Regional Patterns and Physical Controls of Streamflow Generation Across the Conterminous United States

This study unveils regional patterns of dominant streamflow generation mechanisms across the conterminous United States and identifies their climatic and physiographic controls. Six signatures describing the characteristics of rainfall-stormflow responses and the characteristics of base flow response are extracted from continuous rainfall-streamflow time series for 432 US catchments. These study catchments are classified into eight classes based on similarities of the six signatures, and dominant streamflow generation mechanisms for each class are inferred based on the magnitudes of the six signatures. This catchment classification reveals geographically coherent regional patterns across the conterminous United States. Catchment climatic and physiographic characteristics most relevant to this catchment classification are identified using techniques such as correlation analysis and random forest modeling. The most relevant characteristics are climate aridity, median event rainfall volume, topographic slope, soil permeability, rock type, and vegetation density, which are found to be the main controlling factors governing the dominant streamflow generation mechanisms. The linkages between the inferred dominant streamflow generation mechanisms and specific combinations of the climatic and catchment physiographic characteristics identified above are synthesized in a conceptual diagram, as an extension of the classical Dunne diagram. The new findings, while largely consistent with the results of previous empirical and modeling studies, add rich process detail to the transferable understanding of regional patterns of dominant streamflow generation mechanisms and their climatic and physiographic controls.