Humanity pushed the freshwater cycle to its limits 70 years ago

Humanity pushed the freshwater cycle to its limits 70 years ago. Earth's freshwater systems have already reached far beyond the stable conditions that existed before industrialization.

A new study published in the journal Nature reveals that humanity surpassed the planetary limit for freshwater depletion in the mid-20th century. This means that we are using fresh water at an unsustainable rate, which is having serious consequences on the environment and people's water security.

This study is the first time that changes in the global water cycle have been assessed on such a long-term scale using a consistent baseline.

The findings, show that human pressures such as dam construction, large-scale irrigation and global warming have altered freshwater resources to the point that their ability to regulate their vital climatic and environmental processes is threatened.

The international research team calculated monthly runoff and soil moisture with a spatial resolution of approximately 50 x 50 km, using data from hydrological models that integrate all major human influences on the freshwater cycle.

Main causes of depletion of the water cycle

  • The increase in population: The world population has grown exponentially in recent decades, which has increased the demand for fresh water for human consumption, agriculture and industry.
  • Climate change: Global warming is causing changes in precipitation and evaporation patterns, which is leading to greater water scarcity in some regions.
  • Pollution: Pollution of surface and groundwater from agriculture, industry and domestic discharges is reducing the amount of freshwater available for use.
water cycle

How was the research that determines how the depletion of the freshwater cycle occurs

They took as their starting point the conditions of the pre-industrial era (1661-1860). They then compared the industrial period (1861-2005) with the reference period.

Their analysis revealed an increase in the frequency of exceptionally dry or wet conditions: deviations in flow and soil moisture. Since the beginning of the 20th century, dry and wet drift has occurred systematically over large areas compared to the pre-industrial era.

Overall, the global land area experiencing deviations has almost doubled compared to pre-industrial conditions.

Vili Virkki, PhD student at Aalto University and one of the lead authors of the study reported: “We found that exceptional conditions are now much more frequent and widespread than before, clearly demonstrating how human actions have changed the state of the global freshwater cycle."

Because the analysis was performed with high spatial and temporal resolution, the researchers were able to examine geographic differences in variability.

Exceptionally dry flow and soil moisture conditions became more common in several tropical and subtropical regions, while many boreal and temperate regions were affected by an increase in exceptionally wet conditions, especially in terms of soil moisture. 

These models are consistent with observed changes in water availability due to climate change.
In many regions with a long history of land use and agriculture, more complex patterns exist. For example, the Nile, Indus, and Mississippi basins have extremely dry flows and wet soils, suggesting changes due to irrigation.

Consequences of freshwater cycle depletion

  • Lack of water: La lack of water It is already affecting millions of people around the world, and this problem is expected to worsen in the future.
  • Environmental degradation: The depletion of freshwater is causing the degradation of aquatic ecosystems, loss of biodiversity and desertification.
  • Conflicts over water: Water scarcity can lead to conflicts between different water users, such as farmers, cities and industry.

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