater Storage Expected to Amplify Mountain Streamflow Reductions in a Warmer World

ARTICLE PUBLICATION DATE

23-May-2024

Birdsong and human voice built from same genetic blueprint

UNIVERSITY OF TEXAS AT AUSTIN

Syrinx and Larynx evolution figure — IMAGE:
RECENT RESEARCH HAS REVEALED A COMMON GENETIC LINK BETWEEN THE LARYNX – THE VOCAL ORGAN OF MAMMALS, REPTILES, AND AMPHIBIANS – AND THE SYRINX – THE VOCAL ORGAN OF BIRDS. THIS FIGURE ILLUSTRATES THE EVOLUTION OF THE LARYNX AND SYRINX IN DIFFERENT ANIMAL LINEAGES. ALTHOUGH BIRDS ARE DIRECT DESCENDANTS OF DINOSAURS AND HAVE BOTH A LARYNX AND A SYRINX, IT’S UNKNOWN IF DINOSAURS HAD EITHER ORGAN.
view more
CREDIT: MICHAEL CHIAPPONE

Humans have been long fascinated by bird song and the cacophony of other avian sounds — from coos and honks to quacks and peeps. But little is known about how the unique vocal organ of birds — the syrinx — varies from species to species or its deeper evolutionary origins.

A trio of recent studies led by researchers from The University of Texas at Austin is changing that.

The studies include high-resolution anatomical scans of syrinxes from hummingbirds and ostriches — the world’s smallest and largest bird species — and the discovery that the syrinx and larynx, the vocal organ of reptiles and mammals, including humans, share the same developmental programming.

According to Julia Clarke, a professor at UT’s Jackson School of Geosciences, this genetic connection between the vocal organs is an exciting new example of “deep homology,” a term that describes how different tissues or organs can share a common genetic link.

“To me, this is as big as the flippers-to-limbs transition,” said Clarke, who co-led or co-authored the studies. “In some ways, it’s even bigger because the syrinx is not a modified organ with a new function but a completely new one with an ancient and common function.”

The three studies are built on a foundation of collaborative and interdisciplinary syrinx research with physiologists and developmental biologists that Clarke has been leading for over a decade. The research got its start in 2013 when Clarke, a paleontologist, discovered a syrinx in a fossil of a duck-like bird that lived in what is now Antarctica during the Late Cretaceous. The specimen is the oldest syrinx to be discovered. But when she tried to compare the fossil syrinx to the syrinxes of modern birds, she found the scientific literature lacking. Many of the studies dated back to the 19th century, before the advent of modern scientific imaging, or cited claims from those older studies made without double-checking them.

This set Clarke on a mission to modernize — and maximize — syrinx data collection.

“We had this new three-dimensional structure, but we had nothing to compare it to,” said Clarke, describing CT imaging data of the fossil syrinx. “So, we started generating data that did not previously exist on syrinx structure across many different groups of birds.”

Over the years, Clarke and members of her lab have developed new methods for dissecting, preserving and CT-scanning syrinxes that have helped reveal the syrinx in more detail. These enhanced views of the ostrich and hummingbird vocal organ have shown that bird behavior may be just as important as the syrinx when it comes to the repertoire of sounds these birds produce.

For example, in the study of the ostrich syrinx, the researchers found no significant differences in syrinx anatomy between adult male and female birds (previous studies focused only on male ostriches.) However, even though both sexes have the same vocal equipment, male ostriches tended to make a wider variety of sounds than female ostriches, with the sounds often associated with aggressive behaviors between rowdy males. On a visit to a Texas ostrich farm, the researchers recorded 11 types of calls, ranging from high frequency peeps and gurgles in baby ostriches to low frequency boos and booms in adult males. These included a few call types that had never been recorded before. The only sounds definitively recorded from adult female ostriches were hisses. What the females lacked in range, they made up for in attitude said Michael Chiappone, who became involved with the ostrich research as an undergraduate student at the Jackson School and is the lead author of the study.

“They were quite prolific hissers,” said Chiappone, who is now a doctoral student at the University of Minnesota.

For the hummingbird study, the researchers compared the hummingbird syrinx to the syrinx of swifts and nightjars, two close relatives, and found that all three birds have similar vocal folds in their syrinx despite having different ways of learning their calls. Swifts and nightjars work with a limited repertoire of instinctive calls while hummingbirds are able to elaborate on calls by learning complex songs from each other, a trait called vocal learning.

According to Lucas Legendre, a Jackson School research associate who led the hummingbird research, the findings suggest that the common ancestor of all three birds also had a similar vocal fold structure — and that it may have helped lay the groundwork for the evolution in vocal learning in hummingbirds.

“Having all of the [vocal fold] structures already present before vocal learning was acquired by hummingbirds probably made it easier for them to acquire vocal production learning,” he said.

Before the study, it was uncertain if swifts even had vocal folds. As part of the research, Legendre created a 3D digital model of the swift vocal track that takes viewers down the windpipe to the syrinx and to the vocal folds that rest near the top of each branch of the syrinx. The model — dubbed the “magical mystery voyage” by Clarke — shows the advances in anatomical knowledge of syrinx that her lab is leading.

“This is a structure that wasn’t known to exist outside of hummingbirds, but our CT scans revealed that swifts have these vocal folds in the same position,” Clarke said. “This is the kind of voyage we needed to go on to get these answers.”

At the same time Clarke and her team were developing methods to preserve and capture syrinx anatomy across bird species, they were collaborating with Clifford Tabin, a developmental biologist at Harvard University, on investigating the evolutionary origins of the syrinx by tracking the gene expression that accompanied vocal organ development in the embryos of birds, mammals and reptiles.

The research published in Current Biology is a culmination of that collaboration. The study details how scientists discovered the deep connection between the larynx and the syrinx tissues by observing that the same genes were controlling the development of the vocal organs in mice and chicken embryos, respectively, even though the organs arose from different embryological layers.

“They form under the influence of the same genetic pathways, ultimately giving the vocal tissue similar cellular structure and vibratory properties in birds and mammals,” said Tabin, a co-lead on the study.

The study also analyzed syrinx development across bird species — which involved observing gene expression in embryos from 14 different species, from penguins to budgies — and found that the common ancestor of modern birds probably had a syrinx with two sound sources, or two independently functioning vocal folds. This trait is found in songbirds today, allowing many to create two distinct sounds at the same time. The research suggests that that the common ancestor of birds may have been making similarly diverse calls.

These results may shed light on the syrinx’s origins but it’s still unknown when the syrinx first developed and whether non-avian dinosaurs — the ancestors of today’s birds — had the vocal organ, said Clarke. No one has yet found a fossil syrinx from a non-avian dinosaur.

According to Clarke, the best way to understand the possibilities for ancient dinosaur sounds is to continue studying vocalization as it exists today in birds, the dinosaurs that are still with us, and other reptile cousins.

“We can’t start talking about sound production in dinosaurs until we truly understand the system in living species,” she said.

This research was supported by the Gordon and Betty Moore Foundation, Howard Hughes Medical Institute Professors Program and the Jackson School of Geosciences. Chad Eliason, a senior research scientist at the Field Museum of Natural History and former postdoctoral scholar at the Jackson School, was also a major contributor to these syrinx projects and others.

Julia Clarke on Vega Island in Antarctica.

CREDIT

Julia Clarke/ The University of Texas at Austin

Researchers from the Clarke Lab at The University of Texas at Austin record ostrich sounds on a farm in Texas. Carlos Antonio Rodriguez-Saltos (left) holds recording equipment while Michael Chiappone takes photos.

CREDIT

Michael Chiappone