ALBUQUERQUE (AP) – Each spring, farmers cross their fingers for abundant Rio Grande flows that will sustain them through a hot summer.
Now, New Mexico water scientists have found that peak Rio Grande flows could arrive about a month earlier by the century’s end.
The potential change could influence how the state manages its scarce water supplies.
U.S. Geological Survey hydrologist David Moeser said the research began by creating a model for what the Rio Grande “looked like before we got in the way.”
“People look at the Rio Grande and there’s a little bit of water, or no water, and they think that’s just business as usual, but that is really not how the big river used to be,” Moeser said.
Flows at the Colorado-New Mexico state line, for example, have declined sharply in the past century.
That decline is thanks to a precisely managed system of reservoirs and canals that divert water from the river for irrigation and municipal use.
About 75% of Rio Grande flows come from snowpack, while monsoon rains produce the rest.
The team used nearly 30 different climate data sets to show how rising greenhouse gas emissions, temperatures and changes in snowpack could influence when river flows will be at their peak each year.
“Once we superimpose climate change on top of what is already going on in the system, then there is the potential for (streamflow) to be much worse than what we’re seeing from the original model,” said hydrologist Shaleene Chavarria.
Majority streamflow volume in the Upper Rio Grande Basin could arrive about a month earlier by 2099 if global emissions continue to rise, the USGS study found.
“One month earlier means we are getting that water significantly prior to the growing season,” Moeser said. “So, how are water managers going to hold on to that water in order to deliver it in a meaningful way to the people that need the water in our basin? This is a fairly striking result.”
Predicting the precise volume of water in the river proved a murkier task.
But the team did find that the Rio Grande may not have as much water during monsoon season as in years past.
“A lot of the changes that we see in this basin are due to the changes in snow,” Moeser said. “That’s why we see such drastic changes moving forward.”
Theresa Davis is a Report for America corps member covering water and the environment for the Albuquerque Journal.
