| Fuhe River has the largest nitrogen and phosphorus concentration among the 5 major river system in Poyang Lake,and is the main contributing source of nitrogen and phosphorus in Poyang Lake.Current nitrogen and phosphorus prediction studies are primarily based on assumptions of climate change and socio-economic stability,and do not take into account the impact of socio-economic dynamic change on nitrogen and phosphorus load.In this paper,7new climate scenarios SSPs(SSP1-1.9,SSP1-2.6,SSP2-4.5,SSP3-7.0,SSP4-3.4,SSP4-6.0,SSP5-8.5)from the five climate models with scenario refinement in the 6th coupled model comparison program(CMIP6)were selected,and the SWAT hydrological model was used under climate change and dynamic socio-economic,to investigate the spatial and temporal variability of runoff,nitrogen,and phosphorus in the Fuhe River Basin(FRB)from 2021 to2050,as well as the role of climate and socioe-conomic factors in the change in nitrogen and phosphorus load,in order to provide a scientific foundation for improving water quality.The results of the study are as follows:(1)Social and economic changes have been the main driving factor for changes in nitrogen and phosphorus loads.However,the contribution of climate change to the total nitrogen load has increased from 14.4% to 18.2% between 1981 and 2020,and from 13.5% to17.8% for total phosphorus load.These results indicate that the impact of climate change on total nitrogen and phosphorus loads is increasing while the impact of social and economic changes is decreasing.(2)The annual average temperature of the FRB shows a significant increasing trend at a warming rate of 0.14°C/10 a from 1961 to 2019,and the annual precipitation of the basin shows a significant increasing trend at a rate of 25.3 m3/s/10 a.The FRB shows an obvious warming and wetting trend from 2021 to 2050,and the annual average temperature of the basin increases from 2021 to 2030,2031 to 2040,and 2041 to 2050.The annual average temperature in the basin is increasing in 2021-2030,2031-2040,2041-2050,and the rate of temperature increase is accelerated with the strengthening of radiative forcing;the annual precipitation is fluctuating and increasing in 2021-2030,2031-2040,2041-2050.(3)The arable land area in the FRB basin shows a significant decreasing trend and the total population continues to increase from 1961 to 2019.Relative to the base period,Under the SSPs scenario,cultivated area in the FRB generally decreases from 2021 to 2050;total population generally increases from 2021 to 2050.Fertilizer application from agriculture in the watershed generally decreases in 2021-2030,2031-2040,and 2041-2050(except for SSP5-8.5);fertilizer application from domestic wastewater increases in 2021-2030,2031-2040,and 2041-2050.(4)The average flow in the FRB from 1961 to 2019 showed a significant increasing trend at a rate of 18.4 m3/s/10 a,and the annual average flow in the basin also maintained an increasing trend in 2021-2030,2031-2040 and 2041-2050,rising from 4.8% to 16.3%,7.2%to 23.1% and 7.1% to 20.0%,respectively,in the future The water resources in the FRB become more abundant.The monthly runoff and monthly precipitation are distributed in the same way within the year,and the monthly average flow shows a slight increase in spring and summer,but a significant increase in autumn and winter.The future change in the monthly average flow will make the annual distribution of runoff in the basin more uniform.(5)From 1995 to 2014,the multi-year average annual total nitrogen load was about9333.4 t,with a significant decreasing trend at the rate of-113.7(t)/a;relative to the base period,the total nitrogen load in the FRB under the SSPs scenario decreased significantly in2021-2030,2031-2040 and 2041-2050.The monthly total nitrogen load generally decreases significantly in autumn and winter with low precipitation,In contrast,there is a slight decrease in spring and summer with a higher precipitation rate.The spatial distribution of the total nitrogen load is mainly concentrated in the middle and lower reaches of the basin,near the mainstream,while the easternmost and westernmost areas in the middle reaches have lower total nitrogen load,and the areas with higher load are arable land with high fertilizer application and dense urban areas,which are obviously influenced by socio-economic.(6)From 1995 to 2014,the multi-year average total phosphorus load was about 1632 t,with an increasing trend at a rate of 2.1(t)/a;relative to the base period,the total phosphorus load in the FRB under the SSPs scenario showed an increasing trend from 2021 to 2050,with an increase in the average total phosphorus load from 2021 to 2030;there were increases and decreases from 2031 to 2040 and 2041 to 2050.The monthly phosphorus load shows a significant increase in summer,while there is little or no increase in autumn and winter,it is obviously influenced by precipitation and shows positive correlation with monthly precipitation change.In the spatial distribution,the total phosphorus load is mainly concentrated in the watershed outlet and the middle and lower reaches,the areas with higher load are located in the highly inhabited and industrially developed areas in the lower reaches,with lower total phosphorus load in the eastern and upper reaches of the middle reaches.These areas are also influenced by urban home sewage discharge. |
