Moscow, Idaho — A newly published study has revealed that ecosystems can store far more water than previously believed — an insight led by the University of Idaho that could transform how scientists and policymakers understand and manage drought resilience.
By leveraging satellite data from NASA’s GRACE (Gravity Recovery and Climate Experiment) and GRACE-Follow On missions, researchers have developed the first direct observational method to quantify root-zone water storage capacity at large scales. The findings significantly enhance our understanding of how vegetation interacts with water resources.
Water is a critical component of natural ecosystems and human societies. Trees, shrubs and grasses extract water from the ground to support their growth, influencing hydrology and water availability. However, accurately measuring how much water plants can store in the soil has remained a challenge — until now.
“Scientists have long known that vegetation plays a role in the water cycle, but it’s been incredibly difficult to quantify just how much water ecosystems can store,” said Meng Zhao, lead author and assistant professor in U of I’s Department of Earth and Spatial Sciences. “Traditional field measurements are labor-intensive, expensive and limited in scope. Our study is the first to use satellite-based gravity measurements to provide a direct estimate of this crucial variable at a regional and global scale.”
The research utilized data from the GRACE and GRACE-Follow-On satellites, which measure subtle changes in Earth’s gravity. Since water has mass, its movement affects gravitational pull. By tracking shifts in gravity over time with the satellites, the researchers could infer how much water was stored in the soil and used by vegetation. This novel approach has provided unprecedented insights into how ecosystems manage water during wet and dry periods.
Key findings from the study include:
- First-of-its-kind dataset: This is the first time plant root-zone storage capacity has been mapped directly from satellite gravimetric observations.
- Higher-than-expected water storage capacity: Previous estimates suggested an average root-zone water storage capacity of approximately 150 millimeters, but the new study finds this value to be over 200 millimeters. Additionally, findings show that root-zone water storage capacity exceeds 2 meters of soil storage in nearly half of vegetated areas worldwide, far more than previously thought.
- Major scientific implications: The mapped storage capacity is significantly larger than current scientific consensus, which will change our understanding of ecosystem resilience to droughts and heatwaves.
- Improved drought resilience modeling: The research team integrated their findings into a hydrological model developed by the U.S. Geological Survey, demonstrating significant improvements in predicting ecosystem water use during droughts. Incorporating these new storage estimates into a global hydrological model also enhanced evapotranspiration simulations, particularly during drought periods.
- Practical impact on water management: The dataset enhances hydrological modeling, including applications for Idaho’s water resource management, helping policymakers better predict drought impacts and prepare for competition between human and ecological water needs.
“This research has major implications for environmental conservation and water resource management,” Zhao said. “By better quantifying how much water vegetation can store, we can improve hydrological models, predict tree mortality and wildfire risks, and anticipate how ecosystems will respond to climate change.”
The study, “Substantial root-zone water storage capacity observed by GRACE and GRACE/FO,” was published in Hydrology and Earth System Science, a leading journal in the geoscience and water resources field. The research is expected to influence future hydrological and ecological studies globally, providing a more accurate picture of how vegetation interacts with water resources across diverse landscapes.
This project was funded to University of Idaho by the U.S. Geological Survey under award G24AP00031. The total project funding is $618,648, of which 50 percent is the federal share.