A B S T R A C TThis study quantified the long-term response of riverine total nitrogen (TN) export to changes in net anthropogenic nitrogen inputs to forest/agricultural (NANI FA ) and residential (NANI R ) systems across three catchments affected by low (LD), medium (MD), and high (HD) human impacts in eastern China. Annual NANI FA increased by 63-87% in 1980-1999, followed by 0% (LD), À23% (MD) and À40% (HD) changes of NANI FA in 2000-2010, resulting in a net increase of 56-78% in NANI FA in 1980-2010. Annual NANI R increased by 101-152% in the three catchments in 1980-2010. Land-use showed a 58-65% increase in developed land area (D%) and a 96-108% increase in agricultural lands with improved drainage systems (AD%) over the study period. In response to changes in NANI FA , NANI R and land-use, riverine TN flux continuously increased 3.0-to 6.1-fold in the three catchments over the past 31 years. For each catchment, an empirical model incorporating annual NANI FA , NANI R , water discharge, D%, and AD% was developed (R 2 = 0.93 À 0.97) for predicting and quantifying sources of annual riverine TN fluxes. The model estimated that NANI FA , NANI R and other N sources (e.g., natural background, legacy, and industrial N sources) contributed 27-90%, 0-45%, and 10-28% of riverine TN fluxes, respectively. Model results were consistent with spatio-temporal changes of riverine chloride, ammonium, nitrate, dissolve oxygen and pH, as well as changes in available N levels in agricultural soils. In terms of N source management, reduction of NANI FA in catchment LD and NANI R in catchment HD would have the greatest impact on reducing riverine TN fluxes. Furthermore, changes in land use and climate as well as legacy N should be considered in developing N pollution control strategies.