PERSISTENCE AND PEAKEDNESS OF RIVER DISCHARGE ACROSS MULTIPLE TIMESCALES

The amount of discharge routed through a river system scales to the size of the river’s catchment area. The temporal variability of river discharge is strongly influenced by climatic forcing operating at annual and decadal periodicities. Rivers with high discharge variability occur at all latitudes today, and both modeling and interpretation of ancient river systems suggest that amplification of monsoons and other climatic phenomena cause increased discharge variability in river systems throughout earth history. A better understanding of the hydrology of both modern and ancient river systems requires a quantitative assessment of the influence of discharge variability on river dynamics. We take an actualistic approach by assessing discharge variability in modern rivers worldwide using daily gauging station measurements of flow rate. Here we show that while mean discharge scales to catchment area in river systems with very persistent hydrology, in rivers with more variable hydrology this relationship is weak. Higher magnitude flow events have a strong correlation to catchment area across all hydrologic regimes. We conclude that flow events larger than 99th percentile, including flow events of a similar recurrence interval to bankfull flow, are the most characteristic of the runoff capacity of a river’s drainage basin area across different climate zones and hydrologic regime.