| The process of urbanization and its impact on ecosystems is an important part of the study of the Earth's biochemical processes.With the rapid development of global urbanization,more and more attentions have been paid on the research of urban ecosystem.The process of urbanization has caused artificial soil sealing in urban area,which leads to the degradation of soil function and the decrease of vegetation coverage.It also affects the water cycle of urban ecosystem.With the development of the urban scale and population,urban soil sealing areas will continue to increase and change the urban carbon cycle profoundly.The relationship between the change of the urban water cycle and the process of the urbanization has become a global concern.At present,the simulation of water cycle in urban areas was mainly focused on the simulation of urban green space and urban forest carbon fluxes.There were few studies on the process of water cycle and ecosystem services.Therefore,the simulation of water cycle process and ecosystem services in watershed ecosystemthe has great significance to the coordination of urban economy and ecological construction.In this study,we take the Jiu Xiang River Basin in Nanjing as the research area,remote sensing interpretation of impervious surface in 2000,2005,2010 and 2015.On the basis of the previous study of water resources ecosystem services,simulating the surface runoff,evapotranspiration and underground runoff of the Jiu Xiang River Basin and explore the changes of water resources ecological service function between 2000 and 2015 of Jiu Xiang River Basin.On this basis,using CA model to simulate the expansion of the urban agglomeration expansion scenario and the urban decentralized expansion scenario of the Jiu Xiang River Basin.By combining with the the double loop method to measure soil infiltration rate,simulate the changes of the surface runoff depth under the high intensity rainfall in the next ten years of the Jiu Xiang River Basin,and analysis the control scenarios.The influence of the urban expansion process on urban surface runoff will provide reference for future urban planning and development in Jiu Xiang River basin.The main results in this paper are as follows:(1)Based on the study of the process of water cycle under urban impervious surfaces,the model of urban waiter cycle was established with the consideration of temperature,water content and inert.The water cycle model was established by combining the SCS-CN model,the BIOME-BGC model and the water balance formula to simulate the surface runoff,evapotranspiration and underground runoff of urban areas.The results show that the expansion of impervious surfaces cause the increase of annual surface runoff,and increased by 165.31%in 15 years,the decrease of annual evapotranspiration and underground runoff d and decreased by 18.1%?87.12%and 15.38%in 15 years.The simulation results shows that the change of the water cycle has a certain correlation with the expansion of the urban impervious surface.(2)This study calculates 4 main water resources ecosystem services and the turnover rate of water resources ecosystem in 2000-2015 of Jiu Xiang River Basin.The functionof supporting and regulating of water resources have been reduced to a certain extent in the whole research area with time,the decline of support function is most obvious,the turnover rate and the supply function of the ecosystem has rised.From the view of space,the degradation of ecosystem services in the urban concentrated expansion area is the most serious,and the loss of ecosystem services is far greater than that of other areas.The supply function of water resources ecosystem services presents upward trend due to the growth of the impervious surface in the urban area,and the loss of water resources in natural conditions is greatly reduced.The rapid urban development has made the turnover time of water resources ecosystem decreasing a lot,decreasing by 9.88%in 15 years,which has weakened the capacity of coping with the hydrological disaster in the Jiu Xiang River basin(3)We calculated the urban expansion and adaptability index of the study area in different scenarios with the consideration of the current urban development rate and the limiting factors of urban development in the future.The expansion of the city from 2015 to 2025 was predicted by the CA model,which used the urban expansion and adaptability index.In the next 10 years,the expansion of impervious surfaces will happen in the center of the city in the densification scenarios.In the sprawl scenarios,the areas of impervious surfaces will increase in Tangshan District as well as the center of the city,which lead to a situation of multi-core urban expansion.(4)Under the background of urban expansion,this paper puts forward three urban runoff optimization strategies and sets three control scenarios.After studying the optimization effect of three different means of surface runoff under different expansion modes.The efficiency of the impervious surface distribution optimization is the highest under the urban densification expansion model,and the runoff depth can be reduced by 7.68%with an average increasing of 1%of the distribution area.The efficiency of the osmotic surface distribution is the highest under the urban sprawl expansion model,and the runoff depth can be reduced by 2.78%with an average increasing of 1%of the distribution area.The optimization of municipal drainage facilities has the highest efficiency under the urban decentralized expansion model,and the runoff depth can be reduced by 1.06%with an average of 1%drainage capacity.If the urban development is mainly concentrated on the urban densification,the optimization of urban surface runoff should be based on the optimization of impervious surface and the optimization of municipal facilities.If the dispersion and expansion of the city are the main factors,the optimization of urban surface runoff should be based on the optimization of drainage facilities and the urban non permeable land optimization strategy. |
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