| It's obvious that water resources are very important to human beings.Using remote sensing technology to dynamically monitor the earth's surface water resource is an important technical means to study the change of water environment.Compared with the amount of water resources owned by other countries in the world,China ranks first in the total amount,but it is far behind other countries in terms of per capita ownership.Since the reform and opening policy was carried out,the rapid economic development has also caused great pressure on China's ecological environment.At present,the country is vigorously developing the construction of ecological civilization,among which the problem of water ecology is one of the difficult problems that must be overcome.Deyang City,one of the key cities of economic development in Sichuan Province,is very important for the development of Chengdu-Chongqing economic circle.Water resources play a key role in the economic development of the region.Therefore,based on Landsat-5 TM?Landsat-8 OLI and GF-6images,this paper selects the object-oriented classification method to extract the surface water of Deyang City,and analyzes the spatial distribution characteristics and dynamic change characteristics of surface water in Deyang City,so as to provide a certain reference value to the planning and layout of surface water resources in Deyang City.The results are as follows:(1)Based on multi-source remote sensing images,the ESP optimal scale evaluation method is used to establish the optimal segmentation scale and threshold,and create water extraction rules.The surface water bodies in February and August of 2000,2010 and 2020 are extracted based on Landsat images,and the annual change and annual change characteristics of water body area are analyzed.The water bodies in August of 2020 are extracted based on GF-6 images to analyze the spatial distribution of surface water bodies in Deyang City.Finally,the water extraction accuracy of Landsat-5 TM,Landsat-8 OLI and GF-6 images are80.50%,82.70%and 88.04%respectively.(2)Due to the influence of terrain and mountain shadow,and the small rivers,the extraction effect of water body in Landsat Image is poor.Therefore,on the basis of object-oriented method,the method of DEM generating river network is added to assist,and the river network is used to form a buffer zone to replace the water body in mountainous areas,so that the small rivers in Landsat Image can be extracted more accurately.(3)The water body characteristics and extraction results at different scales are compared and analyzed,it is found that the water boundary is fuzzy but uniform in Landsat Image,and the water boundary is clear but uneven in GF-6 image.The extracted result is that the boundary of large water body in Landsat Image is slightly larger,and the extraction effect of gf-6 image is very good,because the uneven color inside the water body is solved by spectral difference segmentation.This shows the difference of water extraction between high-resolution image and medium resolution image.(4)From the perspective of spatial distribution,the distribution of water bodies in Deyang City is uneven.Large rivers are mainly distributed in the central and western regions;The water bodies of pits and ponds are widely distributed in the southeast.Among all districts and counties,Zhongjiang County has the largest area of water body,and Shifang City has the smallest area.From the vertical direction,the water area decreases with the increase of altitude,and most of the water bodies are distributed within 800m above sea level;With the increase of slope,the area of water body first increases and then decreases.The proportion of water body within the first three grades of slope is 95.25%.Among them,the water body within the second grade of slope is the most distributed,mainly in rivers and ponds,while the reservoir is mainly distributed within the first grade of slope.(5)The annual variation characteristics of water body are as follows:in 2000,the water area in wet season increased by 1334.25 hm~2compared with that in dry season,the proportion of reservoirs and ponds decreased,and the proportion of rivers increased;In 2010,compared with the dry season,the water area in the wet season increased by 1037.03hm~2,the proportion of reservoirs and ponds has increased,while the proportion of rivers has decreased;In 2020,compared with the dry season,the water area in the wet season will increase by1410.62hm~2,the proportion of reservoirs and ponds will increase,and the proportion of rivers will decrease.(6)The annual variation characteristics of water body are as follows:from 2000 to2020,the water body area first decreased slightly and then increased significantly.The water body area increased by 857.75hm~2in wet season and 781.38hm~2in dry season.The water body areas of Zhongjiang County,Luojiang District and Mianzhu City showed an upward trend.Zhongjiang County increased the most,Guanghan City,Jingyang district and Shifang City showed a downward trend,and Guanghan City decreased the most.According to the type of water body,the area of river water body decreases,while the area of reservoir pits and ponds increases.From 2000 to 2010,the decline in dry season was 201.78 hm~2and that in wet season was 499 hm~2.From 2010 to 2020,the increase was 983.16hm~2in dry season and1356.75hm~2in wet season.(7)In order to study the influencing factors of water area change,seven factors including annual average rainfall,annual average temperature,total agricultural production value,total fishery production value,population,number of industrial enterprises and GDP were selected to analyze the correlation of water area change in Deyang City.It is found that the change of water area is most affected by rainfall,showing a significant positive correlation,and the partial correlation coefficient is 0.791.There is a certain negative correlation between water area and population,and the partial correlation coefficient is-0.562.In recent 20 years,precipitation,temperature,gross agricultural product and GDP of Deyang City have promoted the increase of water area,while population has inhibited the increase of water area to a certain extent.(8)Through this study,suggestions are put forward for the utilization of water resources in Deyang City:strengthening the protection and economical utilization of water resources;Continue to promote the protection of river and lake ecological functional areas,establish River and lake ecological protection zones and restore the area of wetlands;Actively explore and implement the river length system to realize the optimal protection of water ecological environment;Scientifically implement industrial and agricultural water use,and develop more reasonable diversion irrigation methods and industrial production processes. |
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