UNM researchers examine agricultural water use in New Mexico’s Middle Rio Grande Basin

As climate change intensifies drought conditions across the Southwest, researchers at The University of New Mexico are examining how agricultural water is used in one of New Mexico's most critical river systems.

A new study led by Tosin Olofinsao, Ph.D., in the Department of Economics, alongside mentors Associate Professor Jingjing Wang and Regents Professor Robert Berrens, explores how irrigated agriculture consumes water across different categories of farms in the Middle Rio Grande Basin. The research provides new insight into how water is distributed among small farms and large commercial operations, offering data that could help shape future water management and conservation strategies in dryland regions.

"Agricultural water use in the Middle Rio Grande Basin is shaped not just by a few large farms, but by the combined decisions of thousands of small irrigators," Olofinsao said. "Lasting water solutions will require policies that recognize both the hydrologic realities of water scarcity and the social realities of farming communities in dryland regions."

The study comes at a time when New Mexico and other arid regions face growing pressure from climate variability, shrinking water supplies, and increasing competition between agricultural, urban, and environmental water needs.

According to the researchers, the Rio Grande system is already under significant strain, making it increasingly important to have a current understanding where agricultural water is going and how it is being used.

"Our study examines how irrigated agriculture uses water in the Middle Rio Grande Basin of central New Mexico, a dryland region facing increasing water shortages and climate stress," Olofinsao said. "We wanted to better understand who is using agricultural water, what crops are being grown, and how water use differs between small farms and large commercial farms."

To conduct the research, the team combined satellite-based evapotranspiration data, crop maps, groundwater well records, agricultural census records and GIS spatial analysis tools. Using these datasets, the researchers created a detailed map of irrigated agriculture across the basin during the severe 2021 drought year.

One of the study's most significant findings was that small farms collectively use more agricultural water than large commercial farms. While large farms consume more water individually, the basin contains thousands of micro-scale and small irrigators whose combined water use represents the majority of agricultural consumption.

The researchers also found that alfalfa and hay crops account for nearly three-quarters of total crop water use in the basin. In a high variability water supply system without flexible water-sharing agreement, such crops are relatively tolerant with respect to the ability to deficit irrigate. Deficit irrigation is the deliberate practice, in a water short year, of applying less water than a crop's full evapotranspiration demand. Additionally, groundwater access was found to be highly unequal among farms. Large commercial operations were far more likely to have access to irrigation wells, giving them greater flexibility during drought conditions, while many smaller farms rely primarily on surface water deliveries.

"The most surprising result was how much cumulative water use came from very small farms," Olofinsao said. "Many people would assume that a few large farms dominate agricultural water demand, but our results showed that thousands of small irrigators collectively account for 55.9% of evapotranspiration in the basin."

The study also emphasizes that agriculture in Middle Rio Grande Basin extends beyond commercial economics alone. Researchers noted economic dimensions that are non-market in nature (e.g., agriculture tax exemptions for greenspace etc.), and that many small farms are closely tied to family traditions, cultural heritage, open space preservation, and local identity.

"These findings matter because water conservation policies cannot focus only on large farms," Olofinsao said. "Reliable water management in the Middle Rio Grande Basin will require working with thousands of small irrigators as well."

Given the considerable heterogeneity across agricultural water users, researchers say the findings could help policymakers and water managers design more effective, targeted conservation programs. Such programs could include voluntary fallowing programs, seasonal deficit irrigation, and water leasing strategies designed to reduce water demand while supporting agricultural communities.

Beyond New Mexico, the researchers believe the work has broader relevance for dryland regions around the world facing similar challenges tied to groundwater stress, declining river systems, and increasing climate variability.

"This research highlights that solving water challenges in dryland regions is not simply a technical issue; it is also a social, cultural, and economic challenge," Olofinsao said. "The future of the Middle Rio Grande Basin will depend on finding balanced solutions that support water use continuity while preserving the agricultural traditions, landscapes, and communities that have shaped New Mexico for generations."