The Widths of Rivers and Streams Across Spatial Scales: A Framework for Improving River‐Atmosphere Biogeochemical Exchange Estimates

Abstract The width of rivers, and how it scales from narrow headwater streams to wide basin outlets, is a key yet highly uncertain parameter in estimating river‐atmosphere biogeochemical exchange. This study characterizes the full distribution of river widths across all stream orders in the Mississippi River Basin using multi‐source remote sensing, field surveying, and a nested sampling approach. River widths within each stream order consistently follow a log‐normal distribution. When integrated with basin‐wide river network lengths, these width distributions combine to form an emergent Pareto distribution. Using this newfound width scaling framework for the Mississippi Basin, we estimate a sum river surface area of 17,828 ± 2,563 km 2 , an area broadly consistent with previous evaluations. This study's refined characterization of river widths across scales has wide‐ranging applications including a more accurate accounting of river and stream surface area with implications for global river‐atmosphere biogeochemical exchange assessments.