In a recently published paper, NASA scientists used nearly 20 years of observations to show that the global water cycle is changing in unprecedented ways. Much of these shifts are driven by activities such as agriculture and may have consequences for ecosystems and water management, particularly in certain regions.

"Through data assimilation, we found that human interference in the global water cycle is more important than we thought," said Sujay Kumar, a research scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and co-author of the paper . Proceedings of the National Academy of Sciences.

These shifts have implications for people around the world. Water management practices, such as designing flood infrastructure or developing drought indicators for early warning systems, are often based on the assumption that the water cycle only fluctuates within a certain range, said Nie Wanshu, a research scientist at NASA's Goddard Center and lead author of the study. Paper.

"For some areas, this may no longer be applicable," Nie said. "We hope this study will serve as a guide to improving our assessment of water resource changes and planning for sustainable resource management, particularly in areas where these changes are most significant."

An example of human impact on the water cycle is the North China region, which is experiencing ongoing drought. But Kumar said vegetation continues to flourish in many areas, in part because producers continue to pump more water from underground reservoirs to irrigate the land. Such interconnected human interventions often have complex effects on other water cycle variables such as evapotranspiration and runoff.

Nie and her colleagues looked at three different transitions, or changes, in the cycle: first, trends, such as less water in underground reservoirs; Second, changes in seasonality, such as the typical growing season starting earlier in the year, or earlier snowmelt, and third, changes in extreme events, such as "once-in-100-year floods" occurring more frequently.

The scientists collected remote sensing data from 2003 to 2020 from several different NASA satellite sources: the Global Precipitation Measurement Mission satellite for precipitation data, the European Space Agency Climate Change Initiative's soil moisture dataset, and gravity recovery for land and the Climate Experiment Satellite. Water storage data. They also use products from the Moderate Resolution Imaging Spectroradiometer satellite instrument to provide information about vegetation health.

"This paper combines our team's years of work in developing satellite data analysis capabilities that allow us to accurately model continental water fluxes and storage across the entire Earth," said Dr. Nasa, a research scientist at NASA's Goddard Center and author of the paper said co-author Augusto Getirana. Paper.

The findings suggest that Earth system models used to simulate future global water cycles should continue to evolve to incorporate the ongoing impacts of human activities. With more data and improved models, producers and water managers can understand and effectively plan for the "new normal" of local water conditions, Nie said.

Erica McNamee
NASA Goddard Space Flight Center, Greenbelt, Maryland