Exploring wastewater nitrogen and phosphorus flows in urban and rural areas in China for the period 1970 to 2015

China's nutrient discharge to surface water increased 22-fold from 177 to 3908 Gg N yr−1 and 29-fold from 20 to 577 Gg P yr−1 in urban areas between 1970 and 2015. The ten strongly urbanised and industrialised provinces along the Eastern coast contributed 43% of China's total N and P discharge to surface water in 2015. At present, the contribution of rural areas to total wastewater discharge (2082 Gg N yr−1 and 434 Gg P yr−1) is 35% for N and 43% for P. The model approach and sensitivity analysis of this study indicate that policies aiming at improving water quality need to consider these regional differences. In other words, attention has to be paid particularly to the improvement of the wastewater treatment technology level in Eastern regions and increasing both the sewage connection and wastewater treatment in Central and Western regions.