Evolution of nitrogen and phosphorus load in Fuhe River Basin under climate and socio-economic changes
The current research on nitrogen and phosphorus(NP)projection is mainly based on assumptions of unchanged cli-mate change and socio-economic conditions,lacking consideration of the impact of socio-economic dynamics on NP loads.To study the changes in NP loads under the combined effects of climate and socio-economic factors,7 new climate scenarios(SSP1-1.9,SSP1-2.6,SSP2-4.5,SSP3-7.0,SSP4-3.4,SSP4-6.0,SSP5-8.5)from 5 climate models with comprehensive scenarios in the Sixth Coupled Model Intercomparison Project(CMIP6)were selected.Using the SWAT hydrological model,the spatial and temporal characteristics of the nitrogen and phosphorus loads in the Fuhe River Basin from 2021 to 2050 were simula-ted and analyzed relative to the baseline period(1995～2014)under the combined effects of climate change and socio-econom-ic changes.The results showed that:①socio-economic changes were the main factors affecting the changes in nitrogen and phos-phorus loads.However,the contribution of climate to the total nitrogen load change increased from 14.4%to 18.2%and the con-tribution to total phosphorus load change increased from 13.5%to 17.8%during 1981～2020,indicating that the impact of cli-mate change on total nitrogen and phosphorus loads was increasing,the impact of socio-economic changes on total nitrogen and phosphorus loads was decreasing.②The average annual total nitrogen load in the Fuhe River was about 9 333.4 t,with a signifi-cant decreasing trend at a rate of-113.7 t/a from 1995 to 2014.Compared to the baseline period,the total nitrogen load in the basin from 2021 to 2050 was expected to show a significant decreasing trend.Spatially,the total nitrogen load was mainly concen-trated near the mainstream in the middle and lower reaches of the basin,with lower loads in the eastern and western parts of the middle reaches.③The average annual total phosphorus load in the Fuhe River Basin was about 1 632 t,showing an increasing trend at a rate of 2.1 t/a from 1995 to 2014,and it was expected to increase from 2021 to 2050 compared to the baseline period.In terms of spatial distribution,higher total phosphorus load concentrations were found at the river basin outlet and in the middle and lower reaches,with lower loads in the eastern middle reaches and upper reaches.
nitrogen and phosphorus loadsfuture projectionclimate changesocio-economicsCMIP6SWAT modelFuhe River Basin
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