Expanse Supercomputer Provides High-Res Mapping of Heat Risks in California’s Imperial Valley
Published March 14, 2025
Over the past few years, research regarding urban heat islands—areas with heightened temperatures from heat-absorbing concrete, asphalt and rooftops, and little shade—has been published in many academic studies. High-resolution mapping for rural heat islands, however, is sparse yet critically important in the inland valley of southern California. Specifically, California farmworkers in Imperial Valley on the frontlines of food production are increasingly vulnerable to extreme heat. A new study by San Diego State University (SDSU) researchers using the Expanse supercomputer at the San Diego Supercomputer Center (SDSC), part of the UC San Diego School of Computing, Information and Data Sciences – has revealed that irrigation, a crucial part of farming in the region, can both help and hurt workers’ exposure to heat stress.
“Our models on Expanse showed that irrigation lowers daytime temperatures in the summer by up to 1.3°C due to evaporative cooling,” said Fernando De Sales, an associate professor in the SDSU Department of Geography. “However, at night, the same irrigation practices increased heat stress, raising temperatures by as much as 1.3°C (equal to 34.34° degrees Fahrenheit).”
De Sales said that the added moisture in the air keeps temperatures from dropping, making it harder for workers to recover from extreme heat.
The SDSU study also showed that nearby urban and non-irrigated areas experience heightened heat stress due to moisture moving from irrigated fields.
“These findings highlight the need for policies that protect farmworkers from dangerous heat exposure, especially as temperatures continue to rise over the years,” De Sales said. “With the help of ACCESS allocations on supercomputers like Expanse we are able to better understand and share mapping related to the extreme heat and the impact of increased irrigation.”
The left image shows the study region of interest (d03) over the Imperial Valley while the right image depicts the location of stations used for model validation on a Google Earth image with the Salton Sea at the center. Credit: San Diego State University
The study, entitled Impact of Irrigation on Farmworkers’ Heat Stress in California Differs by Season and During the Day and Night, was published in the Nature Communications Earth & Environment journal.
Computational support was provided by the U.S. National Science Foundation (ACCESS allocation no. EES240026).