Hydrologic connections across the landscape are a primary control on the fluxes of materials from terrestrial to aquatic ecosystems. Recent research has examined the role of hydrologic transport as a control on stream water nitrogen to phosphorus (N:P) ratios at the catchment scale. In this talk we explore hydrologic controls on N:P ratios using a novel nonparametric statistical method that allows large-scale synthesis. This method uses discharge (Q) and TN:TP ratios to allow more direct analysis across a 58-catchment data set. Normalized variables are analyzed with nonparametric smoothing to extract annual signals from catchment classes based on mean annual precipitation. Results from the analysis indicated that TN:TP ratios declined with increasing Q in semi-arid catchments. An opposite relationship, increasing TN:TP ratios with increasing Q occurs in humid catchments. The new information supports the hypothesis of hydrologic control of stream water N:P ratios, except over much larger spatial and temporal scales than previously indicated.