How humans are modifying the global water cycle

Recent modifications in the global water cycle are a significant concern, according to a study conducted by NASA scientists.

Over the past two decades, the experts have observed an unprecedented shift in the water cycle – which they believe is largely influenced by human activities such as farming.

These changes are not just an environmental concern but also impact ecosystems and pose challenges to water management.

“We established with data assimilation that human intervention in the global water cycle is more significant than we thought,” said Sujay Kumar, a scientist at NASA’s Goddard Space Flight Center.

The paper was published in the Proceedings of the National Academy of Sciences.

Impacts of water cycle changes

Radical shifts in the water cycle can have serious implications for communities all over the globe.

Traditional water management practices like flood infrastructure or developing early drought indicators are usually based on the concept that the water cycle fluctuates only within a certain limit.

“This may no longer hold true for some regions,” said study lead author Wanshu Nie.

“We hope that this research will serve as a guide map for improving how we assess water resources variability and plan for sustainable resource management, especially in areas where these changes are most significant.”

The human impacts on the water cycle are perceptible in regions like North China, which is experiencing an ongoing drought. But vegetation in many areas continues to thrive, partially because producers continue to irrigate their land by pumping more water from groundwater storage, noted Kumar.

These interlinked human interventions often have intricate impacts on other water cycle variables like evapotranspiration and runoff.

Distinct shifts in the water cycle

Nie and her team focused on three kinds of shifts in the cycle. First, they analyzed a change in trends – such as a reduction in groundwater reservoirs.

Second, the team examined a shift in seasonal patterns like the typical growing season starting earlier in the year, or a premature snowmelt. The researchers also looked for changes in extreme events, such as “100-year floods” happening more frequently.

The scientists used remote sensing data from 2003 to 2020 that was collected by different NASA satellites.

These included precipitation data from the Global Precipitation Measurement mission satellite, a soil moisture dataset from the European Space Agency’s Climate Change Initiative, and terrestrial water storage data from the Gravity Recovery and Climate Experiment satellites.

The researchers obtained data about vegetation health from the Moderate Resolution Imaging Spectroradiometer satellite instrument.

Integrating human activities into future models

“This paper combines several years of our team’s effort in developing capabilities on satellite data analysis, allowing us to precisely simulate continental water fluxes and storages across the planet,” noted study co-author Augusto Getirana.

The findings of the study suggest that the Earth system models currently used to predict the future global water cycle should be revised to factor in the ongoing effects of human activities.

With more data and improved models, producers and water resource managers could better understand and plan effectively for the “new normal” of their local water conditions.

Interconnected nature of the water cycle

The water cycle is a delicate and interconnected system that regulates the movement of water through the atmosphere, land, and oceans.

Human activities, such as agriculture, urbanization, and industrial processes, are increasingly influencing this natural balance.

When groundwater is over-extracted for irrigation or urban use, it disrupts the natural recharge process, leading to depletion and long-term consequences for regional water availability.

Similarly, deforestation and land-use changes can alter precipitation patterns and runoff, exacerbating the risks of both droughts and floods.

Climate change further compounds these human influences by intensifying weather extremes and shifting regional precipitation patterns. Warmer temperatures accelerate evaporation rates, altering the distribution of water resources across the planet.

This has far-reaching consequences for ecosystems, food security, and the sustainability of freshwater supplies.

Understanding these complex interactions is crucial for developing adaptive water management policies. By integrating human impact data into hydrological models, policymakers and scientists can better predict future water challenges and implement sustainable solutions.

The full study was published in the journal Proceedings of the National Academy of Sciences.

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