Understanding non-stationarity in annual peakflow is critical amid climate change and human interventions1,2. We analyzed trends in peakflow across 3907 streamflow sites with a median record length of 80 years in the continental United States. Results showed that one-third of the sites have significant trends. Of these, two-thirds showed decreasing trends nationwide, while one-third showed increasing trends in the Northeast and Great Lakes regions. We found urbanization and water management as primary drivers, with agriculture and climate as secondary. Urbanization explained up to 62% of the variance in Texas-Gulf, 44% in California, and 32% in the Mid-Atlantic regions. Water management dominated in Tennessee (37%) and Ohio (30%) regions. Agriculture was most influential in the Great Lakes (17%) region, while climate contributed in the Rio Grande (15%) and California (11%) regions. Although the latest climate model provides many realizations, it inadequately captures direct human interventions in the water system.
