Satellites reveal hotspots of global river extent change
Study key findings & significance
- The study looks at eight hotspots of significant river changes, including:
- (1) eastern Siberia, (2) Tibetan Plateau, (3) middle northern Siberia, and (4) middle eastern Asia, where river flow increased, and
- (5) the Great Plains in central North America, (6) middle-eastern South America, (7) western Siberia, and (8) northern India, where river flow decreased
- Climate change generally explains the contrasting pattern of river extent changes in these eight hotspots, except in middle Eastern Asia, where no significant wetting trend was observed.
- Climate warming and wetting trends are likely the main cause of the river widening signal on the pan-Arctic and third-pole regions where other types of human impact have been been limited.
- Decreasing precipitation trends are observed in the Great Plains in central North America and in middle-eastern South America, while significantly increasing trends of actual evapotranspiration are observed in western Siberia and northern India.
Abstract
Rivers are among the most diverse, dynamic, and productive ecosystems on Earth. River flow regimes are constantly changing, but characterizing and understanding such changes have been challenging from a long-term and global perspective. By analyzing water extent variations observed from four-decade Landsat imagery, we here provide a global attribution of the recent changes in river regime to morphological dynamics (e.g., channel shifting and anabranching), expansion induced by new dams, and hydrological signals of widening and narrowing. Morphological dynamics prevailed in ~20% of the global river area. Booming reservoir constructions, mostly skewed in Asia and South America, contributed to ~32% of the river widening. The remaining hydrological signals were characterized by contrasting hotspots, including prominent river widening in alpine and pan-Arctic regions and narrowing in the arid/semi-arid continental interiors, driven by varying trends in climate forcing, cryospheric response to warming, and human water management. Our findings suggest that the recent river extent dynamics diverge based on hydroclimate and socio-economic conditions, and besides reflecting ongoing morphodynamical processes, river extent changes show close connections with external forcings, including climate change and anthropogenic interference.
