2026-01-06 マサチューセッツ大学アマースト校
A map made with SWOT data describing estimated discharge for rivers around the world. This information has numerous applications, from freshwater management to flood prediction. Credit: NASA/JPL/UMass Amherst
＜関連情報＞
- https://www.umass.edu/news/article/unprecedented-data-global-river-quality-quantity-now-gathered-space-powered-umass
- https://construction.tiisys.com/129648/
- https://www.science.org/doi/10.1126/science.adl5728
- https://www.science.org/doi/10.1126/science.adg9430
上流への流量増加と下流への流量減少：世界の河川の形態と機能の変化 More flow upstream and less flow downstream: The changing form and function of global rivers
Dongmei Feng and Colin J. Gleason
Science Published:12 Dec 2024
DOI:https://doi.org/10.1126/science.adl5728
Editor’s summary
Rivers begin as small systems in their headwaters and flow downstream to their mouths, displaying a range of physical and hydrological conditions that affect erosional patterns, sedimentation, energy distribution, and ecological communities. Feng and Gleason mapped daily streamflow in 2.9 million rivers globally to determine how their flow characteristics may have changed over the past several decades. They found that average flow volumes increased in headwaters and decreased in basin outlets since 1984. Among other consequences, these changes increased the frequency of 100-year flood occurrence in headwaters, whereas the flooding potential of downstream regions did not change. —H. Jesse Smith
Abstract
We mapped daily streamflow from 1984 to 2018 in approximately 2.9 million rivers to assess recent changes to global river systems. We found that river outlets were dominated by significant decreases in flow, whereas headwaters were 1.7 times more likely to have significantly increased flow than decreased. These changes result in a significant upstream shift in streamflow experienced by about 29% of the global land surface. We found the most changes in the smallest steams in our study: increases in erosion potential (approximately 5% increase in stream power), flood frequency (approximately 42% increase in 100-year floods), and likely nutrient dynamics (altered seasonal flow regimes). We revealed these changes using “detail at scale” by mapping millions of individual rivers. Widely adopting this approach could reveal other changes to the hydrosphere.
米国の排水網への一時的な河川水の寄与 Ephemeral stream water contributions to United States drainage networks
Craig B. Brinkerhoff, Colin J. Gleason, Matthew J. Kotchen , Douglas A. Kysar, and Peter A. Raymond
Science Published:27 Jun 2024
DOI:https://doi.org/10.1126/science.adg9430
Editor’s summary
Ephemeral streams are short-lived water bodies that flow only after precipitation has fallen. Although they are ubiquitous, little is known about how much they contribute to downstream flow. Brinkerhoff et al. modeled the contributions of such streams to over 20 million more permanent water bodies in the contiguous US, finding that ephemeral streams contributed about 60% of the total discharge from drainage areas (see the Perspective by Harvey and Kampf). This work illustrates how important ephemeral streams are as pathways for the transport of water and pollution into perennial water bodies. —Jesse Smith
Abstract
Ephemeral streams flow only in direct response to precipitation and are ubiquitous landscape features. However, little is known about their influence on downstream rivers. Here, we modeled ephemeral stream water contributions to the contiguous United States network of more than 20 million rivers, lakes, and reservoirs, finding that ephemeral streams contribute, on average, 55% of the discharge exported from regional river systems, as defined by the United States Geological Survey. Our results show that ephemeral connectivity is a substantial pathway through which water and associated nutrients and pollution may enter the perennial drainage network and influence water quality. We provide quantitative insight into the implications of differing interpretations of regulatory jurisdiction under the United States Clean Water Act, including the current standard adopted by the Supreme Court of the United States in 2023.
