Reno, Nev. (September 5, 2024) – Drought remains a significant concern in the Western U.S., prompting water managers to develop groundwater management plans to conserve this essential resource. Groundwater is often pumped to the surface for crop irrigation, with meters traditionally measuring the flow of pumped water. However, these meters are scarce. Scientists at the Desert Research Institute (DRI) investigated whether OpenET, a platform that measures evapotranspiration using satellite data, could bridge this information gap.
The study, published on August 8th in Agricultural Water Management, compared groundwater meter data with OpenET estimates for agricultural fields in Nevada and Oregon. The findings indicate that OpenET can accurately estimate groundwater used for crop irrigation at individual field levels. This research is pioneering in tracking water from a groundwater well to a single field of crops and assessing irrigation efficiencies.
“We knew where the water was drawn from and where it was being applied, and we showed that the satellite data could tell us how much crop water use and pumping occurred for individual fields,” said Thomas Ott, assistant research scientist of hydrology at DRI and lead author of the study. Ott noted that access to detailed meter data is rare; previous studies focused on broader regions without assessing individual field water use.
Evapotranspiration combines evaporation and transpiration processes—returning water to the atmosphere from Earth’s surface and through plant photosynthesis. OpenET utilizes data from NASA and U.S. Geological Survey Landsat satellites alongside weather variables like humidity, air temperature, and solar radiation to estimate evapotranspiration globally.
The study focused on two agricultural regions with irrigation water flow meters: Diamond Valley, Nevada, and Harney Basin, Oregon. Both regions heavily rely on groundwater for irrigating alfalfa and hay. In Diamond Valley, there was a 7% difference between metered data and OpenET estimates for water use; Harney Basin showed a 17% difference. Researchers examined how OpenET performed across different irrigation systems—center-pivot sprinklers in Diamond Valley versus mixed flood irrigation and sprinklers in Harney Basin.
“Our study shows that OpenET can really advance our understanding of agricultural water use, especially in basins without monitoring in place,” Ott stated. He added that traditional methods often overestimate maximum water use based on typical healthy fields annually; satellite data provides more realistic values.
Sayantan “Monty” Majumdar, assistant research professor of hydrologic sciences and remote sensing at DRI and co-author of the study, mentioned that assumed values for water use in Diamond Valley were significantly higher than actual usage according to their findings. The researchers also found high efficiency in water use—90% of irrigation water used by crops in Diamond Valley compared to 83% in Harney Basin.
Ott, Majumdar, and their team plan to expand this research across Nevada as part of the Nevada Water Initiative. Nevada relies on decades-old estimates of water availability; this initiative aims to provide robust assessments using advanced research methods and technology for future water management planning. The project involves collaboration between DRI, the Nevada Division of Water Resources, USGS Nevada Water Science Center, and state agricultural stakeholders.
“The stakeholder engagement for this work is so important,” Ott emphasized. He shared his experience growing up on a dairy farm which helped him connect with local farmers during field surveys—a crucial aspect for future work.
More information: The publication “Toward field-scale groundwater pumping and improved groundwater management using remote sensing and climate data” can be found in Agricultural Water Management at: https://doi.org/10.1016/j.agwat.2024.109000
For more information on OpenET: https://etdata.org/
Authors include: Thomas Ott (DRI), Sayantan Majumdar (DRI), Justin Huntington (DRI), Christopher Pearson (DRI), Matt Bromley (DRI), Blake Minor (DRI), Peter ReVelle (DRI), Charles Morton (DRI), Sachiko Sueki (DRI), Jordan Beamer (Oregon Water Resources Department), Richard Jasoni (DRI).
About DRI:
Founded in 1959 as Nevada’s non-profit research institute focusing on science that matters globally.
