Hydrologist Katrina Bennett describes extreme weather events like droughts and floods as the way that human societies experience climate change. These events are immediately noticeable and can have rippling impacts, including economic repercussions.
These events will become more frequent and intense amid climate change, according to a paper Bennett published in the journal Water on April 1. Bennett’s co-authors include Carl Talsma and Riccardo Boero, who also work at Los Alamos National Laboratories.
The study highlights the need to look at the extreme events together. Their research focused on the Colorado River Basin. The findings were in line with other research, however she said the team took a unique approach.
“Previously a lot of science has been done has been focused on looking at just temperature changes or just precipitation changes, but we’re trying to look at these events that are coupled and so potentially have a larger impact on society,” she said.
Based on their modeling, the team concluded that these concurrent, extreme events will become more common and more intense in the future. For example, warm temperatures that lead to an early snowmelt can cause flooding downstream. Or high temperatures combined with low precipitation will lead to drought.
Boero is an economic modeler and Bennett said the two of them are now partnering to evaluate the economic impact and will have a paper coming out in the future.
In addition, she plans on building on the research by looking at the human impacts. The April 1 paper looked at the natural system in the Colorado River Basin without looking at how the dams and diversions impact it. She said one of the next steps is to evaluate how the human system interplays with the natural one in terms of flooding and flows.
She said climate change will have impacts on human society and people should consider these impacts both in New Mexico and in the Colorado River Basin.
“These are such important systems and we do rely on them for water resources,” Bennett said. “We rely on them working in a consistent way.”
The study comes as all of New Mexico is currently experiencing some degree of drought, with more than half of the state in exceptional drought, according to the U.S. Drought Monitor. Exceptional droughts often involve crop loss as well as increased risk of wildfires. Often government entities issue water emergency declarations during exceptional drought.
In the Middle Rio Grande Valley, lack of monsoon rains have taken a toll
While Bennett’s team focused on the Colorado River Basin, the cumulative impacts of a lack of monsoon season and low runoff are noticed even in the Rio Grande Basin. The Middle Rio Grande Conservancy District ended the irrigation season early last year and delayed the start this year. The CEO Mike Hamman sent a letter to irrigators in February explaining why the irrigation season was delayed and encouraging them to let their fields go fallow or to plant short-season crops.
“What makes or breaks us here in the middle valley is the monsoon rains,” Hamman said.
If monsoon rains come this year, it will help with the delivery of the water that New Mexico owes downstream users like Texas under the Rio Grande Compact.
If the rains do not come and the demands are high and the river dries up, it will be very hard to send the water downstream.
“That’s what’s really driving the whole situation is the lack of monsoon moisture,” he said.
While the spring runoff has been decent, Hamman said the lack of summer, fall and early winter moisture means the watersheds themselves will be taking up a lot of the water. Dry soils will absorb the water rather than letting it run downstream. This reduces the flows in the river.
“It’s all tied together from year to year to year,” Hamman said. “You see a sort of downward spiral.”
The Middle Rio Grande Conservancy District stores water in El Vado Reservoir. This water is used to supply supplemental irrigation water once the runoff has stopped, usually around June.
However, when Elephant Butte and Caballo reservoirs have less than 400,000 acre feet of water in them, article seven of the Rio Grande Compact prevents water from being stored in reservoirs like El Vado that were built after 1929. Article seven is currently in effect and Elephant Butte is currently at nearly 11 percent of capacity.
On top of that, New Mexico cannot store water until it delivers the water that it owes to Texas.
The Middle Rio Grande Conservancy District is allocated about 40,000 acre feet of water. But 96,800 acre feet of water is owed to Texas.
The delay in the irrigation season was done in part as an effort to deliver more water downstream.
Study: Warmer temperatures will lead to less streamflow even if there is more precipitation
Bennett was also the lead author on research published in the April 2020 edition of the Journal of Hydrology: Regional Studies that looked at the future of water resources focused on a study area on the Pajarito Plateau in the Upper Rio Grande Basin.
The research projects there will be less surface water available even if there is more precipitation. This will be caused by increased temperatures, leading to more evaporation.
The study also forecasts a change in the type of precipitation received. The models project less snow and more rain.
Bennett said she plans to continue looking at how climate change impacts water systems in the southwest, including the Rio Grande.