『Abstract
　To evaluate the effect of human activities on the amount of nitrogen (N) transported to the Three Gorges Dam (TGD), we have developed and applied a model to estimate the riverine N transport from watersheds draining into the upper Changjiang River basins. By using this model and a database of agricultural statistics, we study the temporal and spatial changes in N inputs to watersheds and surface waters. The total amount of N transported to the surface drainage waters from the agro-ecosystem in 2000 showed a 2.9-fold increase over that in 1980. considering a constant (37％) loss rate from the river, the annual amount of N transported to the TGD from the agro-ecosystem of the Changjiang river upper basin was about 0.35×10⁶, 0.47×10⁶, 0.59×10⁶, 0.64×10⁶ and 1.01×10⁶ t in 1980, 1985, 1990, 1995, and 2000, respectively. Further, the transported amount of new anthropogenic reactive N approximately quadrupled in 2000, while the amount of riverine N due to rural human waste varied slightly. Of the total N transported to surface drainage waters in 10 watersheds in 2000, the Jiangjiang watershed accounted for 35％; the TGD region, 15％; and the Toujiang, Wujiang and Mihjiang watersheds, 11％ each. In 1980, the N sources were concentrated in the rural areas surrounding Chendu City and Chongqing city; however, these sources considerably expanded in the 1990s. The increased use of synthetic fertilizers and the decrease in the fertilizer N-use efficiency are implicated as major causal factors of increased riverine N transport; the calculated amount of N transported to the main tributaries agrees well with previously reported data.

Keywords: Agricultural field; New anthropogenic reactive N inputs; Riverine N transport; Three Gorges Dam; Upper basin of Changjiang』

Introduction
Data and methods
　Study area
　Basic data
　Methods
Results and discussion
　Anthropogenic reactive N inputs
　N transport to surface drainage waters
　Fertilizer N-use efficiency
　Comparison of the obtained estimates with previously reported measurements
Conclusion
Acknowledgements
Appendix 1
References