Soil Moisture in the Semi-arid Southwest
Although several drought indices exist to help make sense of soil moisture conditions in the semi-arid Southwest, there is little understanding about how to use them in decision making about drought. CLIMAS researchers worked to develop new climate services resources to help land managers better understand the available drought indices, choose the right one for their purposes, and manage drought conditions on their lands. Managers now have a better understanding of how different drought indices work, and how to choose the right one, at the right timescale, for their land management decisions. The project tracked drought on rangelands across southern Arizona, New Mexico, and California, constituting millions of acres of grazing lands. By co-developing this project with land managers and presenting research findings to other end users, researchers have improved the utility of existing drought monitoring indices across the southwest.
"We want to help land managers understand the strengths and weaknesses of these tools, so they don't have to do all the homework to figure out if they need to use this index versus that index. When our partners need to make high stakes decisions, and the data from the drought indices is kind of mediocre, we know how to help them get the best information for those decisions."
–Mike Crimmins, CLIMAS
CLIMAS Lead: Michael Crimmins
Research Team: Craig Rasmussen, Marcel Schaap, Dan Ferguson, Trevor McKellar
Partners: The Nature Conservancy, USDA – Agricultural Research Service, USDA – Natural Resources Conservation Service
Publications
McKellar, T. T., & Crimmins, M. A. (2025). Seasonal precipitation variability controls shallow soil water drought events across the southwestern United States. Agricultural and Forest Meteorology, 363. https://doi.org/10.1016/j.agrformet.2025.110403
McKellar, T. T., Crimmins, M. A., Schaap, M. G., & Rasmussen, C. (2023). Defining the Multiscalar Index Timescale—Soil Water Depth Continuum for the Southwestern United States. Journal of Geophysical Research: Atmospheres, 128(23), e2023JD039348. https://doi.org/10.1029/2023JD039348
McKellar, T.M. (2022). Drought Monitoring in the Southwestern U.S.: Analysis of Seasonal Precipitation, Multiscalar Indices, and Soil Water. University of Arizona.
McKellar, T. (2017). Evaluating How Representative Simple Multiscalar Drought Indices are of Modeled Soil Moisture Across the Desert Southwest United States. University of Arizona.