Geology

Climate change

Streamflow

Biology

Physical geography

Drainage basin

Oceanography

Composite material

Geography

Geotechnical engineering

Ecology

Materials science

Range (aeronautics)

Cartography

Hydrology (agriculture)

Discharge

Environmental science

Biogeochemical cycle

Water Resources Research

Changes in a river's width reflect natural and anthropogenic impacts on local and upstream/downstream hydraulic and hydrologic processes. Temporal variation of river width also impacts biogeochemical exchange and reflects geomorphologic evolution. However, while global maps of mean river width and dynamic water surface extent exist, there is currently no standardized global assessment of river widths that documents changes over time. Therefore, we made repeated width measurements from Landsat images for all rivers wider than 90 m collected from 1984 to 2020 (named Global LOng‐term river Width, GLOW), which consists of ∼1.2 billion cross‐sectional river width measurements, with an average of 3,000 width measurements per 10‐km reach. With GLOW, we investigated the temporal variations of global river width, quantified by the interquartile range (IQR) and temporal trend. We found that 85% of global rivers have a width IQR &lt;150 m. We also found that 37% of global river segments show significant temporal trends in width over the past 37 years, and this number is higher (46%) for human‐regulated rivers. Further, we leveraged machine learning to identify the most important factors explaining river width variations and revealed that these driving factors are significantly different between free‐flowing and non‐free‐flowing rivers. Specifically, the most important factor driving temporal variations in river width is the climate for free‐flowing rivers, and is soil condition for human‐impacted rivers. Finally, we anticipate that this study and the public release of GLOW will improve the understanding of river dynamics and catalyze additional interdisciplinary studies.

How Have Global River Widths Changed Over Time?