More flow upstream and less flow downstream: The changing form and function of global rivers

We mapped daily streamflow from 1984 to 2018 in approximately 2.9 million rivers to assess recent changes to global river systems. We found that river outlets were dominated by significant decreases in flow, whereas headwaters were 1.7 times more likely to have significantly increased flow than decreased. These changes result in a significant upstream shift in streamflow experienced by about 29% of the global land surface. We found the most changes in the smallest steams in our study: increases in erosion potential (approximately 5% increase in stream power), flood frequency (approximately 42% increase in 100-year floods), and likely nutrient dynamics (altered seasonal flow regimes). We revealed these changes using “detail at scale” by mapping millions of individual rivers. Widely adopting this approach could reveal other changes to the hydrosphere.