Changing River Network Synchrony Modulates Projected Increases in High Flows

Projections of change in high-flow extremes with global warming vary widely among, and within, large midlatitude river basins. The spatial variability these changes is attributable to multiple causes. One possible little-studied cause a the synchrony mainstem tributary streamflow during at mainstem-tributary confluence. We examined reconstructed simulated naturalized daily confluences on Columbia River western North America, quantifying future projections estimating impact extremes. In basin, projected flow regimes across colder tributaries initially diverge as they respond climate different rates, leading general decrease synchrony, lower extremes, relative scenario no synchrony. Where sufficiently most subbasins upstream from confluence transition toward rain-dominated, warm regime, decreasing trend reverses itself. At one major (the Willamette River), where are very different, increases and, therefore, magnitudes. These results may be generalizable class rivers contributions flood risk snow (i.e., cold) but that also receive considerable discharge drain warmer