Climate change will result in more drought, heat waves, floods and low river flows in seven western states
DOE / LOS ALAMOS NATIONAL LABORATORY
PICTURE: EXTREME HYDROLOGICAL / CLIMATOLOGICAL EVENTS OVER THE COLORADO RIVER BASIN SHOULD BE STUDIED TOGETHER, NOT IN ISOLATION, TO GET A CLEARER PICTURE OF THEIR DESTRUCTIVE EFFECTS IN THE COMING YEARS. Show more CREDIT: NONE
LOS ALAMOS, NM, April 6, 2021 – In the vast Colorado River basin, climate change is leading to extreme, interconnected events between elements of the Earth system such as weather and water. These events are becoming both more frequent and more intense and, according to new knowledge, can best be examined together and not in isolation.
“We have found that concurrent extreme hydroclimate events, such as high temperatures and unusual rainfall, which rapidly melt mountain snowpack and flood several critical regions of the Colorado River basin, are expected to increase and intensify,” said Katrina Bennett, Hydrologist at Los Alamos National Laboratory and lead author of the paper in Water. “Simultaneous extreme events of more than one kind, rather than single events of a single type, will be the ones that actually harm people, society and the economy.”
Another example of simultaneous hydroclimate events could be low precipitation accompanied by high temperatures, the effect of which is drought. Other factors such as low soil moisture or burn scars on steep slopes contribute to bumps.
“You never have just one major rainfall event that causes a major flood,” said Bennett. “It results from a combination of influences like fire, topography and whether it was a wet or dry summer. So we have to think about these events. “
The Los Alamos study examined heat waves, drought, floods, and low currents in climate scenarios derived from six Earth System models for the entire Colorado River basin. The basin spans parts of Wyoming, Colorado, New Mexico, Utah, Nevada, Arizona, and California.
Using indicators such as maximum temperature, maximum precipitation, dry days, maximum and minimum current flow, maximum and minimum soil moisture, and maximum evapotranspiration, the team performed the models for a historical period (1970-1999) and a planned future period (2070-) . 2099). They examined the difference between the two time periods (future minus historical) for events on four time scales: daily, monthly, seasonal and yearly.
Overall, rainfall in Colorado increased 2.1 millimeters between future and historical periods, with some models showing an increase in precipitation and some a decrease. Nonetheless, the team found that changes in precipitation still led to an increase in simultaneous extreme events in all cases.
Unsurprisingly, the temperature rose on all six models and was an even more powerful catalyst for events. The study consistently found an average temperature increase of 5.5 degrees Celsius across the entire basin between the future and the historical period.
In each scenario, the number and magnitude of each type of extreme event in the Colorado River Basin increased on average for the future period compared to the historical period. These numbers were presented as a statistical expression of the change in frequency between historical and future periods, not as a count of discrete events.
These increases have a significant social, economic, and environmental impact on the entire region, which is a major economic engine for the United States. The study identified four critical watersheds in the Colorado Basin – the Blue River Basin, Uncompahgre, East Taylor, Salt / Verde watersheds – that are home to critical water infrastructure, water resources, and hydrological research that are particularly vulnerable to extreme events in the Colorado. Pools are the future.
More than 40 million people depend on the water of the Colorado River, and it directly supports $ 1.4 trillion in agricultural and commercial activities – about a thirteenth of the US economy, according to 2014 data.
In Utah, Colorado, Arizona, and New Mexico, flooding, drought, freezing events, wildfire, severe storms, and winter storms cost approximately $ 40 billion between 1980 and 2020.
The paper: “Simultaneous Changes in Extreme Hydroclimate Events in the Colorado River Basin”, Katrina E. Bennett (corresponding author), Carl Talsma and Riccardo Boero, in Water 2021, 13, 978, April 1, 2021. https: // doi.org/ 10.3390 / w13070978
Funding: This work was funded by the Los Alamos National Laboratory’s Early Career Laboratory Directed Research and Development (LDRD) program.
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