Revealing the Ripple: How Human Actions are Transforming the Global Water Cycle

In a recently released study, NASA researchers utilized nearly two decades of observations to demonstrate that the global water cycle is altering in unprecedented manners. Most of these alterations are propelled by activities like agriculture and may affect ecosystems and water governance, particularly in specific areas.

“Data assimilation has revealed that human influence on the global water cycle is more substantial than previously understood,” stated Sujay Kumar, a research scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and a co-author of the paper published in the Proceedings of the National Academy of Sciences.

The alterations have repercussions for individuals worldwide. Practices related to water governance, such as infrastructure design for flooding or the development of drought indicators for warning systems, are often based on presuppositions that the water cycle varies only within a certain range, remarked Wanshu Nie, a research scientist at NASA Goddard and the paper’s lead author.

“This may no longer be applicable for some areas,” Nie indicated. “We anticipate that this research will act as a framework for enhancing our evaluation of water resource variability and developing sustainable resource management strategies, particularly in regions where these alterations are most pronounced.”

An example of human influence on the water cycle can be observed in North China, which is currently facing an ongoing drought. However, vegetation in numerous regions continues to flourish, primarily because farmers are still irrigating their fields by extracting additional water from groundwater supplies, Kumar noted. Such interconnected human actions often result in intricate effects on other water cycle components, including evapotranspiration and runoff.

Nie and her team concentrated on three distinct types of shifts or modifications within the cycle: firstly, a trend, such as a reduction in water levels in a groundwater reservoir; secondly, a seasonality shift, like the typical growing season commencing earlier in the year, or an earlier snowmelt; and lastly, a shift in extreme occurrences, such as “100-year floods” happening more often.

The researchers collected remote sensing information from 2003 to 2020 from various NASA satellite resources: the Global Precipitation Measurement mission satellite for rainfall data, a soil moisture dataset from the European Space Agency’s Climate Change Initiative, and the Gravity Recovery and Climate Experiment satellites for terrestrial water storage data. They also leveraged products from the Moderate Resolution Imaging Spectroradiometer satellite instrument to acquire insights on vegetation health.

“This paper amalgamates several years of our team’s endeavors in enhancing capabilities in satellite data analysis, facilitating precise simulation of continental water fluxes and storages across the globe,” remarked Augusto Getirana, a research scientist at NASA Goddard and a co-author of the paper.

The findings of the study indicate that Earth system models utilized to predict the future global water cycle should advance to incorporate the ongoing effects of human actions. With increased data and refined models, producers and water resource managers could gain a clearer understanding and effectively strategize for what the “new normal” of their local water circumstances appears like, Nie remarked.