Impacts of climate and planting structure changes on watershed runoff and nitrogen and phosphorus loss

It is important to explore the influence of climate and planting structure change on runoff and nitrogen and phosphorus loss in watersheds, as well as to clarify the quantitative relationship between each influencing factor with runoff, nitrogen and phosphorus to formulate reasonable soil and water conservation measures and reduce non-point source pollution in the watershed. In this study, the Lizixi watershed of the Jialing River was analyzed using a Global Climate Model to generate precipitation and temperature change sequences and the distributed hydrological model SWAT was used to simulate changes in runoff and nitrogen and phosphorus loss processes in the watershed under different climate change scenarios and planting structure changes. The results indicate that the increase in runoff caused by climate change in the next decade will be accompanied by an increase in the loss of total nitrogen and total phosphorus. Planting sweet potato under historical meteorological conditions had the best effect on controlling nitrogen and phosphorus loss in the Lizixi watershed, while large losses of nitrogen and phosphorus were produced when planting wheat and corn. At the same time, there is a positive correlation between the loss of nitrogen and phosphorus and the amount of fertilizer applied. For every 10% increase in fertilizer application, the loss of nitrogen and phosphorus increased by 1% and 4%, respectively. The results presented herein will serve as a reference for regional land use management planning.