Patterns of similarity of seasonal water balances: A window into streamflow variability over a range of time scales

Recent hydrologic synthesis efforts have presented evidence that the seasonal water balance is at the core of overall catchment responses, and understanding it will assist in predicting signatures of streamflow variability at other time scales, including interannual variability, the flow duration curve, low flows, and floods. In this study, we group 321 catchments located across the continental U. S. into several clusters with similar seasonal water balance behavior. We then delineate the boundaries between these clusters on the basis of a similarity framework based on three hydroclimatic indices that represent aridity, precipitation timing, and snowiness. The clustering of catchments based on the seasonal water balance has a strong relationship not only with regional patterns of the three climate indices but also with regional ecosystem, soil, and vegetation classes, which point to the strong dependence of these physiographic characteristics on seasonal climate variations and the hydrologic regimes. Building on these catchment clusters, we demonstrate that the seasonal water balance does have an imprint on signatures of streamflow variability over a wide range of time scales (daily to decadal) and a wide range of states (low flows to floods). The seasonal water balance is well integrated into variability at seasonal and longer time scales, but is only partly reflected in the signatures at shorter time scales, including flooding responses. Overall, the seasonal water balance has proven to be a similarity measure that serves as a link between both short-term hydrologic responses and long-term adaptation of the landscape with climate.