Research On Spatial Evolution Characteristics And Driving Factors Of Surface Water In Capital Cities In The Process Of Urbanization

Water is the source of life,the essential of production,and the foundation of ecology.Cities are the areas with the highest concentration of human beings,and the relationship between water and people is of great importance.Understanding the temporal and spatial characteristics and driving mechanisms of surface water resources in the process of rapid urbanization is of great significance to understanding the relationship between man and land,especially for the implementation of the concept of harmonious development of urban man and nature with water as the core.Select the regions that can best reflect the evolution of China’s urbanization—36 cities（municipalities/provincial capitals/city/autonomous region capitals）as the research objects.The information of surface water bodies is extracted year by year to form a dynamic and continuous spatiotemporal data set.On this basis,the spatiotemporal evolution characteristics and driving factors of urban surface water area（SWA）are analyzed.The main conclusions are as follows:（1）From the perspective of temporal change characteristics,the seasonal(S_SWA),permanent(P_SWA)and total(T_SWA)of 36 cities in the past 30 years have shown an increasing trend.T_SWA increased by a total of 37.06×10²km²,of which the contribution rate of S_SWA reached 76.93%.In addition,from the perspective of change intensity,the five-year average T_SWA,S_SWA and P_SWA are all in the stage of quality improvement and expansion（2012-2020）,reaching the maximum area;in the stage of rapid urbanization development（2002-2011）,they are at a lower level;（2）From the perspective of the spatial distribution pattern,the spatial pattern of T_SWA and P_SWA is a clustered distribution（Moran I=0.06/0.09）,while the S_SWA is a random pattern（Moran I=0.03）.Secondly,the concentration index of city area SWA,area average SWA and per capita SWA are 0.52,0.53,and 0.71,respectively,showing a state of increasing sequentially.The gravity centers of the three types of urban surface water bodies are all located in Henan Province,but the centers of gravity are different.SSWA is located in the northeast of T_SWA,P_SWA is located in the southwest of T_SWA,and the direction of the center of gravity movement shows the law of moving to the northwest water shortage areas;（3）From the SWA value of a single city,the total SWA of the eastern cities reached5.38×10³km²,accounting for 34.69%of the total SWA.Among them,Wuhan ranks first and Xining the smallest.The variation trend of urban SWA was observed through regression equation,and according to the goodness of fit,the variation trend of SWA in36 provincial capital cities was determined:"S"type（12）,linear（11）,"U"type（8）and Inverted"U"shape（5）;（4）From the perspective of driving factors,the total population,investment in fixed assets,and per capita road area are negatively correlated with the land average SWA,while the green space rate in the built-up area is positively correlated with it.In addition,as the stage of urbanization changes,the negative impact of the total population begins to weaken;fixed asset investment and per capita road area change from negative to positive in a wide range,and the degree of impact gradually weakens from the southeast to the northwest inland;The overall impact intensity of the greening rate in the district showed a trend of first increasing and then decreasing,and the impact intensity gradually decreased from the north to the south;（5）From the geographical distribution of cities with different changing trends,"S"-shaped cities are mostly distributed in the plains and the middle and lower reaches of large rivers,and there are large water surface spaces in the cities,which determine the changing trend of urban SWA;the linear type is distributed in the plateau,hills and the upper reaches of large rivers,and the water resources are relatively scarce;most of the"U"shapes are located in the upper reaches of small watersheds,where water resources are the most scarce,mainly linear water bodies;the inverted"U"shape is mainly distributed in the low hills and the lower reaches of small watersheds in the coastal waters.There are relatively many rivers,and a relatively large number of reservoirs can be built;（6）From the perspective of the influence mechanism of typical cities,according to the goodness of fit,Beijing,Xi’an,Chengdu and Qingdao are selected as the representatives of the four changing trends,and are studied as examples.The results show that Beijing is dominated by large water surfaces,supplemented by some small water surface changes,Xi’an is based on linear water bodies,and various types of rivers,lakes,reservoirs and ponds work together,Chengdu is dominated by small water surfaces,and individual nodes are created based on the current water system,and Qingdao is a planar water body.The water body is the main body,and the sea-land border area changes obviously.