| The Yellow River is the mother river of the Chinese nation.The ecological protection and high-quality development of the Yellow River basin are related to China’s economic and social development and ecological security.Water resources are the core elements of ecological protection and high-quality development in the Yellow River basin.Therefore,it is of great significance to study the situation of water resources in the Yellow River basin for the protection and rational utilization of water resources in the Yellow River basin.The study of the temporal and spatial changes of surface water in the Yellow River basin over the years can provide a scientific basis for the investigation and rational utilization of water resources.Remote sensing has many advantages in surface water monitoring,but because traditional remote sensing methods require a lot of manpower,storage,and computing resources,their efficiency is very low in large-scale applications.Therefore,this paper uses the data call and computing advantages of Google’s geographic cloud computing platform to process 21,788 Landsat image scenes,extracting the largest water bodies,seasonal water bodies,and permanent water bodies in the Yellow River Basin from 2000 to 2017.Based on the water area extraction data of the Yellow River Basin,the changes of the water body area in different water states and different watersheds in the Yellow River Basin are analyzed in time and space.The correlation analysis method is used to analyze the changes in the water body area and precipitation in the Yellow River Basin and the changes in the area of the main lakes and reservoirs in the Yellow River Basin The degree of influence of the factor.The research results of this paper are as follows(1)The Google Geographic Cloud Computing Platform can extract long-term series of high-precision water dataThe water body extraction rules used are based on the existing water body index and vegetation index,which facilitates the monitoring of large-scale long-term remote sensing water bodies.At the same time,the Google Geographic Cloud Computing Platform can achieve more efficient acquisition and processing of remote sensing data,which greatly saves Manpower and time.By calculating the water pixel ratio of all images,according to the obtained water body frequency,the water body can be divided into seasonal water body(water body frequency between 0.25-0.75)and permanent water body(water body frequency is greater than or equal to 0.75).The accuracy of water extraction is 92.41%(2)spatial and temporal variation characteristics of water area in the Yellow River basin were analyzedFrom the perspective of time,the maximum water area of the Yellow River basin showed an increasing trend with time from 2000 to 2017.The average value of the maximum water area of the Yellow River basin in 18 years was 7655.79km2.The maximum surface water area of the Yellow River basin was 8567.24km2 in 2014,and the minimum value was 6413.90km2 in 2000.From 2000 to 2017,the surface permanent water body in the Yellow River basin showed an obvious increasing trend,and the increasing trend rate was larger than that of the largest water body in the Yellow River basin.From 2000 to 2017,the seasonal water body in the Yellow River basin showed a trend of decreasing with fluctuation pattern.From the perspective of spatial distribution,the proportion of surface water in the Yellow River basin is in the middle reaches of upstream > and downstream >.From 2000 to 2017,the seasonal water body in the Yellow River basin changed to permanent water body to a certain extent.In the Yellow River basin,the proportion of the permanent water body in the largest water body shows an overall trend of increase,while the overall seasonal water body shows a downward trend.(3)The characteristics of the spatiotemporal variation of precipitation in the Yellow River Basin are analyzedThe characteristics of the interannual variation of the average annual precipitation in the Yellow River basin from 2000 to 2017.On the whole,the average annual precipitation is on the rise.The average precipitation in 18 years is 481 mm,the highest value is 597 mm in 2003,and the lowest value is 413 mm in 2000.The spatial distribution of the annual average rainfall in the Yellow River Basin is the average annual precipitation in the lower reaches> the average annual precipitation in the middle reaches> the average annual precipitation in the upper reaches.The precipitation trend shows an obvious increasing trend.In the western part of the lower Yellow River Basin and the middle part of the middle reaches of the Yellow River Basin,there is a clear downward trend in precipitation.From the perspective of relative change rate,in the northeast and middle reaches of the Yellow River Basin and the entire downstream watershed,the rate of change of precipitation is very high,and the relative rate of change in other regions is relatively low.(4)Analyzed the spatial and temporal changes of water area changes of important lakes and reservoirs in the Yellow River BasinThis paper mainly analyzes the time series and spatial series changes of water area changes of 6 large lakes and reservoirs,such as Zhaling Lake and Eling Lake,Longyangxia Reservoir and Liujiaxia Reservoir in the Yellow River Basin,Xiaolangdi Reservoir in the middle reaches,and Dongping Lake in the downstream.The change trend of Zhaling Lake and Eling Lake in the upstream from 2000 to 2017 is an upward trend.In terms of spatial changes,the water area mainly changes on small lakes near Eling Lake and the At the northern edge of Zhaling Lake,the area with the largest area change is located in the southwest of Eling Lake.The water area of Longyangxia Reservoir showed an upward trend from 2000 to 2017.In terms of spatial changes,the increase in water storage capacity mainly caused the reservoir to increase The area of the water body is expanding outwards,and a part of it is mainly increased near the mouth of the gorge in the reservoir area of the Yellow River Basin.The water body area of Liujiaxia Reservoir showed a small volatility upward trend from 2000 to 2017.The spatial variation was similar to that of Longyangxia Reservoir.It is due to the increase of water storage capacity and raising the water level,and the area of water body expands outward.In the middle reaches of Xiaolangdi Reservoir,the area showed an overall upward trend from 2002 to 2017.The spatial change in area was also due to the elevation of the water level and outward expansion in 2007.During the period from 2008 to 2008,the area of the water body changed mainly in the Xiaolangdi dam area.The water area of Dongping Lake in the lower reaches has a weak downward trend.The spatial variation of the area is mainly near the Daqing River inlet in the southeast.(5)Correlation analysis of water bodies in the Yellow River Basin and precipitation,main lakes and reservoirsIn terms of precipitation: the correlation between the change trend of the maximum water area on the surface of the Yellow River Basin and the annual precipitation amount is from 2000 to 2003.The correlation coefficient between the two is 0.738.Between 2004 and 2010,the largest surface water body of the Yellow River Basin and the average annual precipitation The correlation coefficient of change is-0.188,indicating that in these years,the correlation between the maximum water area of the Yellow River Basin and precipitation is low.Between 2010 and 2017,the change in the maximum water area of the Yellow River Basin has a certain correlation with the change in average annual precipitation.The correlation coefficient is 0.21,indicating that during this time period,precipitation has a certain influence on the change of water area.By studying the change of the proportion of the various water bodies in the Yellow River Basin,there is a certain relationship with the increase of precipitation in most areas of the Yellow River Basin.Regarding the main lakes and reservoirs: the water area changes of Zhaling Lake and Eling Lake,Longyangxia Reservoir and Xiaolangdi Reservoir have a strong correlation with the permanent water body and the largest water body in the upper reaches of the Yellow River Basin,and the correlation with the permanent water body is greater than Maximum water correlation.The water body area change of Liujiaxia Reservoir has little correlation with the change of permanent water body and maximum water body area in the upper reaches of the Yellow River Basin.The water body of Dongping Lake occupies a small area of the lower reaches of the Yellow River Basin,so it does not have a great influence on the change of the area of the lower Yellow River. |
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