作者：J. W. Harvey and S. K. Kampf

A river's journey typically starts in temporary streams that flow sporadically when wet conditions prevail. During dry periods, streamflow slows and then stops as the waters recede below ground. When streamflow resumes over recently dry streambeds, it mobilizes and transports energy-rich materials and nutrients that stimulate aquatic ecosystem productivity downstream ( 1 ). Temporary streams are present in all climate zones ( 1 - 3 ), and most of the world's streams and rivers do not flow continuously ( 4 ). However, the quantity of flow that temporary streams deliver to larger rivers remains unknown. On page 1476 of this issue, Brinkerhoff et al. ( 5 ) report that ephemeral streams-the class of temporary streams that flow least often-collectively convey on average 55% of the flow to perennially flowing rivers in the conterminous United States. The analysis has implications for downstream water quality and water resources management in the United States and elsewhere.

（来源：Science 2024 Vol. 384 Issue 6703 Pages 1402-1403    DOI: 10.1126/science.adq1714）