How Have Global River Widths Changed Over Time?

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 90 m wide over 1984–2020, we find 66% of rivers have only slightly variable widths Thirty‐seven percent of global rivers show significant trends in width over the past 37 years, and this number is higher for human‐regulated rivers (46%) The most important factor driving temporal variations in river width is the climate for natural rivers and soil condition for regulated rivers